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Photograph - Blocked road gully

Highway Drainage


Our expertise includes the design of highway drainage systems for new roads and the investigation of problems (typically flooding) with existing highway drainage systems. The term 'Highway drain' includes any ditch or pipe which receives surface water from a highway which is maintained at public expense and which 'belong' to the highway.

Drainage for New Highways

We have the capability to design the drainage for new highways subject to adoption under Section 38 agreements together with the drainage associated with section 278 agreements. We can also design highway drainage for new roads to be constructed by the highway authority itself. The design work would be done in accordance with the DMRB or the requirements of the relevant highway authority. We would generally use Micro Drainage System 1 software to design piped highway drainage systems and then subsequently check the design using Micro Drainage simulation software to confirm that the design was satisfactory.

The work may involve the design of SUDS infiltration features including soakaways, infiltration trenches, infiltration basins and swales. If infiltration techniques were not suitable due to ground conditions (low permeability or a high watertable for example), the work could include determining a suitable outfall for the new drainage system. In this case it would be important to ensure that the receiving watercourse or drainage system was not overloaded due to the additional flow. This would be likely to involve the design of alternative SUDS features to attenuate the flow such as detention basins or tanks or retention ponds.

The design of the highway drainage system itself would include determining gully spacing or designing combined kerb/drainage systems. It is also likely to involve the design of filter drains, carrier drains, culverts, watercourse diversions (possibly involving river modelling), oil interceptors and outfalls, etc.

Investigation of existing highways drainage systems

As set out above, we are able to offer an investigative service into problems with existing highway drainage systems such as flooding and this might involve the hydraulic analysis of the system using Micro Drainage simulation software.

Further information

Please contact us for further details of our capability regarding highway drainage systems.

Photograph: Blocked road gully.