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Source: https://erdc-library.erdc.dren.mil/jspui/ The sedimentation study for the Albuquerque Arroyos Flood Control Project was conducted to determine if deposition in the concrete-lined North Diversion and Embudo Arroyo Channels would cause overtopping during the 100-year-frequency flood. The project was originally designed and constructed by the U.S. Army Corps of Engineers for the Standard Project Flood, but the effects of sediment deposition in the channel were ignored. A recent flood deposited significant quantities of sediment in the Embudo Arroyo Channel, raising concerns about the channel 's ability to carry larger flood discharges. The sedimentation study included a geomorphic assessment conducted under contract by Resource Consultants and Engineers of Fort Collins, CO. The geomorphic study assessed the stability of arroyos that drain into the North Diversion Channel and identified primary sediment sources in the watershed. The sedimentation study also included determination of sediment yield for each watershed that drains into the North Diversion Channel. Since there is no generally accepted method for calculating sediment yield, several different methods were used to calculate yield and compared with limited measured data. Trap efficiencies for flood detention reservoirs and sediment traps were estimated. The detention basins had trap efficiencies between 88 and 96 percent. In the larger basins almost all of the sand and greater sediment sizes were trapped. The sediment traps effectively remove between 62 and 74 percent of the sand and greater size sediment. The TABS-1 numerical sedimentation model was used to predict deposition in the concrete-lined channels. The effect of sediment deposits on boundary roughness was determined using analytical techniques. Calculated roughnesses were incorporated into the numerical model and an iterative procedure was used to determine the effect of deposited sediment on conveyance and roughness. The numerical model was circumstantiated using data from a historical flood where significant deposition occurred in the Embudo Arroyo Channel. Sediment inflow to the numerical model was determined using results of the sediment yield and trap efficiency studies. It was determined that the primary source of sediment was the unlined channels upstream from the concrete-lined channels. Considerable uncertainty exists relative to the quantity of sediment delivered by the 100-year-frequency flood. Sensitivity studies were conducted to assess the impact of different sediment loadings. The study concluded that, while channel roughness was increased in certain reaches of the concrete-lined channel, the increase in roughness was insufficient to result in overtopping of the existing channel during the 100-year-frequency flood. The study also concluded that sediment deposition problems in the North Diversion Channel and Embudo Arroyo are decreasing due to continuing channel improvement projects. |
