Early warning system relieves English village after many years of flooding misery  

The multi award-winning Much Wenlock flood alleviation scheme is a £2M project initiated by Shropshire Council, in northwest England, to reduce flood risk to homes, businesses and highways in the small town of Much Wenlock.

Much Wenlock has a long history of flooding. The Shylte Brook and its tributaries run through the centre of the town and are largely culverted running underground. The culverts have a limited capacity and when they are full, the excess floodwater flows over ground through Much Wenlock thus affecting properties, businesses and infrastructure. In 2007 around 64 properties reported flooding to Shropshire Council and an electricity substation caused a power outage to a large part of the town due to the flooding.

Due to its history of flooding problems, Much Wenlock needed a flood prevention system and an early warning monitoring system. The flood prevention system needed to be self-activating and require no power or moving parts to ensure that it would operate reliably.

The monitoring solution needed to be non-contact, require minimal or no maintenance, and be installed in an elevated position in order to prevent the risk of vandalism. With no existing power supply available at the site, ideally the system would need to have its own integral power.

Two sites were identified for the construction of flood alleviation ponds to store flood water upstream of Much Wenlock. One is on the Sytche Brook to the north west of the town and the other on the Shylte Brook to the south west.

Hydro International worked with consultants WSP to size and design the three Hydro-Brake® Flood vortex flow controls which are situated at the outlets of the ponds, restricting the water flow to within the downstream culvert capacities. Between them the two ponds have a water storage capacity of 21,104m3.

Following this initial phase, WSP asked Hydro International to recommend a suitable monitoring system to provide insight into water levels.

Hydro-Logic® Flexi Logger 100’s, paired with Vega WL61 level sensors were chosen - a tried and tested combined solution that provides accurate and reliable real-time information and long-term data gathering. The Hydro International team worked with WSP and contractor Alun Griffiths to develop an effective installation method. One set was installed at each of the flood attenuation ponds.

The completed scheme has reduced flood risk to 171 properties and highways and has also created a public open space and restored the local Westwood Quarry SSSI (Site of Special Scientific Interest) providing additional environmental and sustainability benefits.

Work started on the scheme in 2015 and won the sustainability category in the Environment Agency’s annual Flood & Coast 2018 Project Excellence Awards. In March 2018, it also won the CIHT Sustainability Award and came highly commended in the 2018 BCI Awards for Small Project of the Year and the 2018 IHE Mercia Branch Awards in April 2018.

The £2M scheme was supported by the UK’s Environment Agency and funded through the Severn & Wye Regional Flood Defence Committee by Flood Defence Grant in Aid, local developer contributions and Shropshire Council. The scheme was designed and developed by consultants WSP, with construction by Alun Griffiths.