Drainage Strategies

It is becoming increasingly important to demonstrate to the Local Planning Authority and the Environment Agency that a proposed development has considered the available surface and foul water drainage options during the scheme’s feasibility stage.

This is particularly important if the proposed development is in an area at risk of flooding.

A Drainage Strategy will:

  • Determine how surface water discharge (runoff) will be managed
  • Comply with the requirements of National Planning Policy Framework (NPPF)
  • Determine how foul water drainage will be managed
  • Show whether an upgrade of the existing public sewer network is required

The Drainage Strategy will make an assessment of all available surface water drainage options for the development site, whilst demonstrating that the rate of surface water discharge (runoff) will not exceed the existing site conditions.

If the development is on a previously undeveloped ‘greenfield’ site, the strategy will firstly take into account the topography, ground conditions and the proximity to watercourses and surface water public sewers with respect to surface water drainage.

The desired water management targets are then achieved through the inclusion of features such as soakaways, infiltration basins, swales, permeable pavements, filter strips and balancing ponds.

Our expertise in the design, selection and layout of such features enables us to deliver solutions that are sustainable, cost effective and meet with the required local and national standards.

If the development is on a previously developed ‘brownfield’ site, the strategy will seek to utilise the existing discharge disposal arrangement to watercourses, soakaways or public sewers.

A foul water Drainage Strategy will consider the proximity and capacity of existing foul water public sewers and also the site topography. A capacity check will determine if an upgrade of the existing foul water public sewer network is required.

The Benefits

A professional Drainage Strategy prepared by Cole Easdon Consultants during the feasibility stage of a development will:

  • Provide developers with the information needed by Local Planning Authorities in order for them to grant planning consent
  • Be cost effective and meet the required local and national standards
  • Give an early identification of development constraints such as land take
  • Enable the sustainable management of surface water drainage
  • Reduce the risk of flooding to the development and to the surrounding locality
  • Incorporate features such as permanent ponds, which can improve the local amenity and provide an environment to support biodiversity

How We Can Help

As experts in water management we provide some or all of the following services to help our clients develop effective drainage strategies:

  • Sustainable drainage advice
  • Preparation of foul water & NPPF compliant surface water Drainage Strategies
  • Detailed foul water and Sustainable Urban Drainage Systems (SUDS) design
  • Soil infiltration testing to determine soakaway drainage potential
  • Computer modelling of drainage networks including sewers and watercourses using WINDES software
  • Technical assistance to understand surface water flooding such as drainage exceedance modelling to determine flood volumes, velocities and mapping of flood flow routes

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