Quantifying Long-Term Hydrologic Response in an Urbanizing Basin

Abstract

This paper describes long-term hydrologic response within a rapidly developing watershed in the western suburbs of Washington, DC, within the Chesapeake Bay drainage basin. Data consist of up to 24 years of observed rainfall, basin discharge, and land use/land cover (LULC) from four headwater basins of the Occoquan River in northern Virginia. Basin outlets are monitored for storm and nonstorm flows, respectively, using flow-proportional, volume-integrating storm samplers and continuous stream gaging. Landsat-derived measures of impervious surface are supplemented with regional land use mapping to characterize LULC in each basin. Three of the four study basins, ranging in size from 67 to 400 km 2 , are predominantly forest and/or mixed agriculture. The fourth basin, the 127 km 2 Cub Run watershed, has urbanized rapidly over the past 20 years with approximately 50 percent of current land area classed as urban (18 percent impervious surface). Results indicate a greater hydrologic response in the urbanizing Cub Run basin, compared to the three adjacent basins. Cub Run basin has higher annual and seasonal storm volumes per surface area than non-urban basins after 1983, when estimated impervious surface area in Cub Run basin reached approximately nine percent. In all four study basins, storm discharge per surface area is more responsive to rainfall during winter and spring due to generally denuded dormant season landscapes. Only during the summer and fall is long-term storm runoff in Cub Run basin higher than non-urban basins. This result is significant, as it supports expected biophysical reductions in interception, infiltration, and evapotranspiration during the growing season due to higher imperviousness. Results of this study also support literature regarding increased storm volumes in catchments above 10 percent imperviousness. Increased unit-area storm discharge in Cub Run basin during the growing season has important implications for seasonal NPS pollutant flux which are addressed in the following chapter.

Impact Assessment of Climate and Land-Use Changes on Flooding Behavior in the Upper Ciliwung River, Jakarta, Indonesia

“…Urbanization changes hydrological behavior by reducing infiltration, baseflow and lag time and increasing surface runoff, peak flow, flow volumes, and frequency of flooding [5][6][7][8][9]. Land-use changes coupled with climate change may have adverse effects on hydrological behavior and flooding or drought frequencies [10].…”

Assessing the effects of urbanization on annual runoff and flood events using an integrated hydrological modeling system for Qinhuai River basin, China

“…The expected results of urbanization include reducing infiltration, baseflow, lag times, increasing storm flow volumes, peak discharge, frequency of floods, and surface runoff (Hollis, 1975;Arnold and Gibbons, 1996;Smith et al, 2005;Dougherty et al, 2006;Ogden et al, 2011). Numerous researchers have used many methods to simulate, assess, and predict the effects of urbanization on hydrological response of the watersheds.…”

Watershed urbanization and changing flood behavior across the Los Angeles metropolitan region

“…It is widely recognized that urbanization can have serious implications for the long-term sustainability and health of human dominated stream systems causing problems, such as urban flooding, stream bank erosion, habitat degradation, and downstream pollutant loading when watershed development exceeds a certain impervious surface threshold (Pickett et al 2001;Paul and Meyer 2001;White and Greer 2006;Randolph 2004;Konard and Booth 2005;Dougherty et al 2006). Typically, urbanization refers to urban development and is defined as increasing land surface imperviousness which, in turn, leads to decreases in infiltration and increases in surface runoff.…”

“…Stream flood hydrology changes along with the rainfall-runoff relationship in response to the expansion of the impervious surface in the watershed. Impervious surfaces increase the flood magnitude; shorten the lag time from the center of the rainfall volume to the center of the runoff volume; and increase the temporal and spatial variation in streamflow conditions (Espey et al 1965;Seaburn 1969;Hirsch et al 1990; Arnold and Gibbons 1996;Beighley and Moglen 2002;Konrad and Booth 2005;Randolph 2004;Dougherty et al 2006).…”