The output is coloured to illustrate depth of flooding. There is some initial flooding at the downstream end of the model associated with tidal flooding on the marshes. A flood storage reservoir at the upstream end fills as the flood event commences but the volume of water is so great that overtopping of the downstream embankment occurs and results in significant flooding in the town centre. One of the factors exacerbating the flooding is that the original path of the river in the valley bottom has been modified by human influence and now the river is raised above the town centre. When the river overtops, water flows to the area where the river used to be.

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Based upon the Ordnance Survey Map with the permission of the Controller of Her Majesty's Stationery Office. © Crown copyright. Entec UK Ltd AL100001776