landform report - flood risk management in new

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Delivering flood risk management in new developments

LANDF��RM event: E8510

Supported by: Arup Report of a workshop organised by CIRIA, held at Arup Campus, Solihull on the 9

th

April 2008

LANDF�RM is a new network primarily for local authorities to share experiences and discuss policy and research outputs regarding drainage and flood risk management. LANDF�RM is funded by the Environment Agency, Mouchel and Interpave.

Speakers Peter Bide CLG

Stephen Cook EA

Oliver Boulter Horsham District Council

Simon Purcell WSP

Chairman Mark Fletcher ARUP

THE ISSUES Flood risk management is very much in the public eye in the UK after the widespread flooding events of 2007. The public generally consider that local authorities should take responsibility for flood risk management although in reality there are a large number of stakeholders who each have a role to play in controlling the flood risk to new and existing developments. Flood risk management and flood defence works have traditionally been focussed on coastal and river flooding. However due to increasing levels of urbanisation, ground surface run-off represents a considerable flood risk and played a role in many of the 2007 flood events. The Pitt review ‘Learning lessons from the 2007 floods’ interim report and PPS25 ‘Development and Flood Risk’, highlight the need for local authorities to take a lead role in flood risk management at all stages of the planning process for new developments. A sequential approach to flood risk is specified where development should only be carried out on the lowest flood risk area practically available. There is also an exception test that can be applied which, in exceptional cases, permits necessary development in areas of flood risk where no net increase or an overall decrease in flood risk can be demonstrated. Government housing plans would require that some development take place in areas at risk of flooding in the south east which, if properly planned and designed, need not conflict with PPS25. Delivering PPS25 represents a major challenge for LA’s and there is a need for best practice guidance to follow. This is currently being shaped via the CLG ‘A practical companion guide to PPS25’ which is available on their website as a living draft. Appropriate guidance is essential to ensure that developers, planners and other stakeholders are all starting from a common understanding of flood risk and PPS25, preventing inappropriate development and allowing suitable development to proceed with minimum disruption. LEARNING POINTS 1. CLG have produced a ‘living draft’ guidance document for planners and other

stakeholders to refer to when interpreting PPS25.


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2. The ‘living draft’ has been shaped by consultation feedback and by the Pitt review into lessons learned from the 2007 floods and an updated version will be available shortly.

3. There is a need for a single umbrella body to take responsibility for flooding and drainage 4. The EA should be consulted at an early stage when scoping SFRA’s or FRA’s to ensure

they are adequate. 5. There is a skill shortage with LA’s regarding flood risk assessments. 6. A lack of good practice examples of SFRAs makes it difficult to carry them out correctly. 7. Developers are placed in a frustrating position between planning authorities and the EA,

who have different criteria to meet. 8. A more pragmatic approach to interpreting PPS25 would be welcomed. PETER BIDE, COMMUNITIES AND LOCAL GOVERNMENT (CLG) PPS 25: Planning to manage flood risk Peter is the head of water planning policy at CLG. He is a chartered geologist and engineer and has worked with the British Geological Survey as a policy advisor and with DETR on research policy. He is currently developing policy for planning and water including flooding and coastal erosion. In England alone some 10% of the population live in high flood risk areas. The Stern review considers planning policy as an important element in long term flood risk management. To avoid increasing the proportion of the population at risk, or increasing the severity of existing flood risk, it is essential to have in place proper planning procedures to ensure that new development is sited in appropriate areas and causes no increase in flood risk either on site or elsewhere. Furthermore, with proper planning it is possible to require that new development even decreases the flood risk to the local area. One example is the award winning Sutcliffe Park in Lewisham which transformed a culverted park into a living wetland, creating biodiversity and amenity whilst simultaneously increasing flood plain storage and helping protect Lewisham city centre from flooding. PPS25 was published in December 2006 and requires that flooding be considered at all stages of the planning process by taking a risk based, sequential approach. A three-tiered approach to flood risk assessment is employed. On the broadest scale, Regional Flood Risk Appraisals are to be prepared by regional planning bodies in consultation with the EA, making use of the flood map provided by the EA to develop a regional spatial strategy. In more detail at the community scale, the local planning authority is required to complete a Strategic Flood Risk Assessment (SFRA). This should identify flood zones 1, 2, 3a and 3b in higher resolution, act as a link between spatial planning and emergency planning and identify areas where development can be permitted. At the finest scale, in areas of flood zone 2 or above and for large developments in Zone 1, a site specific flood risk assessment has to be carried out by the developer and submitted to the planning authority, who should then apply the sequential test in accordance with PPS25. A flow chart for decision making with the sequential test is shown below.


