Author(s): Guanghai Gao; Roger Falconer; Binliang Lin
Keywords: Surface water; Numerical modelling; Faecal bacteria; Sediment transport
Abstract: Faecal bacteria exist in both free-living and attached forms in surface waters. The deposition of sediments can take faecal bacteria out of the water column and to the bed. The sediments can subsequently be re-suspended to the water column, which can then lead to resuspension of the faecal bacteria of the attached forms back to the water column. Therefore, the fate and transport of faecal bacteria is highly related to the governing sediment transport processes, particularly where these processes are significant. However, little attempt has been made to model such processes in terms of predicting the impact of the sediment fluxes on faecal bacteria levels. Details are given of the development of a numerical model of faecal bacteria transport, where the sediment transport processes are significant. This model is based on the model DIVAST (Depth Integrated Velocities And Solute Transport). The model was first tested using an artificial flooding study and then by investigating the sediment effects on the faecal bacteria transport processes in the Severn Estuary and Bristol Channel. The model predictions were encouraging, with the results being compared to a traditional faecal bacteria moelling approach, where sediment bacteria interactions are not included. The new model provides improved predictions of faecal bacteria concentrations when sediment transport is included and for the Bristol Channel Severn Estuary it can be seen that the effects of sediments can be significant.