Stormwater and Flooding

Stormwater and Flooding

Stormwater management and flood prevention in northeastern Illinois can be particularly challenging due to the region's flat topography and broad floodplains. 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. As a result, the existing gray and green infrastructure designed to handle runoff is inadequate and requires significant investment in order to reduce negative impacts of pollutants in waterbodies and flooding on private property, local infrastructure, regional transportation, and natural resources.

Stormwater crosses jurisdictional boundaries and the amount of stormwater runoff generated is heavily influenced by land use and transportation. The design of our streets and roads, which generate stormwater runoff and are also in public ownership, can play a key role in reducing the negative impacts of future storm events. Regulations can help prevent new development and redevelopment from contributing to the problem and land use and development activities could potentially offer shared solutions for existing neighborhoods. Implementing ways to better manage stormwater can also help the regional economy by reducing the stress flooding can cause on municipal budgets, the use of clean water and wastewater treatment costs, and private property damage and loss.

Integrating better stormwater management decisions into local planning, municipal operations and budgeting decisions, data and information sharing, and transportation planning and programming will be essential to tackle this problem. GO TO 2040 calls for integrating land use policies and site planning with water resources and identifies compact development, redevelopment, water conservation, and green infrastructure as essential techniques. The plan reinforces the need to not just rely on stormwater detention, but also to reduce the volume of runoff and use green infrastructure to manage stormwater. The plan also recognizes the need to develop sustainable sources of financing for stormwater retrofits and to provide performance data to stormwater managers. CMAP is currently engaged in the following activities related to stormwater management:

Regional Flood Susceptibility Index

The regional flood susceptibility index (FSI) helps prioritize areas susceptible to flooding for planning and mitigation investments. Given the different causes and contributing factors for riverine and urban flooding, CMAP developed two regional flood susceptibility indexes to identify areas across the region that may require closer investigation for flood mitigation activities.

Flood Susceptibility and Stormwater Planning

As more communities experience flooding issues, municipal planning projects are changing to better incorporate stormwater management solutions alongside other community objectives. Historically, flooding concerns have been addressed separately via engineering studies, often missing opportunities to complement other goals or projects within a community. In response to this issue, CMAP has released a Guide to Flood Susceptibility and Stormwater Planning. This GIS-based, planning-level approach is meant to help planners identify areas with potential flooding issues and corresponding land use based solutions for communities in the Chicago region. CMAP is incorporating this approach in local planning projects though the Local Technical Assistance (LTA) Program.

Stormwater Planning Data Inventory

The Stormwater Planning Data Inventory includes a list of datasets that can inform local and regional analyses of flooding issues. Many of these datasets are used in the Guide to Flood Susceptibility and Stormwater Planning and some are available on the CMAP Data Hub.

Calumet Stormwater Collaborative

CMAP is an active member of the Calumet Stormwater Collaborative, which was formed in 2014 to improve stormwater management through investments in and coordination of green infrastructure solutions. The Collaborative developed a repository of resources that can help Calumet communities plan, pay for, and implement effective stormwater management strategies.

Stormwater Utilities

Storm sewers, culverts, and a host of other stormwater infrastructure components need repair, but funding for capital improvements is scarce. CMAP has outlined the legal authority and key components of a establishing a stormwater utility to respond to these challenges.