OBSERVATIONS OF EROSION ON VALLEY FILLS PRODUCED BY MOUNTAINTOP REMOVAL COAL MINING

The Central Appalachian region hosts one of the most extreme anthropogenic landscapes on Earth. Mountaintop removal coal mining levels ridges and fills in headwater streams with large constructed landforms known as valley fills. The geometrically designed landforms can be up to 120 m thick and 200 million m³ in volume. While the resulting changes in stream ecology, hydrologic regime, and geochemistry have been studied, erosional processes operating in this landscape have hitherto gone virtually undocumented. No published governmental or corporate literature on the trajectory of landscape evolution of valley fills exists, so the long-term downstream impacts on stream channels from altered surface processes and exported sediment are difficult to ascertain. Observations of landslides, seepage erosion, gullying, and other processes from seventeen fully reclaimed valley fills produced by mountaintop removal coal mining have been documented in the heavily mined headwaters of the Upper Guyandotte River in Logan County, West Virginia, constituting the first geomorphic field work in this landscape. The field work allowed parameterization of the CAESAR-Lisflood landscape evolution model for the investigation of long-term sediment yield and characteristic landform development. Observations from the field, high-resolution LiDAR, and results from an initial 1000 year run of the landscape evolution model indicate that gully erosion will be the predominant erosional process. Water retaining structures positioned above valley fill side slopes may provide a common pathway to gully erosion or debris flows through failure or overtopping.