The existing Old River Stort in Bishops Stortford is contained in a culvert which passes beneath the town centre and becomes part of the sewer network. The Old River Stort is entirely disconnected from the existing River Stort. East Hertfordshire District Council wanted to de-culvert the Old River Stort and re-align it so that the new open watercourse passes through existing woodland before re-entering the drainage network.
EAS were tasked with consulting the Environment Agency (EA) on their requirements, and then constructing a hydraulic model to help design the new channel. The EA required a ‘high flows’ and a ‘low flows’ channel, so the design was such that both events could be contained without posing a flood risk to others. A 1D HECRAS hydraulic model was constructed to assess the various options and identify any areas where the cross section of the channel needed to be adjusted to contain the water.
Blockage scenarios were also modelled to determine the impact on the flow events.
EAS also made the Environmental Permit application on behalf of East Herts, which the EA required to carry out the works and to ensure the impact to the watercourse were limited.
East Hertfordshire District Council
Hydraulic Modelling, Flood Risk Engineering, Flood Mitigation
Adjacent to Northgate End Car Park, Bishops Stortford, Hertfordshire