Sustainable drainage developments
Our statutory role
We are required to provide technical advice and guidance, to the relevant planning authority, on the:
- suitability and effectiveness of surface water drainage strategies
- designs and maintenance arrangements put forward by developers for any new major development.
Sustainable drainage systems (SuDS) aim to manage rainwater runoff in a natural way by replicating natural processes.
We will base our consultation responses on guidance from:
- existing planning policies
- National Planning Practice Guidance
- Department for Environment Food and Rural Affairs (DEFRA) latest technical standards for the design, maintenance, and operation of SuDS.
As statutory consultees, we will seek to assist the delivery of requirements of the government's National Planning Policy Framework (NPPF). This framework promotes sustainable development and makes specific requirements for the incorporation of SuDS into any new development.
Our Drainage and Planning policy statement sets out how we, as lead local flood authority (LLFA) and statutory consultee, will review drainage strategies and surface water management provisions associated with applications for major development.
New major developments
For all new major developments, as defined under The Town and Country Planning (Development Management Procedure) (England) Order 2015) we expect for it to be demonstrated that:
- appropriate SuDS systems will be incorporated as required by the National Planning Policy Framework
- the minimum standards of operation proposed by the applicant are appropriate and comply, as a minimum, with the requirements of DEFRA’s SuDS National Standards
- there are clear arrangements in place for the ongoing maintenance of any SuDS scheme over the lifetime of the associated development (through the use of planning conditions or planning obligations where appropriate).
Read more about sustainable drainage systems and best practice within the built environment.
Applications for minor development do not fall under our remit and are solely considered by the relevant local planning authority. Although we may offer advice where proposals are in areas of known drainage or flood problems.
This role fits with our existing role of lead local food authority (LLFA) for the county. In which we develop a strategy to manage local flooding from surface water, groundwater and ordinary watercourses.
Revised climate change guidance
As of 10 May 2022, the Environment Agency's climate change allowances have been updated. As part of this update, changes have been made to the 'Peak Rainfall Intensity Allowances' that are used in applying climate change percentages to new drainage schemes.
The LLFA would now seek the 'upper end' allowance is designed for both the 30 year (3.3%) and 100 year (1%) storm scenarios. The latest information on the allowances and map can be found on GOV.UK.
This analysis must determine if the impacts of the greater allowance are significant and exacerbate any flood risk. The design may need to be minimally modified but may also need additional mitigation allowances, for example attenuation features or provision of exceedance routes. This will tie into existing designing for exceedance principles.
Where the proposed lifetime of the development proposals are less than 75 years we can accept lower allowances and, or epochs to be used. We ask you consult with us first.
The Environment Agency statutory role
The Environment Agency remains statutory consultees for all development at risk of flooding from rivers and the sea, defined as flood zones 2 and 3. They should be consulted as early in the development planning process as possible.
Their formal consent will also be required for any works that might affect a main river or flood defence.