1. Background of the Study

Floods of all types present significant economic and social challenges in the United States and around the globe. Losses continue to grow and the potential impact of climate change and population increases are expected to accelerate this rise. Hurricanes Maria,  Harvey, and Irma have reemphasized the magnitude of the impacts that floods pose to the nation. Primary attention has been focused on the flooding that results from the overflow of rivers and from high water along coastlines as a result of sea level rise, tidal variability, and coastal storm surges. However, contemporary analysis in the United States and abroad indicate that a growing segment of flood losses occur because of flooding outside the 1% annual chance flood zone (the regulatory floodplain) of the US National Flood Insurance Program (NFIP) in both coastal and riverine environments. Much of this flooding occurs in more densely occupied urban areas where it has been considered as “stormwater or sewer problems” whose impacts are frequently seen as local and relatively minor. In many of these impacted areas, the population is socially and economically vulnerable and unable to deal with the flood threats it faces on a recurring basis and whose economic resources do not lead to the tracking and reporting of this type of flooding.

Unfortunately, little data are available to determine the extent of losses in these areas, most of which are not mapped with any detail under the NFIP and where the very nature of the hazards (street overflow, sewer backup, groundwater, etc.) are not clear. Although property owners in most of the areas are eligible to purchase flood insurance under the NFIP, problems of lack of understanding of the risks, affordability, policy exclusions (basements), and owner-renter relationships result in limited participation by residents in federal or commercial insurance programs. Pioneering work by the Center for Neighborhood Technology (CNT) and the State of Illinois have identified significant losses within the Chicago metropolitan area and the state that are occurring outside the regulatory floodplain.The State reported that flooding in urban areas in Illinois caused, between 2007 and 2014, at least $2.319 billion in documented damages, of which $1,240 billion were private claims that typically represent basement flooding and sewer backup and that over 90% of urban flooding damage claims from 2007 to 2014 were outside the FEMA Special Flood Hazard Area. Unfortunately, little analysis has been conducted at the national level. 

The University of Maryland Center for Disaster Resilience and the Texas A&M Center for Texas Beaches and Shores, with the support of the Hagler Institute for Advanced Study at Texas A&M University, are conducting a scoping analysis of the extent and consequences of urban flooding and identifying potential solutions for mitigation of such flooding. With the cooperation of the Federal Emergency Management Agency, the National Oceanic and Atmospheric Administration, the Small Business Administration and the Census Bureau, the study team has analyzed data concerning reported flood losses across the country. However, since the majority of these data apply to riverine and coastal flooding and since federal assistance is not normally provided for smaller non-riverine/coastal events, it has been difficult to more precisely identify where urban flooding is a problem for communities. It is clear from the data that has been obtained and spatial analysis of claim locations that substantial flood losses occur outside the 1% floodplain of the NFIP and, in many cases, in areas not connected directly to riverine or coastal sources.