CHANGING RAINFALL‐RUNOFF RELATIONSHIPS IN THE URBANIZING PEACHTREE CREEK WATERSHED, ATLANTA, GEORGIA¹

Abstract

Peachtree Creek is a gaged watershed that has experienced a substantial increase in urbanization. The relationships of runoff to rainfall were studied for total annual flows, low flows, and peak flows. For each type of flow the relationship in the later, more urbanized period was compared to that in the earlier, less urbanized period. An increase in total runoff in wet years was observed as urbanization increased, but a decrease occurred during dry years. For low flows a similar decrease of runoff in dry years was found. An increase in peak runoff was observed over most of the range of precipitation. Increasing peak flows and declining low flows can be adequately explained by urban hydrologic theoryshed. which focuses on the effects of urban impervious surfaces upon direct runoff and infiltration. However, a decline of total runoff in dry years can be explained only by taking into account evapotranspiration as well. The concept of advectively assisted urban evapotranspiration, previously discovered by climatologists, is needed to explain such a loss of total runoff. Urban hydrologic theory must take into account vegetation and evapotranspiration, as well as impervious surfaces and their direct runoff, to explain the magnitude of total annual flows and low flows. Urban stormwater management should address the restoration of low flows, as well as the control of floods.

An approach for evaluating the hydrological effects of urbanization and its application

“…Bonta et al (1997) investigated the changes in Natural Resources Conservation Service (NRCS) curve number, flow-duration curve and peak flow for differing periods of pre-mining, mining reclamation and post-reclamation in three small experimental watersheds in Ohio, USA. Additionally, Ferguson and Suckling (1990) applied polynomial regressive equations of impervious surfaces to analyse the relationship of runoff to rainfall for total annual flows, low flows and peak flows. Furthermore, Tsihrintzis and Hamid (1997) used the Soil Conservation Service (SCS) curve number method and empirical equations developed by the U.S. Environmental Protection Agency (EPA) to compute runoff depth and pollutant loading of urban stormwater runoff from four small sites with different predominant land uses, including low-density residential, high-density residential, highway and commercial, in South Florida, USA.…”

The effect of climate and land use change on flow duration in the Maryland Piedmont region

“…Paul and Meyer (2001) also found that urbanizing watersheds exhibit a larger volume of the received precipitation as surface runoff and less as groundwater flow. Warner (1984), and Ferguson and Suckling (1990) concluded that low flows in urbanized watersheds have a tendency to diminish due to the effects of impervious surfaces by limiting infiltration and enhancing evaporation. However, several other studies (Hollis, 1977;Konrad et al, 2002;Meyer, 2005) have documented increasing low flows from urbanization alone.…”

Effect of growing watershed imperviousness on hydrograph parameters and peak discharge

“…People mainly dwell in the downstream area of a basin, and tribal societies or cities often develop according to the living quality of the environment. The development of an urban area within a watershed causes a drastic change of land use and has major effects on the functioning of the hydrological status of that area during flood conditions (Simmons and Reynolds, 1982;Ferguson and Suckling, 1990;Leopold, 1991;Sala and Inbar, 1992;Singh, 1998;Gremillion et al, 2000).…”