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Avon Ring Road Stage II - Bristol

International Recognition of Innovative Design of 'Rising Limb' Attenuation Reservoir

The Shortwood to Warmley Link (Stage II) completed the Avon Ring Road in September 2001.  This highway system of regional importance discharges stormwater to several watercourses, one of the most sensitive being the Siston Brook.

The reservoir detailed design required an innovative combination of low flow orifice and high flow spillway to discharge storage at the correct time in the hydrograph.

The design concept was published at the International 'NOVATECH' Conference, France, 2001

Catchment and river modelling by the consultant identified potential increases in flood risk to several properties and bridges along the length of the river.

Channel improvements and on-line attenuation were not feasible, so the consultant designed an innovative 'off-line' reservoir sited in a rural area that was shown to be effective in offsetting increases in peak flow on the main river.  The concept made use of natural catchment hydrodynamics, exploiting differences in sub-catchment Time to Peak behaviour.

Client - South Gloucestershire CC (Highways)
Date - October 1996
Funding - DETR, Avon County Council
Support tools - RIBAMAN, MapInfo™, Superplan™