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Flood Risk Assessment For Planning Applications

For Housing, Commercial & Industrial Developments

Our Flood Risk Assessment Reports

Our site specific Flood risk assessment assesses all flood sources. The flood risk assessment complies with all flood risk legislation.

Our flood risk interventions safeguard your site from flooding. 

The Environment Agency and local planning authorities approve our detailed flood risk assessments. We use the most reliable data.

The flood risk assessment cost is as follows:

Flood Risk assessment Minor Development

Minor Development

From £650.00
Less than 9 dwellings. Industrial/office units smaller than 3,000 sqm

Flood Risk Assessment Major Development

Major Development

From £1,850.00
More than 10 dwellings. Industrial/office units bigger than 0.5 Ha.

Flood Risk Assessment Strategic Development

Strategic Development

£ on application
Infrastructure projects as part of strategic sites

First Report ready in 48 hours to validate your planning application 

Our Clients

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How do we Work?

UrbanWater Go Head Flood Risk Drainage

Go Ahead​

Contact the Environment Agency. Get to work on your flood risk assessment report.

Urban Water Initial Finding Flood Risk Drainage

48 Hours Later

You receive a preliminary flood risk assessment with initial findings.

Urban Water Submit Report Flood Risk Drainage

Submit our Report

Submit flood risk assessment planning to validate the planning application.

Flood Risk Assessment

Consultations

Obtain flood levels within four weeks. Submit final flood risk assessment.

Flood Risk Assessment

Final Report Includes:​

Resistance and Resilience Interventions Access and Evacuation Plan Surface Water Management Principles Flood Compensations Calculations Evaluation flooding from other sources.

Case Studies

Projects

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Our Benefits

Time

We will complete our first flood risk assessment in 48 hours. Allows you to validate your planning application.

Support

We support you during the planning application. Our reports are updated as needed.

Success

We give you the best chance to get planning approvals.

No Hidden Fees

We give you a fixed price on all flood risk assessments.

Our Flood Risk Assessment Process

We work with developers, architects, and planning consultants. We develop suitable flood protection.

We provide flood risk assessments for London, England and Wales

urban water location flood risk
Obtain Project Details

We obtain your development details. Such as drawings and survey levels.

Flood Risk Assessment
Consult Databases

We collect flood risk information for all sources of flooding. 

Flood Risk Assessment
Evaluate Flood Risk

We evaluate the flood risk information. It includes flood protection as required.

Flood Risk Assessment
Liaise with Authorities

We consult the relevant statutory authorities. We obtain their appropriate approval

Our Flood risk assessment assesses all flood sources. It complies with flood risk legislation at the planning stage. This will safeguard your development throughout its lifetime.

What Our Clients Say

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Who is Behind the Company

Picture of <b>Argemiro Rivera</b>, BEng(Hons) MSC CEng MICE MCIWEM C.WEM CEnv

Argemiro Rivera, BEng(Hons) MSC CEng MICE MCIWEM C.WEM CEnv

Passion for Water, Flood Risk & Sustainability
I love to dig into complex flood risk and water engineering projects and deliver them. I focus on delivering reliable flood risk information to protect livelihoods and the environment.

Other Services

Hydraulic River Modelling

Cost-benefit river modelling for your developments that is compliant with the Environment Agency requirements.

Flood Risk Assessment

Our specialised planning consultants work to produce compliant reports for local councils.

Drainage Strategy

Drainage strategies comply with national guides and the lead local flood authorities.

Climate Change Adaptation

 Design of Green infrastructure and nature-based solutions to Zero Carbon.

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Our Flood Maps

Our flood risk map tool determines the flood risk assessment for your development.

It has all of the relevant databases. You have all of the flood risk information at your fingertips. Use your postcode and zoom in to find your site.

What can you find:

  • The flooding history of your development
  •  The flood alerts
  • Identify the flood risk by town by using flood risk map Oxford or flood risk map London.

Check out this flood risk assessment map tool

Understanding and Managing Flood Risk on Your Site (2023)

This is a complete Flood Risk Assessments guide in 2023. We use use it as our flood risk assessment template.

Yes, I’ll show you where to find the basic flood risk information

But you are also going to learn how to assess flood risk and apply the latest national guidance

So if you’re looking to improve your understanding of flooding, you’ll love this flood risk assessment guide.

Flood Risk Assessment Guide
CHAPTER 1

The Basic Concepts

In this chapter, I’ll answer the question: “What is a Flood Risk Assessment?”

