Safdar Suffiyan, Jefferson Anne J, Costello David M, Blinn Andrew
Department of Civil & Environmental Engineering, University of Vermont, 33 Colchester Avenue, Burlington, Vermont 05405, United States.
Rubenstein School of Environment and Natural Resources, University of Vermont, 81 Carrigan Drive, Burlington, Vermont 05405, United States.
ACS ES T Water. 2024 Aug 2;4(9):3904-3917. doi: 10.1021/acsestwater.4c00214. eCollection 2024 Sep 13.
Suspended sediment is a critical water quality parameter and an indicator of geomorphic processes, but suspended sediment dynamics in urban streams may not conform to the first-flush model widely used for other pollutants. We analyzed discharge and turbidity data for 367 events from three urban watersheds (impervious cover 16-45%) in Cleveland, Ohio (USA). Less intensely urbanized watersheds exhibit higher turbidity compared to that of the most highly urbanized watershed. Proportionally, more counterclockwise hysteresis is observed in the two less urbanized watersheds, and more clockwise hysteresis occurs in the highly urbanized watershed. However, hysteresis patterns are driven by different mechanisms in each watershed, and geomorphic analysis was critical to identifying the underlying mechanisms. In the least urbanized watershed, spatial rainfall variability controls sediment hysteresis. In the intermediate watershed, the erosion of upstream weathered shale banks during dry periods plays a significant role in the sediment supply and shaping hysteresis. In the most urbanized watershed, high eroding banks in downstream reaches lead to more frequent clockwise hysteresis. Overall, we suggest that as the impervious surfaces increase, the availability of instream sediments (bed and banks) plays an increased role in suspended sediment dynamics, and geomorphology remains essential for guiding management decisions.
悬浮泥沙是一个关键的水质参数，也是地貌过程的一个指标，但城市溪流中的悬浮泥沙动态可能不符合广泛用于其他污染物的首冲模型。我们分析了美国俄亥俄州克利夫兰市三个城市流域（不透水覆盖率为16%-45%）367次事件的流量和浊度数据。与城市化程度最高的流域相比，城市化程度较低的流域浊度更高。按比例来看，在两个城市化程度较低的流域观察到更多逆时针滞后现象，而在城市化程度较高的流域出现更多顺时针滞后现象。然而，每个流域的滞后模式由不同机制驱动，地貌分析对于识别潜在机制至关重要。在城市化程度最低的流域，降雨空间变异性控制着泥沙滞后现象。在中间流域，干旱时期上游风化页岩岸的侵蚀在泥沙供应和塑造滞后现象方面发挥着重要作用。在城市化程度最高的流域，下游河段的高侵蚀岸导致更频繁的顺时针滞后现象。总体而言，我们认为随着不透水表面的增加，河道内沉积物（河床和河岸）的可用性在悬浮泥沙动态中发挥着越来越大的作用，地貌学对于指导管理决策仍然至关重要。
