A Review of Satellite-Derived Soil Moisture and Its Usage for Flood Estimation

Accurate knowledge of the spatiotemporal behavior of soil moisture (SM) can greatly improve hydrological forecasting capability. While ground-based SM measurements exhibit greater accuracy, they tend to be sparse in space and available for limited periods. To overcome this, a viable alternative is space-borne microwave remote sensing because of the near real-time observational capability at the global scale. However, its direct applications have been limited because of the uncertainty associated and the coarse spatial resolution the products are available at. Considering its usefulness and limitations, this paper is intended to provide an extensive review of satellite-derived SM and its applications for assessing flood risk in sparsely gauged or ungauged catchments worldwide. Therefore, we aim to identify and discuss research gaps, and finally propose future research directions for improvement and hydrological applications of these SM products. The paper starts with a brief introduction to satellite-derived SM products and consists of three interdependent focal areas: evaluation, improvement, and application of the satellite SM for flood risk alleviation. © 2019, Springer Nature Switzerland AG.