I’ll also show you when a Flood Risk Assessment is required when applying for planning.

Let’s get started

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What is a Flood Risk Assessment?

A Flood Risk Assessment (FRA) is a report that evaluates the impact of different flood sources.

The flood sources can be rivers, sewers, groundwater, reservoirs, canals and surface water run-off. In this risk assessment guide, we will show how to assess and protect from these sources of flooding.

1. Flood Sources Urban Water

In England, the flood risk assessment gov page that your report should:

  1. Show how the flood risks affect the development
  2. Prove that the development type is appropriate for the location
  3. Determine the flood resistant and resilient protection
  4. Confirm that the development does not increase flood risk elsewhere

This is more that a level 1 flood risk assessment. It also seems complicated; we will go through each of these items through the blog. Each chapter in this risk assessment guide gives clear guidelines on these items.

What is a Flood Risk within this risk assessment guide?

The risk of flooding or flood risk is a combination between the probability and consequence of the flood.

Each flood source has its own probability; we compiled them for you in the table below!. This is the only risk assessment guide with the risk probability tabulated for each type of flooding.

The consequence is the impact on your development. These can be loss of use, damage to buildings or nature, loss of income, and damage to infrastructure. The BBC has created the picture below showing the impact of flooding

Impacts of flooding

Source:bbc

For each flood source, we need to determine their risk. Luckily most of this information is available online

We will show you how to find it!.

There are certain flood types that are top secret.

One of them is the internal flooding from sewers. The DG5 register is protected within the water industry.

Imagine knowing whether a house has flooded internally, its cost will drop immediately!.

Discover Water UK has cool stats about internal sewage flooding for each water company

Internal Sewage Flooding

Source: discoverwater

Private Land and Gardens sewage flood

Source: discoverwater

However, the Strategic Flood Risk Assessment from your local council can give you sufficient information to make an assessment.

On the other hand, there are flood risks that a less relevant for small housing developments. Flooding from Reservoirs is one of them.

Unless you are building a warehouse that storage chemical products or inflammable liquids. Hopefully, you will be using an expert by now!

When is a detailed Flood Risk Assessment required?

Before we start looking at how to evaluate your flood risk, we should check if you actually need a flood risk assessment. This flood risk assessment guide will help you determine the need for a flood risk assessment.

You need a flood risk assessment when:

  • Your development is located within flood zone 2 or 3 river and sea flooding; this applies to minor developments such as extensions, porches and even dormers! or had a change of use for example, it was an office, and now it is a dwelling
  • Your site is greater than 1 hectare (ha) within flood zone 1
  • Your development is smaller than 1 ha within flood zone 1, but it is affected by other sources of flooding, such as surface water drains, reservoirs, canals, and groundwater flooding.
  • The development is within flood zone 1 but is located within a critical drainage area.

When is flood risk assessment required

You might be wondering:

Where do I find all the sources of flooding information, exactly? What is flood zone 1 2 or 3?.

That’s what I’m going to cover in the next chapter of this flood risk assessment guide. Keep reading…

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CHAPTER 2

Finding Flood Risk Information - Flood Map

In this chapter, I’ll answer the question: “What is a Flood Risk Assessment?”

I’ll also show you when a Flood Risk Assessment is required when applying for planning.

Let’s get started

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How to check if your development in the river flood zone?

You can check if your development is in the flood zone by using the relevant agency flood maps.

For England, you should use the flood risk rivers and sea planning map. Get into the site and download the flood map for your site.
The flood maps will give you the basic details of the overall location of the development in the floodplain.

If you development is anywhere within the blue area then your site may be affected by flood water.

The map does not give you the flood depth at the property level.

It is possible that the level of the property is higher than the flood level!.
Flood Zones in relation to site location
The flood level is given directly by each the Environment Agency. We will show you how to order it below.

Before we move on,

I would like to explain the 4 flood zones.

  • Flood Zone 1 has the lowest probability of flooding (less than 1 in 1000yr)
  • Flood Zone 2 has a medium probability (btw 1 in 100 and 1 in 1000yr)
  • Flood Zone 3a has a high probability (higher than 1 in100yr)
  • Flood Zone 3b ( higher than 1 in 25yr)

The higher the probability, the more likely your site will flood. For instance, flood zone 3b is usually the river bed.

I created this short video; hopefully, it will explain better.

