Sustainable drainage developments

Our statutory role

We are required to provide technical advice and guidance on the 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.

Our consultation responses will be based on guidance from:

• existing planning policies
• National Planning Practice Guidance
• national 'non-statutory 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 recommendations for the incorporation of SuDS into new development.

The 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 development it should be demonstrated that:

• an appropriate SuDS system will be incorporated (unless it is clearly demonstrated and agreed that they would inappropriate)
• the minimum standards of operation proposed by the applicant are appropriate
• 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.

We will also be consulted on applications for minor development in areas where there are known drainage problems.

This role fits with our existing role of Lead Local Flood 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 19 February 2016, the Environment Agency published new guidance on how to use climate change allowances in flood risk assessments.

These allowances for peak rainfall can impact drainage design and should be considered within any drainage strategy to be accompanied with a planning application.

As LLFA, we will require the design accommodates the 1 in 100 year storm (a particularly heavy storm that would on average occur once in 100 years) with a 20% allowance for climate change, and any additional analysis should outline the flooding implications for a greater climate change allowance of 40%.

Any climate change analysis must show if the impact of the additional 40% is significant enough to have the potential to cause a flood risk to or from the proposed development. The design of any associated drainage system may need to be modified to accommodate the additional increase, but it may also need additional measures to prevent an increased flood risk (for example, increased freeboard on attenuation features may be required or further consideration of exceedance flow routes might be necessary.)

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.

Read the Environment Agency's guide to your rights and responsibilities of riverside ownership.