national floodplain mapping assessment - final report

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National Floodplain MappingAssessment - Final Report

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National Floodplain Mapping

Assessment

Final Report

June 2014

National Floodplain Management Framework Page i

Public Safety Canada

Executive Summary

Canada has witnessed a notable increase in flooding over the past decade, with total damages

exceeding $10 billion. As part of Public Safety Canada’s mandate to mitigate losses resulting

from natural events, a National Floodplain Management Framework has been prepared as an

initial step in reducing flood risk across Canada.

Starting in 1975 the Flood Damage Reduction Program (FDRP), an initiative of Environment

Canada, was implemented in collaboration with the provincial and territorial governments and

ran until 1996. This very comprehensive initiative led to the thousands of kilometres of flood

hazard mapping across Canada. The FDRP included the development of a comprehensive set of

guidelines and standards that guided the program.

The National Floodplain Management Framework, summarized herein, builds upon the

Emergency Management Framework, the National Disaster Mitigation Strategy and the original

Flood Damage Reduction Program.

The National Floodplain Management Framework includes two key components: Flood Hazard

Mapping and the Flood Risk Database. It will serve as a key document that will help to reduce

and mitigate flood risk across Canada.

The National Floodplain Management Framework that is presented in this document identifies:

• The type and extent of information that must be collected and managed;

• The key standards and guidelines that will apply to the development of Flood Hazard Maps

and the Flood Risk Database.;

• The anticipated cost of updating and preparing new hazard maps, as required, and the

compilation of data for the flood risk data base; and

• A list of initiatives to be completed as part of implementation.

A number of Guiding Principles have been identified to help inform the National Floodplain

Management Framework and its ultimate implementation. Adherence to these principles will

aid significantly in developing the fundamental tools necessary to effectively manage and

mitigate flood risk across Canada.

• Technical Accuracy

• Effective in Assessing and Managing Risk

• Accessibility to the User

• Current

National Floodplain Management Framework Page ii


The first step in developing the National Floodplain Management Framework included review

of practices in seven countries other than Canada, review of current provincial and territorial

practices, and input from subject matter experts.

The international review also provides a point of reference between current practices in

Canada and those across the globe. The countries reviewed included the United Kingdom (UK),

Australia, the United States of America (USA), France, Germany, Switzerland and New Zealand.

Following from the international review, a number of key practices and standards were

identified for consideration in the development of the National Floodplain Management

Framework for Canada.

The flood plain mapping practices, key standards, and unique challenges for each province and

territory in Canada and a compilation of comments and recommendations from a wide range of

subject matter experts were also summarized. All of the information will help to inform the

National Floodplain Management Framework.

The key comments received from across Canada are summarized below.

Technical Accuracy

1. The fact that there is a high degree of uncertainty in all of the steps leading to estimation of

flood risk should be documented and included as part of the presentation of flood risk.

2. Additional streamflow gauging would help with accuracy, particularly in ungauged

watersheds.

3. Standard methods for relating flooding to damages should be updated across Canada.

4. There should be more formal procedures available to complete all steps of the mapping

process.

5. More importance should be placed on both calibration and on-going updates/verification.

Effective in Assessing and Managing Risk

6. There should be a National Vision and set of standards that would apply across Canada.

7. Floodplain management should move beyond hazard mapping to consider risk to

communities, industry and agriculture.

8. Mapping should be extended along more rivers, particularly through urban areas.

9. Events more severe than the 1:100 year event should be considered in hazard mapping and

flood risk assessment; particularly when one considers both the degree of uncertainty

associated with the estimates and that statistically a 1:100 year event has a 65 percent

chance of occurring in a 100 year period.

National Floodplain Management Framework Page iii


Accessibility to the User

10. The public should have much better access to flood risk information.

Current

11. Across much of Canada there is a need for updated floodplain mapping.

The development of floodplain mapping, as it is understood today, began in approximately

1975. Currently mapping is available along some 28,000 km of rivers and streams across

Canada. Most of the mapping was initially developed between 1975 and 1996 through the

federal-provincial Flood Damage Reduction Program (FDRP). However with updates and

additional mapping that have been completed since FDRP, approximately half of the existing

mapping was developed after 1996.

The extent of mapping in each province and territory is generally proportional to the

population. Of the total, 59 percent of existing floodplain mapping is in Ontario, 21 percent is in

Québec, and 10 percent is in British Columbia. The remaining 10 percent is distributed across

the other provinces and territories. This is because the focus has always been on preparing

mapping for the more populated areas.

Overall approximately 35 percent of the mapping is through urban areas. However the ratio of

mapping that is in urban areas varies widely, from a low of 14 percent in British Columbia to a

midrange of 49 percent in Alberta to a high of 75 percent in Québec.

Although the median age of all mapping in Canada is 18 years (1996), there is also a fair

variability in mapping age. The median age of all mapping in Alberta, Québec and Ontario is

approximately 10 years old, while it is in excess of 20 years old in the remaining jurisdictions.

The comparison of current mapping to the proposed mapping standards is based on the

following key standards:

• Base Mapping

• Regulatory Event for Flood Hazard Mapping

• Flood Risk Database

• Age of mapping

• Climate Change Adaptation

It is concluded that existing flood plain mapping across Canada does not meet the majority of

the standards proposed as part of the National Floodplain Management Framework. This

conclusion does not infer that existing mapping is inadequate, but rather that the proposed

standards represent a step forward in defining how floodplains should be mapped and how

flood risk should be documented.

National Floodplain Management Framework Page iv


As a next step it is recommended that a Risk Assessment be completed to better identify and

understand the areas of highest risk. Results of the Risk Assessment would then be used in

establishing priorities for updating mapping in accordance with the proposed standards

The cost of developing updated Hazard Maps and creating the Flood Risk databases is based on

the costs associated with:

1. Preparing base mapping.

2. Completing the hydrologic studies.

3. Completing detailed hydraulic surveys of infrastructure and buildings in the floodplain.

4. Preparing the hazard mapping.

5. Populating the database.

Actual costs will vary widely depending on complexity, width of the floodplain, number of

buildings, density of infrastructure, and approach to calculating flow rates. On average it is

expected that the cost of completing all steps would range from $7,500/km in a rural setting to

$10,500/km in an urban setting assuming a 1-D hydraulic model is employed. For 2-D hydraulic

modelling the cost would increase to $50,000/km due to greater complexity.

The cost of updating existing mapping and creating an additional 15,300 km of mapping is

approximately $365 million. The additional 15,300 km should be sufficient to ensure that

mapping is available for 90-95 percent of the population in flood prone areas. Depending on

the results of the Risk Assessment and the review of new areas to be mapped, it is anticipated

that this cost estimate could change.

The National Floodplain Management Framework will include both Performance Standards and

Technical Standards. The Performance Standards refer to the key standards that define risk.

Three levels of standards are proposed: High, Medium and Low.

• High: Apply to all urban areas and rural areas that are protected by diking

• Medium: Apply to remaining rural areas that include settlements and agricultural lands

• Low: Apply to unpopulated areas, and may be used to guide the development of

infrastructure

Table B1 in Appendix B details the proposed Performance Standards.

The Technical Standards refer to the tolerance requirements that are to be adhered to in

developing the hazard mapping and the flood risk data base. Table B2 (Appendix B) presents

the key technical standards although it is not exhaustive. Many more standards will be

incorporated into the guidelines as part of the various procedures that will be documented. In

fact, many of the Technical Standards listed herein may also be adjusted at that time.

National Floodplain Management Framework Page v


There are a several initiatives that are recommended to be completed prior to embarking on

the update of the flood hazard mapping and the development of the flood risk database. These

initiatives could be undertaken simultaneously over a period of 12 to 15 months.

• Complete a National Risk Assessment to help establish mapping priorities.

• Develop the Guidelines and refine the Technical Standards.

• Develop a framework for the Flood Risk Database.

• Determine the delivery model for preparing mapping and the database.

• Prepare Federal-Provincial/Territorial Agreements.

National Floodplain Management Framework Page vi


Table of Contents

1.0 Introduction ...................................................................................................................................... 1

2.0 Overview of the National Floodplain Management Framework ...................................................... 2

3.0 Approach to Developing the National Floodplain Management Framework .................................. 4

3.1 International Review ........................................................................................................................... 4

3.2 Summary of Key Practices ................................................................................................................. 14

3.3 Canadian Review ............................................................................................................................... 16

4.0 Expert Comments............................................................................................................................ 29

5.0 Status of Floodplain Management in Canada ................................................................................. 30

6.0 Comparison of Existing Mapping to Proposed Standards .............................................................. 33

7.0 The Proposed National Floodplain Management Framework ........................................................ 39

8.0 Initiatives and Next Steps ............................................................................................................... 45

Appendices

Appendix A – Floodplain Mapping Background

Appendix B - Performance Standards and Technical Standards

National Floodplain Management Framework Page 1


1.0 Introduction

Canada has witnessed a notable increase in flooding over the past decade, with total damages

exceeding $10 billion. As part of Public Safety Canada’s mandate to mitigate losses resulting

from natural events, a National Floodplain Management Framework has been prepared as an

initial step in reducing flood risk across Canada. The National Floodplain Management

Framework specifically presents the standards and guidelines that will be applied to the

updating of Flood Hazard Maps and the development of a National Flood Risk Database.

Recent Flooding in Canada

Since 2004, the most notable Riverine1 flood events in

Canada occurred in Alberta in 2005 and 2013, and

Manitoba in 2009 and 2011. In addition, many central

Canadian cities experienced considerable damage due to

Urban Flooding2 associated with intense summer storms.

Key examples include Peterborough in 2004, Hamilton on

several occasions including 2005 and 2012, Montreal in

2011, and Toronto in 2005 and 2013.

The last comparable period was 1948 to 1954 when three catastrophic flood events occurred;

the Fraser River along the lower mainland of British Colombia (1948), the Red River through

Winnipeg (1950), and the Humber

River through Toronto and points

northwest (1954). The total

damage of these events totaled

$17.5 billion3. These three flood

events led to significant investment

in flood mitigation works and the

development of policies to guide

development in flood prone areas.

Public Safety Canada Mandate for Flood Mitigation

Public Safety Canada is the lead federal Agency responsible for disaster mitigation in Canada.

Two notable initiatives include the Emergency Management Framework (EMF) and the National

Disaster Mitigation Strategy (NDMS).

1 Riverine Flooding: flooding associated with a river or watercourse overtopping its banks.

2 Urban Flooding: flooding associated with municipal infrastructure (sewers and streets) exceeding their capacity to convey

runoff. 3 Source: Making Flood Insurable for Canadian Homeowners, A Discussion Paper, Swiss Re, November 2010.



The Emergency Management Framework (EMF) is a joint initiative of federal, provincial and

territorial governments that focuses on saving lives and reducing economic damage associated

catastrophic loss events. The framework is built on four components including: prevention and

mitigation, preparedness, response and recovery.

The National Disaster Mitigation Strategy (NDMS) is also a joint initiative of federal, provincial

and territorial governments with an initial focus on reducing risk associated with natural

hazards. Although natural hazards encompass events such as fires and droughts, flooding is of

primary concern in terms of loss of life and property.

Floodplain Mapping Background

Appendix A includes an overview of floodplain mapping that may be helpful to the reader in

terms of understanding the content and context of this report.

2.0 Overview of the National Floodplain Management Framework

Starting in 1975 the Flood Damage Reduction Program (FDRP), an initiative of Environment

Canada was implemented in collaboration with the provincial and territorial governments and

ran until 1996. This very comprehensive initiative led to the thousands of kilometres of flood

hazard mapping across Canada. The FDRP included the development of a comprehensive set of

guidelines and standards that guided the program.

The National Floodplain Management Framework, summarized herein, builds upon the

Emergency Management Framework, the National Disaster Mitigation Strategy and the original

Flood Damage Reduction Program.

The National Floodplain Management Framework includes two key components: Flood Hazard

Mapping and the Flood Risk Database. It will serve as a key document that will help to reduce

and mitigate flood risk across Canada.

In this context Flood Hazard Mapping refers to traditional flood plain maps that delineate the

extent of flooding for a Regulatory Flood4. However, for infrastructure that is in the floodplain

Flood Hazard Mapping does generally not provide an indication of the likelihood or

consequence of flooding.

A Flood Risk Database refers to the information that must accompany the Flood Hazard

Mapping in order to quantify flood risk (likelihood and consequence of flooding). As an example

the database would include an inventory of buildings in the floodplain including the probability

that the building will flood and possibly the approximate damages associated with the flood.

4 A Regulatory Flood is the flood event that is used to define the floodplain and establish policies specific to development and

redevelopment in the floodplain. Across Canada the minimum Regulatory Flood is the 1-100-year flood, although in many

jurisdictions a more severe event is used for regulatory purposes.



The National Floodplain Management Framework addresses both traditional

Flood Hazard Mapping and a Flood Risk Database that will help to quantify the

likelihood and consequence of flooding.

The National Floodplain Management Framework that is presented in this document identifies:

• The type and extent of information that must be collected and managed;

• The key standards and guidelines that will apply to the development of Flood Hazard Maps

and the Flood Risk Database.;

• The anticipated cost of updating and preparing new hazard maps, as required, and the

compilation of data for the flood risk data base; and

• A list of initiatives to be completed as part of implementation.

Updated Flood Hazard Mapping will provide a clear and consistent understanding of the extent

of flooding across Canada. The Flood Risk Data Base will provide and organize the data

necessary to understand and manage flood risk.

Vision and Guiding Principles

A number of Guiding Principles have been identified to help inform the National Floodplain

Management Framework and its ultimate implementation. Adherence to these principles will

aid significantly in developing the fundamental tools necessary to effectively manage and

mitigate flood risk across Canada.

Technical Accuracy

Two broad technical factors define the accuracy of information that is needed to assess the

likelihood and consequence of flooding. These include hydrotechnical processes and geospatial

information. Among others, hydrotechnical processes include hydrology (flow rates), wave

action, and hydraulics (flood elevations). Geospatial information includes topographic mapping

and infrastructure details. Each of these plays an important role in the development of flood

hazard mapping and a flood risk database.

