When new buildings are planned, it is important to consider the impact this may have on flooding. This page explains how the council helps make sure new developments are built in a way that does not increase flood risk, particularly from surface water (rainfall).
What does the Council do in relation to planning and flood risk?
Cambridgeshire County Council is a Lead Local Flood Authority (LLFA). This means we review planning applications for major developments to ensure they manage their surface water appropriately. The rules for what qualify as a major development are set out in planning law, called the Town and Country Planning (Development Management Procedure Order) (72 pages, opens as PDF at gov.uk).
When we are consulted on a major planning application, we look at:
- How rainwater will be managed on site
- Whether surface water flooding could increase as a result of the development
- How any existing surface water flood risk will be managed safely
- How the effects of climate change are accounted for
- How surface water leaving the site will be of adequate water quality before entering the receiving waterbodies
In reviewing these applications, we use policy and guidance including:
As a householder, what do I need to do?
If you are planning small changes to your home or garden, it is important to think about flood risk and surface water drainage. Even small changes can affect how rainwater flows, not just on your property, but for your neighbours too.
If water cannot soak into the ground or drain away properly, it can cause surface water flooding. Things like new paving, extensions, or garden buildings can stop water soaking into the ground, push water towards buildings or neighbours and overload drains during heavy rain.
Thinking about drainage early can help reduce flood risk and avoid problems later.
You should:
- Check where rainwater will go – try to make sure it soaks into your garden where possible and does not run onto roads, neighbouring land, or your own house.
- Use simple drainage solutions – consider soakaways, water butts, or permeable paving (which allows water to pass through it).
- Check whether permission is needed – some work may require planning permission, building regulations approval or permission to work near a watercourse. This is more likely if you live in a flood risk area or you are altering ground levels. If you are unsure, check with your local planning authority before starting.
As a developer what do I need to do?
All developments, large or small, can affect how water flows across land. Developers are expected to design schemes that manage surface water safely, do not increase flood risk, and follow national and local policy. Early consideration of flood risk and drainage helps avoid delays, redesign, or refusal at the planning stage.
We have published specific guidance on the preparation of surface water drainage strategies for planning applications. This provides information on the level of detail we require, depending on the type of planning application.
This Surface Water Planning Guidance (50 pages, 1.04MB, opens as PDF) document should be used by all developers and their consultants.
Pre-application services
To provide additional support to developers and their consultants we offer a pre-application advice service for all scales of development. We offer:
- Written advice only - most suited to developers who have already advanced quite far with their drainage strategies and are looking for a review of their proposals.
- Meeting with LLFA Officer and written advice – most suited to developers who have ideas about how to approach their drainage strategy, but who would like to discuss the detail with officers. Each meeting is followed up with a written summary of the meeting.
- Free telephone advice – a 15-minute call to discuss surface water drainage proposals. These calls are with a Lead Local Flood Authority officer and are suitable for all application stages. To book a call please email FR.Planning@cambridgeshire.gov.uk.
The pre-application advice service is structured to provide ‘in principle’ feedback on proposals as well as more detailed discussions and negotiations on a scheme prior to formal submission of a planning application.
To take up our pre-application service, please complete the online application form below, this includes full details of the charges.
How Sustainable Drainage Systems (SuDS) help manage rainwater
Sustainable Drainage Systems (SuDS) are a way of managing rainwater safely and naturally. They help slow water down, soak it into the ground, and reduce the risk of flooding.
SuDS have a wide range of benefits. They can reduce flooding, protect the quality of rivers and streams, support wildlife and make places greener and more pleasant to live in.
They can be used in new housing developments, roads, car parks, schools, public spaces, gardens, and small building projects. Examples include:
Soakaways
These are underground features to help rainwater soak into the surrounding ground. They work in areas where soils are made up of gravel or chalk. They do not work where the ground is clay.
SoakawaysGreen Roofs
These are roofs with plants growing on them. They allow rainwater to be stored and treated whilst also providing biodiversity benefits.
Green roofPermeable paving
This is paving that allows water to pass through the gaps into the ground. Once the water has drained through, it can either soak into the ground or flow into underground tanks and pipes to be carried away in a controlled manner.
Permeable pavingSwales
These are shallow grassy channels that guide water slowly. They can also be used to encourage water to soak into the ground. If the swales are planted with the right vegetation, they can also filter water to improve its quality.
SwaleBasins and ponds
These are areas designed to store water during storms and release it slowly in a controlled way. Some hold a small amount of water permanently and others remain dry most of the time, only filling up during extreme rainfall.
Basin and pondSuDS Case Studies
There are lots of examples of SuDS across Cambridgeshire - some of these can be seen in the case studies below:
