Bottom Stability and Sedimentary Processes at Little Lake Harbor, Lake Superior

摘要

The report discusses the relationship of littoral drift to sediment texture and fluctuations in offshore and strandline topography at Little Lake in southeastern Lake Superior. Offshore bars and troughs oscillate about a mean position, depending on the direction and intensity of wave attack. In contrast to the offshore bars and troughs, shallow-water topographic features migrate normal to and along shore with changes in lake level and wave attack. Sediment consists of two distinct populations: pebble-cobble and sand. The pebble-cobble population is relatively immobile and serves as an armor for the beach and nearshore. The sand population is highly mobile and its distribution reveals the effect of the harbor breakwaters on littoral drift. Littoral drift causes harbor maintenance problems, including shoaling in the harbor mouth and beach deterioration adjacent to the breakwaters. A primary cause of the shoaling is entrapment of a portion of the sand fraction bypassing the harbor structures by circulation patterns induced by harbor design. (Author)