Prototype test of new water-purification method in new Nagasaki Fishery Port, Japan

Recently, Komatsu et al.(1997) proposed new water-purification method in semi-enclosed coastal area. In the present method, to activate tidal exchange between 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 this 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, etc.) between before and after setting bottom roughness, it is clear that the condition of water quality in the port has a tendency to be improved.