Consulting the Lead Local Flood Authority
As the Lead Local Flood Authority (LLFA) in Essex, Essex County Council is the appropriate statutory body to approach for advice on major planning applications including SuDS in the county. This includes developments with:
- 10 or more houses;
- a site of over 0.5 hectares where the number of houses is unknown;
- a building greater than 1000 sq m in area; and/or
- a site over 1 hectare in area.
To apply for planning permission, the relevant documents (including any drainage information) should be submitted to the relevant Local Planning Authority.
The level of detail required within the drainage strategy will vary depending on the current stage of the planning process. The following information is required for an outline application:
- An understanding of the natural drainage characteristics within and adjoining the site.
- An outline assessment of existing geology, ground conditions and permeability through desk-based research.
- A Conceptual Drainage Plan including management train, source control details, storage details, conveyance and exceedance flows and runoff details.
- A Conceptual SuDS Design Statement including indicative runoff and attenuation volume calculations, proposed method of flow control and information about proposed treatment stages.
For a full application, the following is required:
- An assessment of suitability for infiltration based on soil types and geology, including infiltration testing.
- A Detailed Drainage Plan including management train, location and type of source control, storage locations, conveyance and exceedance flow routes, the destination of runoff and runoff rate restrictions.
- A Detailed SuDS Design Statement including details of water quality measures, attenuation and discharge quantity for the lifetime of the development, calculations of pre- and post-development peak runoff flow rate for a critical rainfall event and proposed method of control.
- A Method Statement detailing how surface water will be managed during construction.
- Confirmation of land ownership.
- A SuDS Management Plan including responsibility, management goals, description of maintenance schedule and site plan.
- Foul Drainage Proposals.
- For major developments or phasing of minor developments, a plan showing each development plot including the storage and discharge rate accorded to that plot as part of the wider SuDS strategy.
It is important to demonstrate that the sequential test has been carried out where necessary. Within each flood zone, surface water and other sources of flooding must be taken into account in applying the sequential approach to the location of development. It is therefore important that flood risk is considered early in the design process to avoid areas that are at risk of surface water flooding. As well as checking the relevant Strategic Flood Risk Assessment, the Surface Water Management Plans should be checked for more up-to-date flood mapping.
The risk of flooding to a development should be considered as early in the design stage as possible. The precise type or types of flood risk will determine who should be contacted during the design process.
Page updated: 18/02/2019