Urban Water Quality & Quantity
When rain falls on paved surfaces or rooftops in urban areas and cannot soak into the ground, it becomes urban runoff. In developed countries like the United States, runoff from urban areas is one of the leading causes of urban water pollution because it picks up contaminants (trash, feces, and motor oil, among others) as it flows along paved surfaces, and is not often treated before it is discharged to the ocean or other waterbodies. Because pavement keeps runoff from soaking into the ground, runoff volumes are larger and flows are faster in urban areas. This can increase erosion and flooding, damaging wildlife habitat and property. It also exposes aquatic ecosystems and the people who interact with them to urban contaminants, impacting both ecosystem and public health.
My work in this area has involved a variety of contaminants (from pathogens to pesticides) and water quantity metrics (flow frequency, volume, etc.), and focuses on the capacity of green stormwater infrastructure like bioretention systems and constructed wetlands to restore urban hydrology to a pre-urban state while removing contaminants by physical, biological, and chemical means. Bioretention systems are engineered, vertical infiltration systems for stormwater that are vegetated, and often look like gardens. Constructed wetlands are typically surface flow aquatic systems (although subsurface flow systems are increasingly common), and consist of alternating regimes of open water ponds and vegetated macrophyte zones.
Aerial photo of Edinburgh Gardens Bioretention System in Melbourne Australia (courtesy of the NSF Water PIRE's 2016 UPP Down Under Program)
Fig 1 from Peng, Cao, and Rippy et al., 2016
Bioretention schematic showing ponding zone, media layers, and drainage pipe. Four plants with different above and below ground morphologies are shown.
Fig 1 from Rippy, Weiden et al., 2016
Wetland schematic showing processes by which thin films called microlayers form at the wetland surface and concentrate contaminants.