Northern Stormwater Interceptor, Bristol

The Northern Storm Water Interceptor (NSWI) is a large stormwater tunnel that serves as a critical flood prevention measure for Bristol, England. Designated as a Significant Flood Risk Asset by Bristol City Council, it is a key component of the city's flood defence network, operating alongside infrastructure such as the Airport Road Tunnel and the Malago Interceptors (built following the Great Flood of 1968 which inundated Bedminster and Ashton). The Malago Interceptor performs a similar function to the NSWI, diverting the River Malago underground through Southville to the New Cut. Long-term flood risk strategies identify climate change and rising sea levels as significant threats to the NSWI's future efficacy. As sea levels rise, the window of time during which the NSWI can freely discharge into the River Avon via gravity will decrease. Increased occurrences of tide-locking could limit the system's performance, potentially increasing flood risks upstream in Eastville and the city centre during combined heavy rainfall and high-tide events.

Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).