How to obtain the river flood levels?

You need to send an e-mail to enquiries@environment-agency.gov.uk with the site location plan including the obtain the flood levels for free.

Site Location Plan request flood levels

You will get the results within 20 working days.

Risk Assessment Flood Risk From Surface Water

The Surface Water flood risk map is produced by the Environment Agency.

You can access this map by entering the postcode and then following the link to the surface water map.

Once you get to the map, you will notice that the drop down menu in the flood risk has different options.

Surface Water Flood Risk Map

These options relate to the risk of surface water. From this drop-down menu we are only interested in extent and depth (high, medium or low)

Risk Assessment Flooding Risk From Reservoirs

The maps showing the risk from reservoirs are also part of the Environment Agency’s datasets.

This map is part of the drop-down menu of the Surface Water Flood Map

Flood Risk from reservoirs

We are only interested in the Extent item

Flood Risk From Sewers and Groundwater Flood

It is not possible to find online whether a property has been flooded internally.

It is possible to get an idea of the number of flooding incidents in your neighbourhood

To do this, you should find your local council

Strategic flood risk assessment find local council

Enter your postcode, and you are in. Follow the link to the city council/borough council or district council.

Find your local council

Search for Strategic Flood Risk Assessment

Sometimes is better to search for it on google once you know the local council.

Strategic flood risk assessment search local council

Once you get to the document. You need to identify the appendices where the information is available.

Oxford Strategic Flood Risk Assessment

In this case, the information we are after is in appendix A and B

Strategic flood risk assessment table of contents

The appendices in the Strategic flood risk assessment usually don’t have sufficient detail to make an assessment of individual properties.

They give us an indication of the potential flooding.

In some councils, all this information is digital. Such as in The West London boroughs of Brent, Barnet, Ealing, Harrow, Hillingdon and Hounslow.

Risk Assessment Critical Drainage Areas

Critical drainage areas are the most difficult areas to identify when completing a flood risk assessment.

In theory, there should be a list from the Environment Agency with all the critical drainage areas.

It is possible that such a list exists, but so far, it has not been found.

The EA has produced a map showing a partial recount of the critical drainage areas.

Critical Drainage Area Environment Agency

The best way to find the critical drainage areas is by looking at the strategic flood risk assessments.

The critical drainage areas cover most of the town.

Critical Drainage Areas

Now, we have all the information to make an initial flood risk assessment for planning.

Which leads us to our next topic…

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CHAPTER 3

Assessing Flood Risk Information

By now you should have the following info:

  • Flood Risk River and Sea Map – Done
  • Product 4 – Done
  • Surface Water Map – Done
  • Groundwater Maps – Done
  • Critical Drainage – Done

This step-by-step flood risk evaluation will give you sufficient information to complete a basic flood risk.

In short, you will know the level of risk that of your development

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Assessing Flood Risk For Rivers and Sea

This assessment varies substantially depending on the flood risk vulnerability classification of your development and whether you site is affected by a tidal river, protected from a flood defence.

Something to note. This assessment is only my technical opinion based on the experience when dealing with the local councils and the Environment Agency.

I have prepared it to give you guidance and to make you aware of the complexities of assessing flood risk.

The first key item to determine is the flood level Let’s get down to it.

The Flood Risk Vulnerability Classification

The Planning Practice guidance gives us the the vulnerability of the development. This is applicable for a local planning application. 

You just need to know the use of your development and check out the tables below.

For example, if you project is building wind turbine, your development vulnerability is “essential infrastructure”.

You can click (>) on the table below to find more development such as housing (which is more vulnerable).

Now, that you have the flood risk vulnerability classification. You can check the location of the site within the flood zone

Site Location within the Flood Zone – Planning Application

There are two set of data to determine the flood risk

  • The environment agency flood map for local planning
  • The product 4 information

The Environment Agency flood map for local planning shows that this property is in flood zone 3

Environment Agency flood map for planning

The flood maps for local planning gives us an indication of the flood risk however it does not take into account the properties floor level.

We now need to check the flood level in relation to the property.

In some cases, specially if the development is near the edge of the flood zone, the site can be outside of the flood zone.

Flood Levels

Flood Levels are given by the product 4 information (already requested above).

If by any reason, the EA has given you the product 4 information. Then a river modelling should be undertaken.

The flood level is independent from flood defences. Even if your site is protected by flood defences the assessment should take into account the flood level.

