Floodplain Mapping in Response to Surface Mine Reclamation

Abstract

Surface mining and the associated reclamation cause changes in land use and land cover. This change can affect the hydrologic balance. In some cases, an increase in number and magnitude of flood events is observed both on site and in surrounding areas. This research analyzed the hydrologic effects downstream of a reclaimed surface mine, considering the impact of an alternative reclamation technique. Geomorphic landform design (GLD) is a reclamation method that considers the development mature landform shapes to help create a long-term hydrologic balance. Flood maps were created for the pre-mined condition and compared to maps created for three reclamation conditions: conventional reclamation, GLD (During mining) reclamation, and GLD (Post-mining) reclamation. The valleyfill and study site is located in southern West Virginia. Approximately 2.1 km of the adjacent downstream channel were evaluated. The study area receives 101.6-127 cm precipitation annually and has a basin slope range of 0.44-0.56 m/m. GIS data were used to develop a schematic of the downstream channel. Cross-sections were extracted from a triangulated irregular network (TIN) developed from 1/9arc-second elevation data. These geometric data and projected stormflow hydrographs for seven storm events were used to develop both steady and unsteady flow 1-D hydraulic models (HEC-RAS). The resulting water surface elevations were used to display flooding extents over time resulting from each reclamation condition. For smaller storm events (e.g. 2-yr), conventional reclamation resulted in decreased flooding, and increased flooding was observed for large storm events (e.g. 100-yr, 500-yr). The GLD (During mining) reclamation condition resulted in increased flooding; this increase was mitigated with time. The GLD (Post-mining) results were comparable to those of the pre-mining condition. GLD has the potential to mitigate flooding impacts from surface mining in the long-term in southern West Virginia, but is dependent on properly sized channels and stability of landforms. * (Knebl et al. 2005) *Not specified.

Hydrologic Response and Erosion Modeling of Geomorphic Landform Reclamation in Mountainous Terrain

“…Geomorphic landform design has been identified as a potential reclamation practice for surface mined lands and valley fills in Central Appalachia (Russell and Quaranta, 2013;Sears et al, 2013;Sears et al, 2014) due to its successful implementation in areas outside of Central Appalachia, particularly in semi-arid regions of the southwestern U.S. (Measles and Bugosh, 2007;Martin-Moreno et al, 2008;Martin-Duque et al, 2009). Research studies for geomorphic landform design (GLD) in Central Appalachia have focused on establishing design protocol (Sears et al, 2012;Sears et al, 2013), testing slope stability (Russell et al, 2014), evaluating flooding and stormwater movement of a single reclaimed valley fill (Snyder, 2013;O'Leary, 2014), and identifying implementation challenges (Depriest et al, 2015). Limited research has been completed to quantify the effects of surface mining and valley-fill construction on hydrologic response at the landscape scale (>100km 2 ) (Ferrari et al, 2009;Miller and Zegre, 2014).…”

“…Previous research on GLD implementation in Central Appalachia has been performed through modeling, as no GLD site has been constructed in Appalachia to date. Modeling focusing on slope stability (Russell, 2012;Russell and Quaranta, 2013), storm response (Snyder, 2013;Hopkinson et al, 2015b), flooding risk (O'Leary, 2014;Hopkinson et al, 2015b), and implementation challenges (DePriest et al, 2015). However, GLD prediction modeling of erosion at the watershed scale and hydrologic response at the landscape scale have not been researched.…”