Flow and sediment transport disturbance caused by dams

A large number of dams and hydropower plants have been built in mountain regions due to the rich water resources and high potential energy. As a consequence, flow regulation associated with dams has led to profound changes to the intertwined hydrologic, ecologic, and geomorphic functioning of rivers. Understanding the effect of dams on the interaction between hydrologic, ecologic, and geomorphic is critical for river management that aims to maximize a range of potential benefits. Therefore, my Ph.D. research proposed to investigate basic and applied scientific questions about two important disturbances caused by dams on mountain rivers: hydropeaking and reservoir sedimentation.Hydropeaking is defined as rapid variations in power production by hydroelectric plants as a consequence of varying electricity generation and fluctuations in demand in the electricity market. In Chapter 1, public hourly flow data in the state of California was used to reveal the diversity of hydropeaking flow. To process a large amount of data and extract their hydrologic features, an open-source algorithm, Hydropeaking Events Detection Algorithm, was developed. Integratedclustering analysis was applied and identified four underlying hydropeaking patterns.Chapters 2 and 3 moved beyond pure statistical analysis to mechanistic observation and modeling of hydro-morphologic interactions in dam-regulated mountain rivers. Both studies investigated hydraulic and sediment transport regimes upstream of two concrete-arch dams. Chapter 2 exploratively studied hydrologic controls associated with current flow operations in a small dam. A new supplementary reservoir sedimentation management strategy based on water transfer was proposed for small dams. Chapter 3 applies flow convergence routing theory backward to redistribute sediment erosion upstream of the dam. Topographic steering and flow convergence routing was found to be able to redistribute sediment erosion pattern and keep sediment away from the key structure