Strategic flood consequences assessments

Strategic flood consequences assessments

Local planning authorities should carry out a strategic flood consequences assessment (SFCA) for their area. The Welsh Government asked all local authorities to review their SFCAs by November 2022 against the draft TAN15 policy and the Flood Map for Planning.

Local planning authorities produce SFCAs to: 

  • inform their Strategic and Local Development Plans
  • plan and deliver sustainable development
  • provide flood risk evidence for existing communities and new developments

SFCAs identify:

  • where flooding from all sources is a planning constraint
  • where coastal erosion is a planning constraint
  • local flood risk not identified on national maps
  • ways to manage flood risk 
  • opportunities to reduce flood risk for existing communities

What to include in a SFCA

To produce a SFCA, you should refer to chapter 7 of the draft revised TAN15. As a minimum your SFCA should consider:

Consultation

At the scoping stage

At the scoping stage you should consult: 

  • the Welsh Government
  • Natural Resources Wales
  • your Lead Local Flood Authority

for advice about:

  • the scope of the SFCA
  • what relevant information is available
  • whether you need hydraulic modelling 

You should also consult within your local authority and other stakeholders, for instance with: 

  • emergency planners
  • biodiversity teams
  • water and sewerage companies
  • reservoir owners or undertakers

This will help make sure your SFCA informs other work areas and doesn't conflict with other local strategies.

NRWs role

We provide advice on the flood risks from rivers and the sea.

We do not advise on flooding from:

  • surface water or drainage
  • small watercourses
  • groundwater
  • coastal erosion
  • emergency planning
  • reservoir risk 

Read more about what we advise on in Building in flood risk areas and Our service to developers.

We provide flood risk advice and data to help plan and prepare a SFCA:

We may have detailed modelling available. If you need to create a new model, contact us first to agree the scope and objectives:

South West Wales planning service swplanning@cyfoethnaturiolcymru.gov.uk

South East Wales planning service southeastplanning@cyfoethnaturiolcymru.gov.uk

North Wales planning service northplanning@cyfoethnaturiolcymru.gov.uk

Mid Wales planning service midplanning@cyfoethnaturiolcymru.gov.uk

Challenging our flood maps

After agreeing the scope

After agreeing the initial scope, you should engage and collaborate more widely with other key stakeholders, including:

  • emergency services
  • highways authorities
  • regional flood and coastal committees

Producing a SFCA

There are up to three stages in producing a SFCA: 

  • stage 1 - all Local Planning Authorities undertaking a SFCA need to produce this
  • stage 2 - to ensure Local Planning Authorities better understand flood risks when allocating Local Development Plan sites
  • stage 3 - if there are significant flood risks that could impact the soundness of Local Development Plan sites

Stage 1 – gather information on flooding

Stage 1 is a high-level assessment of the flood constraints in the SFCA study area. This will help identify suitable land for development now and in the future. 

You should: 

  • prioritise development in areas where there is little or no risk of flooding
  • consider coastal erosion risks and shoreline management plan policies

Your assessment should include maps showing:

  • all sources of flood risk
  • flood extents from all sources, including an allowance for climate change (up to and including the 1000 year event)
  • historical flooding and their sources
  • overland flood flows
  • flooding from artificial drainage systems
  • flooding from infrastructure failure (including reservoirs and sewers)
  • coastal erosion risks

You should also include a supporting report with information about:

  • the sources of flood risk
  • existing flood risk management infrastructure
  • local physical features (natural or manmade) which could breach or convey flood flow to other areas which aren't directly at risk from the flood source
  • land needed for flood risk management features and structures
  • opportunities to reduce the causes and impacts of flooding
  • how Shoreline Management Plans and policies suggest flood risk and coastal erosion may change over time
  • reservoir risk
  • cumulative impact of development / land use change, and areas of uncertainty

Your maps and report should be in a format that you can easily update, to make sure the SFCA stays as accurate as possible.

Stage 2 - include more detailed information

You will need to do a further assessment if you are considering allocating land in a Local Development Plan in: 

  • areas at risk of flooding
  • where you think development could increase flood risk elsewhere

The stage 2 SFCA should be detailed enough for you to: 

  • identify site allocations/growth areas with the least risk of flooding
  • consider flood mitigation measures for these sites
  • decide whether development can be made safe without increasing flood risk elsewhere

You need to direct development to areas that can acceptably manage the flood risk. This means relying as little as possible on existing or proposed raised flood defences.

Your assessment should include detailed maps showing:

  • sources of flood risk
  • annual flood probability
  • flood depths
  • flood velocity
  • hazards
  • duration
  • breach/blockage impacts
  • communities, properties, structures, and other features affected by flooding
  • vulnerability of proposed land use
  • flood defences and the areas which benefit from these defences

You should also include a supporting report with information about:

  • flood defences (e.g. location, Standard of Protection, ownership, long term maintenance policy)
  • flooding consequences as a result of breach/blockage
  • overloading/exceedance events to infrastructure (e.g., drainage systems, storage areas)
  • other sources of potential flooding within a defended area e.g., from surface water, overloaded drainage etc)
  • evidence to inform a sequential approach to development, for example the severity and variation of flood risks across a site
  • evidence to demonstrate development can be safe over its lifetime, including suitable access/egress
  • evidence to show no increase in flooding elsewhere
  • opportunities to reduce the causes and impacts of flooding
  • opportunities to manage/mitigate flood risk
  • opportunities to provide wider sustainability/environmental benefits

Stage 3 – testing site suitability

You may need to prepare a stage 3 assessment on some proposed sites to confirm the flood risk is manageable to an acceptable level and meets the TAN15 requirements.

Managing flood risk can have a significant impact on the design, cost and viability of developments. A stage 3 assessment should satisfy you that the flood risk management for an allocation is feasible and practicable.

Your stage 3 assessment should: 

  • consider a range of climate change scenarios including upper end estimates
  • demonstrate the development of the site will not increase flood risk elsewhere
  • identify ways of improving flood risk for existing communities
  • identify future infrastructure needs

Find out more about NRW's flood risk management projects

Joint SFCAs 

You can work with other local planning authorities to produce a joint SFCA. This might give you more options and flexibility to manage the causes and impacts of flooding, especially where:

  • the flood risk comes from outside your administrative boundary
  • the best solutions to addressing flood risks lie outside your local authority area
  • land use and development within your authority area affects flood risk elsewhere
  • you share a river catchment or coastal area with other authorities

The sources and causes of flooding are often cross-boundary issues. The Welsh Government's 15 December 2021 letter encourages regional assessments wherever possible.

Strategic documents, such as flood risk management plans, sustainability appraisals and Area Statements can identify and inform catchment-wide solutions.

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