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<br />SANTA MARIA DAM - 8 - July 11, 2013 <br />INUNDATION MAPPING REPORT <br />The flood will spread out over a very wide floodplain after leaving Alamosa. Overbank flooding <br />from Alamosa to the small community of Lasauses about 22 miles downstream is not expected to <br />exceed 3 feet in depth, and will be mostly 1 to 2 feet deep or less. The average overbank velocity in <br />this reach will be less than 1 foot per second, and the peak overbank velocity is not expected to <br />exceed 2 feet per second. The Alamosa County Road S 13.7 bridge and the Conejos/Costilla <br />County Road Z bridge will be overtopped, and a few buildings located within the Rio Grande <br />floodplain will be inundated. The homes in Lasauses are not expected to be flooded. South of <br />Lasauses the flood wave will be contained by a very narrow and deep floodplain that is <br />approximately the width of the Rio Grande main channel itself. The modeling and the delineation <br />of the inundation extents were terminated at this point because the attenuated flow rate due to a <br />clear-day breach of Santa Maria Dam (7,400 cfs) is less than the computed 100-year flow rate <br />(8,000 cfs). <br />