The significant economic, social, infrastructural, and environmental challenges posed by flooding impair communities' efforts to achieve local and regional goals. Chronic flooding damage can make communities less desirable, as does the flood-related deterioration of building facades, streets and sidewalks, and other infrastructure and property. CNT found that wet basements can decrease property values by 10 to 25 percent and are cited as a primary reason for not purchasing a home. According to FEMA, nearly 40 percent of small businesses never reopen after a flooding disaster. Increasing floodwaters also strain our natural and open spaces as streambanks erode, pollutants and invasive species degrade habitat, and groundwater recharge is reduced.
Flooded streets reduce mobility and increase maintenance costs for repair and reconstruction. In addition to the direct costs of delay and reduced access, road and transit closures can cause a cascade of indirect impacts that impair economic productivity, safety, emergency services, bicycling, and walking. When flooding does occur, it does not affect all populations or communities equally. Exposure to flooding risks appears to be greater in populations and communities already facing socioeconomic, demographic, and health challenges and barriers.
[GRAPHIC TO COME: An illustrated graphic explaining the differences between urban and riverine flooding.]
While flooding is a natural occurrence, continued urbanization and climate change are leading to more flooding. Development of impervious cover prevents the infiltration of rainwater and generates stormwater runoff, while climate change results in more frequent and intense storm events. Increased stormwater runoff can overwhelm local drainage systems and lead to urban flooding, such as ponding water in streets and yards, basement seepage, and sewer backups. Stormwater eventually flows to rivers and streams and can cause riverine flooding as water flows over riverbanks and into the floodplain. Buildings and roads in floodplains are at greater risk of flooding and can lead to flooding downstream as the natural function of the floodplain is reduced.
From the extensive network of preserved habitat, open space, and wetlands to the engineered detention basins, sewer systems, and Tunnel and Reservoir Plan, the Chicago region has made significant investments in green and gray infrastructure. However, development in significant portions of the region predated modern stormwater management standards, and even current infrastructure design specifications rely on old data and do not account for a changing climate. Some neighborhoods experience flooding after less than two inches of rain -- small storms that, over time, result in significant harm to property and quality of life.
ON TO 2050 reaffirms GO TO 2040’s recommendation to integrate planning with water resource management. The region can advance stormwater and floodplain management in various ways that include protecting and enhancing the stormwater services currently provided by natural areas and open spaces; avoiding investments in areas where environmental conditions -- from floodplains to low-lying areas -- pose high risk of urban and riverine flooding; and minimizing stormwater runoff volumes through development regulations and design standards. Integrating stormwater management into larger planning can help coordinate investments and leverage limited resources to address flooding while achieving other community goals. CMAP has developed the Regional Urban Flooding Susceptibility Index to help prioritize areas for planning and mitigation investment, particularly in locations with municipal capacity constraints that make it difficult to address these challenges.
The following subsection describes strategies and actions to implement this recommendation.