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Figure 1 – Flow chart of decision making process of sequential test for PPS25 It is evident that if necessary development can’t be located outside flood risk areas, it can take place in flood risk areas if it passes the exception test. This test requires that three conditions be met; the need for development to meet sustainability objectives has to outweigh the flood risk, where possible the land should have been previously developed and finally where measures have been taken to ensure that the development will be safe from flooding without increasing or preferably decreasing the flood risk elsewhere. While PPS25 states what has to be done by planning authorities and other relevant stakeholders there is a need for guidance on how these actions can be best implemented. CLG have produced a practice guide which is available on their website as a ‘living draft’. The practice guide aims to help planners understand the broad objective of PPS25 and flooding issues as a whole. It also tries to clarify the roles and actions various stakeholders should take in the planning and development process and ways in which this can best be achieved. STEVE COOK, EA Development and flood risk – the EA’s approach to PPS25 Steve has worked as an environmental consultant in the public and private sectors for 10 years. He is a national policy advisor on flood risk and spatial planning with the EA and has been involved with regional planning in the south east. The EA is the largest public body involved in managing flood risk and play an important role in PPS25. We look at the bigger picture on a river catchment or shoreline level, which is larger than local planning authorities’ with their smaller geographical remit . Therefore the EA can more readily identify cumulative increases in flood risk from individual small scale developments - the death by a thousand cuts scenario. The EA has carried out a national flood risk assessment for river and coastal flooding and provides a national flood map which is a vital element of all FRA’s – regional, strategic or site specific. We are consulted on the scope and methods of FRA’s and provide advice based on their results . The EA is a statutory

Can development be allocated in Zone 1? (level 1 SFRA)

Where are the available sites in Zone 2? (level 2 SFRA) -can development be allocated within them? (lowest risk

areas first) (Tables D1 and D2)

Where are the lowest risk available sites in Zone 3a? - can development be allocated within them?

(Tables D1 and D2)

Is development appropriate and permissible in remaining areas? (Tables D1, D2 and D3)

Yes

Exception Test if 'highly vulnerable'

Allocate, subject to Exception

Test (Table D3)

Allocate, subject to Exception Test (Table D3)

Yes

Yes

Yes

No

No

No

No

Strategically review need for

development


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consultee on spatial planning at the regional level and on most planning applications proposed in flood risk zones. The EA also has a ‘call-in direction’, which allows it to refer the application to the Secretary of State prior to its approval if it feels flooding issues have not been fully scrutinised by the planning authority. This should encourage LPA’s to take a thorough approach to flood risk assessments. However flooding is a natural phenomenon and cannot be entirely halted. There are a number of potential sources of floods such as coastal, river, groundwater, overland flow and reservoirs which cannot reasonably be defended against everywhere. Flood risk management is a case of making optimal use of investment. PPS25 outlines the following flood risk management hierarchy;

Figure 2 – PPS25 Flood risk management hierarchy The three tiered approach to flood risk assessment starts with RFRA’s, currently led by the Regional Assembly then down to SFRA’s where the LA assumes responsibility and down to site specific FRA’s which are the developer’s responsibility. With a SFRA all flood risk zones must be identified, using the EA’s flood maps as their starting point, and the source(s) and potential magnitude of flooding be identified and mapped.. A good SFRA should be able to identify and show the differing levels of flood risk, both between and particularly within flood zones. This then becomes a major tool to inform where development should be located and what types (residential, commercial etc) are appropriate. An example of this transformation is shown in the figures below. SFRA’s can also help identify areas where surface water flooding will be an issue requiring active management including where SUDS would be most beneficial to implement. Figure 3 – Example of increased understanding of the nature and magnitude of flood risk from EA flood maps (left) by carrying out a SFRA (right) The lack of a SFRAs of adequate quality is the most common reason for the EA objecting to planning proposals. Climate change must be factored into the assessment to ensure the development will be safe over the whole of its lifetime (e.g. 100 years). The information from site specific FRA, complimented by that from an SFRA, will inform the developer what

PPS25 FLOOD RISK MANAGEMENT HIERARCHY

Step 1

Assess

Appropriate flood risk

assessment

Step 2

Avoid

Apply the Sequential approach

Step 3

Substitute

Apply the Sequential test at site

level

Step 4

Control

SUDS, Design, flood

defences

Step 5

Mitigate

Flood resilient

construction

High risk:

Rapid

Inundation

Zone Low risk: “island”

Medium risk

High risk:

Significant depth


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aspects of flooding need to be sufficiently managed through the layout and building design to enable the development to be safe and meet PPS25’s requirements. These flood management measures, for example SUDS, safe egress routes for the residents and access routes for emergency services, should be accounted for in the master plan and not simply bolted on at a later stage. Adding them retrospectively to the development proposals incurs unnecessary costs to the developer and may not provide the optimal results There is not a one-size fits all solution to FRA’s, each must be site specific. Where possible, proposals should try to reduce overall flood risk rather than simply to avoid increasing it. This can help the EA reach decisions more quickly. A thorough SFRA, in conjunction with the sequential approach, should prevent inappropriate development in areas of high flood risk and help shape developments to reduce overall flood risk. There are several very useful sources of information for advice on flood risk and planning such as the Developers Guide, Flood maps and SEA good practice guidance available on the EA website and the CLG Practice Guide to PPS25 available on the CLG website. In summary it is important to talk to the EA at the earliest stage of planning. For development proposals to successfully pass through the planning process, and as efficiently as possible it must be shown that information sources have been utilised, the sequential and exception tests have been properly applied and that the FRA shows the development will be safe for its lifetime, not increase flood risk and possibly reduce overall flood risk. OLLIE BOULTER, HORSHAM DISTRICT COUNCIL A local authorities approach to Strategic Flood Risk Assessment (SFRA) Ollie is a chartered Town Planner and as a senior planner with Horsham District Council has helped prepare their core strategy and been a project co-ordinator for 2 SFRA’s carried out in Horsham. Horsham is a primarily rural area south of London and adjacent to Gatwick Airport. Due to its geographical location there are compelling social and economic reasons for further development in the area. In total Horsham covers around 529km

2 with just 0.18% of the total

area classified as Flood Zone 2, 1.2% classified as flood zone 3a and 5.9% classified as Flood zone 3b which is considered functional floodplain. Three different river catchment areas exist in the Horsham district; the river Adur, the river Arun and the river Mole. In 2007 the council produced documentation to clarify a core strategy, site specific allocations of land and general development control to aid planning decisions in the region. Unfortunately the development plan document (DPD) and core strategy for Horsham were completed just as PPS25 was introduced. These documents did not state a dedicated flooding policy. Flooding was considered only as part of an overarching Environmental Quality policy. Therefore it was necessary to revisit the documents and appropriately incorporate the findings from the SFRA’s into them. To comply with the requirements of PPS25, two SFRA’s were carried out to cover the catchments in the district, one covering the Arun and Adur catchments and one covering the Upper Mole catchment, the latter being a joint collaboration with two other district councils. Due to the limited knowledge of planners at the time, SFRA’s were carried out by independent consultants. A partnership approach to completing the SFRA including two-way communication with the consultants and the EA resulted in robust and high quality SFRA’s. It was recognised that the SFRA should not simply be a box ticking exercise and so the council intends to update both SFRA’s on an annual basis to account for recent development and changes in flood risk assessment methodology. Completing the SFRA was not without some difficulties though. At the time there were no previous examples of other LA’s to follow. One important point is to remain strategic and avoid becoming bogged down in too much detail. There was a clear difference in opinion towards the SFRA between consultants and the EA, who seemed to take a more restrictive


