Matlock Bridge – Flood Risk Assessment
Matlock Sewage Treatment Works (STW) is uniquely situated such that vehicular access can only be obtained via a bridge, spanning the River Derwent.
Uninterrupted access is essential for the running of the STW, with regular maintenance and structural surveys required to ensure that the bridge continues to be suitable for purpose. However, recent surveys revealed the existing bridge is now reaching the end of its life. We were appointed by Severn Trent Water to undertake the Outline Design for a replacement bridge.
About this project
Location
Matlock, Derbyshire
Client
Year
Ongoing
Sector
What We Did
As part of our professional services, we were appointed to provide a Flood Risk Assessment (FRA) with the study focusing on the impact of the works on fluvial flood risk. This was achieved through the application of hydraulic modelling techniques to accurately represent the river, associated structures, and the topography of the surrounding floodplain.
A full review of the existing hydrological inputs used in the model was undertaken to confirm that it was representative of observed flows in the river. An existing model provided by the Environment Agency was enhanced in the area of interest to include all crossings in the 1D network and detailed elevations in the 2D domain including the adjacent Cromford Canal. These were informed by structural and topographic surveys undertaken specifically for this project.
Our Design and Modelling teams worked closely together to ensure that the outline design for the bridge would exceed the required performance criteria. Refinement of the bridge design was undertaken based on modelling outputs.
Outcomes
The proposed bridge was successfully designed to achieve a required 600mm freeboard below the soffit level during a 1 in 200-year storm event. The FRA and hydraulic modelling report forms part of the documentation in which we helped Severn Trent get planning permission.
An additional output from the project is the enhanced model that will provide a valuable tool for use if further projects are undertaken in area. The updated model was submitted to the Environment Agency and passed a full audit demonstrating from a flood risk perspective that the development could proceed.
