Abstract:
The water accumulation induced by mineral resource exploitation and surface subsidence is a significant contributor to arable land degradation in mining areas with shallow groundwater tables, posing a major bottleneck to sustainable development of mines. To address the need for early monitoring and identification of subsidence-induced waterlogging in mining regions, a Mining-area Radar Water Index (MRWI) was developed. A total of 29 SAR images of Sentinel-1 GRD with 10-meter spatial resolution in IW mode during 2017 were collected and processed, and the dynamic monitoring and evolution analysis of water accumulation in the subsidence area were carried out. The monitoring performance of MRWI, Visible and Shortwave Infrared Drought Index (VSDI) and Sentinel-1 Dual-polarized Water Index (SDWI) was compared and analyzed by using three quantitative indexes:
P (precision),
R (recall) and their harmonic mean
F1. The results showed that: MRWI, VSDI and SDWI could effectively identify the range of water bodies in the areas with obvious surface water coverage, and the average values of
P,
R and
F1 of MRWI compared with VSDI reached 94.45%, 94.83% and 94.46%, respectively. Compared with SDWI, the average values of
P,
R and
F1 of MRWI reached 99.86%, 94.03% and 96.85%, respectively. MRWI has a strong ability to detect subsidence and water accumulation in the early stage. Taking the No. 2 water accumulation area as an example, MRWI detected the phenomenon of subsidence water accumulation on June 6, 2017, and neither VSDI nor SDWI can indicate this phenomenon at this time. On or about July 12, 2017, subsidence caused the surface to be covered by water, at which point MRWI, VSDI, and SDWI were all indicative of subsidence. MRWI has strong time series monitoring capabilities. MRWI based on Sentinel-1 radar data can achieve time series monitoring at least once every 12 d, and can use the results of long time series to analyze the temporal and spatial evolution trend of water accumulation in the subsidence area of the mining area. MRWI provides strong technical support for the early monitoring and treatment of subsidence and water accumulation in mining areas with high groundwater level.