• Application of Remote Sensing in Floodway Delineation

      Clark, Robin B. (Arizona-Nevada Academy of Science, 1974-04-20)
      Population pressures on the land resources of Arizona have led to the sale and development of areas subject to flooding and because of the inadequacy of land use controls, the area is open to various land speculation schemes and unplanned subdivision growth. A floodplain delineation project was conducted for the planning department of Cochise County, Arizona, in which imagery acquired by earth resources technology satellite (ERT-1) and by high-altitude aircraft was employed. Parameters of the analysis included soils and geomorphology, vegetation, hydrologic calculations, and historical data. Floodplain soils lack developed b horizons, as compared to older, more mature soils not subject to flooding. General soil maps can only be used as guidelines, but a detailed soil survey can add significantly to the accuracy of image interpretations. Erosion-affected soil tones in areas adjacent to active channels proved beneficial in that the heightened contrast served to enhance resolution of vegetation-type boundaries. Hydrologic calculations were done based on valley cross-sections surveyed at two-to-three mile intervals. The historic data input into the system of floodplain delineation is dependent on the location of high-water marks and on obtaining a record of the amount of rainfall which resulted in the high-water mark.
    • Hydrologic Aspects of Land-Use Planning at Tumamoc Hill, Tucson, Arizona

      Popkin, Barney Paul; Soils, Water and Engineering Department, The University of Arizona, Tucson (Arizona-Nevada Academy of Science, 1974-04-20)
      Tumamoc Hill, an 869-acre (352 ha) desert area near Tucson, Arizona, is being considered as a controlled- access environmental site. Water affects the site's geology, soils, vegetation, wildlife, and archaeology. The Hill is drained by three small watersheds. The largest is rapidly urbanizing upstream. Hydrologic aspects include potential flooding and erosion hazards. These may be reduced simply, economically, and wisely in a land-use plan. Upstream development increases storm runoff volumes, and flood peaks, and frequencies routed through the site, and threatens existing downstream urban development. Return periods of channel-overflow floods become shorter with urbanization. The region may be managed to reduce hydrologic hazards by three procedures: widen channels, install low checkdams, and vegetate drainageways. These methods will slow down runoff velocities, and increase cross -sectional area of flow and roughness coefficient. More water would also be available for vegetation and wildlife. The land-use plan should include environmental education programs. These would present important effects of water on the natural ecology, and hydrologic aspects of watershed urbanization.