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I II I I I I I I I I I I I I I I I I I B. PURPOSE AND SCOPE The purpose of this study is to analyze existing local drainage prob- lems within the defined study area. The objectives are to: 1) Define feasible solutions to the local drainage problems; 2) Develop an internal drainage plan for implementation over a period of time; and 3) Provide the city and county with a drainage plan for use in future development. The study deals with isolated storms over small drainage basins affect- ing the conveyance of water within the designated study area. The study does not address the major 100-year flooding from the Rio Grande River, which would encompass most of the city and adjacent areas. Fol- lowing discussions with city and county officials, a decision was reached to eliminate the Rio Grande River from this study. The Rio Grande 100- year floodplain was delineated by the Federal Emergency Management Agency, formerly the Federal Insurance Administration, in "Flood In- surance Study, A1amosa County," December 1976. Additional studies should be funded by state or federal agencies to evaluate alternatives for protecting the community from flooding by the Rio Grande River. C. STUDY AREA The City of A1amosa and surrounding portions of the county have several distinct natural and man-made physical features that affect drainage and flooding. The Rio Grande River is the predominant natural feature of the area running from the northwest to the southeast roughly form- ing the eastern boundary of the city. The river is the source of major flooding, an outlet for local drainage,and a source of irrigation waters. The. main channel is not sufficient to contain flood waters and develop- ment has occurred too close to the river. Levees have been constructed to reduce the frequency of flooding, but which block local drainage into the river, ~ausing ponding behind the levees. -3-