The product 4 information gives flood levels at certain nodes, these nodes are noted on Maps

Environment Agency Product 4 Map

and also tables

Environment Agency Product 4 Table

From the product 4 information pick the flood level related to the 1% AEP level from the table flows and levels

Use the point closest and most perpendicular to your site, if it is possible.

This is one contentious element when dealing with the Environment Agency.

On tidal rivers, the development are mostly protected by a flood defence to a suitable climate change allowance.

This makes the flood level less important as tidal water should be contained by the flood barriers.

The level to take is the Breach Water level (Inundation level) and the hazard flood maps. Let’s continue reviewing this flood risk assessment guide

Climate Change Allowance

Climate Change allowances depend on the flood vulnerability classification, the lifespan of the development and the river catchment where the development is located.

The EA has a detailed guide on assessing climate change how to make the assessment.

You need to use the Peak River Flood Map, enter the post code and the determine the climate change allowance.

Pro tip: Zoom in in the map and locate your property as the post codes can fall in multiple catchments.

Climate Change Allowances Flood Risk

Depending on the risk vulnerability of your development and the lifespan you will need to assess the Upper, Central or Higher

Key principles:

  1. The 20% increase in river flows is no longer in use
  2. For dwelllings you will be looking at 25% to 70% climate change increase
  3. You should assess the 2080 levels and its impact on the housing development. For temporary developments you can use the 2050s only in agreement with the Environment Agency
  4. You can obtain the climate change flood level by creating a discharge level curve. The curve is an extrapolation the flood levels (intermediate assessment) using the flow (m3/s) and the water levels (in mAOD).

In some cases you can use the basic assessment in which the EA gives you the depth that can be added to your flood level.

This information should be within the product 4 pack otherwise just use the levels for 35% and 70%

Pro Tip: Agree with the EA the type of assessment required before proceeding to the assessment.

Now we have our Flood Plus climate change allowance level.

We are ready to stablish in which flood zone our development is located. Now this flood risk assessment guide will show you how to do this.

Comparing the Flood Levels and Site Levels

The flood levels need to be compared against the ground levels and the levels of the property.

You can do this completing a Topographical Survey

Topographical Survey Flood Risk Zone

We can also determine the ground levels by using LIDAR data from the Environment Agency or LIDAR data for other suppliers

LIDAR data flood risk zone 3

The LIDAR data is not as reliable as a topographical survey but it allows to identify the flood risk in the development at an early stage and without investing substantial money.

Now that you have the flood levels and the levels at the property, You can confirm if your place is located within Flood Zone 1, 2, 3a or 3b.

Flood Risk Compatibility Assessment

You can now use the location of the development in the flood zone and the flood risk vulnerability of the development to check if your development is considered to be inappropriate or an exception test is required. The local planning team will review this assessment in relation to the development’s use. 

If your development is considered to be inappropriate for the flood zone within which the site is located, then planning permission would normally be refused.

Assessing Flood Risk For Surface Water Run-off

The surface water run-off maps were not made to determine the flood risk at a property level.

It just gives us an indication of the potential flood within the area surrounding the property.

Surface Water flood risk areas

In this picture, it shows that area around the property is at risk of surface water flooding.

Although we can see that the property is within the medium to low risk of flooding. We can’t take this as a given.

This data does not take into account the location the location of sewers, drainage channels, pumping stations that can reduce the impact of the flooding.

Nevertheless, we can see the potential flow paths of water.

We can now look at the Medium flood risk depth.

Surface Water flooding Medium flood risk

It shows that the gardens have depth of flooding up to 900mm deep.

We now look at the depth for low risk

Surface Water flooding Low flood risk

The low risk depth also shows that depth of flooding is up to 900mm and occupies most of the properties gardens.

We can conclude that there is a high likelihood that there is a water path on the gardens and that the level of the house is outside of the potential surface water path.

Assessing Flood Risk For Groundwater

You should look at the register of groundwater flood incidents and the flood water susceptibility map produced for the Strategic Flood Risk assessment. You will need a flood risk assessment report that is in compliance with the Environment Agency.

Oxford groundwater flooding incidents register

If this information is not available you can download the groundwater susceptibility map from BGS map showing the likely hood of groundwater flooding.

Groundwater susceptibility map

Groundwater flood risk is divided into 3 levels. Potential GW flooding Below Potential GW flooding Above and Limited potential for GW flooding. In this flood risk assessment guide we will not get into the detail as its control will be part of the flood resilience blog.