Implementation standards and guidelines must provide the assurance that all flood risk

assessments are as accurate and consistent as is practical. As such the implementation

standards and guidelines must address allowable tolerances, methodologies, documentation,

and quality control.




Fundamentally flood hazard mapping and the flood risk database must be comprehensive

enough that they can be used effectively in assessing and managing risk. This means that the

information on the mapping or in the database must address all aspects of risk specific to

infrastructure, industry and commerce, and communities.


The hazard mapping and flood risk data base must be equally available to potential users in

government, industry and the affected communities.

Current

The National Floodplain Management Framework must focus on the development of a dynamic

database that can be continually updated to reflect changes in available data, land use, and

climate change. Furthermore sufficient flexibility should be built in such that advances in the

state-of—the–art can be used to constantly improve accuracy, effectiveness and accessibility.

3.0 Approach to Developing the National Floodplain Management Framework

The first step in developing the National Floodplain Management Framework included review

of practices in seven countries other than Canada, review of current provincial and territorial

practices, and input from subject matter experts. Information derived from these sources then

helped to formulate the proposed approach. All of the collected information is presented in the

background report, Review of International and National Flood Mapping Practices, May 2014,

prepared in support of the National Floodplain Management Framework.

3.1 International Review

The first step in developing the National Floodplain Management Framework was to review

floodplain mapping practices from seven countries other than Canada. The objective of the

review was to understand current international practices with a view to identifying those

practices that could be incorporated into future Canadian practices. The international review

also provides a point of reference between current practices in Canada and those across the

globe. The countries reviewed included the United Kingdom (UK), Australia, the United States

of America (USA), France, Germany, Switzerland and New Zealand.

To guide the collection of the data on international practices we first prepared a template that

would ensure consistency in the approach to data collection. The template was structured to

include the following key components:



• General - recent initiatives related to updating floodplain mapping.

• Meteorology and Hydrology - methods used to calculate rainfall, snow melt and flow

rates that are used for floodplain mapping.

• Hydrotechnical - methods used to estimate storm surges and waves, as well as flood

elevations at any point along a river.

• Governance - responsibility of different government levels as well as policies related to

development in a floodplain.

• Flood Risk Assessment and Mapping - development of base mapping and the types of

information that are included on floodplain maps.

• Database - type of information that is collected and stored in a database.

• Access – the accessibility of the flood hazard mapping and the flood risk database.

Although the template was used as a guide, this did not preclude the collection of additional

information that would help to understand international floodplain mapping practices.

As noted, details of the findings regarding each country are provided in the background

document. The key findings for each country are provided below.

United Kingdom

European Union Requirements

The European Union’s Directive 2007/60/EC requires Member States to “….assess if all water

courses and coast lines are at risk from flooding, to map the flood extent and assets and

humans at risk in these areas and to take adequate and coordinated measures to reduce this

flood risk. This Directive also reinforces the rights of the public to access this information and to

have a say in the planning process….. The Directive requires Member States to first carry out a

preliminary assessment by 2011 to identify the river basins and associated coastal areas at risk

of flooding. For such zones they would then need to draw up flood risk maps by 2013 and

establish flood risk management plans focused on prevention, protection and preparedness by

2015. The Directive applies to inland waters as well as all coastal waters across the whole

territory of the EU.” 5

Related to the Directive, the European Exchange Circle on Flood Mapping (EXCIMAP) was

formed to gather all existing experiences and know-how in Europe and to improve flood

mapping practices. An outcome from EXCIMAP was to establish a guide to give an overview of

the existing good practices for flood mapping in Europe. Nearly 40 representatives from 24

countries or organizations participated in EXCIMAP. This work and collaboration was

prompted by the occurrence of dramatic European floods in the years following 2000.

5 Source: http://ec.europa.eu/environment/water/flood_risk)



Member States are required to undertake a number of specific tasks, including the following

actions, in accordance with various deadlines:

• Preliminary flood risk assessment, by the end of 2011.

• Flood hazard maps and flood risk maps, by the end of 2013.

• Flood risk management plans, by the end of 2015.

UK Compliance

In the UK the first two items have been completed by the target dates, while the third is still

underway. The EU directive stipulates that these activities be revisited on a 6 year cycle of

planning.

Overall responsibility for implementing the EU directive lies with the central government, but

legislation sets out the specific responsibilities of the Environment Agency (EA), who are a

‘non-departmental public body’, under the law. Certain responsibilities are delegated by the

EA to municipal government (referred to as Lead Local Flood Authorities, or LLFAs), whilst the

EA retain overall responsibility for publishing coordinated mapping at the national scale.

Hydrology (Flow Rates)

In the UK a fairly standard and prescriptive method is provided for calculating flow rates for

various frequencies of occurrence. These were initially developed in response to flooding in

the 1960s, but have since been updated. The practitioner is provided with guidelines and

computer programs that lead them through the calculations. There is relatively little latitude

for interpretation or variance from one practitioner to the next. In part, the UK lends itself to

this approach given its relative small geographic area and the availability of measured flow

data for rivers across the country.

Flood Risk Assessment and Mapping

As part of the updates to flood hazard and risk mapping required to comply with the Flood Risk

Regulations, the Environment Agency produced a set of guidelines to ensure consistency and

suitability of data. A key requirement is that floodlines should be delineated for three flooding

events: 1:30 year, 1:100 year and 1:1,000 year.

The revised flood hazard maps published at the end of 2013 (in accordance with the EU Flood

Directive) are available online via the EA website in an interactive map viewer. As per EU

directive requirements:

• Flood hazard areas are delineated as high, medium, low (which relate to return periods

of 30, 100, and 1000 years respectively).

• Flood risk maps are provided for areas where 30,000 people or more could be affected.

Flood risk maps build on the flood hazard mapping but include geo-referenced



information such as hospital and key transportation infrastructure. These risk maps are

published in PDF format on the EA website.

Planning Policy Statement 25 sets out requirements that must be satisfied in order for

development to proceed in certain flood zones. These requirements are intended to prohibit

construction in flood vulnerable areas; although certain types of development can proceed in

lower risk areas subject to passing the required tests (the sequential and exception tests). The

intention is to keep all new development out of medium and high risk areas (Zones 2 and 3),

and to manage new 'water-compatible' development in lower risk areas (Zone 1).

Database and Access to Mapping

The EA have made available various environmental data in GIS format for download from their

website. This includes historic flood data, and flood alert areas. It doesn’t appear to include

current flood hazard/risk mapping though.

Germany, Switzerland and France

Hazard Mapping

Germany

Germany has floodplain maps for most rivers. The maps include flood extent, flood depth,

flood danger and quantitative risk (damage). Other characteristics may include multiple

numbers of classes of flood extent, flood danger, flood risk and return periods. The maps are

used for spatial planning, construction and public awareness. Maps are typically produced for

watercourses with a drainage area exceeding 10 km2.

Mapping is conducted by the various states of the country although in recent years it was

recommended that it be managed by the federal government.

Several different return periods are considered; 1:10, 1:30, 1:50, 1:100, 1:300 years and

extreme events. As a minimum the 1:100 year flood must be considered, although on larger

rivers such as the Rhine the standard may increase to as much as 1:500 years.

Switzerland

Switzerland has floodplain maps for almost the entire country. The information is typically

included for a single return period; however in some cases multiple events may be included.

The maps include flood extent, flood depth, flood danger and qualitative risk. The maps are

used for emergency planning, spatial planning, and construction.

For flood hazard maps developed at a scale of 1:25,000 the extent of the flooding typically

represent an extreme event (generally set equal to a return period of 1:1,000 year). Flood

hazard maps that are developed at a scale of 1:5,000 include floodlines for return periods of

1:30 years, 1:100 years, 1:300 years and the extreme flood event.



France

France has floodplain maps for essentially the entire country. The maps are available on-line

through a simple to use and interactive website. The maps include flood extent and historical

flooding where available, as well as exposure/coping capacity data and qualitative risk. The

maps typically include floodlines for a single return period (1:100 year) but may include

multiple events. The maps are used for spatial planning (binding), construction and public

awareness.

The PPRI maps (Plans de Prévention du Risque Inondation), typically show the extent of one

reference flood; either a historical flood or the 1:100 year flood. “Flood Directive Maps” used

for 120 Areas of Potential Significant Flood Risk include three probabilistic hazard lines

including the 1:100 year flood, as well as one more frequent and one less frequent.

Governance

Germany: Responsibility of mapping has been passed down to regional governments. Each of

the sixteen states (Landen) of Germany produced their own maps but recommendations have

been made to have this done at a national level as per the 2010 LAWA German Working Group

on Water Issues of the Federal States and the Federal Government.

Switzerland: Responsibility of mapping has been passed down to regional governments. Maps

prepared by each of the 26 Cantons indicates areas at risk of various hazards including floods,

avalanches, landslides and rock fall

France: Responsibility of mapping has been passed down to regional governments.

Regulations

Germany: There is binding legislation that restricts or prohibits developments in flood-prone

areas.

Switzerland: Regional governments can decide for themselves how strictly flood zones are

incorporated into their spatial planning policies. However, recommendations made by the

central government regarding flood zones are generally adhered to.

France: There is binding legislation that restricts or prohibits developments in flood-prone

areas. The Code de l'environnement, Chapitre VI - Evaluation et gestion des risques

d'inondation created by Law No 2010-788 on July 12, 2010, Article 221 describes who and how

flood risk areas should be documented and dealt with. (http://www.legifrance.gouv.fr/).

Flood Risk Database

All three countries have a flood risk data base sufficient to produce qualitative risk maps. In

the case of Switzerland and France risk is divided into three to five risk zones. Population,

urban settlement and infrastructure are used as indicators for exposure.



Access

In Germany some maps are currently available on line as PDF files. The objective is to have all

maps available by the end of 2015.

France has on-line interactive flood maps and risk maps for the entire country and its various

regions. An advantage of the system is that it uses a common layout for all departments in

France despite the fact that different sources of information may be at the basis.

Some Switzerland flood maps can be found on line, however, a common site for all cantons

does not appear to be available.

Australia

The Australian Government guides and supports the State and Territory Governments by

providing frameworks within which the states and territories establish legislation, policies, and

standards for flood risk management. Local Governments have significant roles and

responsibilities for disaster mitigation and management at the local level through

arrangements that vary according to state and territory laws, practices and agreements.

The Australia Government is carrying out an ongoing extensive update of its policy documents,

including manuals and best practice guidelines. The focus is on five primary areas to improve

their effectiveness with respect to flood risk management (FRM) and emergency response.

These include:

1. Adopting a whole-of-nation resilience-based approach to disaster management.

2. Developing a nation-wide flood risk information portal to improve the quality, availability

and accessibility of flood information in Australia.

3. Updating of the Australian Emergency Manuals on flood management published by

Emergency Management Australia (EMA).

4. Revising of Australian Rainfall and Runoff (ARR) by Engineers Australia to improve the

estimate of peak flow rates.

5. Generating nationally consistent flood mapping.

It is anticipated that the various FRM initiatives and updates will: allow consumers to be aware

of the natural disaster risks that they face and provide a consistent approach to the collection

and provision of flood risk information; allow stakeholders to access key information to help

them to understand their level of risk and to understand who to approach to obtain detailed

analysis; and allow insurers to have access to the information they need to price flood risk at a

property level and be more willing to provide flood insurance, since they would have the data

that they need.



Extent of Existing Standards

Currently, there are no nationally accepted or consistent standards for models and

approaches, or for the analysis and reporting of flood risks in Australia. It is usually a matter

for each individual State/Territory or local government authority to decide on how the

mapping is to be done and what form the output of the mapping activity might take, including

the level of detail and public availability. It is also recognized that a sophisticated or consistent

understanding of flood behaviour across all areas of Australia is neither practical nor

necessary. The degree of effort required and approaches used will vary depending upon the

complexity of the flood situation, and the information needs of government and the

community to understand and manage risk (McLuckie, 2013).

Hydrology (Flow Rate)

Procedures for calculating flood flows for different return period are documented in the

Australian Rainfall and Runoff (ARR, 1987), which is the national guideline for estimating

design flood characteristics in Australia. The current edition was published in 1987 and an

update is presently underway (Engineers Australia, 2013b). The ARR and other guideline and

best practice manuals identify the following methods as being normally used for flood

discharge estimation: frequency analysis, indexed flood method, or hydrologic modeling.

The SCARM Report6 notes that peak flow rates should be calculated for a full range of return

periods up to and including the Probable Maximum Flood (PMF)7. The return periods that are

used for floodplain mapping and planning purposes (referred to as the Defined Flood Event –

DFE) may vary depending on State and Territory, although the 1:100 year event is most

typically adopted.


According to the SCARM Report, flood maps should ideally show the extent, depth, velocity

and hazard of flooding for the DFE, but should also show the extent of the PMF, which is used

to identify the floodplain and flood-prone lands. Some jurisdictions also require that the

location and floor levels of flood prone buildings be identified on the mapping (QRA, 2011b).

The extent to which the above criteria are actually depicted varies among States/Territories

and local governments. Queensland (QRA, 2011b), for example, requires the inclusion of flood

depths and velocities to be shown, as well as flood risk zones.

In some cases essential infrastructure services such as water supply and electric power are

included on the mapping. In Queensland, Councils are also required to give consideration to

determining appropriate floor levels for habitable rooms, which must be in accordance with

Section 13 of the Building Regulation 2006.

6 SCARM Report: Standing Committee on Agriculture and Resource Management, Report 73, 2000.

7 PMF is determined on the basis of the probable maximum precipitation (PMP), which is the maximum rainfall that could

physically occur at a location of interest.



In addition to the DFE (typically 1:100 year event), mapping may also include the 1:200 year or

1:500 year floodlines, particularly if an essential service is at risk of flooding. In addition to the

DFE water level, a freeboard of 0.3 m to 0.5 m is often designated to be used for government

guidelines and policy instruments to define the standard for new residential development to

limit growth in risk. The freeboard is generally viewed as a “factor of safety” in recognition of

uncertainty in estimating flood risk, and is not intended to increase the flood protection level

or target floods larger than the DFE.

