Geologic Mapping of Flood Hazards in Arizona: An Example From the White Tank Mountains Area, Maricopa County
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Abstract:
Assessment of the character of flood hazards and the extent of flood-prone areas on the piedmonts of Arizona is an increasingly important concern to floodplain managers as urban areas continue to expand. Piedmonts are the low-relief, gently sloping plains between mountain ranges and the streams or playas that occupy the lowest portions of the valleys. Proper management of flood hazards on piedmonts is important because much of southern, central, and western Arizona is composed of piedmonts; they comprise most of the developable land around Phoenix and other rapidly expanding population centers of the State. Management of flood hazards in Arizona and elsewhere in the western United States is complicated because portions of many piedmonts are composed of active alluvial fans. During floods, these fans are subject to widespread inundation and local high velocity flow, and substantial changes in channel patterns may occur. Development that proceeds on piedmonts without regard to the locations of active alluvial fans is likely to place people and property at risk during large floods. Report and 4 map sheets.Keywords:
Alluvial fan
Phoenix
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Ground-water quality data (1917-96) from 772 wells in 16 alluvial basins that have minimal urban development were used to determine the effect of nonurban factors on ground-water quality in south- central Arizona. Characterization of the spatial variability of ground-water quality within and among alluvial basins that have minimal urban development will provide a baseline to which water- quality problems associated with urbanization can be compared. Four water-type categories--calcium carbonate, calcium mixed anion, sodium carbonate, and sodium chloride--were used to classify the 13 alluvial basins for which adequate data were available. Ground-water quality was compared to U.S. Environmental Protaection Agency maximum contaminant levels for drinking water, depth of well, and depth to top of perforated interval for five alluvial basins that represented the four water-type categories. Exceedances of maximum contaminant levels for fluoride and nitrate occurred in three and four basins, respectively, of the five selected basins. Specific-conductance values for ground water in the five selected basins tend to increase in a northwesterly direction toward the central part of Arizona as the extent of evaporite deposits increases. The results of this study, which are part of the U.S. Geological Survey's National Water-Quality Assessment Program, can be used to determine the effects of urban land-use activities on ground-water quality in similar hydrogeologic conditions and may be the best indicator available for nonurban ground-water quality in the region.
Alluvial plain
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Alluvial fan
Alluvial plain
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Economic shortage
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Alluvial fan
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"Canada: land of the mountain and the flood." Journal of Geography in Higher Education, 5(2), pp. 180–181
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