Complex 2D hydraulic modelling using ISIS/TUFLOW to assess flood risk and a flood defence scheme for a major factory in Birmingham

After a major flood incident in 2007, resulting in a multi-million pound insurance claim, in order to maintain affordable ongoing insurance, we were engaged  to quantify flood risk and explore flood defence options at the site.

We visited the site to understand the flood sources, pathways and key vulnerable receptors. We then provided a scoping study report to the client outlining the best process to finding a solution.

With a facility of this scale and profile it is important to engage with all stakeholders as early as possible. Therefore, we initiated the main flood defence project with a meeting involving the client, the engineering works contractors, the insurers and the Environment Agency. This allowed all needs and constraints to be brought to the fore.

We were able to negotiate the use of the Environment Agency’s existing river model at no cost, given that benefits created at the site are expected to be realised by communities further downstream.

We improved the Environment Agency’s ISIS/TUFLOW model by introducing information obtained from a detailed site survey of the site. We further improved the model by repairing several technical faults that were causing gross instabilities. With a more detailed, stable model, we were able to accurately benchmark flood risk at the site and test potential flood defence options.Flood risk at the factory was found to be dependent upon the capacity of a major downstream culvert. Improvement work to the culvert would be extremely costly and may increase downstream flood risk. Under a cost-benefit analysis, a flood defence wall at the site coupled with the creation of flood storage areas (both on the site and at upstream public open space) was found to be the optimum flood defence solution.