Flood control and small-scale reservoirs

Abstract

Flood control defenses such as levees, dams, reservoirs, and weirs are used to prevent rivers from bursting their banks. Among these defenses, the construction of large-scale dams has recently become an important topic of discussion in countries around the world. It is important to construct large dams to secure water for drinking, irrigation, electricity, and industrial use. However, leaders and well-informed persons in many fields have argued that the development of large-scale dams destroys the natural environment, forces residents of entire villages to leave their homes, and consumes too much time and money. In Japan, large-scale dams were initially constructed mainly to supply electric power, but the purpose of dams has now shifted to water supply or flood defense. Whether large-scale dams are necessary is now a source of contention throughout the world, with several advanced nations calling for the removal of dams. The present paper, taking as an example a small-scale reservoir for flood control in a small river in Funabashi City, Japan, makes the following main conclusions: small-scale reservoirs were used as a measure of flood control in many parts of Japan in the past; terraced paddy fields as well as small-scale reservoirs play an active role in flood control measures in place of large dams; flood control measures are reinforced by connecting small-scale reservoirs; small-scale reservoirs spare the environment from destruction caused by the construction of large dams; and small-scale reservoirs can be utilized as recreation sites for fishing, swimming, and walking.