Assessing mining impacts utilizing a Landsat derived vegetation moisture index to characterize impacts of longwall subsidence on forest ecosystems

Abstract:

Subsidence from longwall coal mining impacts the surface and sub-surface hydrology in overlying areas. During longwall mining, coal is completely removed in large rectangular panels and the overlying rock collapses into the void. Though the hydrologic impacts of longwall mine subsidence on overlying vegetation have been studied in more arid systems, in humid-temperate regions these effects are not well understood. In particular, it is not clear how longwall mining will impact water availability to forests. To explore potential impacts, a geospatial analysis of tree canopy water content using Landsat satellite imagery of southwestern Pennsylvania was carried out. The normalized difference moisture index (NDMI) derived from Landsat imagery was applied to expose patterns of vegetation water stress, which were then compared across a temporal gradient of mined panels. NDMI values associated with panels from 2000 through 2014 were assessed within September 2014 Landsat NDMI imagery and compared to a population of pixels un-impacted by mining. This study elucidates mining impacts to forest canopies and the landscape features driving patterns of tree canopy moisture content in southwestern, PA.