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Action Plan City <br />of Saro Marcos, TX <br />According to the City's Hazard Mitigation Plan, flooding is the foremost hazard that threatens <br />the City of San Marcos. The severity of a flood event is determined by a combination of several <br />major factors including: stream and river basin topography and physiography; precipitation and <br />weather patterns; antecedent; recent soil moisture conditions; the degree of vegetative clearing <br />and impervious surfaces; and drainage system capacity and condition of infrastructure. Floods <br />can be short-term or long-term in duration, ranging from several hours to several days. <br />The location oflow water crossings, 8awell asthe 196(1 hand O.296(5O0-year) Annual <br />Chance Event (ACE) floodp|aino for the City of San Marcos are shown in Figure 3. This figure <br />represents the locations within the planning area that are most affected by riverine flooding and <br />is based upon newly developed hydrologic and hydraulic analysis. The new analysis is <br />considered the best information available to date. The total acreage of the city that is located in <br />the 196floodplain is4'25Oacres and 0.296 is 5'938 acres. The new Atlas 14 data indicates the <br />average 24-hour precipitation depth for 196flood event is 13.3 inches and the .0296 is 19.9 <br />inches. Both events represent a significant increase over the previous USGS 1998 depths. <br />Figure 3 Special Flood Hazard Areas and Low Water Crossings, City ofSan Marcos <br />6ourc*City ofSan Marcos Hazard Mitigation Plan <br />13 <br />