Water Impounding Structures and Flood Risk

Water impounding structures such as reservoirs or dams constitute a potential source of flood risk that can have serious consequences. Flooding of downstream areas within what is known as the area of inundation may ensue if the structure fails or is overtopped. Downstream flooding may also arise from the controlled release of water from the reservoir, for example via spillways during periods of high flows due to weather conditions. This is normal practice to avoid capacity exceedance and overtopping. In any of these circumstances there is potential for rapid inundation of downstream areas and response times to flooding are likely to be short. This is especially the case where failure of reservoir structures triggers land slips resulting in a sudden uncontrolled release of water.