The SCARM Report recognizes the importance of updating flood risk information on a regular

basis. Flood risk and floodplain mapping should be reviewed and updated as required at

regular intervals of not more than 5 to 10 years. Such updates may be triggered by various

major developments such as constructing a new dam, or where there have been rapid land-

use changes in a relatively short time frame.

Database and Access to Flood Maps

The National Flood Risk Information Portal, to be hosted by Geoscience Australia, was

announced in November 2011. The Portal, which is currently in a BETA phase, provides a single

access point to existing flood mapping data for users throughout Australia. In addition, a new

national standard has been developed to provide a framework to guide organizations in

providing nationally consistent datasets to be used for the Portal (NFRIP, 2012).

It is expected that once the nation-wide flood risk information portal is fully commissioned,

access to flood information and mapping will be significantly enhanced, and so will community

awareness of flood risks, which will in turn improve and better inform decision making in a

wide range of areas including emergency management, land use planning and provision of

insurance.

New Zealand

The two main pieces of legislation in New Zealand relevant to climate change and flood risk

management are the Resource Management Act 1991 (RMA) and the Civil Defence Emergency

Management Act (CDEM) 2002.

The RMA requires regional authorities to control the use of land for the avoidance or mitigation

of natural hazards. Territorial authorities are required to control the actual or potential effects

of the use, development or protection of land, including for the purpose of avoiding or

remedying natural hazards. The Resource Management (Energy and Climate Change)

Amendment Act 2004 further requires local authorities to have particular regard to the effects

of climate change.



The CDEM Act is another key piece of legislation for flood risk management. The Act primarily

focuses on the sustainable management of hazards, resilient communities and on ensuring the

safety of people, property and infrastructure in an emergency. The CDEM Act recommends an

approach based on risk reduction, readiness, response and recovery.

Standards and Guidelines

New Zealand does not have existing national technical standards for the preparation of

floodplain maps or assessing natural hazards. There is no National Policy Statement (NPS) for

river flooding under the RMA. A draft NPS was completed around 2007 and a board of inquiry

was established, but, the NPS process stalled around matters of cost-benefit and the NPS has

not been made released for public comment.

The Flood Hazard Risk Standard (NZS 9401:2008) was developed by committee and released in

2008. The purpose of the standard is “to provide an agreed best practice approach for local

and central government, professionals (planners, engineers, hydrologists, scientists, risk

managers, lawyers and so on), developers, utility suppliers, property owners and communities

to ensure that proper consideration is given to all aspects of flood risk when making decisions,

so that over the long term, the risk of flood damage decreases”. The standard is a voluntary

tool that provides a set of principles to help decision making and promote good practice in

flood risk management and is not technical, prescriptive or performance based.

The Flood Risk Management Governance Group comprising representatives of local and

central government and the Institute of Professional Engineers developed a draft New Zealand

Protocol on Managing Flood Risk in 2005. Under this umbrella it was intended to develop

implementation guides and modules for a number of flood topics such as catchment

management and risk communication but funding was not obtained to continue this work.

The National Institute of Water and Atmosphere (NIWA) is currently developing tools that will

aid practitioners and managers to better assess flood risk. The system is referred to as the

High Intensity Rainfall Design System (HIRDS). The High Intensity Rainfall Design System is a

web-based program that can estimate rainfall frequency at any point in New Zealand. It can be

used to estimate rainfall depths for hydrological design purposes, and to assess the rarity of

observed storm events.

In urban areas, the standard is usually protection for floods up to the 1:50 year return period,

however, in many cases a higher level of protection is provided.



United States of America

Of the nations reviewed, the USA has the most extensive nationwide program in terms of

identifying, publishing and updating flood hazard information. The Federal Emergency

Management Agency (FEMA), as the lead agency, publishes a series of documents that

encompass both standards and guidelines for all aspects of floodplain mapping, from

hydrology and hydraulics through to the development of base mapping and data bases.

The focus in the USA is the identification of flood risk in the context of flood insurance and less

on controlling development in the floodplain. Even the terminology used, such as, Flood

Insurance Rate Maps (FIRMs) and Flood Insurance Study (FIS) reports relates to an insurance

focus. Although, the products produced (i.e. maps, reports and databases), are essentially the

same as other countries and jurisdictions.

Standards and Guidelines

FEMA has produced extensive guidelines and specifications covering all aspects of the

implementation of the NFIP and production of flood risk maps. In total, 10 guidelines

documents are available. They address methods for completing calculations, reporting

requirements, and flood risk database requirements.

The base flood that is used for assessment and mapping is the 1% annual chance flood (i.e.

1:100 year flood) but any of the following lines may also be shown on the maps:

• 0.2% (1:500-year) Annual Chance Flood Hazard area.

• Area with reduced flood risk due to Levees.

• Floodway.

• Flood Insurance Zones.

• Future Conditions 1% Annual Chance Flood Hazard area.

Regulations

The Regulatory Floodway is defined as the channel of the river or other watercourse and the

adjacent land area that is reserved from encroachment in order to discharge the Base Flood

(1:100 year) without cumulatively increasing the water surface elevation by more than 0.3 m.

This criterion is used unless the State has established more stringent regulations for the

maximum rise in water surface elevations, through legally enforceable statutes.

Within the Regulatory Floodway communities must prohibit encroachments, including fill, new

construction, substantial improvements and other development unless it has been

demonstrated through hydrologic and hydraulic analysis that the proposed encroachment

would not result in any increase in flood levels within the community during the base flood

discharge (1:100 year).



Communities must require that all new construction and substantial improvements of

residential structures within the floodplain have the lowest floor (including basements)

elevated to or above the base flood (1:100 year) level.

Mapping

FEMA has detailed documents for topographic base mapping (Appendix A: Guidance for Aerial

Mapping and Surveying and Appendix L: Guidance for Preparing Digital Data and Flood

Insurance Rate Map Databases) for use in the preparation of floodplain mapping products that

are updated as required. Therefore, the guidelines include and consider new technologies such

as LIDAR. The basic contour interval specified for the base mapping is a 0.6 m (2 ft.) equivalent

contour interval for flat terrain and a 1.2 m (4 ft.) contour interval for rolling to hilly terrain.

The floodplain maps (FIRM) include standard base information such as buildings and the road

network and, depending on the levels of study, various floodplain information as detailed

above. FEMA has also developed a database to store digital GIS data used in the map

production process, as well as, tabular information found in the FIS report.

Public Accessibility

FEMA has developed a Map Service Centre portal where the public can access maps, Flood

Insurance reports and other information. It contains information specifically targeted to

homeowners, real estate agents and insurance agents and also has a ‘Live Chat” service. FEMA

is also adding GIS information layers.

3.2 Summary of Key Practices

Following from the international review, a number of key practices and standards were

identified that will help to inform the development of the National Floodplain Management

Framework for Canada. Each of these, including how they tie to the Guiding Principles, is

summarized below.

Technical Accuracy

1. Comprehensive Guidelines are a key requirement in ensuring that mapping is as accurate as

possible. As an example, the USA through the Federal Emergency Measures Agency (FEMA)

has the most extensive set of standards and guidelines used to prepare and update

floodplain mapping. They address all aspects of floodplain mapping, from data collection and

required analyses through to the preparation of flood hazard mapping.

2. Methods for Calculating of Flow Rates used for Floodplain Mapping can be highly variable

and inconsistent. Often this translates directly into significant over or under estimation of

flood risk. To address this concern there is merit in developing a consistent and prescriptive

approach across similar geographic regions. The UK and the USA in particular are fairly

prescriptive in providing guidelines and parameters for estimating flow rates, whereas

others may rely on the development of hydrologic models for individual watersheds.



3. Vertical Basemap Accuracy - There is a trend to more accurate base mapping through the

use of LiDAR. Where mapping is more recently developed on a regional basis (UK and

Alberta) vertical accuracy is in the range of 0.15 metres.


4. Integration of Mapping and Flood Risk Data is fundamental to managing flood risk. All

countries are generally moving from static hazard mapping through to more dynamic

mapping that is integrated with a flood risk database. However, in all cases this is a work in

progress.

5. Mapping of More severe Events allows for a better understanding of risk. Most commonly

Hazard Mapping include the worst of the 1:100-year event and the historical flood of record,

However, current standards in several countries recommend that more severe events also

be mapped. These range from 1:300 years to 1:1,000 years in Europe to as much as the

Probable Maximum Flood in Australia. These more severe events are more often used to

understand risk and are not necessarily used for flood hazard mapping or for regulatory

purposes.

6. Management of New Development in Floodplains is inherent to flood plain management in

all jurisdictions. Standards and methods vary considerably between jurisdictions. However a

minimum standard seems to be that any new development should be protected from

flooding for a minimum of the 1:100 year flood, and that any new development should not

increase upstream flood risk.

7. A National Mandate can be effective in providing consistency in both vision and in priority.

In the countries reviewed the development of standards is generally the responsibility of the

national or federal government although implementation occurs at a lower tier.

8. Flood Risk Assessment can be used to establish priorities and perhaps in providing variable

standards. Some countries such as the UK consider risk as a factor in establishing the

standard for flood protection.


9. On-line Access is the most effective manner to ensure that flood risk information is readily

available. On-line access to Flood Hazard mapping is either available or will be available in

most countries. In addition, coordination and distribution of this information is more

typically a national/federal responsibility.



Current

10. Climate Change can have a significant impact on flood risk. There is a recognition across

most nations reviewed that Climate Change affects risk, but there does not appear to be a

consensus how this should be incorporated into mapping and risk assessment.

11. Sea Level Rise is of particular concern in coastal areas that are either low-lying or have

dynamic shorelines that are prone to erosion. Although further work is required, there is a

clear understanding of the need to consider and account for sea level rises coupled with

storm surges in assessing and managing coastal flood risk.

3.3 Canadian Review

Flood plain mapping in Canada, as it is understood today, began in the 1960s. However, prior

to 1975 mapping across Canada was relatively limited and inconsistent in terms of approaches

and standards. In 1975 the federal government established the Flood Damage Reduction

Program (FDRP) to map existing flood hazard and to discourage development in flood prone

areas. FDRP was implemented over approximately a 20 year period as a joint federal-provincial

initiative for all provinces and territories except Prince Edward Island and the Yukon Territory.

Through the program, flood hazard mapping was prepared for more than 900 communities

across Canada. In Ontario alone the mapping extended along 15,000 km of watercourses and

lake shorelines. Following termination of the program, floodplain mapping in each province

has been solely the responsibility of the provincial or territorial governments.

The first part of this section of the report summarizes flood plain mapping practices, key

standards, and unique challenges for each province and territory in Canada. Additional detail is

provided in Review of International and National Flood Mapping Practices, May 2014 . The

second part presents a compilation of comments and recommendations from a wide range of

subject matter experts. All of the information in this section of the report will help to inform

the National Floodplain Management Framework.

British Columbia

Summary of Current Practices

Province wide flooding in 1974 prompted British Columbia to start a Floodplain Mapping

Program and floodplain maps were produced which provided mapping for many of the major

populated areas along major rivers. Local governments used these maps to develop floodplain

bylaws and the Province and some local governments used them to adjudicate applications for

subdivisions. Later the Province stopped producing new floodplain maps and discontinued

updating and maintaining the maps. Then in 2004, the Provincial Government passed the Flood

Hazard Amendment Act which transferred more authority to local governments to manage land

use in floodplain areas and local governments became responsible for creating new floodplain

maps and for updating existing ones.



During this transition, the Province undertook an extensive mapping initiative to provide

floodplain and flood hazard assessment information (maps and reports) that had been done to

date and made it accessible to local governments. Interactive maps that identify water bodies,

high hazard areas, suspected high hazard areas, flood protection works and floodplain extents

were made available to local governments. Polygons of hazard areas and floodplain extents

were provided to municipal governments for inclusion in land development bylaws. The

database is current to 2003.

Today a few municipalities have updated some of the floodplain maps and some have initiated

their own studies of new areas previously unmapped (Personal Communication 2014).

However, most of the floodplain maps produced under the Floodplain Mapping Program and

the Flood Hazard Maps produced in 2004 have not been updated/maintained and are now

considered historic information. The Province remains engaged, in a limited way, with some

strategic provincial level projects such as developing guidelines for assessing flood hazards.

Key Map Standards and Regulations

Two-zone mapping is not used in BC; the current Floodplain Mapping Guidelines and

Specifications for BC (FBC 2004) instead references the “Design Flood Level” and the “Flood

Construction Level”. British Columbia uses the 1:200 year event or the flood of record as the

design flood for floodplain mapping. The “Design Flood Level” is the water surface level

associated with the design return period event applicable for a given river. A “Flood

Construction Level” is then determined by adding an allowance for freeboard on top of the

Design Flood Level, which defines the minimum elevation of the crest of a standard dyke or

defines the elevation where construction can commence. The Flood Construction Level is the

higher of a freeboard of 0.3 m added to the design peak instantaneous flow or a freeboard of

0.6 m added to the design peak daily flow. (FBC 2004)

Unique Challenges

Challenges that remain unique to floodplain management in British Columbia relate to coastal

flooding, flooding due to debris flows on alluvial fans in the mountainous areas, and possible

failure of managed and “orphan” dikes, putting protected communities at increased risk.

In some areas of British Columbia (mainly the SE Kootenay Region) the Flood Hazard Maps

have gone beyond typical floodplain mapping by also identifying and mapping areas subject to

high erosion hazard (shifting channels and debris flows and alluvial fan hazards. The polygons

of these mapped high hazard areas have been adopted into some municipal development

bylaws, similar to floodplain extents. Flows through alluvial fans are extremely unstable. Large

flows from high mountain elevations can accumulate an enormous volume of sediment, forest

material, and gravel. They travel down well-defined and stable mountainous channels. At the

base of these hardened, relatively narrow, channels, the flow enters a broad flood area, losing

speed and depositing debris in a “cone-shaped” alluvial fan.



This hazard of alluvial fans and debris flows is unique to mountainous areas of Canada,

especially British Columbia. British Columbia has provided mapping resources to municipalities

to identify the locations of these hazards. Polygons of these hazard areas have, in some cases,

been adopted into local government bylaws so that development is actually prevented.

