Assessment of Regional Variation in Streamflow Responses to Urbanization and the Persistence of Physiography

Abstract

Aquatic ecosystems are sensitive to the modification of hydrologic regimes, experiencing declines in stream health as the streamflow regime is altered during urbanization. This study uses streamflow records to quantify the type and magnitude of hydrologic changes across urbanization gradients in nine U.S. cities (Atlanta, GA, Baltimore, MD, Boston, MA, Detroit, MI, Raleigh, NC, St. Paul, MN, Pittsburgh, PA, Phoenix, AZ, and Portland, OR) in two physiographic settings. Results indicate similar development trajectories among urbanization gradients, but heterogeneity in the type and magnitude of hydrologic responses to this apparently uniform urban pattern. Similar urban patterns did not confer similar hydrologic function. Study watersheds in landscapes with level slopes and high soil permeability had less frequent high-flow events, longer high-flow durations, lower flashiness response, and lower flow maxima compared to similarly developed watersheds in landscape with steep slopes and low soil permeability. Our results suggest that physical characteristics associated with level topography and high water-storage capacity buffer the severity of hydrologic changes associated with urbanization. Urbanization overlain upon a diverse set of physical templates creates multiple pathways toward hydrologic impairment; therefore, we caution against the use of the urban homogenization framework in examining geophysically dominated processes.

The role of storm scale, position and movement in controlling urban flood response

“…However, several studies have found mixed effects of urban-ization on peak flows and response times, associated with a combination of imperviousness and flood mitigation measures, especially for basins where urbanization has predominantly taken place after implementation of stormwater control legislation (e.g. Smith et al, 2013a;Hopkins et al, 2015;Miller et al, 2014). Niemczynowicz (1999) and Schilling (1991) pointed out the importance of spatially distributed rainfall information at high resolution to study response in urban basins.…”

Statistical analysis of hydrological response in urbanising catchments based on adaptive sampling using inter-amount times

“…On the other hand, several studies have found mixed effects of urbanisation on flow peaks asso-ciated with a combination of imperviousness and flood mitigation measures, especially for basins in the USA where urbanisation has predominantly taken place after implementation of stormwater legislation to lower peak discharges (e.g. Smith et al, 2013;Hopkins et al, 2015;Miller et al, 2014). For the basins in Charlotte watershed, urbanisation has taken place before as well as after stormwater legislation, and a combination of flow regulation by detention facilities and peak flow restrictions induced by capacity constraints results in an overall effect of peak flow reduction associated with urbanisation.…”

From Rain Tanks to Catchments: Use of Low-Impact Development To Address Hydrologic Symptoms of the Urban Stream Syndrome

“…18 In principle, the first limitation can be addressed by adding terms to the catchment water balance eq 1 that account for regional variations in the import and export of water over annual time scales. Addressing the second and third limitations, on the other hand, may require more sophisticated (spatially and temporally explicit) models that capture the influence of surface and subsurface storage and local hydrogeology on intrastorm, as well as interstorm, streamflow variability (see modeling tools in Section 4).…”

“…dams and reservoirs) can also increase dry weather streamflow. 18 All of these catchment modifications, in addition to altering stream hydrology, degrade streamwater quality by raising stream temperature, changing the balance of nutrients, carbon, and oxygen in a stream, and facilitating the mobilization and transport of fine sediments, chemical pollutants, and human pathogens and their indicators. 1−3,19−25 Changes in water quality and hydrology (both symptoms of catchment urbanization) affect stream morphology, stability, ecology, and chemistry.…”