When ten inches of rain fell on saturated Indiana soils, it flowed into streams already swollen from a wetter than normal spring. The heavy rainfall resulted in severe flooding, causing three deaths, evacuation of thousands of residents, and hundreds of millions of dollars of damage to residences, businesses, infrastructure and agricultural lands. In all, 39 Indiana counties were declared Federal disaster areas. To make informed decisions, timely flood data were needed by Federal, State and local agencies.
Purdue’s School of Civil Engineering, Geomatics Engineering produced flood maps and a Google Earth application for Indiana using Landsat satellite images. The images were acquired during the height of the flooding period and made available courtesy of the US Geological Survey (USGS). Once the areas of water were identified, basic information was layered over the images, including topographic elevation, city and county boundaries, roads and hydrography. Stream gauge data from USGS was used to determine water depth, and compared with normal levels found in Landsat images from earlier in the year.
This information was made available to the Indiana Department of Homeland Security and other emergency management officials who were coordinating the disaster response and recovery efforts. The information was published to Google Earth and as static maps.
Results
These data layers, landsat images, high-resolution aerial images and most importantly, flood inundation areas, provided a quick-look flood damage estimate for emergency managers from all levels of government. Having pdf’s of the inundation maps and a Google Earth application gave users, many of whom did not have a GIS background, a choice between a static map of the state and a user-defined area of interest. Access to user-friendly quick-look flood inundation data provided officials with vital information to mitigate, respond and recover from this and other flood disasters.
