Abstract
There are numerous examples of past and present mine disposal into freshwater and marine coastal bays and riverine environments. Due to its high spatial resolution and extended water penetration, coastal light detection and ranging (LiDAR), coupled with multispectral scanning (MSS), has great promise for resolving disturbed shoreline features in low turbidity environments. Migrating mine tailings present serious issues for Lake Superior and coastal marine environments. Previous investigations in Lake Superior uncovered a metal-rich “halo” around the Keweenaw Peninsula, related to past copper mining practices. For over a century, waste rock migrating from shoreline tailing piles has moved along extensive stretches of coastline, compromising critical fish breeding grounds, damming stream outlets, transgressing into wetlands and along recreational beaches and suppressing benthic invertebrate communities. In Grand (Big) Traverse Bay, Buffalo Reef is an important spawning area for lake trout and whitefish threatened by drifting tailings. The movement of tailings into Buffalo Reef cobble fields may interfere with the hatching of fish eggs and fry survival, either by filling in crevices where eggs are deposited or by toxic effects on eggs, newly hatched larvae or benthic communities. Here, we show that the coastal tailing migration is not “out of sight, out of mind”, but clearly revealed by using a combination of LiDAR and MSS techniques.
Highlights
We combined two complementary remote sensing techniques to examine the issue of mining impacts in coastal regions, to address the recent “out of sight, out of mind” mentality of discharging tailings into coastal environments
Underwater regions southwest of the original tailing pile reveal stamp sand bars moving over
We showed that stamp sands were surrounding Buffalo Reef and that portions were actively encroaching into boulder fields
Summary
Light detection and ranging (LiDAR), is an active remote sensing approach, used here in the ALS (airborne laser scanning) version, where an airborne laser-ranging system acquires high-resolution elevation and bathymetric data [1]. The. Compact Hydrographic Airborne Rapid Total Survey (CHARTS) LiDAR data (see the Methods) are collected with aircraft-mounted lasers capable of recording measurements at a rate of 10–2,000-kHz pulses for above-water topographic surveys and 1–10-kHz for coastal water-penetrating bathymetric surveys, with a vertical precision of ±15 cm [2]. The LiDAR sensor records the time difference between the two signals to derive detailed measurements of water depth and bottom bathymetry. Under ideal conditions in coastal waters, blue-green laser penetration allows the detection of bottom structures to a depth of approximately three times passive light reflection, i.e., as deep as 22 m in the northern Great
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