Comparison of Infiltration and Detention in the Georgia Piedmont Using Recent Hydrologic Models
Ellington, M. Morgan
Ferguson, Bruce K.
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Infiltration is a possible alternative to detention for control of urban stormwater. Infiltration is capable of controlling peak flows as is detention, but also promises the advantages of flow volume control, base flow augmentation, and water quality improvement. However, the feasibility of infiltration in the Georgia Piedmont has been questioned because of the region's combination of high rainfall and slowly permeable soils. To test the feasibility of infiltration in this region, Patton (1986) designed infiltration systems as hypothetical replacements for existing detention systems on two urban development sites in the Atlanta area. Both the detention and infiltration systems were based on the Rational formula and equivalent design storms. When the two types of systems were compared, Patton found that infiltration, when designed to meet the same hydraulic standards as detention, was surprisingly feasible in terms of construction cost and land area occupied while offering more environmental benefits than detention. This paper summarizes a study (Ellington, 1991) to update Patton's work. In this study both detention and infiltration systems on Patton's study sites were redesigned using two relatively recent hydrologic models, the Soil Conservation Service (SCS) method of estimating storm runoff, and the long-term water balance as it applies to accumulation of standing water in closed reservoirs. Hydrologic performance was modeled, and cost indicators estimated, for four conditions: undeveloped, developed with no stormwater control, developed with detention, and developed with infiltration.