Survey of Point Beach, Wisconsin, September 2020

Lake Michigan experiences quasi-decadal fluctuations between high and low water levels, resulting in variable impacts to navigation and tourism, as well as changes in shoreline position and coastal habitat extent. Recent high water levels are a concern for homeowners and policy-makers due to significant shoreline recession. Nearshore waves, currents and bathymetry are major factors influencing local sediment transport and shoreline behavior, but rigorous models of these processes are largely absent for Lake Michigan and frequent “real-time” surveying can be cost prohibitive for small communities. As such, there have been few attempts to quantitatively estimate potential rates and extents of wave-driven erosion and nearshore sediment transport at sandy coastal systems in the Great Lakes, particularly related to fluctuations in lake level. In this study we numerically model nearshore sediment transport and resulting changes in sandy beach and nearshore morphology in order to estimate future coastal geomorphic change in response to storms and varying lake levels.

密歇根湖水位在高低之间经历准十年期的波动，导致对航行和旅游业产生可变的影响，以及海岸线位置和沿海栖息地范围的改变。近期的高水位对居民和决策者来说是一个担忧，因为显著的岸线退缩。近岸波浪、水流和海底地形是影响局部泥沙输送和海岸线行为的主要因素，但密歇根湖的这些过程模型大多缺乏严谨性，而对于小型社区来说，频繁的“实时”调查成本高昂。因此，对五大湖中沙质海岸系统在湖水位波动影响下，波驱动侵蚀和近岸泥沙输送的可能速率和范围进行定量估计的尝试寥寥无几。在本研究中，我们通过数值模拟近岸泥沙输送以及由此导致的沙滩和近岸地形形态的变化，以估算风暴和湖水位变化引起的未来海岸地貌变化。