Abstract
Izunuma & Uchinuma, designated as Wetlands of International Importance especially as Waterfowl Habitat, in the Ramsar Convention on Wetlands, are famous swamps visited by migratory birds. The level of the water pollution in these swamps has exceeded the environmental quality standards in terms of chemical oxygen demand (COD) (5mg·l-1) for the last ten years. It is considered that the sediment removal from the bottom of these swamps is necessary in order to improve water quality and prevent shallowing. However, conventional methods of sediment dredging affect the ecosystem greatly, require a lot of time and are costly. Thus one of the authors, Shibasaki, suggested a more efficient plan, i.e., the sediment removal of employing the “resuspension phenomenon” resulting from gale force winds. In 2000 and 2001, two experiments based on Shibasaki's proposal were carried out in Izunuma & Uchinuma. About one-twelfth of the annual deposit of sediment was removed in the first experiment. It is clear that this “resuspension phenomenon” method is very effective in preventing the swamp from shallowing.
