This advice sets out the requirements that the LLFA has for drainage strategies and surface water management provisions associated with applications for development.
This section lists the evidence that an applicant is required to provide when submitting an application.
RBWM has created a Surface Water Drainage Summary Pro-forma which can be used as a summary of the information required. We recommend that the pro-forma is completed in full and submitted alongside the drainage statement and additional evidence listed below.
| Evidence required | Further details | Application type |
|---|---|---|
| Surface Water Drainage Strategy/Surface Water Drainage Layout | This should include; existing drainage arrangements with detail of how the site currently drains and a topographical survey, a surface water drainage layout with the location of drainage components, pipe gradients/numbers/diameters, storage volumes, outfall location, exceedance flow routes, proposed impermeable areas, infiltration areas, attenuation devices, design levels that function hydraulically, topographical survey detail and a method of surface water disposal in line with the SuDS Management Hierarchy. |
Pre-App Outline Full |
| Flood Risk Assessment | This should include; surface water, groundwater, fluvial, reservoir, sewer and any artificial waterbodies, consideration of how flood risk may change in the future such as climate change, application of Sequential Test and Exception test if criteria met, demonstration of a sequential approach to locating a development and consideration of mitigation measures. |
Pre-App Outline Full |
| Outline Calculations | This should include; Greenfield, Brownfield (if applicable) and post-development runoff rates, volumes of attenuation required. | Outline |
| Full Calculations | Surface Water drainage modelling calculations (e.g. MicroDrainage) which show the attenuation volumes provided on site for the 1 in 30 year and 1 in 100 year + Climate Change events. |
Full Reserved Matters Discharge of Conditions |
| Groundwater Investigation (Infiltration only) | This should include; evidence of ground conditions, groundwater levels and site- specific infiltration tests in line with BRE 365 regulations. |
Outline Full Reserved Matters Discharge of Conditions |
| Water Quality Assessment | This should be completed using the Simple Index approach as detailed in the CIRIA SuDS Manual (C753). | Full |
| Flood Exceedance Plan | Plan indicating where surface water would flow in exceedance events. If flooding is modelled to occur on site during 1 in 30 or 1 in 100yr + Climate Change, the estimated volumes and depths should be included on the plan. |
Full Reserved Matters Discharge of Conditions |
| Maintenance Plan | Full Description of required maintenance activities or each drainage element and who is responsible for carrying this out. The site layout should include access routes and space for maintenance activities to commence. |
Full Discharge of Condition |
| Development and Construction Plan | Details of surface water management plans through construction. This should include details of flow routes and how these will be manged and maintained during development. |
Full Reserved Matters Discharge of Conditions |
|
Discharge Agreements (temporary and permanent) |
Confirmation that any required discharge agreements with third parties are in place. |
Full Reserved Matters Discharge of Conditions |
|
Evidence of third party agreements if required. |
Proof that any proposed modifications to watercourses and/or connections to third party infrastructure receiving water are viable and acceptable. This can be agreement in principle. |
Outline Full |