These 3 levels should be used as a guide to undertake more investigations such as boreholes in order to provide further information on:

  • The proposed development’s groundwater flood risk
  • You should look at SUDS methods also need to be considered as part of the assessment and limited permeability may not be suitable for infiltration SUDS
  • Depending on the construction of the development, you should also look at the construction methods which may interfere with groundwater flood risk and affect flood risk to adjacent

And finally, you should include the effects of climate change that may have on the water-table and how this could affect the groundwater within the development

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CHAPTER 4

Managing Flood Risk

Managing flood risk is one of the important elements in a flood risk assessment.

And for good reason:

If you can’t manage the flood risk you can’t have a development

And as for the development, it has a direct impact on the layout and architectural design of the buildings.

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Flood Risk For Rivers and Surface Water Management

For this flood risk assessment guide, the golden rules are:

  • Aim to stablish the final floor level of the new houses as high as possible from the flood level+ CC if you can.
  • Create space for water, allow for flow paths and integrate water within the fabric of the development
  • You can break up your development user allow for less vulnerable areas (shops etc) closer to the areas at higher risk of flooding.

Raised construction Hafencity Hamburg Mathieu Schouten

Determining the Final Floor Levels of Dwellings

In general, there are two options of final floor levels.

The options depend on the water compatibility of development.

Option 1: Avoidance. Lifting the FFL 300mm above the 1% AEP + CC (allowance)

This approach is used for more vulnerable developments and developments where access is not compromised.

Option 2: Water entry, resistance, resilience or repairable. The FFL is the same as the ground level.

We use this approach mostly for water-compatible developments and small extensions.

The water resilience design should follow the detail given in the Improving the Flood Performance of New Buildings Flood Resilient Construction document.

Improving the Flood Performance of New Buildings

Creating Space For Water

In this area, you will need to look for options to integrate green areas, evacuation routes and the flood zones

There are great examples in the Netherlands and in Germany about integrating flooding within the build environment.

Flood management HafenCity Hamburg

 

meander medical centre

 

Flood Risk From Groundwater Management

Groundwater flooding although is not as prevalent, it is a complex issue.

I suggest if you a building a basement within an area of potential (above or below) for ground water flooding. Then an site investigation is undertaken as early as possible.

If you have a site that has potential for above groundwater flooding, then work should be completed to clearly allow for potential for this flooding.

For instance by locating the ground floor well above the ground level or building a concrete slab and allow for flotation.

Flood Risk Mitigation within Critical Drainage Areas

The mitigation within critical drainage areas depends on the prevalent flood risk. i.e. surface water run-off, groundwater or sewerage flooding.

In most cases, it relates to a combination of these three flood risks with a greater emphasis on sewerage flooding.

You can mitigate the impact of surface water sewer flooding by providing a sustainable drainage systems that has adequate capacity to manage and control this flood.

Critical Drainage Areas SuDS

You can also alleviate the foul sewer flooding by providing sufficient capacity and non-return valves or pump NRVs for your site.

Critical Drainage Non return valve
Critical drainage areas Pump NRV

Site Access and Egress

Safe Site access and egress must be provided for all developments affected by flooding.

The evacuation paths should be above the 1%+CC or the breach flood levels +CC.

In order to evaluate the safe paths, you should use the also use the flood water depth and velocity together with the flood risk hazard map provided by the Environment Agency in the product 4 package.

Flood risk assessment flood risk hazard map

The flood hazard map should be compared against the hazard to people in relation to flood depth and velocity matrix

Flood Risk Hazard table classification

The different classifications will have an impact on the users of the site

Flood Risk Hazard to People Function of Velocity and Depth

This categorisation help us to determine the planning of safe access and exit for your development.

If you have a site that it is not possible to safely exit or access the site.

Then you could look at designing a ‘safe haven’. This is the most likely scenario in areas where there is a flood defence breach.

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CHAPTER 5

Assessing Off-Site Impacts

Now that you have managed the flood risk on you site.

We are going to determine the off-site impacts.

By the way this is set out in the NPPF

There are 3 items that you need to look at.

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Surface Water Management

Include the use of Sustainable Drainage Systems in your development. In this flood risk assessment guide, we can see that the basic drainage parameter can be established by knowing the soil condition, proximity to a watercourse and flood risk, let’s dive in.

