Building Rain Resilience
As cities struggle to adapt to climate change, they must consider the impact of more frequent rainfall and more severe storms. Many cities are aware of, and working on, riverine and coastal flooding risks, but fewer have considered the hazards posed by localized flooding. Flooding from rain may be a less obvious threat than that from bodies of water, but can cause the same types of property damage, street closures, and public health dangers.
Currently, most cities only have a map of floodplains, which fails to consider elements that cause flooding from rain. Most critically, floodplain models do not account for the level of impervious surface cover in a neighborhood that affects how much rain can be absorbed versus how much runs off, especially into lower areas nearby. Discrepancies also exist between listed elevations for floodplain purposes and effective elevation due to basements. Mapping specifically for rain-based flooding can be a first step to assess the most vulnerable areas, whether undertaken through flood complaint data, detailed topography, or even more qualitative measures to identify problem spots. Whatever the specific tool used, a clearer picture of where rain accumulates in an urban environment is an essential first step. This information can both help inform citizens and emergency crews during a flood event, and help cities plan infrastructure better.
There are a range of tools to help prevent flooding by managing rain where it falls. Many cities are innovating with green infrastructure, a tool that emphasizes capturing water onsite, and either infiltrating it into the ground or saving it for future use. Either way, less runoff reaches areas at risk of flooding. More routine tracking and maintenance of traditional gray infrastructure problem areas can also keep localized flooding in check.
For any infrastructure project, funding is a key consideration, and there are a few successful ways to pay for improved rain resilience. Instituting a stormwater management fee based on impervious surface area can serve to both generate funding for necessary upgrades while also incentivizing property owners to reduce the volume of runoff generated by their site, alleviating burdens on infrastructure. Integrating stormwater infrastructure renovations into other projects like street upgrades, green job training programs, or recreational area enhancements can spur funded partnerships with other government agencies.
Flooding from rain will continue to pose a serious risk, but cities have multiple tools to build their rain resilience before its necessary.
Ten Actions for Cities + Towns, The Center for Neighborhood Technology, January 8th, 2016. Read more.
Reducing Damage from Localized Flooding: A Guide for Communities, Federal Emergency Management Agency, June 1st, 2015. Read more.
Illinois Urban Flooding Awareness Act Report, Illinois Department of Natural Resources, June 1st, 2015. Read more.
A Rain Ready Nation: Protecting American Homes and Businesses in a Changing Climate, The Center for Neighborhood Technology, January 1st, 2015. Read more.
Our Changing Climate: Heavy Downpours Increasing, National Climate Assessment, October 1st, 2014. Read more.
Banking on Green, American Rivers, the Water Environment Federation, the American Society of Landscape Architects, and ECONorthwest, April 1st, 2012. Read more.
Understanding where and how often rain falls in your city is a key first step to targeting flood prevention. Seattle has developed a system to monitor rainfall and plans to expand to add modeling that can further target areas in most need of flood mitigation upgrades, while Washington, DC has projected future precipitation to assist with planning. A handful of smaller cities like Salem, OR and Charlotte are also implementing rainfall monitoring systems, linking alerts directly to public works crews and emergency responders for rapid interventions during intense storms. For monitoring after-the-fact, some cities are working with universities or their own GIS staff to map elevation along with known flooding incidents to identify target areas. Even low-tech interventions can be powerful, such as asking residents in neighborhoods known to be flood-prone which spots get hit hardest.
Green infrastructure can be a powerful intervention to build rain resilience. Camden partnered with other stakeholders in the area to implement green infrastructure in a park prone to sewage-laden flooding; Houston also has upgraded a park that serves as a filtering retention basin in the wake of heavy rains. Integrating green infrastructure into other priority projects like street upgrades can reduce flooding while providing other benefits, as seen with Green Streets policies in Tucson and Philadelphia. The former mayor of Nashville led an initiative to upgrade alleys, a project to prevent flooding while increasing volunteerism. Beyond infiltration, green infrastructure focused on rain capture for reuse can mitigate flooding while enhancing conservation, as Tucson and Pittsburgh demonstrate.
Cities have discovered a few successful approaches to funding rain resilience. Camden’s SMART Alliance, referenced above, shows that collaborating with partners can increase both the funding and technical assistance available to a city. Fort Worth, TX has implemented a stormwater fee and collaborated with partners to fund upgrades to flood prevention infrastructure.
|Read more about building resilient cities in our report Cities at Work: Progressive Local Policies to Rebuild the Middle Class.|