Catastropic flooding could be predicted nearly a year in advance through satellite-based assessments of impregnated watersheds, asserts a new study.
The satellites in NASA's Gravity Recovery and Climate Experiment (GRACE) were used in several case studies to determine how much lead time could be acquired by examining saturated watersheds, tracts of land that funnel water into a water bodies. Nature Geoscience published the study, "River Basin Flood Potential Inferred Using Grace Gravity Observations at Several Months Lead Time."
Jay Famiglietti, a senior author from the study, said the Grace data can help predict flooding by depicting the events that lead up to it.
"These data can show us when river basins have been filling with water over several months," said Famiglietti. "We're not talking about actual flooding but about the saturation level of the ground and its predisposition to flooding. When it finally rains and the basin is full, there is nowhere else for the water to go."
Grace's twin satellites measures gravitational anomalies in Earth's landmasses, changes that can be observed when the ground shifts or begins to fill with precipitation.
"Applying a time-lagged autoregressive model of river discharge, we show that the inclusion of Grace-based total water storage information allows us to assess the predisposition of a river basin to flooding as much as 5-11 months in advance," stated the study. "Additional case studies of flood events in the Columbia River and Indus River basins further illustrate that longer lead-time flood prediction requires accurate information on the complete hydrologic state of a river basin."
The Missouri and Souris rivers flooded between May and August of 2011, caused an estimated $2 billion in damage and claiming the lives of five people. Using the Grace satellites, researchers were able to review the progress of the flood and determine that an established system using Grace, or satellites similar to those in the project, can effectively predict major floods in the future.
"Here we demonstrate that basin-scale estimates of water storage derived from satellite observations of time-variable gravity can be used to characterize regional flood potential and may ultimately result in longer lead times in flood warnings," stated the study. "We use a case study of the catastrophic 2011 Missouri River floods to establish a relationship between river discharge, as measured by gauge stations, and basin-wide water storage, as measured remotely by NASA's Gravity Recovery and Climate Experiment (GRACE) mission."
The review of other floods helped the researchers conclude that a lengthy history of an entire river basin helps make the most accurate forecasts as it factors in total water storage as well as snowfall and river run rates.
