This presentation is part of the Supporting Sediment Transport organized session.
Coastal erosion and the impacts associated with it such as infrastructure damage and habitat loss are ubiquitous issues throughout the Great Lakes region. During periods of high lake level, these issues are at the forefront of management concerns within coastal communities. While decades of coastal change research have been conducted throughout the Great Lakes region and our scientific understanding of the driving processes of coastal erosion continues to grow, we generally lack the ability to accurately predict future coastal changes. This stems primarily from the challenge in predicting future lake levels, which are inherently tied to weather patterns that cannot be reliably forecasted beyond 6 months. While an understanding of the predictive limitations helps to set realistic expectations for coastal managers, it does not provide meaningful planning assistance which is requisite for working towards coastal resilience. To address this, our recent research has focused on developing simple methods for predicting the likelihood of beach recovery following high lake levels at coastal sites along the Great Lakes. The foundation of our approach is to utilize publicly available datasets, such as NOAA lake level data and the USACE Wave Information Studies hindcast wave data, and simple to collect beach and nearshore morphology data that can be generated either by research teams or community scientists. With these data, we utilize fundamental morphodynamic relationships to predict the active zone of coastal sediment transport under past and present wave and water level conditions. The likelihood of sediment transport can then be estimated for varying morphodynamics conditions (e.g., erosive, accretionary) and compared to present morphology to infer whether beach recovery is probable for a site. Case studies along the eastern coast of Lake Michigan were used to develop and evaluate this approach and revealed that moderately erosive conditions that preferentially pull sand lakeward are the most dominant morphodynamic condition. Accretionary conditions that lead to beach recovery occur less frequently (generally less than 25% of the time) and only operate on a narrow portion of the nearshore, within 100 m of the shoreline. These results mechanistically explain why shoreline armoring leads to the loss of beach area and minimizes beach recovery as armoring drives sand lakeward of the zone where accretionary waves operate. This approach provides coastal managers with a probabilistic tool for predicting future coastal change and is currently being scaled up and operationalized throughout the State of Michigan.
