How we plan and prioritise our flood risk management work

We take a risk-based approach to managing flood risk prioritising investment to those people and communities most at risk. We do this in line with the Welsh Government National Flood and Coastal Erosion Risk Management Strategy. 

Identifying what is at risk of flooding

We use flood risk maps to help us to identify what is at risk of flooding. Although they show us areas at risk of flooding - divided into high, medium and low risk categories - they don't tell us: 

• which areas are most at risk in comparison with others 
• how flooding impacts are different if something is at risk from rivers, the sea or from surface water and small watercourses 

In order to make decisions about where we need to undertake flood risk management activities, we use a tool to help us called the Communities at Risk Register. 

How we use the communities at risk register

We developed the communities at risk register (CaRR) as an objective way for us to identify flood risk. We use it as an aid to help us prioritise flood risk management activities at a community level. 

Using the CaRR, we can compare which communities are at risk of flooding across Wales using our national scale models. A community is defined from the Ordnance Survey towns' dataset where an area is drawn around each town point to make a community. There are 2,207 communities identified this way in the CaRR. 

CaRR score 

The CaRR calculates a 'danger score' for communities in Wales. This allows us to rank communities at risk of flooding, from highest to lowest.   

It identifies and ranks individual communities in Wales for both: 

• a natural ‘undefended’ scenario, where there are no flood defences or flood warning service in place 
• a managed scenario, where there are flood defences and flood warnings in place 

We calculate the natural 'undefended' danger score using the following data:  

• flood extents: the area covered by flooding  
• receptors: what is at risk of flooding 
• hazard: how deep and fast the flood water is predicted to be 
• speed of onset: how soon after rainfall the river rises to its highest level 
• frequency: how often flooding is expected to occur. 
• social vulnerability: the vulnerability of social groups to the impacts of flooding, including injury, loss or disruption of livelihood  

To calculate the managed risk, we use the same data and include:

• data on what flood warnings are available 
• what flood defences are present in flood risk areas 

This exercise helps us understand how the danger score changes for communities where we have put in place flood risk management actions.  

The CaRR uses this data to calculate a community level danger score. We use this to rank communities across Wales. 

The CaRR methodology comes from 2006 research by the Department of the Environment, Fisheries and Rural Affairs (Defra) into calculating risk to the population based on flood hazard and the vulnerability of both people and area.  

The CaRR will not give an answer as to whether a project might be possible, nor will it consider the merits of different options to manage flood risk locally. These are considered by further detailed project work. 

What the CaRR does not include 

The CaRR does not include:

• indicative scoring for individual properties at risk - the CaRR indicates risk at a community wide scale only 
• a score for surface water and small watercourses managed risk: there is only a single undefended score for surface water and small watercourses 
• ground water flood risk - the risk of ground water flooding in Wales is not considered as significant a problem in comparison to other sources of flooding 
• reservoir flood risk - reservoirs are managed by a strong regulatory regime which reduces the likelihood of flooding to a very low level 
• flood defence failure - it is assumed that flood defences will not fail but will be overtopped if the level of flooding is higher than the defence  
• flood risk from wave overtopping in coastal areas - only still water flood levels without waves are used

How to access the CaRR

The CaRR is available as a map and Excel spreadsheet on DataMap Wales where the CaRR score and rank are shown for each community. The map is also available on the Environmental Portal. 

Updating the CaRR

The CaRR is not fixed. We have an ongoing development programme that we will use to make improvements to the CaRR that is published every two years in the spring. The next update will be in spring 2025.  

Other CaRR users

We distribute the CaRR to Lead Local Flood Authorities (LLFAs). They can use it as an aid for their flood risk management decision making. The Welsh Government use it to inform their funding allocations through the Flood and Coastal Erosion Risk Management Programme.  

How we secure funding for flood risk management work

We use our flood risk maps, the CaRR and information about which communities have experienced impacts from flooding in recent years to take a risk based approach to prioritising flood risk management projects. 

For those communities where we think a flood risk management project is needed, we undertake an assessment at a local level to understand the opportunities, constraints, costs, benefits and risks of progressing work. If we decide a project is needed following this assessment, we formalise this work through a business case developed in line with Welsh Government’s Flood and Coastal Erosion Risk Management business case guidance. 

All NRW and Lead Local Flood Authority proposed projects are submitted to Welsh Government. They are then assessed against specific criteria. This includes: 

• the level of flood risk (determined through the CaRR) 
• recent flood history (frequency and number of homes flooded) 
• other factors including the number of homes benefitting from the project 

If approved, the proposed project receives funding on an annual basis via Welsh Government’s investment into Flood and Coastal Erosion Risk Management. 

We manage our Flood Risk Management projects within our Flood Risk Management Capital Programme. The programme includes between 200 to 300 projects each year. Outcomes delivered through it include properties benefitting from a reduced risk of flooding as we build or improve flood alleviation schemes across Wales.

A significant proportion of the funding each year is used on large scale flood alleviation schemes. Other important elements of the programme include:  

• maintenance of existing flood defences 
• repair works 
• flood risk modelling projects 
• enhancing and improving critical FRM systems and services 
• investing in our network of river level monitoring stations 
• replacing the equipment required to deliver our activities, including vehicles and machinery  
• developing long term strategies for our structures in response to the Climate Emergency  

View all our flood alleviation scheme projects at Flood defence projects.

Contact us if you have feedback or would like to know more: fra.wales@cyfoethnaturiolwales.gov.uk