MODELING THE INFLUENCE OF VEGETATION AND SOIL PROPERTIES ON THE SURFACE EVOLUTION OF MINED LANDS

With the ongoing energy transition, it is becoming increasingly important to understand how mined lands evolve after extracting the minerals needed for modern technology. Reclaimed coal mines in the Appalachian Coalfields offer excellent opportunities to study the evolution of landscapes affected by surface mining. Surface mining has altered the topography, material properties and vegetation composition of landscapes, raising the question of how these changes will influence future erosion on a landscape scale in mined drainage basins.

To understand the influence of surface mining on subsequent erosion dynamics, we leveraged the availability of digital elevation models (DEMs) that both pre- and post-date surface mining to model how landscape evolution differs on these unnatural landscapes.

We used the SPACE landscape evolution model to predict erosion trajectories over the next 10ka years for a 10km2 headwater drainage basin with half of its area impacted by surface mining.

First we compared the evolution of the pre-mined, and mined DEMs under the assumption that the change in topography from mining is not accompanied by any other important changes (e.g., to vegetation). We found that simulations on the pre-mining DEM yielded 20% greater sediment flux out of the watershed relative to the post-mining DEM due to the decreased frequency of steep slopes in the mined area. However, this is not consistent with prior field observations that found patterns of increased sediment yields from mined basins.

Next, to incorporate more realistic mining effects, we increased the fluvial erodibility within the mined areas to accommodate the change in soil cohesion due to loss and recovery of vegetation, and change in soil material properties typically associated with mining activities. These changes triggered a 25% increase in sediment flux from the post-mine basin relative to the pre-mining basin, mainly occurring at the margins of the surface mine - a result more consistent with field observations.

Our results show that topography alone is not a sufficient parameter to capture the effects of surface mining on surface processes. Our work in parameterizing a model with accurate local vegetation and soil properties will contribute to the understanding of how large-scale mining operations change Earth’s surface erosion rates.