Sustainable Drainage System Flood Management

You don’t need to calculate the volumes and areas

You should give the principles of draining the site using Sustainable Drainage systems.

Did you know your local water company will give you a wastewater management discount if the SuDS are adopted.

Ideally the SuDS should reduce the run-off to the greenfield flow rate. Each LLFA has their own standards!.

SuDS also help on flood conveyance and also in the management of flood and movement of water (conveyance) within you site.

Flood Flow Conveyance

It refers canalisation of flow in your site which in turn affect areas up and down stream of the site,

The University of Tulane has created an article explaining the type of channels.

Flood flow conveyance straight channel

Tulane University

The key is to avoid is straight, deep and smooth channels in the river network. The channel can sometimes be created by roads or retaining elements.

For complex site, it is recommended that a 2D model should be created to determine the flood conveyance risk. You can see the results of our flood modelling below. We have our services flood for additional information of the flood conveyance.

Flood flow conveyance 2D modelling

Now we move to calcualte the storage volume taken from the flood zone

Flood Compensation Storage

This is one of the most contentious items with the Environment Agency.

As Flood Compensation should be level for level and should take into account how water enters and leaves the flood compensation areas.

Level per level compensation, is complete by creating cross sections and slices every 200mm showing the volume taken and the volume “created” at the same level. The easiest way is to create a 3D model of the site.

Flood Compensation volume

For small developments, a cross section showing the levels is usually accepted by the EA.

How water enters the compensation volume is important as it also has an impact on the river flow during time of flood.

Flood Compensation is provide to the level of 1% (1 in 100year) + Climate Change. For flood compensation under buildings and structures

The Environment Agency prefers to have voids 1m wide every five meters on all sides of the building.

Some local councils, may allow compensation at small depths under the buildings.

This is usually when surface water flooding is very deep and there is sufficient space (more than 1.2m ) under the building’s floor.

This flood risk assessment guide is based on the most up-to-date feedback received when submitted our flood risk assessments.

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CHAPTER 6

Determining Residual Flood Risk

The residual flood risk refer to

  • Site access and public safety and Flood Warning and evacuation Let’s dive into it.
  • We almost have assessed flood risk for a site
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Site Access and Public Safety

Safe access should be provided above the 1% +CC level. This is applicable to all new site with new dwelling houses.

The increase in surface water could be seen as a increase risk on public safety , specially in areas of high surface water levels.

Include SuDS and you development will be ok.

Flood Warning and Evacuation

Check that the development is in an area with the service to receive early warnings of imminent flood hazard.

Create a Flood Warning and Emergency Response Plan for the site.

Frequently Asked Questions

A flood risk assessment is a process used to identify and evaluate the potential hazards and consequences of flooding in a specific area. The assessment is used to determine the likelihood and potential impact of flooding and to develop strategies to manage and mitigate the risks.

The process typically begins with a thorough analysis of historical flood data and current hydrological conditions. This information is used to create a flood hazard map, which identifies areas at risk of flooding. The assessment then considers factors such as the area’s topography, the local infrastructure’s type, and condition, and the area’s population density and demographics to determine the potential consequences of a flood. In a site specific flood risk assessment the use of the buildings are evaluated agains the impact of the flooding on the users.

Once the hazards and consequences have been identified, the assessment will consider various flood management options. This may include physical measures, such as building flood defences, water resistance and resilience interventions to building and infrastructure, or non-structural measures, such as creating evacuation plans and educating the public about flood risks.

The final stage of the assessment is to evaluate the proposed flood management measures’ effectiveness and make recommendations for further action. This may include ongoing monitoring and maintenance of flood defences or implementing new policies to reduce the risk of flooding.

Overall, a flood risk assessment aims to provide a comprehensive understanding of the potential hazards and consequences of flooding in a specific area and to develop effective strategies to manage and mitigate those risks. It is a critical step in protecting communities and infrastructure from the devastating impacts of flooding.

A flood risk assessment is required when a site is located within an area at a medium to high risk of flooding.  You can check the flood maps.

The National Planning Policy Framework (NPPF) ) aims to move properties away from flood-risk areas. The flood risk assessment should assess low-risk flood sites.

A level 2 flood risk assessment refer to a desktop assessment of risk. A level 3 flood risk assessment relates to the creation of a river model.

The Environment Agency approves Flood Risk Assessments.  They use the National Planning Policy Guidance. The local council will likely provide feedback on the Flood Risk Assessment if your project is an extension.

