Assessment of distributed environmental control applications for urban stormwater management using EPA SWMM

ABSTRACT

Rapid urbanization and the expansion of impervious surfaces intensify pluvial flooding in densely developed metropolitan districts such as Esenyurt, Istanbul, Türkiye, by reducing infiltration, accelerating surface runoff, and increasing pressure on stormwater drainage systems. This study presents a comparative scenario-based assessment of Distributed Environmental Control/Low Impact Development (DEC/LID) measures, represented by green roofs, permeable pavements, and rain barrels, using EPA SWMM 5.2. A baseline case without DEC implementation and eight incremental implementation scenarios ranging from 5 to 40% coverage were simulated under 2-, 5-, 10-, 25-, 50-, and 100-year design rainfall events. The resulting outlet peak discharges were evaluated at three outflow points, O1-O3. Because observed discharge records were unavailable for the study area, formal model calibration and validation could not be performed; accordingly, the reported reductions are interpreted as relative model-estimated responses under the adopted rainfall inputs and parameter assumptions rather than as absolute predictions of field performance. Across the investigated scenarios, increasing DEC/LID coverage produced monotonic reductions in simulated peak discharge. At 40% coverage, the estimated peak-discharge reductions ranged from 7.57 to 7.98% at O1, from 4.12 to 7.98% at O2, and from 17.40 to 24.61% at O3. The outlet-dependent response indicates that the relative benefit of distributed source controls varies across the drainage system and should be considered when prioritizing phased implementation. Within the limitations of an uncalibrated event-based model, the results provide planning-oriented evidence for evaluating integrated DEC/LID strategies in rapidly urbanizing catchments.