Flood Susceptibility and Stormwater Planning

Urban flooding is a common concern among the region's municipalities, yet many lack the resources to identify opportunities and strategies to address flooding issues. For example, a village may be aware of an area that floods regularly, but they may not know the cause or the drainage area that flows to the flooded area. One strategy for addressing this is to better integrate stormwater management into decisions about land use and development. The location and form of our development patterns play a large role in the amount of stormwater runoff generated and can be a key part of the solution.

To better position communities to improve stormwater management, CMAP has developed an approach to help identify problem areas and causes and begin to articulate discrete, on-the-ground opportunities for improvements that can reduce flooding. The purpose of this approach is to present a cost-efficient planning tool to assess flooding issues, inform stakeholders and decision makers about potential flood mitigation options, particularly green infrastructure and land use solutions, and to incorporate those solutions into land use and transportation decisions. The approach utilizes the Regional Flood Susceptibility Index, which was developed to identify priority areas across the region for flood mitigation activities. CMAP is using this approach in local planning projects though the Technical Assistance Program.

With support from the MacArthur Foundation, CMAP created a step-by-step guide to the spatial analysis and a stormwater planning data inventory to assist partners in planning efforts. A Guide to Flood Susceptibility and Stormwater Planning details the four main tasks of the approach, including data collection and development of a GIS database, data analysis to identify flooding problems and opportunities in a community, prioritization of implementation, and preparation of a draft plan.

Given the severity of urban flooding in northeastern Illinois, and the large, watershed-scale challenge of addressing overbank flooding, this methodology concentrates more on localized drainage problems and less on riverine flooding. This approach is not meant to identify specific engineered structural (gray infrastructure) solutions to the identified problems, which require advanced engineering analysis by the municipality, county stormwater management agencies, or other entities.