From USGS Ecosystems Land Change Science Program:
USGS researchers are leveraging advances in satellite-based monitoring to better characterize and predict flood inundation, which is essential for effective emergency response and water management planning.
Atmospheric rivers (ARs) are long corridors of water vapor transport that extend from the tropics to mid-latitudes. These meteorological phenomena can bring large amounts of rain or snow to the western United States each year. In locations like California, AR storms are responsible for the largest magnitude floods in the state. Emergency responders, water managers and planners need to be able to predict where flood inundation will occur due to an AR storm. But the complex connection between AR precipitation and flooding – which is needed for these predictions – is only partially understood.
How remote sensing is helping complete the picture
Fortunately, advances in satellite-based monitoring enabled USGS researchers to create long-term map records of surface water dynamics (including flooding) from 20 years of MODIS satellite imagery. These new records are high frequency (monthly) and cover the entire year. The winter-time record is especially valuable; previous research using Landsat excluded this time period due to wintertime cloud cover limitations in the satellite image record.
In collaboration with the Desert Research Institute and other federal and academic partners, USGS scientists used these map products to investigate the connection between ARs and wintertime flooding in California’s Central Valley. Their study was recently published in the Journal of Flood Risk Management. The researchers compared spatially explicit locations of winter inundation to a chronology of atmospheric river landfalls, the corresponding integrated vapor transport associated with each storm (a measure of the total amount of precipitation passing over a specific area), and surface conditions (i.e., antecedent soil moisture).
They found significant relationships between inundation patterns and climatic factors, helping identify specific locations and conditions under which flooding occurs in relation to ARs. The findings also indicate areas where surface water frequently occurs outside of designated flood boundaries.
Actionable science
By revealing the relationship between AR storms and winter inundation patterns, the scientists were able to assess infrastructure flood exposure and identify possible floodwater management strategies, specifically the opportunity to use floodwaters for aquifer recharge. This knowledge can help inform land use planning, like infrastructure development and cropland distribution. The findings also highlight where AR-driven flooding occurs, driving home the importance of revising flood boundary maps and management strategies. Overall, remote sending products are a valuable decision-support tool for enhancing flood risk mitigation and groundwater recharge efforts in the region and beyond.
