What is a Flood Risk Assessment
A Flood Risk Assessment (FRA) is a systematic process which aims to identify the sources and level of flood risks of a property or site. The UK Environment Agency requires property investors and developers to complete an FRA prior to development within key flood zones.
This article covers 1) when you need to perform an FRA; 2) what is involved in an FRA; and 3) template reports you can use to prepare for your FRA.
Click this link to download flood risk assessment templates instantly.
When to Perform an FRA
All UK property developments within a medium to high probability flood zone require an FRA to be completed. Each flood zone represents a probability of river and sea flooding, ignoring the presence of defences. Find out which flood zone your development is in using the UK Environment Agency’s online tool.
What is involved in a flood assessment
Completing a flood risk assessment involves a systematic process before proceeding with any major decision. Here are the three essential stages in conducting a comprehensive flood risk assessment:
Stage 1: Flood Mapping and Planning
Once you have identified that you are within a medium to high probability flood zone you will begin with the planning and preliminary assessment stage. This stage includes detailed mapping of the proposed development site with a focus on areas at risk of flooding. It also involves a review of floods that have taken place and floods that could take place in future.
Stage 2: Identifying Sources of Flood Risks
The most essential part of completing an FRA is to determine the vulnerability of the site or property from any flood occurrences. Flood risks can be both natural or artificial.
Here are 8 major sources of flood risks to look out for during flood assessments:
- Fluvial - also known as river flooding, this occurs when a nearby river or stream was not able to take on water causing an overflow above its banks down to the mainland.
- Coastal - this occurs due to bad weather conditions such as high tides, storms and surges which rises sea water levels.
- Canals - flooding occurs when canals are impounded above surrounding ground levels and when retaining structure fails.
- Groundwater - this occurs when water table rises above ground elevations and usually after a long period of continuous rains.
- Reservoirs and Water bodies - large water bodies or reservoirs are used to retain water in times of flood. However reservoirs and water bodies could overtop which can lead to rapid outpouring of water to floodplains.
- Pluvial Runoff - a gradual flooding of low-lying areas after prolonged and intense rains. This happens when soil infiltration and drainage infrastructure capacities are overwhelmed and inadequate.
- Sewers - sewer flooding are due to excessive flows or blockage in the infrastructure such as manholes and gullies, which can also generate overland flows.
- Effect of Development on Wider Catchment - catchments or watersheds are areas of land where a river or lake collects water from rain. Development with catchments can increase flows into sewer networks.
Stage 3: Flood Risk Mitigation
The final stage of an FRA is to set out mitigation measures to address and reduce flooding risks within acceptable levels. This includes installation of flood defences to control potential negative effects of flood waters, managing residual risks, and improving water systems and infrastructure.
Capturing Flood Risks with a Powerful Mobile App
iAuditor is the world’s #1 mobile inspection app you can take anywhere to capture sources of flood risks. Take photo evidence of flood risks, record detailed notes, and generate comprehensive reports on the spot.
To help you get started we have created this free flood risk assessment template you can download and customize. Click here to see an example completed report.