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and onerous approach. There were also difficulties in deciding how to best disseminate the knowledge acquired from the SFRA. Implementing the SFRA has been a learning experience for the council. Key to the success of any SFRA is for the local authority to be knowledgeable of PPS25. Working in partnership with a consultant specialising in flood risk assessments can help improve the knowledge base of the local authority in producing a SFRA. Consulting with the EA from the beginning of the process ensures that an SFRA of adequate quality is produced and will not be a possible point of objection during future planning decisions. A pragmatic approach from all partners was required in order to arrive at a satisfactory conclusion. Annual updating of the SFRA should improve the quality of the document as best practice examples are produced. SIMON PURCELL, WSP Flood risk – the developer’s perspective Simon is a chartered engineer with 20 years experience in the water industry. He is a technical director with WSP and has recently been involved with several large scale developments looking at flood risk and drainage aspects. According to PPS25 a flood risk assessment is required for all developments proposed in flood zones 2 and 3 and, where development covers more than 1 hectare, in flood zone 1 as well. There are three stages in a flood risk assessment; screening, scoping and the detailed assessment Assessments must be supervised and signed off by a CIWEM or ICE chartered engineer. The assessment must take into consideration factors such as sources of potential flooding, climate change, flood mitigation, off-site impacts and surface water drainage. Therefore it is extremely important for developers to be capable of carrying out the flood risk assessment properly and in accordance with PPS25 to ensure that where appropriate, planning permission can be obtained. PPS25 places restrictions on development in flood zones 2 and 3. However the office of the deputy prime minister is stating that around 2.8 million new homes are required in the East of England by 2021 and that the Thames Gateway development should proceed. In these areas a considerable amount of land is classified as flood zone 2 or 3. Figure 4 shows highlights the extent of flood risk areas in the Thames gateway. Figure 4 – Thames Gateway with flood risk areas highlighted


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The contrast between local planning policy and government housing policy is creating confusion amongst local authorities in the south east as to whether proposed development in flood zone 2 or 3 in the Thames Gateway is deemed necessary enough to pass the exception test. LA’s are responsible for carrying out SFRA’s of their local area and this is to be used as a starting point for any site specific FRA’s. Due to a lack of expertise in this area LA’s invariably put SFRA’s out to tender to specialist consultants. However there is a real danger that the winning, and also cheapest, bids fail to complete a detailed enough SFRA, leaving the LA with an oversimplified assessment of their area. There are examples of SFRA’s being tendered for £8000 which roughly equates to two weeks of a senior engineers time. The compensation culture that has grown in the UK in recent years means that FRA’s lean towards the conservative side. However we have to realise that some development on the floodplain is inevitable and that with improved knowledge of flood risk modelling and sustainable drainage systems we can use development that demonstrably reduces flood risk overall. PPS25 outlines a clear assessment process however there are areas which are open to interpretation in the sequential test and exception test. How sustainable and necessary does a development have to be to pass the exception test? Sometimes objections are made by the EA or LA on the basis that drainage has not been considered early enough in the design but often the masterplan is still very sketchy at this stage. Designs have to demonstrate a dry escape route from the development during a 1 in 1000 year flood event plus climate change. But how do you quantify the increase in a flood event by climate change? With SUDS in designs there is the thorny issue of who should adopt the drainage system once development is completed. There is a lack of consistency in the interpretation of PPS25 between LA’s and this may be due to a difference in knowledge base or due to previous flooding issues in the area. In any case it only adds to the confusion from the developer’s perspective. One example WSP have been involved with was a development in SE England where a new town was proposed in a socially deprived area, with 1000 existing homes at risk of flooding. The proposal was objected on the basis that the sequential test was not followed. Even though new wetlands would have been created and the new development would provide a secondary defence to the existing homes at risk, with a fully compliant SUDS scheme, the LA used PPS25 to refuse planning permission. When flood events occur, the public looks towards the local authority to blame as they originally granted planning permission for the houses and shops that flooded. However fear of blame should not be sufficient grounds to object to a planning proposal that has obvious wider benefits. A more pragmatic approach to development by the EA and LA would help negate the poacher/gamekeeper mentality that exists between developers and planning authorities. Surely it is better to see development as an opportunity, using PPS25 as a tool to work in a constructive partnership, to improve the wider sustainability of existing communities and reduce flood risk overall in an area. DISCUSSION Q Is the change of use of an existing site subject to a flood risk assessment if it is

located in flood zone 2 or 3? And if so would it apply to sites of all sizes or only above a certain size?

A There is a need to clarify vulnerability classifications like this. Interpretation of PPS25

is still an evolving issue. The end point is clear but several iterations are needed to get there as examples of good practice arise to follow. The guidance document to PPS25 is currently a living draft but the next version will be much tighter.

Q Is the EA’s internal guidance available to CLG and the public?


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A It is a public document, our Standing Advice provides an overview of our approach and what we require. The EA are currently setting up a database and consulting on what documents are best to include.

Q The flood map provided by the EA for coastal and river flooding is a very interesting

tool. However many of the 2007 floods, particularly in Lincolnshire, were caused by surface water flooding. This should be considered in future, updated flood maps.

A Yes, although it will be more challenging to map than fluvial and tidal flooding we are

currently working on mapping areas at risk from surface water flooding. It is vital for comments such as this to be included in feedback to the Defra consultation on surface water .

