Combining Engineering Applications and Monitoring to Evaluate New Strategies for Protecting Barrier Islands in Western Lake Superior

In recent years, sustained high water levels and wave action have degraded beaches and eroded banks of barrier islands in western Lake Superior. The U.S. Army Corps of Engineers (USACE) began exploring the beneficial use of dredge material from the St. Louis River Estuary to nourish beaches and prevent further degradation of barrier islands. However, high resolution digital elevation models (DEMs) were needed to establish pre-nourishment conditions and evaluate changes to the beaches post nourishment.

Therefore, the USACE partnered with the U.S. Geological Survey to collect integrated shoreline elevation and nearshore bathymetry data to develop a high-resolution DEM for the beach area at Minnesota Point in western Lake Superior. In August 2019, multibeam and single beam bathymetry data were collected simultaneously with boat-mounted terrestrial LiDAR data to create a 10-meter DEM referenced to the International Great Lakes Datum of 1985. The first beach nourishment occurred in mid-November 2019. However, within a couple weeks of the beach nourishment, a large snowstorm created heavy waves and caused the USACE to be concerned about erosion of the new material. Therefore, additional elevation data of the beach land area were collected using an unmanned aircraft system and structure for motion (SFM) photogrammetry.

The results of SFM surveys are currently being compared against original pre-nourishment survey data. Additional surveys and beach nourishments are planned for summer and fall of 2020, respectively. Similar beach nourishment and survey techniques could be used to maximize beneficial uses of dredge material and preserve barrier islands throughout the Great Lakes.