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What we do

Herrington Consulting has extensive experience in flood risk management and we are adept at appraising the risk of flooding to a site, which can occur through a variety of mechanisms including; flooding from rivers, the sea, groundwater, surface water runoff, sewers, reservoirs and other man-made sources. Herrington Consulting provides professional Flood Risk Assessment services to NPPF (Formerly PPS25), SPP7 and TAN15 standards throughout the United Kingdom, with an excellent success rate.

Our clients range from private individuals, looking to create a single dwelling, to major developers aspiring to construct a large number of properties. We also work closely with local authorities and other government organisations, providing advice on flood risk and helping to develop strategies, schemes and mitigation measures to reduce the impact of flooding.

Our key aim is to help our clients develop sustainable and appropriate developments, and secure planning permission, whilst at the same time providing robust advice to enable our clients to gain a better understanding of the risks associated with flooding.

Numerical Modelling

Although some Flood Risk Assessments can be relatively straight forward, others may require more detailed analysis to be undertaken in order to quantify the type, depth and velocity of flooding at a site.

To ensure that the most suitable and cost efficient methodology is employed for our clients, Herrington Consulting utilise a suite of state-of-the-art numerical modelling software to provide accurate, high resolution flood data and animations for a range of flood scenarios.

Our modelling suite includes:

  • 1D and 2D river models
  • Coastal breach models
  • Wave overtopping models
  • Coastal morphology models
  • Wave transformation models
  • Nearshore wave models
  • Rainfall models
  • Surface water runoff and Drainage models (including SUDS)
  • Flood comparison models

Click here to find out more about this service ›

Case Studies

At Herrington Consulting we pride ourselves on providing our clients with high quality reports that accurately appraise the risk of flooding to a specific site. Each Flood Risk Assessment is bespoke to the particular development and consequently our team pride itself on delivering innovative solutions to overcome challenging issues facing a development. Below are a few examples of the types of developments we have worked on and example case studies, the list is not exhaustive and we would advise that you contact us for a free-of-charge, no obligation, quotation to ensure that we can deliver the most suitable solution for your project.

Examples of previous projects include:

For further examples of SFRAs undertaken by Herrington Consulting visit the Case Studies section located on the Coastal Management Services Page.

Coastal Management - Case Studies ›


  1. What is a Flood Risk Assessment?

    A flood risk assessment is a study to assess the risk to an area or site from flooding, now and in the future. It also assesses the impact that any changes, or development, will have to flood risk at the site and elsewhere. It may also identify, particularly at more local levels, how to manage those changes to ensure that flood risk is not increased.

  2. When is a Flood Risk Assessment needed?

    A flood risk assessment is required if a site falls within Flood Zones 2 or Flood Zone 3 identified on the Environment Agency’s flood map in Engalnd or Wales, or in a risk area identified on the Scottish Environment Protection Agency (SEPA) Indicative River and Coastal Flood Map.

    A Flood Risk Assessment is also required if the site is greater than 1 hectare, or if the Local Planning Authority (LPA) deem it necessary, regardless of which flood zone the site is located within.

  3. Why is a Flood Risk Assessment required?

    A flood risk assessment is required to satisfy the requirements of the local Planning Policy for the location in which the development is sited. i.e. National Planning Policy Framework (NPPF) [formerly Planning Policy Statement 25 - PSS25] - in England, Technical Advisory Note - TAN15 (Flood Consequence Assessment FCA - in Wales) and Scottish Planning Policy 7 - SPP7 (in Scotland).

  4. When should the flood risk consultant be engaged?

    In many situations, the findings and recommendations of the FRA will be such that mitigation measures will be required in order for the LPA to approve the planning application. These may be subtle and not affect the scheme, however, in many cases it may be necessary to change the layout of the scheme, raise floor levels and possibly incorporate significant SuDS features. Consequently, the early consideration of flood risk can avoid abortive work.

  5. What is Planning Policy in relation to Flood Risk?

    Planning Policy regarding Flood Risk is about positive planning at all levels and is aimed at delivering appropriate, sustainable development in the right places, taking full account of flood risk. NPPF (Formerly PPS25), TAN15 and SSP7 all set out the policy approach. The key message of these planning policy documents is to avoid inappropriate development and to locate development away from flood risk whenever possible.

