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.

How will anthropogenic valley fills in Appalachian headwaters erode? Miles Reed Mountaintop removal/valley fill (MTR/VF) coal mining in the Central Appalachian region has created the most extreme anthropogenic landscape on Earth by lowering ridges and infilling headwater stream valleys. No studies have attempted to detail erosional processes active on MTR/VR landforms. A combination of field work and LiDAR data observations documents erosional features on MTR/VF landscapes. Landscape evolution modeling explores future possibilities in valley-filled catchments. LiDAR data also allows for the quantification of valley-filled catchment alteration with statistically significant differences in both drainage density and depression storage capacity between "less disturbed" and valley-filled catchments. Field and LiDAR data observations show that the drainage systems associated with the periphery of the MTR/VF landscape are particularly vulnerable to gully erosion. This study also provides evidence of landslides occurring within fully reclaimed valley fills. Landscape evolution modeling reproduces gully erosion mechanisms documents in the field. Modeled erosion rates based solely on bedload averaged 10.9 mm kyr-1. Modeled erosion rates are higher on valley fills with constructed drains in the center of the valley fill relative to those with drains along the sides.

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The zone of weathered and fractured regolith between fresh bedrock and mobile soil is of wide interest. It is a common feature of terrestrial landscapes (Graham et al., 1994;Riebe et al., 2021) and it forms the thickest portion of the Critical Zone-the region between the top of the forest canopy and unweathered bedrock at depth-in many regions (