Intrusion of Turbid Water in Stratified Lakes Driven by Resuspension of Sediments on Sloping Boundaries

Abstract

The thermal ‘staircase’, a layer of constant temperature, was observed in seasonal thermoclines following the resuspension of cohesive sediments resuspension on the shore slope of Lake Biwa. When a moderate onshore wind blew, the bed materials were resuspended up to the mid thermocline with height of 2.5 m above the bottom, and settled down forming the staircase above the intrusion. As the consequence, the thermocline was divided into two layers by the staircase with a thickness of 0.7 m. To investigate the resuspension and settling process due to surface and internal waves in stratified lakes, laboratory experiments were conducted using a tank with a partial slope at one side. When the internal waves generated as the barotropic waves in the tank, the resuspension phenomena occurred frequently. Both surface and internal waves are essential for the resuspension process. In the stratified fluid, the distance and duration of suspended sediment transport are very long compared to that in the non-stratified one due to occurring of the intrusion into the stratified layer.