The SRA’s catchment approach
The SRA will take a catchment-based approach. A catchment is an area of land from which water - especially rainwater - drains and flows down into streams, rivers, lakes and often the sea.
Somerset's five main river catchments are the Tone, Parrett, Axe and Brue, the Somerset Frome (also known as the upper part of the Bristol Frome), and West Somerset Streams. Pictured at the top of this page is Cheddar in the Axe catchment.
Parts of the River Exe headwaters, the Dorset Stour and East Devon catchments also flow out of Somerset.
We will analyse catchments to understand problems with excessive amounts of flood water, we will select issues about which the SRA can do most in line with our objectives, and we will fund proposals which duly benefit Somerset people and places.
Approaches will be taken which balance investment between upper, mid and lower catchment areas, and combine different measures. For instance, in general terms, SRA partners may seek to slow the flow of water down through upper catchments, store it in mid-catchments, and through lower catchments convey it safely out to sea or - when and where conditions are right - let it spread over floodplains.
We will draw together on a wide range of insights won through years of carrying out and assessing many different techniques of land, watercourse and infrastructure management, and of working with communities, businesses and special environments.
The ideal sought is to have right amounts of water in right places at right times, while recognising that definitions of ‘right‘ will always be subject to negotiation, compromise and what in practice it is possible to achieve.
To support our catchment approach and inform future funding proposals to the SRA we are preparing summaries of the five main catchments in Somerset.
Our catchment analyses include:
- Catchment descriptions
- Summaries of specific local flood issues
- Maps showing areas at risk of flooding
- Indications of key infrastructure
- Details of SRA-funded schemes and activities in the catchment
- Notes on SRA-funded studies that could lead to SRA-funded works
- Notes on works planned by SRA partners
- Areas of opportunity for the SRA
These sub-catchment overviews will be key documents shaping SRA-funded activities. Proposals to the SRA for funding will have to show how they tackle issues of interest to the SRA and support SRA objectives.
The SRA wants to fund projects that are integrated with other relevant actions across catchments and tackle flood risk from many angles. We want more working together across organisations, leading to the cost-effective delivery of schemes and activities that have multiple benefits.
Each year as we develop a programme of works, we will bring together our partners and key stakeholders. We will understand what is already being done and identify where – with SRA help – more can be done.
The expertise and knowledge of SRA partners and stakeholders will be crucial to the success of this approach.
Catchment issues and types of work
Listed below are examples of different types of works generally thought suitable for different parts of catchments, as responses to some common problems.
Uplands and hills
Common issues
Sheets of water flowing overland; localised surface water flooding; flooding from small watercourses.
Possibilities
Increase the volumes of flood water that can be stored and held back in features such as ponds and swales.
Work with farmers and landowners to reduce runoff, for example through better soil management so that more water can percolate into the ground.
Slow the flow of water down to vulnerable areas by using techniques of Natural Flood Management (NFM), such as forming woody dams and planting trees and hedgerows.
Mid-slopes
Common issues
Fast runoff causing flash flooding, particularly during intense periods of heavy rain.
Undersized channels and undersized structures such as bridges can make problems worse, especially if there are also blockages.
Possibilities
Work with farmers and landowners to store water and slow its flow.
Maintain and improve watercourse systems and structures, for example by removing blockages, increasing capacity or diverting water in suitable ways.
Support flood resistance and resilience measures for properties.
Improve flood warning systems.
Lowlands
Common issues
Flooding from rivers overflowing their banks, often for a long time, because of extended periods of rain or combinations of events.
Problems are worsened - particularly in areas below high-tide / river / flood bank level - if outfalls to the sea become tide-locked and drainage systems get overwhelmed.
Possibilities
Maintain and improve watercourses, flood banks and associated infrastructure such as pumping stations, and increase capacity where feasible.
Consider land use changes, such as growing climate-resilient crops, or paying farmers and landowners to store floodwater.
In the longer term, consider restoring natural watercourses and floodplains and providing more space for water, as part of agreed moves towards adaptation.
Urban areas
Common issues
Flash flooding because of surface water running off from impermeable areas (such as concrete, tarmac, and hard paving) and a lack of capacity in drainage systems and small watercourses.
In built-up areas nearer the sea, water can back up in rivers and drainage systems because of high sea levels.
Possibilities
Identify capacity issues.
Maintain and improve drainage systems and small watercourses, for example by removing blockages, increasing capacity, and retrofitting Sustainable Drainage Systems (SuDS) for more natural ways of storing and conveying runoff.
Discourage paving over domestic gardens with impermeable surfaces and encourage SuDS techniques, like de-paving and using water butts.
Improve flood awareness, resilience and adaptation.
Catchment-wide
Common issues
All types of flooding; community resilience and adaptation; strategic road network and infrastructure resilience.
Possibilities
Work with communities to help them better help themselves, for example by setting up flood action groups to identify and tackle local flooding problems (for example, through doing suitable maintenance tasks) and to support each other after a flood.
Work with riparian owners (who own land next to rivers) to help them understand and fulfil their responsibilities effectively.
Along roads, assess any drainage blockages, maintain and improve.