Using storage of coal-mining subsidence area for minimizing flood

Floods are one of the most devastating natural disasters, especially in the midstream plain area of the Huaihe River Basin (HRB) in China, where it is densely populated. This region has suffered from serious backwater flood problems due to its topography and geomorphology. Additional storage space is critical for this region in order to control flood. The middle reach of the Huaihe River is a coal-rich region. The large subsidence areas caused by coal mining may help reduce the issue of insufficient flood storage space, and therefore evaluation of the flood storage capacity in the subsidence areas becomes necessary. A distributed coupled surface water - groundwater model, MODCYCLE, was redeveloped to simulate the interaction between the rivers, the water in the subsidence areas and groundwater. The model was used to simulate maximum flood storage capacity in the subsidence areas and the ability to reduce flood peaks. Two scenarios were created for land subsidence conditions in 2010 and 2030 where typical flood events in 2003 were used. It is revealed that for the 2010 scenario, there was flood overflow even with the maximum storage space used, whereas for the 2030 scenario, the subsidence areas could completely contain the flood water, and therefore eliminate the backwater flood problem. Compared with the 2010 subsidence scenario, the water levels in the depressions can also be significantly reduced in the 2030 subsidence scenario. Our results, from an integrated hydrological modeling's perspective, suggest that using the subsidence areas caused by coal mining for flood storage has the potential to alleviate the problem of backwater flood in the study area, and in the meantime provides an alternative management approach for handling the subsidence areas.