JAWRA - Stormwater Runoff - Laserfiche WebLink

Home Browse Search

STORMWATER RUNOFF QUALITY AND QUANTITY FROM TRADITIONAL AND LOW IMPACT DEVELOPMENT WATERSHEDS existed before urban development (USEPA, 2000). The LID concepts utilize various best management practices (BMPs) such as bioretention, cluster hous- ing, grassed swales, and public education (Prince George's County, 1999). Most studies of stormwater BMPs have focused on individual treatments, and few have incorporated more than one BMP into an investigation (Richards et al., 1981; Urbonas, 1994; Legret and Colandini, 1999; Davis et al., 2001a; Kopp and Guillard, 2002; Deletic, 2005). Such studies have examined perme- able pavements (Brattebo and Booth, 2003), educa- tion (Dietz and Clausen, 2004), and vegetative swales (Rushton, 2001). There are even fewer studies on LID designs, and these have relied mostly on assumptions about their effectiveness for stormwater management. For exam- ple, a survey of local governments in several states concluded that planned greenfield developments, which utilized LID methods, surpassed traditional developments in terms of watershed protection (Berke et al., 2003). Also, a modeling approach was used to predict runoff from low impact urbanization by estimating the ability of LID to infiltrate storm - water (Holman -Dodds et al., 2003). However, no stud- ies have monitored the effects of a LID design on stormwater runoff. This study, known as the Jordan Cove Urban Watershed project, investigated the effects of LID on stormwater quality and quantity. This paper reports the comparison of the quality and quantity of storm - water runoff from a traditional and a LID watershed during the postconstruction period. Previous papers have addressed the stormwater impacts during con- struction (Phillips et al., 2003), compared stormwater runoff from different driveway types (Gilbert and Clausen, 2006), and compared discharge lag times between traditional and LID watersheds (Hood et al., 2007). METHODS Study Site The project was located near the Long Island Sound in the town of Waterford, Connecticut. The watersheds studied consisted of a control and two watersheds (traditional and LID) that were studied prior to, during, and after residential development. The traditional watershed originally contained a poultry hatchery and storage buildings. During cali- bration, samples were collected at the discharge point of overland flow from a lawn. The LID watershed originally was a closed -out gravel pit. During calibra- tion, samples were collected at the discharge point for the restored pit. The treatment watersheds were adjacent and. the control watershed was 0.8 km away. Study watersheds were relatively small, with small lot sizes, gentle slopes, and total imperviousness varying, depending on the treatment (Table 1). The control watershed was developed in 1988 (Figure 1). The traditional watershed used minimum 0.2 ha lot zoning, a standard 8.5 m wide asphalt road, and a curb and gutter stormwater collection system (Figure 2). Roof runoff was directed to either grassed lawns or onto driveways. The LID watershed had 26% open space, mostly along the periphery (Figure 3). Two main features of the design were the replacement of traditional curbs and gutters with grassed bioretention swales and the asphalt road with a narrower pervious concrete -paver road. A bio- retention cul -de -sac, which allowed for retention and infiltration of runoff, was used instead of the tradi- tional impervious asphalt area. Individual bioreten- tion areas (rain gardens) were incorporated into each lot to detain roof and lot runoff. These were designed to contain the first 2.54 cm of runoff from their indi- vidual watersheds. Shared driveways were used in 10 of the 12 lots and were composed of asphalt, pervious concrete pavers, or crushed gravel. Cluster housing TABLE 1. Characteristics of Study Watersheds. FIGURE 1. Control Watershed Subdivision for the Jordan Cove Project, Connecticut. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 999 JAWRA Control Traditional LID Watershed area (ha) 5.5 2.0 1.7 No. of lots 43 17 12 Average lot size (ha) 0.16 0.15 0.10 % Total impervious 29 32 22 Average slope (%) 1.0 1.5 1.8 FIGURE 1. Control Watershed Subdivision for the Jordan Cove Project, Connecticut. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 999 JAWRA