Abstract
Regulating reservoirs are artificial ponds used for preventing floods by gathering water which does not percolate through the soil in residential areas. Recently, as people's interests in natural environments have increased, regulating reservoirs have been increasingly used as places where people can commune with nature.
Investigations conducted in Chiba and Kawaguchi cities showed that most of the reservoirs were located on the foot of tablelands or the bottom of yatu valleys, where rich wildlife was supported. Most reservoirs did not contain water constantly, and thus many regulating reservoirs were used as sports grounds, parks, and other open spaces. Three types of reservoirs were recognized: natural type, which has dirt sides and bottoms; semi-box type, which has concrete sides and dirt bottoms; and box type, which has concrete sides and bottoms. Half of the reservoirs was box type. Natural type reservoirs had the highest coverages of vegetation and water, and those of the box type had the lowest. The results suggested that many regulating reservoirs may be required to restore natural habitats which are valuable not only for wildlife conservation but for human recreation in urban cities.