Another unique challenge that the Province has addressed related to floodplain mapping is the

risk of coastal flooding. In 2011, BC produced Coastal Floodplain Mapping – Guidelines and

Specifications (KWL 2011) as a standalone document apart from the 2004 Floodplain Mapping

Guidelines (FBC 2004). Not only does it take into account design storm impacts for defining the

Flood Construction Level, but it also specifies choosing a design year so that an appropriate

allowance for future sea level rise can be estimated. The Flood Construction Level for coastal

mapping takes into account the “higher high water large tide”, the sea level rise, a factor for

storm surge, a factor for wave effect, and a nominal freeboard of 0.6 m. Tsunami design

elevations (produced by EMBC) are also included on coastal floodplain mapping along with the

Flood Construction Level. The Guidelines (KWL 2011) reference numerous other studies and

guideline reports that address coastal flooding design challenges.

Finally, British Columbia faces the challenge of over 1,100 km of dikes that provide flood

protection. Dikes are used both in inland communities and coastal communities to protect

against floods. Numerous dike breaches have been documented from past flooding, and the

possibility for future breaches is an ongoing risk especially where “orphan” dikes exist (about

100 in the province). Orphan dikes are dikes that are not maintained by a diking authority.

Many of these orphan dikes were constructed under emergency conditions and generally lack

adequate planning and engineering design. The FBC Guidelines address the need for modelling

dike breaches when assessing floodplain maps and provide specifications for how to do so.

The risk to the Lower Fraser River Floodplain (one of Canada’s most intensely developed

floodplains) is affected by dike protection, highlighting this critical focus on understanding,

modeling, and managing dike breaches.

Alberta


After the FDRP ended, Alberta initiated the provincial Flood Hazard Identification Program

(FHIP), which built on the FDRP foundation and continues to assist municipalities in identifying

flood-prone areas.

The River Hazard Management Team of Alberta Environment and Sustainable Resource

Development currently manages provincial floodplain and hazard mapping. Alberta has a

recognized strength in geomatics and has invested in making their mapping and products

publically available through an online data portal.

Updates to historic floodplain mapping studies are ongoing. Calgary’s original floodplain

mapping study completed in 1983 has undergone multiple updates, the most recent being in



2012. With the recent flooding events of 2013, floodplain management continues to be a

provincial priority. A recent update of the Municipal Government Act, specifically Bill 27, has

changed the way that development and floodproofing in the floodway may be approved in the

future, and may impact how the floodway and the flood fringe areas are defined or managed.

This policy shift has brought necessary questions to the forefront of provincial discussion,

including what to do with the existing floodline if different standards are applied.


Alberta uses a two-zone mapping standard for floodplain mapping in the province, which was

encouraged through the FDRP and continues to be applied through the FHIP Guidelines

(Alberta Environment 2011). The entire floodplain is known as the “Flood Hazard Area”. The

“floodway” is defined as the channel where the entire design flood flow can be conveyed with

a maximum 0.3 m water level rise due to river encroachment or where there is a depth of at

least 1 m, or where there is a flow velocity of at least 1 m/s. The “flood fringe” is the

remainder of the flood hazard area that falls outside the floodway, with water depths less than

1 m and water velocities less than 1 m/s. These zones define where development can occur;

new development is largely prohibited in the floodway and any development in the flood

fringe must be floodproofed to the appropriate flood protection level.

For defining the flood hazard area, Alberta uses the maximum of the 1:100 year return period

floodlines or the flood of record. As ice jams can significantly impact water levels, the 1:100

year water levels must be based on the greater of ice-impacted water levels or open-water

levels.

Unique Challenges

Distinct challenges for floodplain management in Alberta include unique weather patterns,

mobile beds, sedimentation, and debris flows. The weather patterns are impacted by the

mountain ranges along the western border of the Province. Storms heading north from the

warm south hit the mountains at high elevations and cause large amounts of precipitation

combined with melt events in the headwaters of the mountain streams that lead to extreme

flow events as the rivers flow out onto the prairies. Due to the distance between the storms

causing flood events and the greatest flood impacts, a typical approach in some other

provinces of applying a “regional storm” over a watershed to predict resultant flows is not

applicable in Alberta. Therefore, flood frequency analysis based on these large events is the

basis of determining flood levels for individual rivers instead of using design storm inputs to a

hydrologic model.

A related, yet separate, challenge has to do with mobile beds, debris flows, and sedimentation.

Along with those extreme flows, high sediment load including debris, can be transported into

the flatter plains or more undulating foothills, where sedimentation occurs as flow velocities

decrease. Although Alberta does not explicitly map hazard areas that are associated with these

debris flows, they are a recognized risk to impacted communities.



Another hazard that has widespread impacts is high water levels due to ice jams and ice flows.

There are two primary phenomena that can cause high water levels due to ice impacts: one is

due to break-up ice and the second is due to frazil ice. Break-up ice is frequently washed

downstream prior to high spring flows occurring. However, if high flows coincide with the

timing of ice break-up, water levels can be significantly increased (relative to open-water

levels). Frazil ice (i.e., ice crystals that form in flowing streams when the water surface is

supercooled) can often form in streams and rivers. It can form blockages below the water

surface and can develop concurrently with high spring flows, significantly increasing upstream

water levels and causing flooding. Historic high water levels due to ice flows can be higher

than flood levels caused by open-water flows. In either case, the higher 1:100 year return

period levels (cause either by ice or open water) is chosen as the design water level for

floodplain delineation in Alberta.

Alberta has also recognized the need for a different approach to flood hazard mapping of its

alluvial fans (similar to British Columbia) as a result of the 2013 events in the Bow Corridor,

and is now looking at developing a framework for hazard mapping in these areas.

Saskatchewan


Updates to floodplain mapping are ongoing, including a recent update to the hydraulic

modelling of Regina. There is no current provincial strategy for updating the mapping,

although there are frequent emergency flood damage reduction programs put in place to

respond to annual flood risks.

Digitization of the original floodplain maps is being completed by the Water Security Agency; a

combination of the updated digital maps and the original floodplain maps are accessible to the

public via GeoSask (GeoSask 2013), an online portal where the static maps can be

downloaded.

Key Map Standards

Saskatchewan has gone well beyond the minimum standards set by the FDRP in mapping the

floodplain; they use a 1:500 year return period flood, with an additional 0.5 m freeboard, for

defining the estimated safe building elevation. Saskatchewan does not have provincial

guidelines for floodplain mapping, but continue to use the guidelines from the FDRP. The

floodway is determined as the channel having equal or greater than 1 m depth or equal or

greater than 1 m/s velocity, with the remaining floodplain zoned as the flood fringe.



Manitoba


Since the end of the FDRP, no further communities have been mapped. Currently,

development in the floodplain rests with local governments and municipalities. Two

exceptions to this management structure are within two provincial “Designated Flood Areas”:

The “Red River Valley Designated Flood Area” and the “Lower Red River Designated Flood

Area”. The Provincial Government is tasked with setting flood elevations and approving

development within these areas.

Manitoba does not have an online floodplain mapping website where the public can access

floodplain maps, but maps may be available through municipal government offices.

Key Map Standards

Manitoba continues to use the Flood Damage Reduction Program guidelines for floodplain

mapping. The Province uses the 1:100 year design flood, or the flood of record, to define the

total floodplain, except in the City of Winnipeg, where the 1:160 year design flood is used.

Manitoba uses a two-zone mapping approach to differentiate between the floodway and flood

fringe. The floodway is defined where the depth of flooding is greater than 1 m. In the City of

Winnipeg, the floodway also takes into consideration the point at which the water level rises

0.1 ft. (i.e., 0.03 m) due to constraining the effective flow area. The flood fringe is the

remainder of the floodplain beyond the floodway.

Unique Challenges

Manitoba has had extensive flooding along most rivers in the province. Flood protection

infrastructure, such as the Winnipeg Floodway, has been developed to deal with major runoff

events. The significant flood events of 1997 and 2010-2011 also saw flood mitigation works

implemented through the Canada-Manitoba Floodproofing Programs to help develop flood

protection for homes, farms, businesses and communities to help alleviate risk of future

damages.

Ontario


From an administrative perspective Ontario is unique among the provinces in that floodplain

mapping is administered through the 36 Conservations Authorities, or the Ministry of Natural

Resources in areas that are not served by one of the Conservation Authorities. Overall in

excess of 90 percent of floodplain mapping is administered by the Conservation Authorities.

The status of mapping and the extent of any updates are highly variable across Ontario. In

urban growth areas mapping is continually being updated, however in areas that are less

populated or are not undergoing rapid growth the mapping tends to remain unchanged from

what was prepared under FDRP.



Since the majority of the maps are held at individual Conservation Authorities the accessibility

of the maps and floodplain information is also variable. While all Conservation Authorities use

and are willing to share the information, it may require a visit to the Conservation Authority

office to view the maps. Most Conservation Authorities have at least digitized the paper maps,

some have digitized the floodline with the ability to place the line as a layer on other bases and

some Conservation Authorities have fully integrated Digital Elevation Models (DEM). Maps for

many Conservation Authorities are accessible on their web sites or paper copies can be

obtained upon request (sometimes for a fee). The MNR has digitized all their floodplain maps

and they are available through Land Information Ontario (LIO).


In Ontario the Regulatory event used for flood hazard mapping varies by geographic location.

As defined in the MNR’s Technical Guide8, the flooding hazard limit is the greater of:

1) The flood resulting from a rainfall actually experienced during a major storm such as the

Hurricane Hazel storm (1954) or Timmins storm (1961), transposed over a specific

watershed and combined with the local conditions, where evidence suggests that the storm

event could have potentially occurred over the watersheds in the general area;

2) The one hundred year flood; or

3) A flood which is greater than 1) or 2) which was actually experienced on a particular

watershed or portion thereof, for example as a result of ice jams and which has been

approved as a standard for that specific areas by the Minister of Natural Resources; and

The exception is where the use of the 1:100 year flood or actually experienced event as the

flood standard for a specific watershed, even, though it does not exceed the Hazel or

Timmins event, has been approved by the Minister of Natural Resources, (where past

history of flooding supports the lowering of the standard)

In practice this means that there is considerable variance in the event that is used for defining

flood hazards. For example, in central Ontario, including Toronto, Hurricane Hazel is used for

mapping purposes. Although it does not have a defined return period, runoff is typically 3 to 5

times greater than the peak generated by a 1:100 year storm. In contrast eastern Ontario,

including Ottawa, uses the 1:100 year event to define flood hazard limits.

Within Ontario there are three approaches to floodplain management; one zone concept, two-

zone concept and Special Policy Areas.

• Under the one-zone concept the Regulatory floodplain is treated as a single unit and all

development is prohibited or restricted within the floodplain. Development in all flood plains

in Ontario is subject to the one zone concept unless otherwise approved.

8 Source: Technical Guide – River and Stream Systems Flooding Hazard Limit, 2002



• Under the two-zone concept the Regulatory flood plain is divided into the floodway where

development is prohibited and the flood fringe where development may be permitted

subject to certain conditions. Two-zone floodplains are common in existing urban areas, but

are rarely approved for new development.

• Special Policy Areas (SPA) are applied within a community that has historically existed in the

floodplain where the one zone and two zone flood plain management approaches have been

demonstrated to be too stringent and would likely cause significant social and economic

hardships to the community. The area specific policies of the SPA are intended to provide for

continued viability of existing land uses while being sufficiently protective against natural

hazards. It is not intended to allow for new or intensified development and site alteration, if

a community has feasible opportunities outside of the flood plain.

Ontario also has been active in developing coastal (lakeshore) natural hazard mapping, defined

as the 1:100 year lake level plus the worst case of: wave uprush, 1:100 year toe erosion plus

stable top of slope, or wave uprush plus dynamic beach allowance. The Regulation Limit, where

permits are required for development is defined by adding an additional 15 metres to the

above.

Unique Challenges

Although floodplain maps have been produced for in excess of 15,000 km of watercourse and

shorelines within Ontario, one challenge is that there are also still areas of the province that

are not mapped, where the mapping is dated, or where the mapping is an estimate only.

Another challenge is lack of consistent guidelines and implementation standards for the

analysis and delineation and mapping of flood hazards since the termination of the FDRP. In

part this is because the development of floodplain mapping is the responsibility of individual

Conservation Authorities with widely varying resources available to maintain and/or update

mapping.

Québec


Currently, most of the hydrologic / hydraulic analyses and floodplain mapping has been/is

being done in-house by the Centre d’expertise hydrique du Québec (CEHQ). Some 5,800 km

of watercourses or shorelines have been mapped between 1979 and 2010.

Statistical hydrologic analyses are preferred over hydrologic modelling with design storms in

determining design peak flows. Steady state hydraulic modelling is, for the most part, used to

determine flood water levels. All maps are available in GIS formats.

Impacts of climate change are considered in urban areas where design storms are used to

generate flows. This is addressed by increasing rainfall intensity by 10 to 20 percent depending

on the design storm.




There are currently no officially published standards, in the province of Quebec, for the study

and preparation of floodplain maps. However, based on a preliminary set of guidelines

prepared in 1998 by the Ministère de la Sécurité Publique and the Ministère de

l’Environnement et de la Faune, and further referred to in a 2007 working document by the

Centre d'expertise Hydrique, two flood levels are determined under free flowing conditons;

one for the 1:20 year flood and one for the 1:100 year flood.

With respect to regulated flood zones in Québec, two flood zones are considered; i) high risk

areas for return period flows of zero to 20 years where no development or construction of

new works are permitted (with a few exceptions), and ii) moderate risk areas for return period

flows of 20 to 100 years where filling and the construction of buildings is prohibited without

flood proofing for the 1:100 year event.

Unique Challenges

Québec has over 1,000,000 lakes and 130,000 streams of which 4,500 are rivers. In all, 2

percent of the world's fresh water is in Québec. Only a small portion of these bodies of water

have flood maps. The lack of available funding and the absence of a provincially regulated

framework to produce flood maps is limiting the extent of this work.

