Effectiveness of best management practices to increase infiltration in urban and rural environments

Karnatz, Camille
Major Professor
Janette R. Thompson
Committee Member
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Natural Resource Ecology and Management

Source-control best management practices (BMPs) have been designed and promoted as flexible alternatives for runoff mitigation in both urban and agriculturally developed landscapes and are likely to become more important given climatic predictions of more frequent and intense rain events. Strategies that incorporate vegetative elements and natural soil water infiltration to reduce runoff delivered to conventional sewer or tile drainage systems and increase groundwater recharge are compatible with other characteristics of urban and agricultural landscapes. However, the rate of adoption of BMPs has been slow as a result of uncertainties about maintenance, effectiveness when incorporated during retrofitting, and long-term benefits that have been under studied. In the first part of this study I examined the efficacy of three common stormwater BMPs in a variety of urban (residential, recreational and commercial) environments. Specifically, I examined bioretention cells, native landscaping (restored prairie), and vegetated riparian buffer practices. In the second component of this study, I examined the similarities and differences in performance for a single BMP, vegetated riparian buffers, when used in both urban and rural landscapes. For both studies, I examined performance capacity based on the spatial extent of each BMP (receiving area) to its subwatershed (contributing area). I also conducted rainfall simulation to measure infiltration, absorption capacity, runoff characteristics and collected soil samples to characterize pollutant accumulation. Among the urban BMPs in the first study, bioretention cells and wooded zones of the buffers had the lowest soil bulk densities, highest infiltration rates, and smaller runoff volumes than did their contributing areas. In the second study, I observed that urban buffers, although generally smaller, had larger practice to contributing area ratios, indicating that spatial constraints may not diminish buffer effectiveness in these landscapes. Rural and urban buffers demonstrated analogous performance for buffer areas compared to their respective contributing areas. In both landscape settings the buffer areas had the highest infiltration rates and the wooded buffer zones demonstrated significantly greater time-to-runoff compared to their contributing areas. In both studies, I determined that the effectiveness of BMPs observed could be enhanced if their surface area was enlarged, or if they were implemented as clustered practices. Further, my findings suggest that while implementation of these practices is likely to reduce runoff volumes and improve water quality, their performance could be improved using site-specific practice designs rather than following more generic technical recommendations.