  6. How long does it take to prepare a Flood Risk Assessment?

    As far as timescales are concerned, we are often constrained by the 20 working-day response time of the Environment Agency/SEPA. Additionally, if other consultees are involved then we may be dependent on their turn-around times too. However, we usually anticipate that the assessment will take between 3 and 4 weeks from commission. Notwithstanding this, in some circumstances we may be able to move the process along quicker and consequently, we would encourage you to contact us directly if time is of a major concern/constraint to your project.

  7. How much does a Flood Risk Assessment cost?

    The cost of a flood risk assessment is dependent on the nature of the development and site characteristics. We provide a bespoke service and prefer to gather as much information about the site and the development as possible, to enable us to provide a competitive and accurate free-of-charge quotation.

  8. I’ve been told I only need a 'Basic' Flood Risk Assessment.

    All flood risk assessments are required to satisfy either; NPPF (Formerly PPS25), TAN15 or SPP7. In our experience, if a "watered-down", or "light" flood risk assessment is submitted then the Environment Agency’s response will often request that a full "Flood Risk Assessment that is fully compliant with Planning Policy" is re-submitted. Consequently, this can delay the application process quite considerably. Therefore, we would recommend that a Flood Risk Assessment that is fully compliant with the requirements set out in Planning Policy Statement 25 is commissioned from the start.

  9. Who is the Flood Risk Assessment submitted to?

    The flood risk assessment is submitted as part of the planning application which goes to the Local Planning Authority (LPA); which is usually the relevant district, city or borough council. The LPA then pass the flood risk assessment to the EA/SEPA. As the statutory consultee on flood risk, EA/SEPA will then advise the LPA on the appropriateness of the proposed development based on the findings of the FRA.

  10. Does the Environment Agency/SEPA write Flood Risk Assessments?

    No, the Environment Agency/SEPA do not write flood risk/consequence assessments, they do, however, comment on the content.

  11. What do the Environment Agency flood maps show?

    The Environment Agency flood maps show the risk of flooding to a particular location. There are two different kinds of area shown on the flood map and both of these areas show the extent of the natural floodplain, i.e. if there were no flood defences, other manmade structures or channel improvements present.

    These areas can be described as follows:

    • Dark blue colour delineates the area that could be affected by flooding, either from rivers or the sea, if there were no flood defences. This area could be flooded:
      • from the sea by a flood that has a 0.5 per cent (1 in 200) or greater chance of happening each year.
      • or from a river by a flood that has a 1 per cent (1 in 100) or greater chance of happening each year.
    • Light blue shows the additional extent of an extreme flood from rivers or the sea. These outlying areas are likely to be affected by a major flood, with up to a 0.1 percent (1 in 1000) chance of occurring each year.

    Although some Environment Agency maps do show some areas benefit from flood defences that have been constructed within the past 5 years, these flood defences do not completely remove the risk of flooding, as they can be overtopped, or fail in extreme weather conditions. 

  12. What do the Scottish Environment Protection Agency (SEPA) Indicative River & Coastal Flood Maps show?

    The SEPA flood maps show the risk of flooding to a particular location (in Scotland). There are three different kinds of area shown on the flood map and these areas show the extent of the natural floodplain, i.e. if there were no flood defences, other manmade structures or channel improvements present.

    These areas can be described as follows:

    • Little or no risk area - Annual probability of watercourse, tidal or coastal flooding: less than 0.1% (1:1000), i.e. less frequently than the so-called 1:1000 year flood.
    • Low to medium risk area - Annual probability of watercourse, tidal or coastal flooding: in the range 0.1% – 0.5% (1:1000 – 1:200)
    • Medium to high risk area - Annual probability of watercourse, tidal or coastal flooding: greater than 0.5% (1:200) Generally not suitable for essential civil infrastructure, such as hospitals, fire stations, emergency depots etc. schools, ground based electrical and telecommunications equipment. The policy for development on functional flood plains applies. Land raising may be acceptable.

    Although some areas shown on the SEPA maps are shown to benefit from flood defences, these Flood defences do not completely remove the risk of flooding, as they can be overtopped, or fail in extreme weather conditions.

  13. What does climate change have to do with flood risk?

    All Flood Risk Planning Policy recognises that there is an increasing body of scientific evidence showing that the global climate is changing as a result of human activity. NPPF (Formerly Annex B of PPS25), for example, provides details on the allowances to be made for climate change effects when assessing flood risk. These include increases in: sea level; peak rainfall and peak river flow, over a 100 year time frame.