New Brunswick


While the Province of New Brunswick continues to map the extent of major inland flood events

as they occur, it is not currently performing any systematic, on-going activity to update

predictive floodplain mapping. Government-sponsored research (flood frequency analysis, etc.)

has been initiated to support the future renewal of provincial floodplain maps, however, much

of the recent flood mapping effort has focused on coastal flood hazard mapping, accomplished

in partnership with municipalities and the federal government under the Atlantic Regional

Adaptation Collaborative. It should be noted that little inland mapping has been done since the

mid-1990s because it was largely performed under the FDRP. Digital floodplain maps are

available to the public on the GeoNB website, though they cannot be ordered or downloaded. A

provincial flood risk reduction strategy is currently being finalized for release. Among other

things, it is expected to identify a path forward for future floodplain mapping in the province.

Key Map Standards

The events mapped have generally been the 1:100-year and 1:20-year floods (1% and 5% risk

respectively). Mapping is primarily a provincial responsibility, but some municipalities have

completed mapping in partnership with other stakeholders. There are, however, no province

wide standards or regulations with regards to one-zone or two-zone approaches or managing

development in floodplains.



Nova Scotia


Floodplain mapping was produced for five river systems in Nova Scotia under the Flood

Damage Reduction Program in the 1980s. The Province is presently developing an application

based funding program to provide financial assistance to municipalities to conduct flood

assessments including producing floodplain mapping. For the previous mapping produced, the

area within the 1:20 year floodline defined the floodway and the remaining area up to the

1:100 year floodline defined as the flood fringe.

Prince Edward Island


The Province of Prince Edward Island has completed very few riverine floodplain studies. Their

hazard concern is directed toward coastal flooding and coastal erosion. The entire province,

however, is mapped with LiDAR, generally at low tide to get the largest area of coverage.

Limited inland flood mapping was completed in the Hillsborough River watershed in 2010-2012.

Unique Challenges

Prince Edward Island is uniquely placed as the only province which is also an island. As such, the

primary interaction with hydraulic forces is not from rivers, but from coastal factors. The major

issue for Prince Edward Island from coastal interactions, however, is not coastal flooding, which

does occur in localized areas, but rather it is coastal erosion. Every year, the province loses a

significant portion of its land area to the sea. Consequently, flooding is not the dominant hazard

around which provincial action is required. Instead, based on erosion estimates, slope failure

hazard limits are set to keep properties safe. In riverine applications, similar slope hazard limits

are also set and are often significantly higher than the 100-year flood line, essentially offering

dual protection. Prince Edward Island also has a unique jurisdictional issue regarding data

collection for their coastal risk modelling. Coastal data collection is the responsibility of the

federal government, and not of the province. The federal government operates only a single

coastal gauge near the city of Charlottetown. As the area of interest moves further away from

this gauge site, data uncertainly increases and so does modelling error, making the hazard limits

less certain.

Newfoundland and Labrador


In the 1980s and 1990s a number of communities in the province with a known history of

flooding were mapped under the FDRP. In 2008, the province funded a new study for

Stephenville. The Hydrotechnical Study of Stephenville was one of the first in Canada to

delineate climate change based flood risk mapping. In 2010, following the success of the 2008



study, a partnership with Natural Resources Canada funded climate change flood risk mapping

studies for additional areas, including Corner Brook and St. John’s in 2013. The general principle

is to update the maps every 10 years.

The work that is done to determine the flows and flood modelling results are reviewed by a

technical committee. The only models approved for use are part of the USACE suite of

programs (e.g. HEC-RAS, HEC-HMS, etc.). The preferred mapping is to have LiDAR, but there are

no official mapping standards except to have sufficient accuracy to reasonably accomplish the

task of flood mapping. Maps are all added to a GIS database, and they are available to the

public digitally through the government website.


The flows mapped are generally the 1:100 year and 1:20 year floods (1% and 5% risk

respectively), but these flows are also projected to 2020, 2050, and 2080 based on climate

change projections.

Generally, a flood fringe zone is adopted where some development is allowed, but no

development is allowed in the floodway. Flood fringe developments must generally be non-

structural, water related, or minor structures relating to other projects such as pipelines, where

only soil disturbance is involved and not changing the grading of the land.

Yukon


A Flood Damage Reduction Agreement was never negotiated with the Yukon Territory under

the FDRP. Currently, the development of the floodplain and flood risk mapping is seen

primarily as a territorial responsibility with a potential role for municipalities as well.

Flooding is a key vulnerability for Yukon communities given that they are likely to encounter

more frequent flooding into the future as a result of climate change. The need to better

identify floodable areas has been recognized by the Government of Yukon’s Emergency

Measures Organization (EMO). EMO has plans in place for LiDAR surveying to be done in 2014

and 2015 for 13 community areas identified by Yukon staff as the most flood prone areas. The

LiDAR data will be used to produce up-to-date Digital Elevation Models for the flood risk

mapping. Existing elevation data is accurate to the nearest 1 m at best. The LiDAR surveying is

being funded through the federal (AANDC) Climate Change Adaptation Program.

The areas to be surveyed are: Old Crow, Dawson/Klondike Valley, Mayo, Carmacks, Ross River,

Upper Liard, Marsh Lake/Tagish, Carcross (Bennett Lake), Teslin, Whitehorse, Pelly Crossing,

Lake Laberge and Burwash/Destruction Bay.



The creation of a GIS data base is currently in progress. Digital maps are not yet made available

to the public however when the mapping is completed it should be made available to potential

users via on-line pdfs and GIS data. Paper maps would be provided on request.

In addition the Yukon Research Centre, Yukon College has conducted a number of studies on

landscape hazards and climate change adaptation including hydrology-based work in Mayo

and Pelly Crossing areas. These studies used past discharge data to look for trends and

relationships between climate and environmental conditions, such as snowpack, and spring

flooding. In 2014 and 2015 the College will be conducting a similar study in Old Crow that will

also look at the hydrology and flooding.

Key Map Standards

There are documented procedures in place for calculating design flood flows for different

return periods using single station flood frequency analysis (FFA) with regional analysis based

on drainage area. The return periods to be calculated and used for floodplain mapping

purposes have yet to be determined. At this time no standards currently exist for base map

accuracy or for the information that should be included.

Unique Challenges

Challenges facing floodplain management in the Yukon include: sparse data regions, thermal

erosion, coastal erosion and flooding (including at historic sites such as Herschel Island),

flooding due to ice jams (with sudden rise and lowering in water levels that cannot be

forecasted), and the need for hydrologic response scenarios associated with climate change in

the preparation of flood risk mapping.

There are concerns regarding infrastructure such as bridge abutments and community dikes

and their ability to withstand flood waters.

Northwest Territories


FDRP flood risk mapping was completed for nine NWT communities in the Mackenzie River

basin. Scanned copies (PDF) of the flood risk maps as well as shape files derived and/or

adapted from these floodlines are provided to communities by the Lands Administration

Division, Department of Municipal and Community Affairs (MACA), Government of the

Northwest Territories.

MACA staff have re-created the floodway and flood fringe areas from the FDRP maps using

updated (and sometimes expanded) DEM grids of the nine communities and the FRDP flood

elevations. This is a desktop exercise using GIS mapping to demarcate all elevations lower than

the flood level as the floodway and all areas within 1.0 metre as the flood fringe. The

community base mapping used to create these maps is updated every five years.



Unique Challenges

Challenges facing floodplain management in the NWT include: limited capacity for undertaking

the floodplain mapping tasks including few human resources and the lack of in-house expertise

within the territorial government and local institutions; changes in climatic conditions which

are resulting in thermal erosion (coastal areas) and the need to update the mapping more

frequently in these areas; and the current situation where communities can elect to use the

mapping or not use the mapping. Limited capacity not only affects NWT’s ability to

produce/update official flood zone maps but also the territory’s ability to understand and use

these products at the community and territorial levels. This situation is seen as a major factor

in a community’s decision to use or not use these maps.

Nunavut


The Nunavut Territory was established in April 1999. Previously the Nunavut area was part of

the NWT. None of the FDRP mapping done for the previous NWT was within the area which

now forms Nunavut. Nunavut government officials contacted to date are not aware of any

existing flood risk mapping in the Nunavut territory.

Unique Challenges

Climate change is a key challenge in Nunavut; resulting in precipitation events, surface run-off

and coastal erosion not previously encountered. Nunavut has extremely limited to no capacity

for undertaking the floodplain mapping tasks including the human resources and a lack of in-

house expertise within the territorial government and local institutions to produce and update

floodplain mapping.

Floodplain Mapping on Aboriginal Lands

In Canada flood plain management essentially falls under the jurisdiction of the provinces, as

they are primarily responsible for water resources and land use matters. In the Yukon and

NWT, land and water management responsibilities have been devolved from the federal

government to the territorial governments. No such devolution of these responsibilities has

occurred in Nunavut.

In addition to the provincial and territorial agreements under that program, the departments

of Environment and Indian and Northern Affairs signed a Memorandum of Understanding

(MOU) in 1985 respecting Flood Risk Mapping of Indian Reserve Lands and Other Lands Set

Aside or Held for Indians. The FDRP archived website states that under this MOU, studies were

conducted to identify priority flood prone areas, and 44 mapping projects were undertaken.

Aboriginal Affairs and Northern Development Canada (AANDC) staff located the FDRP mapping

for four of the 44. All four are in Indian Reserves in Alberta: #6645 - BLOOD 148; #6639 - TSUU

T'INA NATION 145; #6683 - SAWRIDGE 150G; and #6642 - STONEY 142-143-144.



4.0 Expert Comments

Input and opinion was solicited from subject matter experts in all aspects of floodplain

mapping. The approach was to prepare a survey template where opinion was sought in the

broad categories of base mapping, hydrology, hydraulics, governance, and flood risk data and

mapping. The completed surveys are included in the background report, Review of International

and National Flood Mapping Practices, April 2014. The key comments received are summarized

below, and are organized based on the Guiding Principles set out on Page 3. The majority of the

comments refer to improving technical accuracy of mapping and providing added information

to improve overall effectiveness in understanding and managing flood risk.

Technical Accuracy

1. The fact that there is a high degree of uncertainty in all of the steps leading to estimation of

flood risk should be documented and included as part of the presentation of flood risk.

2. Additional streamflow gauging would help with accuracy, particularly in ungauged

watersheds.

3. Standard methods for relating flooding to damages should be updated across Canada.

4. There should be more formal procedures available to complete all steps of the mapping

process.

5. More importance should be placed on both calibration and on-going updates/verification.


6. There should be National Vision and set of standards that would apply across Canada.

7. Floodplain management should move beyond hazard mapping to consider risk to

communities, industry and agriculture.

8. Mapping should be extended along more rivers, particularly through urban areas.

9. Events more severe than the 1:100 year event should be considered in hazard mapping and

flood risk assessment; particularly when one considers both the degree of uncertainty

associated with the estimates and that statistically a 1:100 year event has a 65 percent

chance of occurring in a 100 year period.

10. The capacity for undertaking the floodplain mapping tasks including the human resources

and in-house expertise varies across the country. Certain jurisdictions, particularly NWT

and Nunavut, have limited to no capacity to produce and update floodplain mapping and

have limited to no experience and expertise in the use of the mapping at the community

and territorial levels.




11. The public should have much better access to flood risk information.

Current

12. Across much of Canada there is a need for updated floodplain mapping.

5.0 Status of Floodplain Management in Canada

The development of floodplain mapping, as it is understood today, began in approximately

1975. Currently mapping is available along some 28,000 km of rivers and streams across

Canada. Most of the mapping was initially developed between 1975 and 1996 through the

federal-provincial Flood Damage Reduction Program (FDRP). However with updates and

additional mapping that has been completed since completion of FDRP, approximately half of

the existing mapping was developed after 1996.

This section of the report documents the status of existing mapping across Canada, compares

the existing mapping to standards associated with the National Floodplain Management

Framework, provides a Risk Assessment approach for updating existing mapping, and provides

a guideline cost estimate to complete the update of the mapping.

Collection and Presentation of Existing Mapping

The first task was to compile a database of existing mapping, including any available

information related to the location, age, and scale of the existing mapping. Apart from Ontario,

existing information was collected by contacting each province and territory. Ontario is unique

in that the majority of floodplain mapping is developed and maintained through the 36

Conservation Authorities, with the remainder administered through the Ministry of Natural

Resources.

A map of Canada was developed, viewable through Google Earth, which illustrates all

watercourses that have been mapped. In most cases, the compiled map only illustrates the

sections of the watercourse that have been mapped. In the remaining cases the compiled map

illustrates the horizontal limits of the flood hazard mapping. The map of floodplain limits was

then overlaid on a map of urban boundaries in order to estimate the fraction of the hazard

mapping in each province that is urban.

Summary of Existing Mapping

As noted, floodplain mapping is available for approximately 28,000 km of watercourse across

Canada. Figure 1 presents a graph of the extent of existing mapping based on the year it was

prepared, while Table 1 provides a summary based on 10-year increments. Table 2 summarizes

the mapping available for each Province and Territory, including the fraction that is in urban

areas and the median age of the mapping.



As illustrated by Figure 1, new or updated mapping has been developed each year since 1975.

There have been a couple of periods where the development of new mapping has been most

active; 1985-1990 and 2004-2009. The median age of mapping across Canada is 1996, with 25

percent completed prior to 1987 and 25 percent since 2006.

The extent of mapping in each

province and territory is generally

proportional to the population. Of

the total, 59 percent of existing

floodplain mapping is in Ontario,

21 percent is in Québec, and 10

percent is in British Columbia. The

remaining 10 percent is

distributed across the other provinces and territories. This is because the focus has always

been on preparing mapping for the more populated areas.

Overall approximately 35 percent of the mapping is through urban areas. However the ratio of

mapping that is in urban areas varies widely, from a low of 14 percent in British Columbia to a

midrange of 49 percent in Alberta to a high of 75 percent in Québec.

Although the median age of all mapping in Canada is 18 years (1996), there is also a fair

variability in mapping age. The median age of all mapping in Alberta, Québec and Ontario is

approximately 10 years old, while it is in excess of 20 years old in the remaining jurisdictions.

