Department of Biological System Engineering, Virginia Polytechnic Institute and State University, United States of America; Transportation Business Line, Gannett Fleming, Inc., Fairfax, VA, United States of America.
Department of Biological System Engineering, Virginia Polytechnic Institute and State University, United States of America.
Sci Total Environ. 2019 Jun 25;671:215-231. doi: 10.1016/j.scitotenv.2019.03.248. Epub 2019 Mar 19.
Thermally enriched runoff from urban impervious surfaces can be harmful to aquatic life; however, only limited information is available on how to mitigate these impacts at the watershed-scale. This study evaluates the effects of retrofitting an urban watershed with thermal mitigation practices (TMPs) relative to thermal toxicity thresholds for aquatic species. The Minnesota Urban Heat Export Tool (MINUHET) and Storm Water Management Model (SWMM) models were used to evaluate TMPs that help reduce temperature and total heat loads (THL) from the Stroubles Creek watershed in Blacksburg, Virginia. We used the aquatic health criteria for brook trout (Salvelinus fontinalis), the most sensitive species present downstream of the watershed, as a performance measure. TMPs included bioretention systems, methods for reducing the albedo of surfaces (cool surfaces), and increasing forest canopy. Performance metrics included Event Mean Temperature (EMT), and the Percentage of Time Temperature Exceeded the 21 °C Acute Toxicity Threshold [Percentage of Time above the Threshold (PTAT)] for brook trout; these metrics were used to quantify reductions in heat loads and temperatures. TMPs were evaluated during continuous simulation and selected storm events. Increased forest canopy alone produced the greatest reduction of stream temperature, as quantified by EMT and PTAT metrics during continuous and event-based simulations. In contrast, cool surfaces reduced THL more than any other individual TMP for the continuous simulation. A comprehensive mitigation plan (CMP) integrating all three TMPs reduced THL by 62.3%, and PTAT by approximately 12%, for the entire summer of 2015. The CMP was also applied to select storm events, during which streamflow EMT was reduced up to 9%, and PTAT was reduced nearly to zero. This study, which is the first to simulate watershed-scale TMPs for a large, complex urban area, demonstrates the application of appropriate strategies for restoring aquatic habitats in the thermally impacted Stroubles Creek.
城市不透水面的热富集径流可能对水生生物有害；然而，关于如何在流域尺度上减轻这些影响，只有有限的信息。本研究评估了在弗吉尼亚州布莱克斯堡的斯特劳布溪流域采用热缓解措施（TMP）相对于水生物种热毒性阈值的效果。MINUHET 和 SWMM 模型用于评估有助于降低温度和总热负荷（THL）的 TMP，该模型用于评估弗吉尼亚州布莱克斯堡的斯特劳布溪流域。我们使用了该流域下游最敏感的物种溪红点鲑（Salvelinus fontinalis）的水生健康标准作为性能指标。TMP 包括生物滞留系统、降低表面反照率的方法（冷表面）和增加森林树冠。性能指标包括事件平均温度（EMT）和超过 21°C 急性毒性阈值的时间百分比[超过阈值的时间百分比（PTAT）]，这些指标用于量化热负荷和温度的降低。TMP 在连续模拟和选定的暴雨事件中进行了评估。仅增加森林树冠就产生了最大的溪流温度降低效果，这在连续和基于事件的模拟中通过 EMT 和 PTAT 指标来量化。相比之下，冷表面在连续模拟中比任何其他单个 TMP 都能更有效地降低 THL。综合缓解计划（CMP）整合了所有三种 TMP，在整个 2015 年夏季将 THL 降低了 62.3%，PTAT 降低了约 12%。该 CMP 还应用于选定的暴雨事件，在此期间，溪流流量 EMT 降低了高达 9%，PTAT 降低了近 0%。本研究首次对大型复杂城市流域进行了流域尺度 TMP 模拟，为恢复受热力影响的斯特劳布溪的水生栖息地提供了适当的策略。
