Where light penetration is excellent, the combination of LiDAR (Light Detection And Ranging) and passive bottom reflectance (multispectral, hyperspectral) greatly aids environmental studies. Over a century ago, two stamp mills (Mohawk and Wolverine) released 22.7 million metric tons of copper-rich tailings into Grand Traverse Bay (Lake Superior). The tailings are crushed basalt, with low albedo and spectral signatures different from natural bedrock (Jacobsville Sandstone) and bedrock-derived quartz sands. Multiple Lidar (CHARTS and CZMIL) over-flights between 2008–2016—complemented by ground-truth (Ponar sediment sampling, ROV photography) and passive bottom reflectance studies (3-band NAIP; 13-band Sentinal-2 orbital satellite; 48 and 288-band CASI)—clarified shoreline and underwater details of tailings migrations. Underwater, the tailings are moving onto Buffalo Reef, a major breeding site important for commercial and recreational lake trout and lake whitefish production (32% of the commercial catch in Keweenaw Bay, 22% in southern Lake Superior). If nothing is done, LiDAR-assisted hydrodynamic modeling predicts 60% tailings cover of Buffalo Reef within 10 years. Bottom reflectance studies confirmed stamp sand encroachment into cobble beds in shallow (0-5m) water but had difficulties in deeper waters (>8 m). Two substrate end-members (sand particles) showed extensive mixing but were handled by CASI hyperspectral imaging. Bottom reflectance studies suggested 25-35% tailings cover of Buffalo Reef, comparable to estimates from independent counts of mixed sand particles (ca. 35% cover of Buffalo Reef by >20% stamp sand mixtures).

This report details the process of developing and validating a multidimensional hydrodynamic, salinity, sediment transport, and coastal wetland morphology model of the Lower Mississippi River Delta. This model has been developed to run various sediment diversion scenarios. The results of these scenario analyses are documented in this report.The morphologic modeling results for the diversion scenario analyses show net land gain in the near vicinity of the diversion outlets and net land loss farther away from the outlets. The areas of land gain roughly correspond with the zones of sand deposition whereas the areas of largest land loss correspond with areas where there is diversion-induced inundation but not significant deposition of sediment from the diversion. The modeling results indicate that diversion-induced inundation results in a reduction in plant productivity, which induces an acceleration of land loss.Significant uncertainty exists with respect to the response of the existing wetland vegetation to diversion-induced inundation. The magnitude of this uncertainty can only be narrowed with further consensus building within wetland science.With respect to salinity, the receiving waters tend to freshen significantly during diversion operations. However, when operations cease, the recovery of salinity is almost entirely determined by prevailing offshore and/or riverine conditions.

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