Doctoral Dissertation Research: The Effects of Run-of-River Dams on Stream Morphology

水坝在美国各地的河流系统中随处可见。对水坝的科学调查表明，它们将泥沙蓄积在上游，并严重侵蚀下游的河道，其影响沿着河流进行，距离水坝很远。到目前为止，研究主要集中在大型蓄水大坝上，而忽略了较小的径流(非蓄水)大坝。由于人们对河流恢复的兴趣与日俱增，为了预测大坝拆除对河流动态的影响，需要了解径流大坝对地貌特征的现场影响。这个博士论文研究项目调查了流水大坝如何影响伊利诺伊州五个地点的河流地貌。本项目提出了以下问题：(1)径流坝对每个坝上和坝下的水系的影响是什么？(2)本研究中所有大坝的这些影响有什么相似之处和不同之处？(3)与蓄水坝相比，径流坝造成的影响如何？该方法包括纵向和跨海峡地形测量，以及对每个大坝附近和上游控制点的河床材料进行采样。此外，将在每个大坝后面的储存沉积物中收集两个岩芯，用于铯-137测定，以确定是否存在沉积物分层，作为这些大坝的捕集效率的指标。初步的现场考察表明，尽管这些大坝位于伊利诺伊州同一地理区域，但不同大坝的地貌效果有所不同。在这个项目中获得的数据将在不同的地点之间进行比较。它还将与为伊利诺伊州蓄水大坝收集的类似数据进行比较，以确定两种大坝类型之间的地貌效应差异是否具有统计学意义。预期的结果是，这些结构对地貌条件的影响空间范围和程度将小于较大的大坝，并且大坝之间的影响将存在差异。这项研究将有助于我们了解径流坝对河流地貌的影响的空间范围和程度。了解径流水坝对河流系统的影响，将有助于更好地预测一旦大坝被拆除，河流系统可能会如何反应。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Dams are ubiquitous on river systems throughout the United States. Scientific investigations of dams have demonstrated that they impound sediment upstream, and significantly erode river channels downstream, with the effects proceeding along the river at distances far from the dam. Studies thus far have focused mainly on large impoundment dams, ignoring smaller run-of-river (non-impoundment) dams. Because of a growing interest in river restoration, knowledge of the in situ impacts of run-of-river dams on geomorphic characteristics is required to forecast the effects of dam removal on river dynamics. This doctoral dissertation research project investigates how run-of-river dams have impacted river geomorphology at five sites in Illinois. This project poses the following questions: (1) What is the impact of run-of-river dams on stream systems above and below each dam?; (2) What are the similarities and differences of these impacts across all dams in this study?; and (3) How do the effects caused by run-of-river dams compare to their impoundment counterparts? The methodology involves longitudinal and cross-channel topographic surveys and sampling of bed material near each dam, and at a control site well upstream. Additionally, two cores will be collected in the stored sediment behind each dam for Cesium-137 determination to ascertain whether sediment stratification exists, as an indicator of the trap efficiency of these dams. Preliminary site visits suggest that geomorphic effects differ among the dams, despite their location within the same physiographic region within Illinois. Data obtained in this project will be compared among the sites. It will also be compared to similar data collected for impoundment dams in Illinois to establish whether differences in geomorphic effects among the two dam types are statistically significant. The expected outcome is that the spatial extent and degree of impact of these structures on geomorphic conditions will be less than that for larger dams, and that variations will exist among the impacts across the dams. This research will contribute to our understanding of the spatial extent and degree of impact of run-of-river dams on river geomorphology. Understanding the effects that run-of-river dams have on stream systems will allow better forecasting of how a river system might respond once a dam is taken out. As a Doctoral Dissertation Research Improvement Award, this award will also provide support to enable a promising student to establish a strong independent research career.