The role of non-prevailing wind direction on resuspension and redistribution of sediments in a shallow lake

Abstract

Sediment resuspension can significantly affect the light climate and internal nutrient loading in shallow lakes. To predict wind-induced resuspension, a critical bottom shear stress or critical depth for the whole lake is typically used. It is suggested here that the availability of resuspendable material must also be considered and that this availability depends on local wind characteristics. The objective of this study was to show a connection between patterns of resuspension and accumulation of sediments and the prevailing wind directions. The near-shore sediments in the shallow Lake Krankesjon (surface area = 3 km2) in southern Sweden were characterized by a 5-graded resuspension potential scale and organic content. The spatial variability in sediment characteristics was compared to local wind statistics. This comparison showed that bottoms with low resuspension potential (sandy with low organic content) were located where waves from prevailing wind direction were acting, and bottoms with high resuspension potential (soft sediments with high organic content) were located to the lee-side of the prevailing wind directions. Intensive continuous turbidity measurements showed that winds above 10 m/s in directions other than the prevailing ones brought much material in suspension, while winds in the prevailing direction did not cause any increase in turbidity. The prevailing winds erode the bottom on one side of the lake, depositing resuspended material predominantly on the opposite side, where it can be resuspended by winds from non-revailing directions. Information about the local wind pattern can improve modeling and understanding of resuspension and redistribution of ediments in shallow lakes.