bio’s relative sea level rise estimates

BIO’s relative sea level rise estimates

0.4-0.9m on 50-year time scale

0.9-1.6 on 100-year time scale

Example from

County of Colchester / Truro

MSC’sSTORM SURGE MODEL

Tell us the impacts you are seeing and at what water levels!

Model based on OUTPUT WINDS


Map display; every hour for 48 hrs out from when model run

Time series graph; point forecast for specific location. Show stage 1, 2 or 3 flooding based on past events.


Does NOT include wave run up

Add 10% to surge levelsif wind facing shoreline . . .

. . . then add tide level


65cm surge predicted at nearly high tide = 2.9m

75-80 cm surge experienced = so 3m + at least another 10cm for wave run up

(more if wind from S/SE)

Geohazards?

1. What’s the short-list of geohazards potentially relevant to my MCCAP?

2. How are they relevant, and are they priorities?

THANK YOU!• Garth DeMont, Geoscientist with NS Department of Natural Resources• Gavin Kennedy, Hydrogeologist with NS Department of Natural Resources• John Drage, Hydrogeologist with NS Department of Natural Resources

Assessing Geological Hazards 4 of 30

. . . to develop a methodology to incorporate geology into the land use planning process

• coastal flooding & riverine flooding• coastal erosion• land sinking – sinkholes• contamination of water from heavy

metals in soil or acid rock drainage• landslides / slope failure

Geo-events that pose threats

Picture from NS DNR Geological Services Division




Geohazard—Coastal erosion


The need to establish setbacks should be informed by geology – both bedrock and surficial

Coastal erosion risk will increase with sea level rise.




Geohazard—Karst


Occurs inlimestone & gypsum

• sinkholes• water contamination

Under the Nova Scotia Treatment Standard for Municipal Surface Source Water Treatment Facilities, once designated, karst areas are subject to water treatment standards.

Changing Precipitation

Assessing changes in precipitation




Update the Draft Stormwater Management Plan

Recommend BMPs so that future development won’t increase peak runoff flows


Update the Draft Stormwater Management Plan

Recommend BMPs so that future development won’t increase peak runoff flows

Assess the effects of climate change on rainfall intensity and the effects of these changes on the storm water mgt plan

SWMM5

Stormnet


New climate-wise design rainfalls

Stormnet


What’s the rainfall pattern during the day: sub-day durations? (used for IDF curves)



Conclusions:

•Predicted magnitude of the increase in precip volume expected in 1 day is 29%

•Predicted increases for 24 hr rain are higher than increases in annual rainfall

•Predicted increases for shorter durations are greater than increases for longer

durations


StormnetDesign Storms


•redefine peak flows to be associated with

potential future rainfall events

•estimate the equivalent pipe diameter of culverts required to convey the peak flows, and

•estimate the costs for culvert replacements to accommodate peak flows


Minor Drainage System


Designed for rainfall events with return periods of1 in 5 to 1 in 10 , based on HISTORICAL RECORD.


Designed for rainfall events with return periods of1 in 5 to 1 in 10 , based on HISTORICAL RECORD.

Rainfall events in exceeding this cause surcharge:Up-the-pipe-flooding


Major Drainage System

Natural water channels tend to have capacity for a 1 in 2 year rainfall event, based on historical records



The level of service expected by the public and other stakeholders is rising


Recommendation:

All structures with capacity less than the estimatedmaximum peak runoff flows predicted by the

(stormnet) modeling should be upgraded.



4 Recommendations:

1. Examine each watershed in the Town, starting with the watershed where the potential risk of flood damage is greatest, and figure out:

• if and where there are opportunities to increase the capacity for water storage/detention and

• if existing culverts and structures could withstand a 1 in 100 year return period rainfall as defined by simulated rainfall events modeled in the study.



4 Recommendations:

2. Identify flood limits generated by the design rainfall event with 1 in 100 year return period on Town Land Use Mapping



4 Recommendations:

3. DEFINE acceptable level of (stormwater mgt) service in consultation with stakeholders



4 Recommendations:

4. Develop a prioritized list of modifications to existing structures (e.g. culverts), based on what they now knew about the condition and capacity of existing culverts, as well as stakeholder views on acceptable levels of flood risk


. . . to develop a methodology to incorporate geology into the land use planning process Plan to adopt the

updated Plan at the Jan. 2013 Council mtg


. . . to develop a methodology to incorporate geology into the land use planning process A stormwater mgt

plan will have to be submitted as part of all development applications



Take away messages:

•Work at the watershed level

•Engage climatologists to model and downscale design rainfalls

•Ask about the modeling software

•Visually present flood hazard and risk to stakeholders



Take away messages continued:

•Gauge stakeholder risk tolerance

•A lower level of service is inevitable

•Development controls crucial to SWMM

•Again…make sure stakeholders understand the risks

Anne [email protected] 431 7168

www.elementalsustainability.ca

bio’s relative sea level rise estimates

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