POL 03 - Flood Risk Management and Reducing Surface Water Run-off

Adoption of road in the development - KBCN0331

Where a development includes roads, these are often adopted by a statutory authority (for example the Highways agency or the local authority in the UK). Where the authority will be taking responsibility for the roads, the following guidance should be followed to determine if the water run-off from the roads needs to be considered as part of the assessment:

If the road drainage system bypasses the new development's network to connect directly to the local drainage network, then the water running off from the roads does not need to be considered for this assessment. Evidence will need to be provided to demonstrate if this is the case.
If the road drainage system connects to the development drainage network before connecting to the local drainage network, then the water run off from the roads must be considered for the assessment.

Where the authority will NOT be taking responsibility for the roads, the BREEAM criteria should be followed for all drainage on site.

Flood risk – Site situated across numerous flood zones - KBCN0532

Where a site is situated across more than one flood zone, the flood zone with the highest probability of flooding, i.e. the worst case scenario, must be considered for the purpose of the BREEAM assessment. An exception to this would be where the areas in the higher probability zone include only soft landscaping and it can be demonstrated that access to the building will be maintained in a flooding event. This is to ensure that the site has adequately managed the worst case scenario level of flood risk associated with the site's location.

07/03/2018 Updated to include circumstances where an exception may apply.

FRA more than 5 years old - KBCN1580

Where more than five years have passed since the FRA was carried out, to be able to use the FRA in your assessment evidence would be required to demonstrate that the basis of the FRA has not changed in that time.

Minimising water course pollution – no water courses present - KBCN0550

The credit for 'minimising water course pollution' has to be assessed even in cases where no water courses are in close vicinity to the site under assessment. This is because the aim of this credit is to encourage developments to minimise water course pollution by restricting the discharge of potentially contaminated water from entering the public sewer. Minimising water course pollution does not focus on water directly entering water courses.

No discharge for up to 5mm rainfall - KBCN0599

The criterion requires no run-off to leave the developed site into the local watercourse(s) for a storm event that results in rainfall depths up to 5mm. It is not acceptable to collect the rainfall within an attenuation tank and allow the runoff to be released from the site at a restricted rate. This simply slows the rate at which it is released to the watercourse(s). The 5mm rainfall event is considered one of the most common rainfall events and, therefore, a system should be designed to prevent this run-off leaving the site thus protecting a receiving watercourse from pollution.

Scope of different parts – Error in compliance note - KBCN1261

CN3 Includes the following error:

Where it reads: ‘Criteria 6 - 15 are not applicable’
This should read: ‘Criteria 7 - 15 are not applicable’

Technical manual to be updated accordingly in next reissue.

Watercourse pollution from indoor parking - KBCN0545

If the design team can demonstrate that there will be absolutely no run-off from the indoor parking then the intent of the credit will be met. However, such proof would also have to demonstrate that no hydrocarbon spillage from vehicles found its way into the watercourse/sewer. It is likely that there would be water ingress from outside or that internal parking areas would have drains fitted and be cleaned regularly. In such conditions, the criteria are still applicable. The intent of this criteria is to ensure no hydrocarbons run off to any watercourse.

[KBCN Withdrawn] ~ Confirmation of low flood risk without an FRA - KBCN0582

The KBCN has been withdrawn and is no longer valid. This is because its content was created on the basis of a very specific case and should not be applied generally. The authority/organisation's confirmation is no more robust or detailed than reference to flood maps, which are not in themselves compliant without a FRA.

KBCN withdrawn on 31/03/17:

Where a national or local authority/organisation has confirmed, in writing, that the site has a low risk of flooding from all sources and that a Flood Risk Assessment (FRA) is not required then this is acceptable and the two credits can be awarded.  The authority/organisation's written confirmation is a sufficient indication that an appropriate level of flood risk assessment has been completed.  Please note that the use of relevant flood maps without this additional confirmation from the authority/organisation is not acceptable.

Refurbishment and Fit Out / International / 2015 / 09 - Pollution /