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The objective of the study is to estimate the flows at the four locations for bridge design, and on the Trinity River at Douglas City. The study provides the 50- and 100-year return period flow values at four bridge locations. These four structures are located between 5.1 and 14.6 river miles downstream from Lewiston Dam. The structures, in order of location moving downstream from Lewiston Dam are: Salt Flat Bridge, Bucktail Bridge, Poker Bar Bridge, and Treadwell Bridge (also referred to as Biggers or Steel Bridge). Discharge estimates at Douglas City for the 50- and 100-year (plus other) return periods are also included to show the comparison of this study with a previous FEMA study. The discharges are determined using a probabilistic study with inputs from background information, an operational study, balanced hydrographs, flood routings, regulated flows from the reservoir, and previous studies.