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Indiana: Developing Real Time Flood Inundation Model

Resolution of seemingly small issues can lead to greater collaboration. Team members were aware of differences between USACE and Indiana Department of Natural Resources (IDNR) data; differing boundaries used in the models produced elevation differences of up to two feet. The Silver Jackets team facilitated resolution, and within a short time, the data were aligned. Without Silver Jackets, neither agency would have pursued resolution. The state sees this as a valuable service; when all agencies can agree on a single set of data, the state mitigation program benefits.

Success in resolving these differences led to a discussion of current needs, and the team devised a real-time flood inundation model. The National Weather Service projections and hydrology from the Advanced Hydrologic Prediction Service are combined with real-time gauge data from the U.S. Geological Survey (USGS). Models create a real-time view of the location and depth of flooding. When overlaid with tax assessment data, construction data, and structural value information for residential and commercial structures, an accurate prediction of potential damage can be calculated, employing the USACE depth-damage curve and Hazards United States (HAZUS) modeling. Although each database/model was originally written with a different digital structure, Indiana and Purdue University developed a bridge program to draw the individual models and programs together under an open architecture format and allow a person to run the program automatically upon demand in real time.

The program will run automatically when river levels reach a set trigger point and provide both current inundation information and predictive information for response and mitigation actions. The project allows emergency management personnel and the public to view current and predicted extent and depth of flooding through a Web portal. The near real-time and forecast flood inundation mapping, in addition to being viewable through a Web portal, will be downloadable in the form of Geographical Information Systems (GIS) files that can be imported into GIS applications such as the Federal Emergency Management Agency's HAZUS-MH hazard mitigation and loss estimation program. The overall cost for the pilot project was $750,000. No one single agency had the funding or the personnel to complete this project alone, yet with the collaboration of skills and funding, the pilot project was created using a minimal investment. The state of Indiana is now planning to utilize recently awarded Community Development Block Grant funds to apply the tool state-wide. The opportunity for major cost savings from damages avoided is tremendous. The effort provides a better predictive capacity, which will assist in zoning and planning, as well as targeting areas for mitigation such as acquisition or elevation.

After talking with the Indiana Silver Jackets team, the Mississippi "Camo" Jackets team has begun a similar effort. While no technical assistance funding is provided by USACE, the project was initiated due to Silver Jackets team collaboration. The Forrest County Board of Supervisors entered into a joint funding agreement with the USGS to initiate a cooperative program for flood inundation mapping with the Cities of Hattiesburg and Petal and the Forrest County Emergency Management District. Through assistance of the National Weather Service, this data is provided online and can indicate which community structures are likely to be impacted by floodwaters. Inundation maps also provide local officials additional information needed to better mitigate the impacts of flooding and build more resilient communities. The first phase of a multi-year flood inundation mapping project will include the USGS evaluation of existing flood models on the Leaf River and the initial construction and instrumentation of a new flood-monitoring site on the Bouie River at Glendale Avenue. The $26,000.00 cost will be shared equally by the USGS and Forrest County, with support from the cities of Hattiesburg and Petal. Hazard Mitigation Grant Program funds will be applied to assist with a portion of the local share. Upon completion of the project, both the Leaf and Bouie Rivers will provide real-time river stage data via the internet during flood hazard events, and local residents and emergency managers will have valuable information for hazard mitigation.