Hydro-environmental modeling of proposed Severn barrage, UK

Abstract

This paper presents details of a numerical modelling study of the Cardiff–Weston barrage proposal for Britain’s River Severn, previously studied by the Severn Tidal Power Group. The study focuses mainly on investigating the potential far-field and near-field hydro-environmental impacts of the barrage by using an integrated one- and two-dimensional numerical hydro-environmental model. The model was set up for a large domain, starting from the outer Bristol Channel close to Lundy Island to the River Severn tidal limit near Gloucester. Potential changes in water elevations, tidal currents and consequently flood risk, sediment concentrations and background bacterial levels were assessed by comparing the model predictions for both the existing conditions and those with the barrage included. The results of the study show that the barrage has the potential to reduce maximum water elevations and tidal currents in this highly dynamic estuary. As a result of changes in tidal currents, a corresponding reduction in suspended sediment levels will lead to a predicted reduction in the concentration levels of faecal bacteria, which are associated with sediment deposition/erosion and increased light penetration within the water column. An increase and change in the benthic biodiversity of the estuary is also predicted to occur.