IMPROVEMENT OF WATER QUALITY IN A SMALL PORT BY CONTROL OF TIDAL CURRENT

摘要

Komatsu et al. (1997) have recently proposed a new water-purification method in a semi-enclosed coastal area. By means of this method, to activate the tidal exchange between the inner and outer sea area, a pattern of tidal residual current is controlled by setting many bottom structures "BOTTOM ROUGHNESS", which have an unsymmetrical 3-dimensional shape. In order to confirm the effect of the present method in an actual coastal area we started prototype test from May, 2000 in New Nagasaki Fishery Port, Nagasaki, Japan. In the present test, 60 units of bottom roughness were set on the bottom near mouth of the port in May, 2001. As a result of field measurements of water quality (COD, DO, Water Temperature, Salinity etc.) between before and after installing bottom roughness, it becomes clear that the condition of water quality in the port had improved.