Flooding is one of the most devastating aftermaths of hurricanes after landfall. NASA’s SeaWinds scatterometer, a stable and accurate radar aboard the QuikScat satellite, has a unique capability to identify potential flood areas. This is accomplished by using QuikScat data to map areas where soil moisture increases significantly from precipitation water that reaches to and accumulates on land surface, leading to a saturation condition in soil wetness. Such maps provide timely information on the location and extent of areas susceptible to flooding, which is crucial for managing flood disasters.

Potential flood areas (yellow) associated with hurricanes Ike and Hanna.

The 2008 hurricane season has been a busy one so far, and has affected NASA facilities. Hurricane Ike made landfall at Galveston, Texas, on September 13, 2008 as a category-two hurricane, heading directly to Houston. Ike forced the closing of NASA’s Johnson Space Center in Houston and shut down the International Space Station Flight Control Room. On September 14, 2008, QuikScat detected several potential flood areas in Texas and surrounding states (left panel in the figure above). However, these areas were separated and localized in different locations without forming a widespread band of flood potential over an extensive region. Although Ike caused extensive damages by strong winds, it did not carry an extreme amount of rainwater and widespread flooding did not occur, except in areas affected by the storm surge near the coastline.

Unlike Ike, Hanna made landfall near the North and South Carolina border as a tropical storm on September 6, 2008, just a week prior to Ike’s landfall in the United States. The QuikScat map in the case of Hanna on September 6, 2008 (right panel in the figure above) delineated a widespread band of flood potential extending over several states across the northeastern United States. Areas of increased soil moisture were also observed (green-red) in both North and South Carolina. Although Hanna’s winds were weaker than Ike’s, Hanna carried excessive rainwater that was deposited over an enormous region, causing floods in many areas up to New Hampshire. These QuikScat results show that wind and flood are disparate characters of storms and hurricanes: a weaker storm may carry more water and have a higher flood potential.