0

200

400

600

800

1000

1200

1400

1600

1800

1974 1979 1984 1989 1994 1999 2004 2009 2014

Flo

od

pla

in M

ap

pin

g (

km

)

Year

Figure 1: Date of Floodplain Mapping

TABLE 1: AGE OF EXISTING MAPPING

Period Total (%) Percentile Year Completed

1970-1979 7 25 1987

1980-1989 24 50 1996

1990-1999 22 75 2006

2000-2009 39

2010-2013 8

TOTAL (km) 28,100



TABLE 2: MAPPING SUMMARY

Total Length

(km)

Urban

(km)

Rural

(km)

Urban

(%)

Median

age

British Columbia 2,656 369 2,286 14 1989

Alberta

960 472 488 49 2007

Saskatchewan 253 98 155 39 1989

Manitoba

363 126 237 35 1993

Ontario

16,675 4,500 12,175 27 2002

Québec

5,800 4,345 1,450 75 2003

New Brunswick <500 132 368 26 1992

Prince Edward Island <50 25 25 50 --

Nova Scotia <500 132 368 26 1980

Newfoundland and Labrador 228 60 168 26 1990

Yukon

- -- -- -- --

Northwest Territories 110 -- 1101 -- 1986

Nunavut - - - --- --

CANADA 28,100 10,300 17,800 35% 1996

1 mapping centred around remote northern communities

The vast majority of maps were prepared in accordance with FDRP standards or more recent

guidelines such as the Flood Hazard Identification Program Guidelines (Alberta, 2011) or the

Technical Guide – River and Streams Systems: Flooding Hazard Limit (Ontario, 2002). In most

cases the printed scale is 1:2,000 or 1:5,000, however with digital mapping the scale is not as

relevant as in the past.

It is difficult to precisely measure that fraction of the Canadian population living in flood prone

lands that have actually been mapped. The reason that it is difficult is that it is not currently

known how many watercourses in populated areas have not been mapped and, to a certain

extent, the floodplain area is not known until it is mapped. However, it is clear that in some

jurisdictions (including much of Ontario) coverage likely exceeds 95 percent of flood prone

residences. Overall, across Canada it is estimated that approximately 65 percent of residences

located in flood prone areas currently have floodplain mapping coverage. This is based on a

high level review of the extent of unmapped watercourses in populated areas.

Figure 2 provides an estimate of the magnitude of mapping required for each province and

territory to increase coverage across Canada to 95-100 percent of all flood prone residences. It

should be cautioned that the estimate for additional mapping is a very preliminary estimate

and would need to be updated as part of the proposed Risk Assessment. Nevertheless the

information provided can serve as a starting point in understanding the need for additional

mapping. The default increase in mapping was set to 50 percent; however the increase was

refined for provinces and territories where there was a better understanding of future

requirements.



FIGURE 2: MAPPING COVERAGE ACROSS CANADA

Province/Territory Existing

(km)

Additional

(km)

Bar Chart Showing

Current and Proposed Coverage (%)

0 20 40 60 80 100

British Columbia 2,656 2,650

Alberta 960 770

Saskatchewan 253 125

Manitoba 363 185

Ontario 16,675 500

Quebec 5800 10000

New Brunswick <500 250

Prince Edward Island <50 25

Nova Scotia <500 250

Nfld. & Labrador 228 115

Yukon - 2601

Northwest Territories 1102 30

Nunavut - 1303

Existing

Proposed

Notes

1) Includes flood prone community areas identified for 2014-2015 LiDAR surveying.

2) FDRP mapping that requires updating and verification.

3) Includes mapping for communities subject to coastal and shoreline flooding; estimate based on 25

communities approximately 5+ km/community.

6.0 Comparison of Existing Mapping to Proposed Standards

The following provides a discussion of how current mapping compares to the proposed

mapping standards. For discussion purposes, the comparison is based on the following key

standards:

• Base Mapping.

• Regulatory Event for Flood Hazard Mapping.

• Flood Risk Database.

• Age of Mapping

• Climate Change Adaptation.



Base Mapping

The most significant standards related to base mapping is Vertical Accuracy. The proposed

standards calls for a vertical accuracy of 0.15 metres (95 percent of the time), and is based on

the fact that this degree of accuracy is usually achievable based on recent advances in mapping

technology. Virtually all existing base mapping is based on a lower standard (typically 0.3 to

0.5 metres). However, it should be cautioned that the historical standard of 0.3 to 0.5 metres is

reflective of the state-of-the-art at the time the mapping was prepared, and does not suggest

that existing mapping is inadequate.

More recent hazard mapping projects in some jurisdictions have started to require base

mapping with a vertical accuracy of 0.15 metres, however a relatively small fraction of

floodplain mapping is currently based on this new standard.

Regulatory Event for Flood Hazard Mapping

Floodplain mapping across Canada can be defined as Hazard Mapping in that it focuses on

defining the extent of the floodplain based on the Regulatory Event.

The most common Regulatory Event used for Flood Hazard Mapping in Canada is the 1:100 year

flood; however, there are several jurisdictions where a more severe flood is used for regulatory

purposes. These include:

• British Columbia – 1:200 years.

• Saskatchewan – 1:500 years.

• Northern Ontario – Timmins Storm (Historical Event).

• Central Ontario – Hurricane Hazel (Historical Event).

The proposed standards detailed in the National Floodplain Management Framework

recommend the Regulatory Event used for creating Flood Hazard Maps should have a return

period of no less than 350 years. Where the two-zone concept is applied the 350-year floodline

would be the outer limit of the Flood Fringe.

A flood with a return period of 350 years is recommended for several reasons:

• With the degree of uncertainty associated with estimating flow rates, the 1:100 year flow

rate will often be significantly over or under estimated.

• A 1:100 year event has a 64 percent likelihood of occurring in the next 100 years.

• A return period of 350 years is already used to guide development in some flood prone

jurisdictions in southern Ontario.

• International practices often include flood hazard mapping ranging between 1:300 years to

1:1,000 years (e.g. Germany and United Kingdom).



• Given all of the above, the 350 year return period provides a margin of safety and reduces

the likelihood of a flood of this magnitude occurring or being exceeded in the next 100

years from 64 percent to 25 percent.

Given that flow rates associated with Hurricane Hazel are typically greater than the 1:350 year

flow rate, and given that approximately two-thirds of the flood hazard mapping in Ontario is

based on the Hurricane Hazel, it can be concluded that 30 to 40 percent of the mapping in

Canada satisfies the proposed standard for the Regulatory Event.

Flood Risk Database

For the existing mapping, floodlines are commonly plotted for two events; the Regulatory event

and a more frequent event. There is limited additional information on the maps in terms of

flooding associated with alternative return periods, depths or velocities. However, most maps

are supported by a hydrotechnical report that would have included flood elevations and

sometimes velocities for the Regulatory Event and additional events with return periods

ranging from 2 years to 100 years. In a limited number of cases there is a flood risk database

available although it is not necessarily linked to the mapping.

The proposed standards detailed in the National Floodplain Management Framework

recommend that flood elevations, depths and velocities be calculated for return periods up to

the 1:1,000 year event in order to facilitate a more complete understanding of risk.

Furthermore, it is recommended that a geo-referenced database be prepared that includes key

risk information such as building opening elevations, flood elevations for return periods up to

1:1,000 years, flood depths and velocities. Current mapping does not generally meet the

proposed standards.

Age of Mapping

As previously noted 50 percent of existing mapping was prepared prior to 1996, meaning that

half of the mapping is between 18 and 40 years old. The proposed standards recommend that

the need to update mapping be reviewed every 5 years in urban areas and every 10-20 years in

rural areas.

Climate Change Adaptation

Until recently climate change was not considered in determining the return period of a flood

event of a given magnitude. However in recent years, some jurisdictions have started to include

an allowance for increased runoff in future years. For example, in British Columbia the

Professional Practice Guidelines- Legislated Flood Assessments in Changing Climates in BC

(APEGBC, 2012) recommends a minimum increase of 10 percent in flow rates to account for

climate change. However, virtually all of existing mapping would not have accounted for

change.



The National Floodplain Management Framework does not have specific standards for Climate

Change; however the framework recommends that climate change be addressed in the

proposed Hydrology Technical Guidelines.

Conclusions

Following from the above discussion, it is concluded that existing flood plain mapping across

Canada does not meet the majority of standards proposed as part of the National Floodplain

Management Framework. This conclusion does not infer that existing mapping is inadequate,

but rather that the proposed standards represent a step forward in defining how floodplains

should be mapped and how flood risk should be documented.

As a next step it is recommended that a Risk Assessment be completed to better identify and

understand the areas of highest risk. Results of the Risk Assessment would then be used in

establishing priorities for updating mapping in accordance with the proposed standards.

Recommended Risk Assessment

Where Floodplain Mapping Already Exists

The following provides a general approach to completing the Risk Assessment where floodplain

mapping already exists; however a much more comprehensive methodology will need to be

developed prior to proceeding. The proposed steps are as follows.

1. Based on Table 3, assign a risk category to all floodplains based on existing mapping.

2. Starting with Very High risk areas, assess existing floodplain mapping relative to

proposed standards, and conclude which of the following need to be included in the

update:

a. Base Mapping.

b. Hydrology including consideration of Climate Change.

c. Hydraulics including field survey.

d. Hazard Mapping and Flood Risk Data.

3. Repeat for High, Moderate and Low risk areas.

4. Summarize all findings in a Risk Assessment Database that will guide priorities in terms

of implementing the recommendations of the National Floodplain Management

Framework.



TABLE 3: RISK PRIORITY TABLE

URBAN RURAL

VERY HIGH

Urban lands inundated by 1:100-year flood,

including all areas protected by diking.

HIGH

Rural lands inundated by 1:100-year flood, where

density of buildings exceeds a specified threshold1

per hectare, or where protected by diking.

HIGH

Urban lands inundated by the greater of the

Regulatory Event or the 1:100-year plus 1.0 metres.

MODERATE

Rural lands inundated by 1:100-year flood, where

density of buildings does not exceed a specified

threshold1 per hectare.

LOW

Remaining urban watercourses.

LOW

Remaining rural watercourses.

Note 1: Threshold to be determined as part of the Risk Assessment.

Where Floodplain Mapping does not exist

There are many areas where mapping has not been created. Of highest concern would be

urban areas along small or moderate sized watercourses. Rather than completing a Risk

Assessment for these areas, it is recommended that they be mapped, with priority ranking

based on the following considerations.

1. The size of the upstream catchment area draining to the watercourse (size increases risk).

2. Known history of flooding (increases risk).

3. Density of development (increases risk).

4. The presence of a well-defined valley system where development is not permitted

(decreases risk).

Costing

The cost of developing updated Hazard Maps and creating the Flood Risk databases is based on

the costs associated with:

1. Preparing base mapping.

2. Completing the hydrologic studies.

3. Completing detailed hydraulic surveys of infrastructure and buildings in the floodplain.

4. Preparing the hazard mapping.

5. Populating the database.



Actual costs will vary widely depending on complexity, width of the floodplain, number of

buildings, density of infrastructure, and approach to calculating flow rates. On average it is

expected that the cost of completing all steps would range from $7,500/km in a rural setting to

$10,500/km in an urban setting assuming a 1-D hydraulic model is employed. For 2-D hydraulic

modelling the cost would increase to $50,000/km due to greater complexity.

Table 4 presents the costs of updating existing mapping and creating 15,300 km of additional

mapping. From the review of existing floodplain mapping in Canada it was determined that 60

percent was produced in the year 2000 or earlier. Therefore, the figures shown in Table 4

assume that 60 percent of the existing floodplain mapping is to be updated. The additional

15,300 km should be sufficient to ensure that mapping is available for between 90-95 percent

of the population in flood prone areas. The distribution of this additional mapping, for costing

purposes, is divided as 35 percent in the urban area and 65 percent in the rural area. Since 2-D

hydraulic modelling is only required in specific situations, the costs shown in Table 4 assume

that 10% of the floodplain mapping length in the urban area would be completed using 2-D

hydraulic modelling and 5% in the rural area. Depending on the results of the Risk Assessment

and the review of new areas to be mapped, it is anticipated that the cost estimate shown in

Table 4 could change.

Table 5 shows a breakdown of required funding by province and territory. Again it should be

stressed that the estimate of additional mapping required for each province and territory is a

very preliminary estimate that will be updated as part of the proposed Risk Assessment. Since

the magnitude of additional mapping is a major component of the total cost, the division of

funding shown in Table 5 should also be considered a preliminary estimate.

TABLE 4: SUMMARY OF COSTS TO CREATE HAZARD MAPPING AND FLOOD RISK DATABASE

Unit Cost

($/km)

Length (km) Cost ($million)

Update

Existing

Mapping

Additional

Mapping

Update

Existing

Mapping

Additional

Mapping Total

Urban–1-D

model

$ 10,500 5540 4,815 $ 58.2 $ 50.6 $ 108.7

Urban–2-D

model

$ 50,000 615 535 $ 30.8 $26.8 $ 57.5

Rural-1-D

model

$ 7,500 10,165 9445 $ 76.2 $ 70.8 $ 147.0

Rural-2-D

model

$ 50,000 535 495 $ 26.7 $ 24.8 $ 51.6

Total -- 16,855 15,290 $ 192.0 $ 173.0 $ 365.0



TABLE 5: MAPPING SUMMARY

Total Length of

Existing Floodplain

Mapping (km)

Additional Floodplain

Mapping to be

Completed (km)

Required Funding1

($million)

British Columbia 2,656 2,650 $ 48.2

Alberta

960 770 $ 15.2

Saskatchewan 253 125 $ 3.2

Manitoba

363 185 $ 4.5

Ontario

16,675 500 $ 119.6

Québec

5,800 10,000 $ 152.8

New Brunswick <500 250 $ 6.2

Prince Edward Island <50 25 $ 0.6

Nova Scotia <500 250 $ 6.2

Newfoundland and Labrador 228 115 $ 2.8

Yukon

- 260 $ 2.9

Northwest Territories 110 30 $ 1.1

Nunavut - 130 $ 1.5

Total 28,100 15,290 $ 365.0 1to update existing floodplain mapping and produce new floodplain mapping

A typical project may encompass updating of mapping in an individual watershed or

community. The project would entail development of base mapping, hydrologic analyses to

estimate flow rates, survey and hydraulic modelling to develop hazard mapping and build the

risk data base, reporting and public consultation. The project would require specialized skills

including expertise in cartography, survey, hydrology, hydraulics, GIS, and public consultation.

