Almadani Mohammad, Nietch Christopher, Massoudieh Arash
Civil and Environmental Engineering, King Abdulaziz Univ., Edarah St., Jeddah 21589, Saudi Arabia.
Office of Research and Development, Center for Environmental Measurement and Modeling, Watershed and Ecosystem Characterization Division, Watershed Management Branch, USEPA, 26 West Martin Luther King Dr., Mail Stop: 236, Cincinnati, OH 45268.
J Sustain Water Built Environ. 2023 Feb;9(1):1-15. doi: 10.1061/jswbay.sweng-460.
To evaluate the effectiveness of dispersed stormwater control measures (SCMs), it is important to consider groundwater-surface water interactions and their consequences for stream hydrologic responses relevant to channel geomorphic stability and ecology. This study aimed to evaluate the effectiveness of different SCM design scenarios and implementation alternatives on exceedance levels and volumes of streamflow at the watershed scale. For this purpose, a process-based block-connector model of Sligo Creek, an urban watershed (29 km) in the suburbs of Washington, DC, was used to study the effects of SCM system design on the stream hydrograph. The watershed has 34% impervious area (IA), which was discretized into 14 similar-sized subwatersheds, each consisting of pervious and impervious surface areas. Each subwatershed was compartmentalized with the representative overland flow, unsaturated flow, groundwater blocks, and links to main channel segments. The model was calibrated and validated to existing conditions using a 3-year time series of observed flow data. Afterward, a predevelopment simulation was configured. Three SCM unit designs and IA diversions through the SCM retrofit system were simulated. The three unit design scenarios represented a simple pond with surface storage and overflow or SCMs that infiltrate with an engineered soil layer and with or without an underdrain pipe. Differences among the model simulations were evaluated using flow exceedance probability curves. The area of the SCM system was modeled as 5% of the IA retrofit. Three implementation levels, including 10%, 50%, and 90% of the IA diverted through SCMs, were considered for each SCM unit design. The results showed that at least a 50% retrofit of runoff from IA watershedwide would be needed to achieve similar predevelopment base flows and peak flows. Intermediate flows could not be matched but were closest for the infiltration with the underdrain pipe design scenario. It was also found that concentrating the SCMs in the lower portion of the watershed resulted in more effectively achieving the predeveloped exceedance curves than uniform SCM implementation. The results are relevant to planning-level decisions that depend on effectiveness predictions of different SCM unit designs and implementation alternatives in developed watersheds.
为评估分散式雨水控制措施（SCMs）的有效性，重要的是要考虑地下水与地表水的相互作用及其对与河道地貌稳定性和生态相关的河流水文响应的影响。本研究旨在评估不同SCM设计方案和实施替代方案对流域尺度上河流流量超标水平和流量的有效性。为此，使用了位于华盛顿特区郊区的一个城市流域（29公里）斯利戈溪的基于过程的块连接模型，来研究SCM系统设计对河流流量过程线的影响。该流域有34%的不透水面积（IA），被离散化为14个大小相似的子流域，每个子流域由透水和不透水表面区域组成。每个子流域被划分为具有代表性的坡面流、非饱和流、地下水块以及与主河道段的连接。该模型使用3年的实测流量数据时间序列进行校准和验证，以符合现有条件。之后，配置了一个开发前模拟。模拟了三种SCM单元设计以及通过SCM改造系统的IA分流。这三种单元设计方案分别代表一个具有地表蓄水和溢流功能的简单池塘，或带有工程土壤层且有或没有排水管道的可渗透SCMs。使用流量超标概率曲线评估模型模拟之间的差异。SCM系统的面积建模为IA改造面积的5%。对于每个SCM单元设计，考虑了三个实施水平，包括通过SCMs分流的IA的10%、50%和90%。结果表明，如果要实现与开发前类似的基流和峰值流量，至少需要对IA流域范围内50%的径流进行改造。中间流量无法匹配，但对于带有排水管道的渗透设计方案最为接近。研究还发现，将SCMs集中在流域下游比均匀实施SCMs能更有效地实现开发前的超标曲线。这些结果与规划层面的决策相关，这些决策取决于发达流域中不同SCM单元设计和实施替代方案的有效性预测。
