Using LiDAR to reconstruct the history of a coastal environment influenced by legacy mining

LiDAR (light detection and ranging) data can be used to create fine digital elevation and bathymetric models (DEMs). Here we examine natural coastal erosion in Grand Traverse Bay, Michigan, a part of Keweenaw Bay in Lake Superior, and discuss how a variety of geological features (submersed river bed and channels associated with the Houghton Low; Nipissing dunes) interact with long-term sediment accumulation patterns. The geological features also modify migrating tailings from a legacy mining site. The combination of LiDAR derived images and aerial photographs allowed us to reconstruct the historical movement of tailings along the coastline. A total of 22.8 million metric tonnes (Mt) of stamp sand were discharged into the coastal environment off Gay, MI. Over a span of 80 years, beaches to the southwest of Gay have progressively received 7.0 Mt (30.7%) of the mass eroded from the original pile, whereas 11.1 Mt (48.7%) have moved into the bay. The total amount accumulated along the beaches now greatly exceeds the mass remaining on the original tailings pile (3.7 Mt; 16.2%). Bathymetric differences between two LiDAR surveys (2008 and 2010) were also used to estimate the mass, and to track the movement of migrating underwater stamp sand bars. These bars are moving southwesterly towards Buffalo Reef, creating a threat to the lake trout and lake whitefish breeding ground.