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LABORATORY-SCALE SIMULATION OF RUNOFF RESPONSE FROM PERVIOUS-IMPERVIOUS SYSTEMS
Citation:
SHUSTER, W. D., E. Pappas, AND Y. ZHANG. LABORATORY-SCALE SIMULATION OF RUNOFF RESPONSE FROM PERVIOUS-IMPERVIOUS SYSTEMS . JOURNAL OF HYDROLOGIC ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 13(9):886-893, (2008).
Impact/Purpose:
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Description:
Urban development yields landscapes that are composites of impervious and pervious areas, with a consequent reduction in infiltration and increase in stormwater runoff. Although basic rainfall-runoff models are used in the vast majority of runoff prediction in urban landscapes, these models do not typically account for how impervious extent, connectivity, and the antecedent soil water status of adjacent pervious areas might more specifically affect the production of runoff. We used rainfall simulation with a relatively intense (5-year, 46mm over 1.5 hours) rainfall structure to generate runoff from different arrangements of impervious and pervious surfaces (0, 25, 50% impervious) with different connectivity to the outlet (disconnected, connected), and under two different antecedent moisture conditions for pervious areas (dry, wet). These treatments were implemented in the form of 0.6 m2 boxes (impervious, pervious-soil) 0.2 m deep that were connected together in series to create the different treatment configurations called for in this study. The time to initiation of runoff was significantly regulated by extent impervious area (p = 0.003) and an interaction between antecedent soil moisture status and connectivity (p < 0.001). Runoff ratios were strongly affected by antecedent moisture condition (p < 0.001), and somewhat less significantly by an interaction (p = 0.10) between impervious area extent and its connectivity status. The 0% impervious treatment showed decreased time to runoff initiation for wet than dry treatments, and final runoff ratio was increased to 0.77 in wet versus 0.65 for dry. We found that the connectivity of 25% impervious area arrangement accounted for differences in runoff ratio only early in the simulation, and eventually response from connected and disconnected 25% treatments converged to a runoff ratio of 0.68 and 0.80 for dry and wet antecedent soil moisture status, respectively. Dry 50% impervious arrangements converted just as much rainfall to runoff as 0% pervious treatments. Runoff ratios were maximized overall for wet 50% impervious, and overall maximized for the connected scenario. Empirically derived curve numbers ranged from 93 to 99 for 0% and connected 50% impervious cover, respectively. Although specific to this study, this curve number representation is used to illustrate the practical realizations of mechanistic differences in runoff response from pervious-impervious systems; and points out certain limitations on the application of the TR-55 method to pervious-impervious systems. Overall, our results may suggest some general rules for runoff response for modeling codes that incorporate a spatial grid representation of runoff generation from heterogeneous surface coverage.
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