Sediment Resuspension Caused by Wind-Induced Current in Lake Izunuma

Abstract

Lake Izunuma is a shallow lake located in the north part of Miyagi prefecture, whose water quality has been extremely deteriorated. One of the phenomena that influence the water quality is behavior of sediment that has accumulated on the bottom of the lake. In this study, field measurements were conducted during the windy season of winter, when resuspension of sediment is most active. Turbidity, water velocity, wave height were continuously measured in the lake for about three weeks. From the observed data, wave height and velocity oscillation had much to do with increase in turbidity. This fact indicated that resuspension of sediment was mostly caused by wind wave turbulence, which was affected by not only wind speed but also fetch determined from the planar shape of the lake and wind direction. Considering this effect, history and distribution of turbidity during the strong wind event was reproduced with a hydrodynamic numerical modeling.