One way this may occur is by the conversion of the sand dunes from nonactive to active. In the Sand Hills, vegetation is the principal factor that contributes to stability of the dunes. Without soil and vegetative cover, these sand dunes may become mobile. An aerial photograph of part of the Nebraska Sand Hills is shown in figure 1. Part of the Nebraska Sand Hills.
Bright areas depict active sand dune areas.
Program was established by the USGS to provide a hydrologically based, long-term method of assessing the quality of a large representative part of the Nation's water resources. The results of the projects are distributed in a variety of reports to local, State, and Federal agencies and the public as results become available. In response to extensive flooding in the Midwest during summer 1993, the White House Interagency Floodplain Management Task Force directed seven Federal agencies to establish the Scientific Assessment and Strategy Team to determine the immediate effects of flooding and longer term implications for floodplain management within the region. The team was hosted by the USGS because of its extensive computer-based technological capabilities, multidisciplinary staff, and experience in the development, scientific application, and management of large amounts of geographically referenced information. The data base includes graphically referenced information on manmade structures, hazardous and toxic waste sites, and water-treatment facilities, land cover and land use, fish and wildlife habitats, rainfall, topography, surficial geology and soils, stream and river hydrology and hydrography, demography, and economic bases.