Operation of Water Resources Systems for Efficient Defense from Floods

Abstract

Defense from floods is defined as any set of human activities which decrease losses of lives, property and production due to floods in comparison with the consequences of floods if those activities were not undertaken. A precise determination of floodplain boundaries for given flood flows is required of river reaches, lake or sea shores, which are selected for defense from floods. The reach or the shore may be devoid of flood defense measures, or it may have flood control structures, measures and floodplain management activities. Similarly, the river basin upstream of the defense reach may contain a variety of structural or non-structural flood control and mitigation measures. This is true for the river section downstream, which may be affected by flood defense activities upstream. The operation of water resources systems during a flood may have significant effects on flood defense along the reach or the shore. Reservoirs and floodplain release basins are among the most influential of such operations, affected crucially by the reliability of flood forecasts, especially of flood magnitude and the lapse time between forecast and occurrence of predicted flood values. Pre-emptying of reservoirs and release basins, protection of levee and dike systems, and flooding of the least economically impacted land behind levees in the upstream river basin in emergencies, are among the most important operational tools for minimizing losses through defense from floods. Floods which inundate floodplains may have also beneficial impacts. They bring moisture and nutrients to soil, control weeds and pests, supply wetlands with water and fine sediment, remove the accumulated salt in the soil, help stabilization of river channel, etc. These benefits from flooding be preserved as much as possible in planning improvements in the standard of flood defense.