The field measurements on the behavior of silt curtain were conducted under stormy waves and currents. The field measurements were successfully completed and supplied the data required to estimate the drag coefficient of flared curtain structures. Each of the drag coefficients for both stormy waves and currents was predicted to be 1.0. Since the large velocities of wave and current are induced at the same time by storm, the estimated drag coefficient of 1.0 is reasonable for that designed under wave and current.
The silt curtain is very popular in Japan to prevent the pollution due to spoiling or dredging accompanied by coastal zone development. The silt curtain is normally applied to inner bay with high tranquillity. Extension of construction area causes the increase of importance to invcstigate the applicability and the responsibility of silt curtain to the stormy wave and current. Because of the lack of information on the behavior of silt curtain under storm the silt curtain is sunk into sea water during stormy wave condition. Since the construction is suspended through storm, this procedure is reasonable but costs a lot. When designing the silt curtain the drag force due to wave or current is estimated by the drag coefficient for the resting body such as a sphere or a rectangular prism. Japan Sea Pollution Prevention Association(JSPPA) employs the drag coefficients of 1.2 for both wave and current. The silt curtain is often flared by current. The treatment of silt curtain as a resting body has to be examined by physical modeling or field confirmation. To obtain the drag coefficient of flared silt curtain both the drag force and the deformation due to wave and current are required. The pioneering research for designing the floating silt curtain was done by Milgram(l971).