Urban flooding has caused growing social, environmental and economic losses in Baltimore, where flood records date back to 1748. Researchers say those impacts are likely to become more frequent and intense as the climate changes. Conventional defenses that rely on concrete and other impermeable surfaces can also perform poorly in cities because they prevent rainwater from soaking into the ground.
A team led by Penn State researchers developed an alternative approach with Baltimore residents and city officials. Over three years, workshops helped identify local flooding concerns, feasible interventions and areas that should be included in the model. The work focused on pluvial flooding, which results from rainfall rather than river overflow or storm-driven high tides.
The researchers modeled two strategies selected through the community discussions: green stormwater infrastructure and storm-inlet cleaning. Green infrastructure can include rain gardens, green spaces and permeable surfaces that absorb water and slow runoff. Cleaning involves removing leaves and debris that can block inlets along streets and sidewalks.
The combined measures produced the largest reduction in the model, lowering flood depths by as much as 55% in selected locations. However, the researchers said the combination performed only slightly better than cleaning inlets alone, which was the more effective individual measure.
Building and checking the model presented challenges. Urban flooding can develop and disappear within hours, making it difficult to observe with satellites or conventional sensors. Small features such as the roughly 15-centimeter difference between a curb and a road can also determine where water flows, but may not appear clearly in remotely sensed elevation data.
Because Baltimore lacked sensors in some streets affected by this type of flooding, the team used geotagged social media posts and news images to help validate the model. Those records allowed researchers to compare visible water levels with known reference points, including curbs.
The findings were published in Sustainable Cities and Society in a paper titled “Co-designing stormwater adaptations through community-informed urban pluvial flood modeling.” The researchers said that involving residents helped ensure the proposed measures were relevant and achievable, while also strengthening trust between communities and scientists.
The project forms part of the Urban Integrated Field Program, which brings together researchers from fields including hydrology, ecology and landscape architecture with planners and community members. The team plans to examine how the Baltimore findings compare with other climate adaptation studies through the Baltimore Social Environmental Collaborative.
Future work will also consider how adaptation measures can address several hazards at once. While rain gardens may be less effective for flood reduction than inlet cleaning in some locations, the researchers said they could provide additional benefits for urban heat. The team hopes the community-engagement approach can be applied in other cities developing responses to climate impacts.
Sources: Phys.org.