Bioswales: A Solution for Flooding, Traffic Calming, and Urban Cooling
See Chris Pittman give a brief city council comment on this topic, here
A bioswale is a shallow, vegetated engineered channel designed to manage stormwater runoff. Using plants and green spaces, their gently sloped sides and layered structure (vegetation, sand, gravel, and sometimes an infiltration pipe) allow them to slow, filter, and absorb rainwater as it moves downstream. Bioswales are typically integrated along streets, in medians, or adjacent to sidewalks, making them flexible for urban applications.
Summary:
Bioswales offer a multi-functional approach to urban challenges to help mitigate flash floods, improve water quality, calm traffic, encourage walking and biking, reduce urban heat, and beautify neighborhoods. Their implementation in Amarillo could address both immediate risks and broader goals for a safer, healthier, and more resilient city.
Primary Benefits of Bioswales
Flood Mitigation: Bioswales are highly effective at reducing the risk and severity of flash floods by absorbing and slowing down stormwater, reducing the burden on drainage systems
Water Quality Improvement: As water moves through the bioswale, pollutants and sediments are naturally filtered out by the plants and soil, resulting in cleaner water entering local waterways
Groundwater Recharge: By allowing water to infiltrate the soil, bioswales help replenish groundwater supplies
Biodiversity and Habitat Creation: The use of native plants in bioswales supports local wildlife, including pollinators and birds, enhancing urban biodiversity
Secondary Benefits
Aesthetics and Community Value: Bioswales enhance the visual appeal of streetscapes
Urban Heat Island Reduction: Large bioswale vegetation like trees and shrubs provide shade and cool the surrounding air helping to reduce the urban heat island effect.
Traffic Calming & Active Transportation: When bioswales are installed along streets, in medians, or as part of curb extensions, they can visually and physically narrow the roadway. This encourages drivers to slow down, making streets safer for pedestrians and cyclists.
Key Actions to Encourage
1. Update Stormwater Management Policies
Direct staff to review and update the city's Storm Water Management Criteria Manual to explicitly include bioswales as an approved best management practice for stormwater control and flood mitigation
Require bioswale installation in new developments, major roadway projects, and city-led infrastructure upgrades
2. Develop a Green Infrastructure Ordinance
Propose an ordinance that encourages or mandates the use of green infrastructures like bioswales, rain gardens, and permeable pavements
Include incentives for private property owners and developers to install bioswales, such as stormwater fee credits or expedited permitting
3. Integrate Bioswales into Traffic Calming and Streetscape Projects
Direct the transportation and public works departments to incorporate bioswales into street redesigns, curb extensions, medians, and sidewalk buffers
Prioritize areas near schools, parks, and neighborhoods with high pedestrian activity to enhance safety and encourage walking and biking
Examples / Additional info
Integrated Stormwater Management (iSWM) case studies - Case Studies in North Dallas cities
Houston Green Streets - Details on Houston's bioswale projects
Bioswales - NACTO - High-level overview of Bioswales as a traffic calming device
SPROW-Presentation-02-05-2025.pdf - Examples of putting bioswales in places like Curb extensions, bumpouts, and traffic circles