Q Who is responsible for draining urban developments? With SUDS who is supposed to

adopt? Doesn’t seem to be the highways authority or water utilities. A Urban drainage is the primary responsibility of the landowner or property manager.

Although SUDS represent a contentious issue because for example, if someone in the future builds on porous paving the drainage system will be compromised.

Q With drainage design there are so many different standards out there it is impractical.

Sewers for adoption, SUDS, highways adoption and now flood risk assessments. Can a more integrated approach not be introduced?

A Well having these rigid standards in place may be cumbersome but if we came up

with a one-size fits all approach there is the probability that the uniform standard would be way too detailed to cover all possible different aspects of urban drainage and consultants would end up referring to a set of encyclopaedias.

Q For example PPS25 requires developments to withstand a 1 in 100 year event yet

water utilities require sewers that cope with a 1 in 30 year event and may reject larger sewers. The issue of SUDS adoption still remains too. We have been talking about such problems for almost 10 years, why has nothing been done yet?

A Hopefully the DEFRA consultation for surface water management plans will prove to

be a turning point. There are too many organisations, each with their own rules, responsible for surface water management. An analogy for the current mess would be like a rugby match between a rugby union and a rugby league team. There is a need for a single body to be responsible for surface water management and it is hoped that the Pitt Review will prompt Westminster to make this happen. Another point of concern is that there are no representatives here from the water industry.

Q Virtually every LA has been ill equipped to deal with PPS25 independently and have

had to contract out work to consultants to complete SFRA’s. Are there any training courses for LA’s to become competent in flood risk assessments?

A In the early 1990’s LA’s possessed the relevant expertise for technical aspects of

planning proposals but with privitisation unfortunately many of these skills have been lost. There is a need for upskilling and perhaps a dedicated strategic drainage department in every LA. This would have the advantage of greatly speeding up the planning process and perhaps allow a more pragmatic approach to be taken. This is especially pertinent as the EA’s resources are particularly stretched. Often there are difficulties contacting the EA for pre-application discussions and any problems are not ironed out until the final application which, if rejected can lead to a costly inquiry.

Another point is that LA’s are an important source of local knowledge of drainage and

flooding. As older staff leave and are replaced with graduates who increasingly rely on models and flood maps there is a loss of local knowledge.


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Some neighbouring LAs are collaborating on their SFRAs, appointing a single contractor to undertake each of them can be more efficient in both time and money.

Q How can we get Highway engineers engaged in FRA’s? A In Lincolnshire we do get them engaged, the problem is when we try to interact with

the planners. It is vital to get housing and highways and planning people in the same room – again the need for an overarching single body is evident.

Q Why are we scrutinising new developments so tightly when most of the problem is

caused by existing development? Should we take a wider scope to SFRA’s? A The best solution has to be catchment wide, it is the only way. A lot of small solutions

implemented in concert with each other may be more appropriate than one ‘big’ solution. There is a need for local authorities to communicate with each other when they share a catchment.

Q So is there legislation in the pipeline that could form a single drainage body? A Pitt called for a single body and if the Defra water strategy consultation also states

this then the government should be compelled to act. As stakeholders you should state this in your feedback to the Water Strategy consultation.

Q A major event is needed to get politicians to act. If insurers suddenly stopped insuring

certain areas this could be sufficient. Do you think this is likely to happen? A The government is currently talking to insurers. It is necessary for insurers to be

proactive and involved in planning decisions in the sense that they should be consulted and state if they would be willing to insure a particular development before it receives final planning permission.

It is unlikely for insurers to not insure areas for an extended time if floods don’t

happen for a few years. Amongst householders there is a serious denial mentality. People are so concerned

about being able to sell their house they can often be irritated to hear or sign up to EA flood warnings. Flooding has changed as urbanisation has spread. Previously it was mainly river and coastal flooding but now sewer and surface flows are causing floods. Some areas and roads are designed to sacrificially flood during heavy storm events but people don’t realise this and think it is a bad thing. There is a need to accept the truth that flooding is an entirely natural phenomenon and cannot be completed extinguished.

Q? Why should a development that can be shown to decrease flood risk be objected to? A? Avoiding inappropriate types of development in flood zones 2 and 3 is one priority of

PPS25 and the EA and LA’s must take account of that Government policy requirement. However if the sequential test and exception test (where required) have been passed then a development that shows it will decrease flood risk shouldn’t have an objection made against it.

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