A Flood Risk Assessment (FRA) is a requirement for any development proposed to be built in a flood-prone area, as determined by the Flood Zone map and flooding for other sources maps. The Flood Zone map is created by the Environment Agency, the government body responsible for managing and protecting England and Wales from flooding and coastal erosion.

Flood Zones 1, 2, and 3 indicate the flood risk level in a specific area. Flood Zone 1 has a low probability of flooding, Flood Zone 2 has a moderate probability of flooding, and Flood Zone 3 is considered to have a high probability of flooding.

When trying to obtain planning permission, an FRA is required if the site is within Flood Zone 2 or 3. However, an FRA is also required for sites located in Flood Zone 1 or greater than one hectare. This is because, although the probability of flooding is considered low, there is still a risk of flooding from other sources.

Examples of different sources of flooding include groundwater flooding, which occurs when the water table rises, and water enters the ground and can affect buildings, infrastructure, and the surrounding environment. Surface water run-off occurs when rainwater is not absorbed into the ground and runs off into rivers and streams, causing them to overflow and flood. Critical drainage areas are areas where the water table is high, drainage systems are under capacity and the soil is poorly drained, making them more susceptible to flooding.

The FRA should also consider the potential impact of climate change, which can increase the frequency and stringency of extreme weather circumstances such as heavy rainfall and flooding. Therefore, an FRA must be conducted to identify and evaluate the potential hazards and consequences of flooding and to develop strategies to manage and mitigate the risks.

It takes 20 working days to get flood levels from the Environment Agency. The Environment Agency flood team supply the latest flood levels.

A hydraulic model mimics the movement of water over a surface using.

The model uses hydraulic equations and LIDAR data.

The hydraulic models provide all levels, velocities and volumes of water.
See how we complete our hydraulic models.

• Obtain the address of the property and create a site location map.
• Email to enquiries@environment-agency.gov.uk , provide your contact details and request flooding history.
• Use our flood risk map.
• Contact the local surveyors and property agents to request property details.
• Use the internet or local newspapers.

Yes. Canals flood when the flood river levels are high and do not allow the canal water to discharge freely.

Canal floods are less likely to occur as weirs control water levels in the channel. Despite this, canals that overtop have a higher risk to users and properties in their vicinity.

A high-risk flood area is flood Zone 3. Flood Zone 3 is where the river flows and flood water is stored. It is uncommon for basements and critical infrastructures to receive planning approval (even with a flood risk assessment) in these areas.

Global warming increases the chances and consequences of flooding.

Climate change means that the current flood levels would rise by at least 600 mm (2 feet) in some areas!

The models provided by the Environment Agency allow for 30% and 70% climate change.

A flood risk assessment should include:

  • Site Location of the development site.
  • Review of the local Strategic Flood Risk assessment.
  • Apply the sequential test or standing advice.
  • Evaluate and manage flood hazard assessments, including flood defences, surface water run-off, areas with critical drainage problems and groundwater.
  • Evaluate the off-site impact of the flood risk.
  • Take into account the impacts of climate change.

This is the main government guidance

You need a flood risk assessment if your development is in Flood Zone 3 or 2 or if your site is more than 1Ha located within Zone 1.
You also need a flood risk assessment if your development is less than 1 ha, is affected by surface water or groundwater, or is in a critical drainage area.

A Flood Risk Assessment takes 48 hours to complete.

The initial flood risk assessment does not have flood levels.

But it allows you to register the planning application.

The final report with levels takes 25 days to undertake. The Environment Agency releases the flood level information within 20 working days.

For Scotland, the SEPA has produced their flood information.

Flood Zone 1 means that the river flood level of risk for your development is low.

The site only needs a flood risk assessment if it is more than a hectare or affected by other flooding sources.

 It is possible to build within flood zone 3a. You can extend your house or create a development that fully integrates flooding. It is very unlikely for new buildings in flood zone 3b to be built.

The mitigation strategy must comply with the following:

  • CLG 2007 Improving the Flood Performance of New Buildings publication” for new buildings
  • Preparing for floods, Interim Guidance for Improving the Flood Resistance of Domestic and Small Business Properties for existing buildings.
Compensatory flood storage is your site’s volume taken from the Flood Zone. The compensation must be provided level by level at 100mm intervals. The compensated volume must be greater than the volume taken from the flood zone.