The Lake Michigan icefoot complex : conditions of formation and destruction, and an evaluation of winter erosion at Wilmette, Illinmois
Miner, James Jon
MetadataShow full item record
During winters 1987-88 and 1988-89, the Lake Michigan icefoot complex at Wilmette, Illinois, was monitored to determine its conditions of formation and destruction, and to determine the relative importance of those factors. Icefoot-complex formation is controlled primarily by air temperature, with all ice additions to the complex occurring in subfreezing conditions. Wave- heights above 0.4 meters are a secondary facilitating factor, as is the presence of preexisting ice fragments offshore. Icefoot-complex destruction is primarily mechanical, caused by wave impacts. After breakup, ice fragments are transported from the area by longshore currents. Air temperature has only a gross correlation to ice destruction, probably due to the relatively slow speed at which ablation operates. Another secondary destructive process observed to occur is wind transport of ice fragments, which only occurs under limited circumstances. A sediment budget for the complex was prepared through sampling of the ice. The concentration of sediment in the complex is related to the type of incorporated ice. The total amount of sediment incorporated in the 1988-89 complex and transported by mechanical ice breakup was 2.6 cubic meters/meter of shoreline. In comparison, at the same time, wave and wind transport accounted for 105.4 and 1.25 cubic meters/meter, respectively.