Flood management advice for developers

Your application submission should include a Surface Water Drainage Strategy. Within this you will need to consider:

• local planning obligations.
• the existing drainage arrangements 
• detail how the site currently drains
• Carry out a topographical survey to understand any sub-catchments of site and any existing drainage infrastructure
• the proposed drainage arrangements, following the drainage hierarchy contained in the National Planning Policy Framework (NPPF):

1. Use rainwater harvesting/blue roofs
2. Use infiltration technique
3. Attenuate rainwater in ponds or open water features for gradual release
4. Attenuate rainwater by storing in tanks or sealed water features for gradual release
5. Discharge rainwater direct to a watercourse
6. Discharge rainwater to a surface water sewer/drain
7. Discharge rainwater to the combined sewer
8. Discharge rainwater to the foul sewer

You should provide clear justified reasons if your development does not include features higher up the hierarchy.

• calculations for 
• greenfield runoff rates
• existing runoff rates
• proposed discharge rates
• attenuation volume required to reach greenfield runoff rates
• attenuation volume required to reach the proposed discharge rate
• half drain down times for a 1-in-30 year return period within 24 hours
• half drain down times for infiltration systems
• storage calculations to show 1-in-100 year return period plus 40% climate change allowance is safely contained on the site
• the maintenance tasks, frequencies and owners of the drainage features

Your application should also include a SuDS Proforma. Find more information on London Sustainable Drainage Proforma on London City Hall.

Your application may also require a Flood Risk Assessment if the criteria in Footnote 55 of NPPF are met.

An ordinary watercourse is any river, stream, ditch, drain, cut, culvert, dike, sluice or other water passage that is not designated as a main river (see the EA Main River Map). Redbridge Council have permissive rights under the Land Drainage Act 1999 to ensure ordinary watercourses in its area are properly maintained irrespective of ownership.

Our main permissive rights are:

• to ensure all ordinary watercourses in its area are maintained to a standard that allows water to flow through them freely.
• to inspect all works carried out to or within three metres of an ordinary watercourse regardless of its ownership status and insist on any changes needed to protect both upstream and downstream users.

Land Drainage Consent must be applied for if any of the following conditions apply to any works you wish to carry out:

• works that will affect or add flow to any open or piped ordinary watercourse.
• works to the embankments, ditch bottom or any part of a piped ordinary watercourse.
• works within 3 metres of any open or piped ordinary watercourse.
• works to connect new pipes or watercourses to an existing open or piped ordinary watercourse.

To apply for Land Drainage Consent please contact to highwaysg@redbridge.gov.uk. If you wish to discuss Land Drainage in more detail, please email highwaysg@redbridge.gov.uk.

Permits may be required from the Environment Agency if you carry out these works along main rivers.

As the Lead Local Flood Authority, we have powers to designate structures or features with a significant impact on flood risk. We do this to protect structures or features that play a role in reducing flood risk. If we have designated something it usually means that a number of properties would be at a greater risk of flooding if that structure or feature was removed.

The Environment Agency also have powers to designate structures you can find out more on this at Flood and sea defences: designated assets on your land - GOV.UK

A record of the designation will be put onto the Local Land Charges so that subsequent landowners will be made aware of the designation. Once we have designated a feature, the owner must seek consent from us to alter, remove, or replace it.

If you make a change to a designated feature without our consent, we may issue an enforcement notice which will set out the steps that must be taken to restore the feature. You may appeal against a designation notice, refusal of consent, conditions placed on a consent or an enforcement notice.

Contact us at highwaysg@redbridge.gov.uk to find out the structures that have been designated and discuss consent to alter a feature or structure that has been designated.