From beginning to end, mapping in one watershed or community would take 6 to 12 months.

To update all mapping and develop recommended additional mapping across Canada would

take 5 to 10 years of intensive effort.

Beyond the cost of the mapping itself, upfront costs will include development of the Technical

Guidelines and Database, development of the delivery mechanism, and program

administration.

7.0 The Proposed National Floodplain Management Framework

The National Floodplain Management Framework will provide Public Safety Canada and federal,

provincial and territorial partners an essential tool in managing and reducing flood risk across

Canada. More specifically, the ultimate implementation of this framework will address many of

the key flood management challenges experienced across Canada.

The diversity in challenges across Canada is predominately related to variances in population

density, ongoing urban growth, climate and geography. The key challenges summarized below

are a compilation of both the challenges summarized in the previous sections of this report, the



extensive surveys that were completed for jurisdictions across Canada and the opinions

provided by subject matter experts.

Key challenges across Canada

1. Inconsistency across Canada in estimating flood magnitudes for specific return periods,

in part because of variances in guidelines, available resources, and processes to ensure

consistency and accuracy.

2. Complexity - Difficulty in quantifying flood risk as a result of complex processes such as

ice movement or dynamic mountain watersheds.

3. Increased Risk - Increased coastal flood risk and erosion potential, particularly in the

face of rising sea levels and storms with increased intensity.

4. Extensive Flooding across broad areas including urban and rural areas protected by

diking.

5. Dated Flow Estimates - Mapping is often based on flow estimates calculated in excess of

25 years ago. Updates based on more recent data and climatic trends will often yield

flow rates that are noticeably different than are currently assumed.

6. Dated Mapping - A substantial number of watercourses that do not have mapping, or

have mapping that is in excess of 25 years old; and a lack of financial and technical

resources to update and maintain mapping.

7. Accessibility - Flood Hazard Mapping and Flood Risk Data is often not readily available

or accessible.

8. Capacity – The capacity for undertaking the floodplain mapping tasks including the

human resources and in-house expertise varies across the country. Certain jurisdictions,

particularly NWT and Nunavut, have limited to no capacity to produce and update

floodplain mapping and have limited to no experience and expertise in the use of the

mapping at the community and territorial levels.

As outlined at the outset, implementation of the National Floodplain Management Framework

will build on the Guiding Principles and the Key Challenges, leading to comprehensive

understanding of flood risk across Canada including the information necessary to quantify risk,

establish priorities, and evaluate mitigation strategies. More specifically, implementation will

lead to the compilation of:



• Flood Hazard Mapping - updated flood hazard mapping for rivers and coastlines across

Canada, including areas that currently do not have mapping.

• National Flood Risk Database - with sufficient information to define flood risk (likelihood

and consequence) associated with communities, buildings and infrastructure across

Canada.

The National Floodplain Management Framework will include four main components;

Guidelines, Performance Standards, Technical Standards, and Initiatives.

Framework Scope:

Guidelines Identifies purpose and general content

Performance Standards Identifies key standards that help define risk

Technical Standards Recommends proposed standards that contribute to accuracy

Initiatives Identifies purpose and general content

Guidelines

The Guidelines will address the methodologies to be used, quality control and peer review

requirements, updating requirements, and documentation to be prepared. The following lists

the Guidelines that will be required. All of these documents exist across Canadian jurisdictions

and in the countries that were reviewed. Moreover, versions of most of these documents were

prepared as part of the FDRP program.

In preparing these Guidelines it will be important to also cross reference other guidelines (i.e.

dam safety guidelines) to ensure consistency in approach and data collection.



Technical Guidelines Purpose and Content

1. Base Mapping and Field

Survey

Will provide guidelines necessary to ensure that all base mapping,

topographic data, and structures are sufficiently accurate to

facilitate the development of meaningful flood hazard mapping and

flood risk assessments.

Will identify all aspects of developing base mapping and completing

field surveys; extending from photography through to the detailed

survey of structures such as dams and bridges.

2. Hydrology

Will provide clear guidance to the development of flow rates for a

range of probabilities that are as accurate as possible, and reflect

local characteristics such as rainfall, snowmelt, topography, soils,

and watershed characteristics.

Will provide a methodology for addressing climate change.

3. Hydraulic Analysis

Will provide clear guidance to the hydraulic analyses that will

combine mapping and hydrology in order to estimate flood

elevations for a range of flow rates.

Will address complicating factors such as ice, ice jams,

scour/sedimentation, and debris blockage.

4. Coastal and Shoreline

Flooding

Will provide guidelines for assessing coastal and shoreline flood risk,

including the anticipated impacts of climate change. Where possible

it will be integrated with similar analyses related to shoreline

erosion.

5. Policy Framework

Will identify a minimum set of policies that will define what can be

constructed within a floodplain. The provinces, territories and/or

municipalities may prescribe more stringent requirements.

6. Flood Risk Assessment

and Mapping

Will identify the minimum level of analysis required to assess flood

risk for existing or proposed buildings in the floodplain.

Will identify the type of information that must be included on the

floodplain maps, and will include methods for relating inundation

depth/frequency to damage.

7. Geo-referenced Data

Base

Will identify all information that must be included in the database

that will form an integral part of the floodplain mapping and risk

assessment.

Will identify all protocols for developing the data base and ensuring

its accuracy.



Performance Standards for Flood Risk Assessment

The Performance Standards refer to the key standards that define risk. Three levels of

standards are proposed: High, Medium and Low.

• High: Apply to all urban areas and rural areas that are protected by diking.

• Medium: Apply to remaining rural areas that include settlements and agricultural lands.

• Low: Apply to unpopulated areas, and may be used to guide the development of

infrastructure.

Table B1 in Appendix B details the proposed Performance Standards.

Base Mapping

Base mapping is foundational, in that the information provided through base mapping is used

for both mapping and determining the frequency and depth of flooding.

Performance Standards for base mapping refer to accuracy and the information that should be

provided on the base mapping. Specifically the standards address horizontal and vertical

accuracy, and mapping information such as watercourses, dams, dykes/berms, roads, and

building envelopes. The most significant standard would be vertical accuracy; proposed to be

0.15 m for medium and high risk areas; and 0.3 m in low risk areas.

Hydrology

The only Performance Standard specific to Hydrology is the design events that will be generated

and used to estimate riverine flood elevations. It is recommended that the design events used

to calculate flood elevations have return periods ranging from 2 years to 1,000 years. The

generated flood elevations would contribute to an understanding of flood risk but would not

necessarily be used for creating flood hazard mapping or regulating development in the

floodplain. In addition, the worst event on record should also be included. This event could

have occurred in the same watershed or in an adjacent watershed with similar climatic

conditions.

Hydraulics

Performance Standards for Hydraulics refer to the extent of information that must be collected

through field surveys to ensure that calculated flood elevations, depths of flooding and

velocities are as accurate as possible. These standards specifically refer to data associated with

buildings in the flood plain, culverts and bridges, and weirs and dams.

Coastal Flooding

Performance Standards specific to coastal flooding refer to design events and to the buildings

that are at risk of damage due to wave action.



It is recommended that the design events used to calculate storm surges, wave heights and

wave run-up have return periods ranging from 2 years to 1,000 years. The generated elevations

in land intrusion would contribute to an understanding of flood risk but would not necessarily

be used for creating flood hazard mapping or regulating development.

Policy Framework

The Policy Framework performance standards refer to the policies that will guide the

construction of new development within a flood plain. The standards refer to the events that

should be used for defining the floodplain and determining the extent of encroachment into

the floodplain. A minimum standard is proposed recognizing the development in floodplains is

generally mandated at a provincial or municipal level. The proposed minimum Regulatory

Event is the 1:350 year flow rate and floodplain, with no encroachment allowed within the 1:50

year flood plain. The noted exception would be existing urbanized areas where development

policies may be established on a case by case basis as guided by municipal and provincial

requirements.


The performance standards required for flood risk assessment and mapping refer to the

inventory that must be compiled in the flood risk database, and the floodlines that must be

delineated on the base mapping.

Technical Standards

The Technical Standards refer to the tolerance requirements that are to be adhered to in

developing the hazard mapping and the flood risk data base. Table B2 presents the key

technical standards although it is not exhaustive. Many more standards will be incorporated

into the guidelines as part of the various procedures that will be documented. In fact, many of

the Technical Standards listed herein may also be adjusted at that time.



8.0 Initiatives and Next Steps

There are a number of initiatives that are recommended be completed prior to embarking on

the update of the flood hazard mapping and the development of the flood risk database. These

initiatives could be undertaken simultaneously over a period of 12 to 15 months.

Initiatives and Next Steps

1. Complete a National Risk Assessment to

help establish mapping priorities

The risk assessment should include a review of

existing mapping to determine the areas that

have the highest degree of risk and also have

mapping that does not meet the proposed

standards. The risk assessment may also identify

areas that are at risk but do not currently have

any mapping.

2. Develop the Guidelines and refine the

Technical Standards

All guidelines should be completed and

approved prior to embarking on an update of

the mapping and risk database. Furthermore,

training and certification of practitioners may be

considered.

3. Develop a Framework for the Flood Risk

Database

In parallel with the development of the

Guidelines, the framework for the database

should be developped. Once complete the data

base would be ready for populating as mapping

projects are finished.

To reach its full potential as a powerful analytical

tool the database must be thoroughly vetted to

ensure that it includes all collected information,

incorporates appropriate quality control

standards, and is dynamic and adaptable.

4. Determine the delivery model for preparing

mapping and the database

Alternative delivery models should be

investigated and the preferred approach

mapped out in detail.

5. Prepare Federal-Provincial /Territorial

Agreements

As per FDRP, federal-provincial/territorial (FPT)

agreements will be required. Separate

agreements or Memorandums of Understanding

will also be required to address floodplain

mapping of First Nations and Aboriginal Lands.

APPENDIX A


National Floodplain Management Framework – Appendix A Page 1



Floodplains are low lying periodically flooded lands, adjacent to rivers, lakes and shorelines. In

a riverine the floodplain stretches from the banks of a channel to the base of the enclosing

valley walls and experiences flooding during periods of high discharge. A floodplain map

produced in Ontario, under the Flood Damage Reduction Program (FDRP), is shown on the

following page. There are several attributes noted on the map:

• Flood line – The solid black line, on both sides of the watercourse channel, shows the

area that would be physically flooded (covered with water) during the flood event that

has been assessed.

• Fill line – In Ontario the fill line was the extent of the Regulated area with respect to

Section 28 of the Conservation Authorities Act. The fill line is generally no longer used.

• Cross-Section – The lines across and perpendicular to the watercourse are the locations

of cross-sections that are used in the hydraulic model to calculate water elevations.

This will be explained in more detail later in this section.

• Cross-section Number – Each cross-section is given a number in the hydraulic model for

ease of reference. Often the cross-section number relates to the distance from the

downstream end of the watercourse.

• Water Elevation – The water elevation for the flood event analyzed at each cross-

section is shown on the map.

There are four key steps in producing a floodplain map:

1) Base Mapping – Topographic mapping.

2) Hydrology – The calculation of peak flows.

3) Hydraulics – The calculations of flood elevations.

4) Floodplain mapping - The mapping of floodlines and elevations.

Base Mapping

The base mapping for the production of floodplain maps consists of topographic mapping

derived from aerial photographs or LiDAR (Light Detection and Ranging). The topographic

information will be shown as contours and spot elevations and the map will also show ground

features such as extent of vegetation, building outlines, roads and watercourses. Contour lines

and spot elevations are noted on the example map. Typically maps will have contour intervals

of 0.5 to 1.0 metres and be printed at a scale of 1:2,000 (1 cm equals 20 metres).

National Floodplain Management Framework – Appendix A Page 3


Hydrology

Hydrology refers to the calculation of flows. One method to complete this calculation is

employing a statistical frequency analysis of an existing flow gauge on a watercourse. Flow

gauges continuously measure flow values at set time periods at a specific location. Water

Survey of Canada publish data from their flow gauges and, if there are sufficient years of data,

a frequency analysis can be completed to obtain return period peak flows such as 2 year, 5

year 50 year or 100 year. A return period is related to the probability of exceedance in a year.

Therefore, a 2 year return period has a 50% probability of being exceeded in any one year, a 5

year return period flow a 20% probability, a 50 year return period flow a 2% probability and a

100 year return period flow a 1% probability of being exceeded in any one year.

Another method to calculate flows is to develop a hydrologic model. A hydrologic model

simulates the physical response of the runoff produced in a watershed due to rainfall and/or

snowmelt. A watershed is an area of land where all runoff produced drains to a particular

watercourse and is defined by the height of land or ridges at the boundary.

Inputs to a hydrologic model include drainage

area (defined by the watershed boundary) and

factors to account for topography, soil, land use,

imperviousness and vegetation cover. The other

main input is rainfall or snowmelt parameters.

Various rainfall distributions and durations can

be applied. With a hydrologic model the output

is a time series of flows called a hydrograph. An

example of a hydrograph is shown on the next

page. Typically only the peak flow from a

hydrograph is used to calculate flood elevations.

Draft National Floodplain Management Framework Page 4


Hydraulics

The hydraulic analysis determines the flood elevations corresponding to the flows calculated in

the hydrology analysis. This usually requires application of a hydraulic model that requires as

input:

• Topographic information from the base mapping.

• Bathymetry (below water) information and river crossing (e.g. culverts, bridge).

information, usually obtained from field surveys.

• Flow values.

• Various additional parameters such as channel and floodplain roughness.

The majority of hydraulic analyses assume one dimensional (1-D) flow conveyance. This means

that the flow is in one direction, generally following the path of the watercourse, from

upstream to downstream.

