DMRB CD 529 – Design of outfall and culvert details

Access free from the DMRB website. Also available from CIS.

This document gives the requirements and advice for the design of outfalls and culverts. It supplements the guidance given in CIRIA C786 [Ref 1.N] and explains how the guidance in that document applies to motorways and all purpose trunk roads.

In this document ‘outfall’ is a physical asset at the point where a drainage system discharges into a different type of drainage system. The purpose of such an outfall is to discharge water from a drainage system into a receiving water body at a specific location without causing erosion or embankment instability. Note that the definition for an outfall used in this document is focused on a different aspect of an outfall relative to the definition given in CD 535 [Ref 3.I] . In CD 535 the emphasis is on an ‘outfall’ demarcating the ownership boundary between an Overseeing Organisation’s highway drainage network and a third party drainage system and might, or might not be coincident with a physical asset.