The HEC-RAS can also compute sediment transport capacity using the following equations: Ackers and White Engelund and Hansen Larsen Meyer-Peter and Müller Geomorphic Analysis For medium and high risk dam removals, a geomorphic analysis is recommended, by an experienced geomorphologist. Initially, the geomorphic analysis utilize historic aerial photographs, geologic maps, soil maps, topographic maps, historical ground photographs and accounts, and field reconnaissance. Additional analysis may require collection and interpretation of sediment and soil samples. The geomorphic analysis will describe the physical setting of the dam, reservoir, and river channel, a description of geologic controls, significant water and sediment sources, and characterization of the river and reservoir sediment. The geomorphic analysis also will identify historic channel trends and allow for estimates of future channel evolution trends following dam removal. For dam removals with a significant reservoir drawdown and reservoir shoreline slopes, the potential for landslides during reservoir drawdown should be investigated. There are numerous references for geomorphic analysis of stream channels. The ASCE Sedimentation Engineering Manual provides two chapters: Fundamental of Fluvial Geomorphology (Biedenharn et al., 2008) Engineering Geomorphology (Schumm and Harvey, 2008) The ASCE Sediment Dynamics upon Dam Removal also provides a chapter on the geomorphic effects of dam removal (Skalak et al., 2011). Numerical Modeling, Laboratory Modeling, and Field Experiments Numerical models, laboratory models, and field experiments can be used to help understand and simulate reservoir sediment erosion and the downstream transport and deposition. If potential consequences are important, consider applying numerical and physical models and field experiments. Experiments always work best when hypotheses or predictions are made in advance to guide the measurements and interpret the results. Laboratory or physical models can provide useful qualitative predictions of complex processes such as knickpoint erosion, armoring, channel widening, braiding, some meandering, downstream transport, and deposition. There are sediment scaling issues with laboratory models that make quantitative predictions difficult. For example, the specific gravity, particle fall velocity, and the grain sizes of clay, silt, sand, and gravel cannot be scaled in the same way. Therefore, the exact physical properties of coarse and fine sediment (including cohesion) are not easily replicated in the laboratory. Bromley et al. (2011) constructed a physical model to simulate the sediment erosion in Lake
The HEC-RAS can also compute sediment transport capacity using the following equations: Ackers and White Engelund and Hansen Larsen Meyer-Peter and Müller Geomorphic Analysis For medium and high risk dam removals, a geomorphic analysis is recommended, by an experienced geomorphologist. Initially, the geomorphic analysis utilize historic aerial photographs, geologic maps, soil maps, topographic maps, historical ground photographs and accounts, and field reconnaissance. Additional analysis may require collection and interpretation of sediment and soil samples. The geomorphic analysis will describe the physical setting of the dam, reservoir, and river channel, a description of geologic controls, significant water and sediment sources, and characterization of the river and reservoir sediment. The geomorphic analysis also will identify historic channel trends and allow for estimates of future channel evolution trends following dam removal. For dam removals with a significant reservoir drawdown and reservoir shoreline slopes, the potential for landslides during reservoir drawdown should be investigated. There are numerous references for geomorphic analysis of stream channels. The ASCE Sedimentation Engineering Manual provides two chapters: Fundamental of Fluvial Geomorphology (Biedenharn et al., 2008) Engineering Geomorphology (Schumm and Harvey, 2008) The ASCE Sediment Dynamics upon Dam Removal also provides a chapter on the geomorphic effects of dam removal (Skalak et al., 2011). Numerical Modeling, Laboratory Modeling, and Field Experiments Numerical models, laboratory models, and field experiments can be used to help understand and simulate reservoir sediment erosion and the downstream transport and deposition. If potential consequences are important, consider applying numerical and physical models and field experiments. Experiments always work best when hypotheses or predictions are made in advance to guide the measurements and interpret the results. Laboratory or physical models can provide useful qualitative predictions of complex processes such as knickpoint erosion, armoring, channel widening, braiding, some meandering, downstream transport, and deposition. There are sediment scaling issues with laboratory models that make quantitative predictions difficult. For example, the specific gravity, particle fall velocity, and the grain sizes of clay, silt, sand, and gravel cannot be scaled in the same way. Therefore, the exact physical properties of coarse and fine sediment (including cohesion) are not easily replicated in the laboratory. Bromley et al. (2011) constructed a physical model to simulate the sediment erosion in Lake
dam_removal_analysis_guidelines_2016-12-14.docx