  14. Why do I need a Flood Risk Assessment when the site has not flooded?

    Although a site may not have flooded in recent or living memory, it may still fall within a flood zone, which may suggest that the site could flood under an extreme event in the future. Although the Environment Agency’s/SEPA’s flood maps do not take into account existing flood defence infrastructure, they do identify that there maybe a residual risk of flooding to a site if the defences were to be overtopped or to fail. In this instance, it is still necessary to submit a flood risk assessment so that this residual risk can be appraised accurately, which in some circumstances may involve undertaking detailed numerical modelling.

  15. The development is only a change of use/extension, so why do I need a Flood Risk Assessment?

    Even if the development is only a change of use, or an extension to an existing building, a flood risk assessment may still required if the development falls within a flood zones on the Environment Agency/SEPA Flood Zone Maps and is of a certain size. This is because the risk of flooding maybe increased as a result of the development proposals.

    For example, by changing the use of a building from commercial use to one of residential use, the risk to human life is considered to be increased as occupants are to be permanently located within a flood risk area. In the case of an extension, it may be that the development results in displacement of floodwater and consequently, flood storage compensation may need to be considered.

  16. Do I need a Flood Risk Assessment if I am only extending an existing building?

    If the planning application is for a non-residential extension with a footprint of less than 250sq. metres or a domestic extension, it is not within 20 metres of main river and does not involve culverting or obstruction to the flow of a river or stream, then a full FRA may not be required. If you are unsure whether you require a FRA, please contact us and a member of our team will be happy to advise you.

  17. What is a Sequential Test?

    The Sequential Test is a decision-making tool designed to ensure that sites are at little, or no risk of flooding and are developed in preference to those areas at higher risk. The Sequential Test is a key component of the hierarchical approach to avoiding and managing flood risk.

    The Sequential Test does not technically form part of the FRA and undertaking it is the responsibility of the Local Planning Authority (LPA). In many cases we find that the LPA has sufficient information and resource to apply this test, however, in some circumstances the LPA will request that the developer provides evidence to support the application of the Sequential Test.

    Our FRAs do include a brief statement on the Sequential Test, which for many small developments is sufficient to satisfy the LPA’s requirements. Some larger, or more complex sites do, however, require more detailed research into planning policy and historic applications and such work is outside of the scope of the FRA. We would, nevertheless be happy to provide a free-of-charge fee quotation for undertaking this work if required.

  18. What is the Exception Test?

    According to The National Planning Policy Framework (NPPF - Formerly PPS25), if following the application of the sequential test it is not possible, consistent with wider sustainability objectives, for the development to be located in zones of lower probability of flooding, the exception test can be applied.

    For the Exception Test to be passed there are three criteria that must be satisfied:

    • that it can be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk.
    • that the development is on developable (defined by PPS3 as a site that is in a suitable location for housing) or previously developed land (commonly known as brownfield land).
    • that a FRA demonstrates that the development will be safe, without increasing flood risk elsewhere, and where possible, will reduce flood risk overall.

    Demonstrating that the development provides wider sustainability benifits and is on ‘developable’ land is outside the scope of the FRA appraisal and is generally a decision that is made by the planning authority. Therefore, the primary focus of an FRA is to satisfy criterion (c) of the above.

  19. What is A Flood Evacuation Plan (FEP)?

    A Flood Warning and Evacuation Plan is a document designed to enable a site, shown to be at risk of flooding, to be evacuated safely – ideally before the onset of flooding. The plan aids residents to safely evacuate the site during a flood and the plan should be adopted by the owners of the building, as it includes references to the practical access/egress routes to/from the site during times of flooding. The plan also refers to the Environment Agency’s Flood Warning System and identifies how regular updates can be obtained on both a local and regional scale, through the use of media such as radio, television and the internet.

  20. What is A Strategic Flood Risk Assessment (SFRA)?

    A Strategic Flood Risk Assessment is a large scale assessment of the flood risk undertaken for the key areas within a council’s boundary. The document identifies all of the different mechanisms and sources of flooding and is designed as a high-level strategic document, to aid Local Planning Authorities supply the Sequential Test and to aid a Flood Risk Assessment to be prepared. The SFRA document will often contain an array of flood and hazard maps that cover the Council’s district/borough etc. and will also identify any specific planning policies that relate to the risks that have been identified.

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