0

40

80

120

160

200

0 5 10 15 20

Flow (m

3/s)

Duration (hours)

Flow HydrographLittle Etobicoke Creek at Dixie Dundas SPA

Regional Hydrograph



For a 1-D hydraulic model topographic data is

entered at each cross-section. The model then

calculates the water level at each cross-section,

corresponding to the flow entered.

1D -Hydraulic Model (HEC-RAS) Channel and Crossing Representation



2-D hydraulic models typically use a square grid digital elevation model to represent the flow

regime in the channel and floodplain. Often the theory of one dimensional open channel flow

is not applicable to urban flood flows, for example, where extreme non-uniformity and

variability of flow patterns is common. Flows may occur in sequences of fast moving shallow

flows and large still pond areas, rather than in the form of channels that are well defined over

long distances. Therefore a 2-D hydraulic model should be applied to represent this situation.

The flow vectors, as shown in the figure below, can be calculated in various directions in a 2-D

model. Because of model complexity the cost to assemble a 2-D model is much higher.

2-D hydraulic model output

Floodplain Mapping

The last step is to combine the base mapping with the hydraulic information that has been

generated. As shown on the example floodplain map this typically takes the form of floodlines

on the map that show the area that would be covered with water during a flood event. The

data shown on the maps, for more complex scenarios, may also include flow velocities, depths

etc.

Floodplain Terminology and Management

There are a number of common terms that are used in floodplain management to describe the

various components of the floodplain.



Using the One Zone concept the entire floodplain is treated and managed as a single unit and

typically all activities within the flood plain (development, alterations, filling etc.) are

restricted.

One Zone Concept

Under the Two Zone Concept the floodway and flood fringe areas are identified within the

floodplain and thus it is divided into two zones. The floodway is usually the central area of the

floodplain required for the conveyance of flood flow and/or that area where the flood depths

and/or velocities are the highest. The floodway is the most hazardous area of the floodplain.

The flood fringe is the portion of the floodplain where depths and flow velocities are lower and

less hazardous. From a floodplain management perspective activities or development within

the floodway are usually severely restricted while activities or development within the flood

fringe may be permitted subject to certain standards and procedures. In some jurisdictions or

countries there may be more than two zones delineated within the floodplain, but the concept

is the same, to administer activities within the floodplain considering the flood hazard of

various locations.

Two Zone Concept

Freeboard is usually a component of flood proofing. It is the elevation that the development

(e.g. low openings, windows, doors or living space) must be constructed at, above the flood

hazard elevation. For example, new development may have to be constructed at 0.6 m above

the 100 year flood level. In this case the freeboard would be 0.6 m.



Flood Hazard Mapping refers to traditional floodplain maps that illustrate the limits of a

floodplain but do not specifically refer to risk to the community or its infrastructure. Flood

Hazard Mapping is predominately what is in place across Canada. The sample floodplain map

in this section is an example of a flood hazard map since it simply shows the area of land that

would be covered during a flood, but does not directly show other information such as flood

depth or flow velocities. Flood Risk Mapping refers to the collection and management of data

that can be used to understand and quantify flood risk; and as such may more appropriately

be referred to as a Flood Risk Database. This information could include attributes such as flood

depths, flow velocities, develop type (residential, industrial), number of structures within the

floodplain and minimum floor levels of buildings. All this information would be advantageous

in determining not only the physical extent of the floodplain but also the risk and potential

flood damages of various flood events.

APPENDIX B

Performance Standards

Technical Standards

TABLE B1

PROPOSED PERFORMANCE STANDARDS Category

Description Proposed Canadian Standard

High Medium Low 2.0 Base Mapping Content

Watercourses

Include top of banks, or centreline where width is less than 5 metres

Dams Include top of dam and spillway as determined through field survey or existing records.

Dykes and Berms Include top of dykes and berms as determined through field survey or existing records, with points every 100 metres or

where top elevation changes by more than 0.2 metres

Roads Include edge of pavement and edge of gravel shoulder

Buildings Building footprint inside or within 100 metres of Regulatory floodplain

Vertical Accuracy Elevation 0.15 m 0.15 m 0.3 m Horizontal Accuracy 0.5 metres 0.5 metres 1.0 metres

3.0 Hydrology

Modeling

Design Events

Annual Return Period: 2, 5, 10, 25, 50,

100, 350, 500, 1000


100, 350, 500


100, 350, 500

Historical storm in or near watershed



4.0 Hydraulics

Field Survey

Buildings

Lowest opening elevation

First floor elevation

Lowest ground elevation adjacent to

buildings

Purpose

Type of structure

Number of storeys

Presence of basement

Photographic Record


Purpose

Type of Structure

Number of storeys


Photographic Record

n/a

Field Survey

Culverts and Bridges

Structure Description

Inlet/outlet description

Obvert and invert elevations

Length

Overtopping description, profile and

width

Photographic Record




Length


width

Photographic Record




Length


width

Photographic Record

Field Survey

Weirs and Dams


Structure Details

Gate details and dimensions

including widths and sill elevations

Overtopping Details including

elevations and width

Spillway details including elevation and

width

Photographic Record


Structure Details

Gate details and dimensions including

widths and sill elevations




width

Photographic Record


Structure Details

Gate details and dimensions including

widths and sill elevations




width

Photographic Record Freeboard

Determining ultimate level used for

building openings 0.3 (minimum)

0.3 (minimum)

0.3 (minimum)

TABLE B1

PROPOSED PERFORMANCE STANDARDS

Category Description Proposed Canadian Standard

High Medium Low

5.0 Coastal Flooding

Field Survey Buildings Lowest opening elevation

First floor elevation

Lowest ground elevation adjacent to

buildings

Purpose

Type of structure

Number of storeys


Purpose

Type of Structure

Number of storeys


Photographic Record

n/a

Field Survey Buildings Presence of basement

Photographic Record

Analysis

Frequency Annual Return Period: 2, 5, 10, 25, 50,

100, 350, 500, 1000 Annual Return Period: 2, 5, 10, 25, 50,

100, 350, 500

n/a

6.0 Policy Framework

Regulatory Events

The event(s) or flow rate(s) that will

be used for flood hazard mapping or

guiding new development within a

Municipally/Provincially determined but minimum shall be steady state flow rate with a return period of 350 -years. (25% probability of occurring within 100 years)

Two Zone

Policy Areas

Flood plain areas that are subdivided

into Floodways and Flood Fringes,

where development (subject to

meeting specific criteria) is allowed in

the Flood Fringe

To be defined as a Two-Zone Policy Area with the following minimum standard:

No development in the Floodway. Development in the Flood Fringe is flood proofed and has safe access/egress as defined below.

Floodway

The section of the floodplain where

development is prohibited

Definition of Floodway:

Municipally/Provincially determined but as a minimum:

50-year flood plain zone required to convey 350-year flood without increasing upstream flood risk. Maximum allowable increase is 0.1 m unless analysis demonstrates greater increase is acceptable.

New Development

in Flood Fringe

Flood Risk criteria used to determine where new development is allowed in Flood Fringe (floodplain outside of Floodway)

Municipally/Provincially determined but as a minimum no development prohibited if all of the following criteria are not met,

unless area defined as Special Policy Area with own unique set of policies to guide development:

Safe access provided for 350-year

event (25% probability of occurring

within 100 years) as per Safe Access

Criteria.

Buildings flood proofed to greater of

500-year event or 350-year event plus

0.3 metre freeboard.

Safe access provided for 350-year event

(25% probability of occurring within 100

years) as per Safe Access Criteria.

Buildings flood proofed to greater of 500-

year event or 350-year event plus 0.3

metre freeboard.

Safe access provided for 350-year event

(25% probability of occurring within 100

years) as per Safe Access Criteria.

Buildings flood proofed to greater of 500-

year event or 350-year event plus 0.3 metre

freeboard.

New Development

in Flood Fringe

Save access/egress criteria

Event: 1:350 year flood

Pedestrians:

o Depth (d) <= 0.8 metres o

Velocity (v) < 1.0 m/s

o Depth-velocity product <= 0.4.x m2

/s

Pedestrians:

o Depth (d) <= 0.8 metres o Velocity (v)

< .0 m/s


/s

Pedestrians:

o Depth (d) <= 0.8 metres o Velocity

(v) < 1.0 m/s


/s

Emergency Vehicles:

o Depth (d) <= 0.5 metres Emergency Vehicles:

o Depth (d) <= 0.5 metres Emergency Vehicles:

o Depth (d) <= 0.5 metres

TABLE B1

PROPOSED PERFORMANCE STANDARDS

Category Description Proposed Canadian Standard

High Medium Low

7.0 Flood Risk Assessment and Mapping

Inventory Inventory of all buildings in or adjacent to floodplain including geo- referenced coordinates.

For all buildings in Regulatory floodplain

inventory to include building opening

elevations and flood elevations for all

return periods


inventory to include building opening

elevations and flood elevations for all

return periods


inventory to include elevations for all

return periods

Mapping Delineate flood lines on base mapping

As a minimum delineate the 100-year

event, the Regulatory event, and the

Floodway where applicable



Floodway where applicable



floodway where applicable.

In reaches where there are buildings in

the floodplain, map the following:

o Flood depths for Regulatory event

using maximum interval of 0.5 m

o Velocity using maximum interval of

0.5m/s

o Product of velocity and depth in

increments of 0.4m2/s

In reaches where there are buildings in

the floodplain, map the following:

o Flood depths for Regulatory event using

maximum interval of 0.5 m

TABLE B2

PROPOSED TECHNICAL STANDARDS Category


High Medium Low 1.0 Level of Detail

Urban

All Urban Areas,

n/a

n/a

Agriculture

and

Recreation

Agriculture lands

Agriculture lands with defined floodplain

valley that contains 1:100year event. All other Agricultural lands.

Recreation lands where flooding would

occur during 1:50 year flood All other Recreation lands.

n/a

Other n/a n/a All other lands.

2.0 Base Mapping

LiDAR

Season of Flight

After leaves fall; prior to snow

LiDAR

Overlap

50%; flown in opposite directions

contour Interval spot elevations 0.5 m 0.5 m 2.0 m Update Frequency 5 years where development on-going;

otherwise 10 years 10 years where development on-going;

otherwise 20 years 20 years

3.0 Hydrology

Meteorological Data

Number of stations and length of

record

All stations within watershed, but a

minimum of three closest station with

records exceeding 50 years.


minimum of three closest stations with

records exceeding 25 years.


minimum of three closest stations

with records exceeding 15 years.

Meteorological Data Design Storms and Snowmelt

Sequences

n/a

Snowmelt

Data and method

The Guideline should include baseline data to be used for snowmelt calculations and should provide clear instructions on

how to calculate snowmelt and incorporate into a hydrologic model. The baseline data may include mapping for each

province that indicates the snowback water equivalent for the following return periods: 50-years, 100-years, 350-year, 500-

years.

Land Use

Existing and Future Land Use

Future to be the greater of 20 years or

planning horizon as defined in the

municipal Official Plan.

Existing only

Existing only

Topography Contour interval for catchment

delineation

0.5 m contour

1.0 m contour

2.0 m contour

Frequency Analysis

Years of Record

Minimum of 25 years where frequency

analysis is the primary method for

estimating flow rates up to 100 year

event. Increase to 50 years for rarer

events

Minimum of 20 years where frequency

analysis is the primary method for

estimating flow rates.

Minimum of 20 years where

frequency analysis is the primary

method for estimating flow rates.

4.0 Hydraulics

Field Survey

Cross-section Survey

Spacing of Cross-sections the lesser of

300 metres or 0.5 metre hydraulic

gradeline change or significant change in

cross-section

Spacing of Cross-sections the lesser of 500 metres or 0.5 metre grade change

or significant change in cross-section.

In-water details; (top and bottom of banks, minimum of 5 points between top of banks with horizontal spacing between

surveyed points not to exceed 10 percent of channel width. Vertical distance between adjacent points not to exceed 20

percent of bank full depth.

TABLE B2

PROPOSED TECHNICAL STANDARDS Category


High Medium Low

Field Survey

Cross-section Survey

Floodplain details: Survey from top of

bank to at least the limits of Regulatory

floodplain, with horizontal surveyed

point spacing to be no less than 5

percent of floodplain width. Vertical

distance between adjacent points not

to exceed 10 percent of bank full depth.

Floodplain details: Survey from top of bank to at least the limits of Regulatory

floodplain, with horizontal surveyed point spacing to be no less than 10 percent fo

floodplain widths. Vertical distance between adjacent points not to exceed 20

percent of bank full depth.

Modelling

Manning’s n (channel and flood plain

roughness parameter)

Selected as per Guidelines

Photographic Record on reach-by

reach basis


Photographic Record on reach-by reach

basis


5.0 Coastal Flooding

Analysis

Storm Surge and Wave Effects

Modelling

Future events

Mapping

Elements

6.0 Policy Framework

Special Policy Areas

Existing developed areas that are

within the Floodplain. Redevelopment

is allowed subject to meeting criteria

related to safety

Areas that have existing development but do not meet the Two-zone Policy Areas requirements can be defined as

Special Policy Areas.

Policies for these areas must balance the needs for flood protection and reduction of flood risk, while at the same time

recognizing the social and economic needs of the community. As such the policies must prescribe what is allowed in terms

of property improvements, zoning, and new development.

New

Development

outside of the

Regulatory

Freeboard to opening elevation for

buildings outside (but adjacent to

Regulatory floodplain)

New buildings adjacent to Regulatory floodplain flood proofed to greater of the 500-year event or 350-year event plus

0.3 metre freeboard.

7.0 Flood Risk Assessment and Mapping

Mapping

Elevations and Cross-sections

Label all cross-sections and include, as a

minimum, the 100-year event and the

Regulatory event

Label all cross-sections and include, as a

minimum, the 100-year event and the

Regulatory event

Label all cross-sections and include,

as a minimum, the 100-year event

and the Regulatory event

national floodplain mapping assessment - final report

Engineering

flood risk information

flood risk database

updated floodplain mapping

andmitigate flood risk

presentation of flood

national vision

flood risk data base

flood hazardmapping