Peripheral gully and landslide erosion on an extreme anthropogenic landscape produced by mountaintop removal coal mining

Abstract

Mountaintop removal/valley fill coal mining (MTR/VF) in central Appalachia has buried an estimated 4000 km of headwater streams, but the long‐term geomorphic consequences of the anthropogenic valley fills and associated mined landscapes are poorly understood. These anthropogenic landscapes are not intended to be maintained in perpetuity once reclamation is complete. Here we present the first ever field‐based study of erosional landforms on this type of mined landscape paired with the subsequent examination of 10 regional LiDAR (light detection and ranging) datasets for gullies and landslides in a transect from eastern Kentucky to central West Virginia. Field observations indicate that overtopping of or intentional discharge from drainage systems and overtopping of valley fill terraces can initiate gullying. We manually extracted 1328 gullies from 512 km2 of mined landscape within the LiDAR datasets. Gullies are predominantly located along the perimeter of the mined landscape with the majority of gullies associated with drainage systems. The number of gullies linearly scales with mined area (R2 = 0.66). We observed 387 landslides along the perimeter of MTR/VF. Within the datasets, landslides per km2 ranged from 0.1 to 3.9. We observed 34 landslides within fully reclaimed valley fills, a heretofore undocumented phenomenon. Over 90% of these landslides were in Kentucky datasets, which covered only 47% of total mined area analyzed. Previously measured regional differences in the angle of friction of mine spoils or construction practices may explain the abundance of gullies and elevated level of landslide occurrence in eastern Kentucky valley fills relative to West Virginia. Observations of erosion on regionally extensive MTR/VF landscapes warrant further study to better ascertain ecological impacts. Large‐scale alteration by surface mining in steep landscapes may generally lead to peripheral gully erosion. © 2020 John Wiley & Sons, Ltd.

Identifying Geomorphic Process Domains in the Synthetic Landscapes of West Virginia, USA

“…They attribute gullies to overtopping of saturated terrace flats of valley fills creating localized saturation excess overland flow, with more than half of the gullies located peripheral to the edge of the valley fill. In addition, gullies were also identified by Reed and Kite (2020) on what were described as “relatively undisturbed slopes below mined areas.” In MTM landscapes, soil removal may limit incision depth of gullies once gullies incise to coarser valley fill fragments at least in the short term; soil production rates may increase with time since completion of mining and reclamation activities. Gullying is an introduced fluvial erosion process that is not characteristic of forested, soil mantled steep lands (Luffman et al., 2015) but appears common in the MTM landscape and which has been widely documented in other large scale surface mining sites, notably in drier, Mediterranean climates (Tarolli & Sofia, 2016).…”

“…Therefore, the fact that landslides on MTM lands were identified largely in Kentucky may be a product of the underlying geology and potentially the influence of chemical weathering Reed & Kite, 2020). For example, weathering solutes in Kentucky can be 2–10 times higher than those in streams studied by Ross et al.…”

“…Unmined regions are predominantly forested with dispersed residential land use (Maxwell & Strager, 2013). Along with extensive MTM, this region has a >100 years history of subsurface and contour surface mining, which included blasting bedrock along coal seams that followed the contours of the mountainside and depositing overburden downhill (Bell et al., 1989) but which represents a less extreme landscape change relative to MTM activities (Doerr & Guernsey, 1956; Reed & Kite, 2020).…”

“…In surface mining, humans excavate tens to hundreds of vertical meters of bedrock, radically altering local topography and geomorphic structure (Reed & Kite, 2020; Ross et al., 2016; Tarolli & Sofia, 2016) creating what may be considered “synthetic landscapes.” People alter landscapes to varying degrees (Lewin & Macklin, 2014), so we designate synthetic landscapes as these extreme cases of vertical rock excavation in which the resulting landscape form is uncoupled from the dominant historical geomorphic process that shaped it. Rather, the overall character of the current landform is dictated by engineering design and legal mandates such as the Federal Surface Mining Control and Reclamation Act (1977).…”

The Development Law of Mining-Induced Surface Cracks in Shallow Coal Seam Through Double Gullies Terrain: A Case Study in a Mine

“…Yushen Coalfield is located in the transition zone between the Loess Plateau and the Mu Us Sandy Land with rugged topography, and a gullied surface [9], under gullies topography, mining-induced surface cracks is a severe threat to the local fragile ecological environment [10][11][12][13]. Researchers have studied the influence of valley topography on mining-induced surface cracks using numerical simulation [14][15][16][17],…”