Abstract
Flood risk analysis is the instrument for local officials to create a sound strategy and adaptation plans for the impacts of inundation due to heavy rains, climate change and sea level rise. Hence, cities with aging infrastructure are retrofitting their stormwater management systems to mitigate the impacts. However determining the most at risk areas and the options for corrections is more challenging. As a result, there is an urgent need to develop a screening tool to analyze watersheds and identify the most at-risk areas. High-quality, open source data and sophisticated spatial analysis techniques allow engineers to create innovative ways to conduct watershed wide inundation analysis. In this study, the investigators developed a screening tool to identify at-risk properties by combining readily available data on topography, groundwater, surface water, tidal information for coastal communities, soils, open space, and rainfall data. Once the screening tool is developed, the means to identify and prioritize improvements to be funded with scarce capital funds is the next step. A tool box of solutions was developed to address flood risk and vulnerability. Testing of the screening tool was conducted in Broward County, Florida and shows encouraging results. Comparison with FEMA Flood maps and repetitive loss mapping indicates that the process works in a coastal community. The framework appears to be viable across cities that may be inundated with water due to sea-level rise, rainfall, runoff upstream, and other natural events.
Highlights
According to the Federal Emergency Management Agency (FEMA), over 98% of counties in the United States have experienced a previous flooding event, and just one inch of water can cause up to $25,000 in damage (FEMA, 2017)
Flood risk analysis is the instrument by which floodplain and stormwater utility managers create a sound strategy and adaptation plans to reduce flood potential in their communities
The goal of this study was to demonstrate a screening tool to identify areas at higher risk of flooding by implementing a water surface derived from groundwater levels, surface gage heights, and tidal influences to create a map of minimum soil storage capacity
Summary
According to the Federal Emergency Management Agency (FEMA), over 98% of counties in the United States have experienced a previous flooding event, and just one inch of water can cause up to $25,000 in damage (FEMA, 2017). To meet the longer-term goal of protecting life and property, FEMA created the National Flood Insurance Program’s (NFIP) Community Rating System (CRS) in 1990, to encourage community floodplain management activities. Under the CRS program, flood insurance premiums are discounted to reward community actions that meet the three goals of the CRS, which are to 1) reduce flood damage to insurable property, 2) strengthen and support the insurance aspects of the NFIP, and 3) encourage a comprehensive approach to floodplain management. The Florida Division of Emergency Management (FDEM) and FEMA funded development of template and prototype watershed master plans (WMPs) to improve the safety of the public, reduce property losses, and limit economic disruption while providing an annual savings of $60 million in discounted premiums for communities where the watershed plans could improve the community rating from a class 5 to a class 4. The grant funded development of a consistent framework to create WMPs across the state
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