Drainage Strategy

Drainage Strategies

Water management is an important priority for developers and planners across the country, made more crucial by worsening climate change, increased urbanisation and a lack of resilient infrastructure.

With that in mind, local planning authorities ask that detailed assessments are carried out as a way of explaining just how new sites will handle surface water runoff.

A drainage strategy gives developers and planners a structured and compliant solution, ensuring that each proposed development considers flood risk, long-term stability and water quality through sustainable drainage systems (SuDS).

What is a Drainage Strategy?

A drainage strategy is a planning document required for both minor and major developments.

It explains how the excess runoff of surface water will be managed using a sustainable drainage system (SuDS) in accordance with the national planning policy framework (NPPF).

It could also include a flood risk assessment (FRA) to address any existing flood risk.

What is Included in a Drainage Strategy?

Within a drainage strategy, you would usually find the following components:

Possible Purposes for Drainage Strategies

Although a drainage strategy could help with a few different problems, the most common reasons are to meet the requirements of the local planning authority, guarantee that the site supports green infrastructure and water quality, and comply with the guidance from the Environment Agency (EA) on surface water discharge.

When Do You Need a Drainage Strategy?

Strategies may be needed for:

• Developments on Brownfield or Greenfield Land
• Major Applications
• Outline Applications
• Projects with Excess Runoff Risk
• Sites Located Within Flood Risk Zones

Benefits of Getting a Drainage Strategy

Among the advantages of having a drainage strategy put together, the main examples include:

• Addressing Climate Change and Exceedance Routes
• Creating Clear Volume Control and Peak Flow Reduction
• Proving the Site’s Suitability for Development
• Supporting Approval by the Local Authorities

Drainage Discharge Flow Rates

An important part of any surface water drainage strategy is demonstrating how much runoff will leave the site and at what rate.

Local planning authorities typically require that discharge rates from a proposed development are restricted to existing greenfield runoff rates or as close as possible, avoiding any chance of increasing downstream flood risk.

Any development on previously undeveloped land or a brownfield site often needs to reduce the flow of water. At very least, it cannot make the flow of water worse.

Calculating appropriate discharge rates involves considering factors such as:

• Available Discharge Points
• Impermeable Areas Within the Proposed Development
• Infiltration Capacity
• Soil Geology
• Topographical Survey Data and Slope Profile

Such figures are used to design the SuDS system, ensuring compliance with the SuDS hierarchy, protecting water quality and supporting long-term flood risk reduction.

Approach to Creating a Strategy

For more information on how we create a strategy for the management and maintenance of a drain, the section below explains our usual process, the consultants in charge of assembling each strategy, and how you can get in touch with our team about getting a strategy made for your site.

Stages in the Strategy Process

With a drainage strategy, a developer or planner can show that the site is ready for development, reduce long-term flood risk and align with all national and local planning frameworks.

As set out below, each stage plays a crucial role in this journey:

1. Pre-Planning and Feasibility Stage

At the start of the process, it is vital to evaluate the site’s capacity for sustainable drainage.

It includes reviewing soil geology, conducting a topographical survey, and identifying feasible drainage points.

Results from this stage will help to determine whether the proposed site can support a compliant and sustainable drainage system, as well as flag any early limitations that could affect the layout or viability.

2. Full Planning Application Stage

The drainage strategy is formalised for submission alongside the planning application.

Within the submitted document, there will be a completed SuDS report, a detailed design for the proposed drainage infrastructure and the calculations for volume control and peak flow.

3. Post-Planning and Discharge of Conditions Stage

After planning permission has been granted, drainage conditions often need to be discharged.

The local authority and the EA need to confirm that the design of the development complies with all relevant environmental and planning requirements.

4. Construction and As-Built Stage

Both during and after construction, the focus changes to implementation, ensuring that drainage systems installed on the site correspond with the approved designs.

The stage could involve updating drainage models and submitting as-built records.

Knowledgeable Drainage Experts

When it comes to assembling a surface water drainage strategy, surveyors are available for servicing different parts of the country. Working on both bigger and smaller developments, our drainage consultants are able to create strategies, as well as undertake other steps in the process, including completing a flood risk assessment (FRA), helping with outline applications, putting together a SuDS design, and integrating the readings from a topographical survey.

Whatever the circumstances of your development site and planning project, we ensure that every strategy aligns with your expectations and requirements. All of our team has the necessary training, licensing and qualifications to correctly make drain strategies for clients, giving them everything developers and planners need to remain compliant with regulators, transparent to the local authorities and realistic with their design team.

Discuss Your Needs with Our Team

From the early stages of an appraisal in preparation for a proposed development site to the full planning application process, our surface water management and monitoring services cover the needs of all clients.

Our understanding of the subject spans from flood risk to the use of a sustainable drainage system. If you could benefit from a drain strategy on your site, speak to our team, and you will receive a free quote based on your specifications.