PNNL

Abstract

The Lower Mississippi River Basin (LMRB) has experienced significant changes in land cover and is one of the most vulnerable regions to hurricanes in the United States. Here we study the impacts of land cover change on the hydrologic response to Hurricane Ida in LMRB. By using an integrated surface-subsurface hydrologic model, ELM-ParFlow, we simulate the effects of different land cover scenarios on the flood volume and peak timing induced by rainfall from Hurricane Ida. The results show that land cover changes from 1850 to 2015, which resulted in a smoother surface and less vegetation, exacerbated both flood peak time and volume from Hurricane Ida. The effects of land cover changes can be decomposed into two mechanisms: a smoother surface routes more water faster to a watershed outlet, and less vegetation allows more water to contribute to surface runoff. Simulations isolating the two mechanisms show that a smoother surface has larger impact on flood volume and peak time than vegetation cover change. The study provides important insights into the complex relationship between land use, land cover, and hydrologic processes in coastal regions.