Agenda - 11-27-1995 - C-1-b - Laserfiche WebLink

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In rural areas, home and farm needs can be met by ground water yields of as little as three to five gallons per minute. In 1987, the U.S. Geological Survey conducted an analysis of well yields in the Blue Ridge and Piedmont portions of the state. Shown on the accompanying table are the average yields obtained from wells, by both geologic and hydrogeologic (water bearing potential) rock unit classification. WELL YIELDS- PIEDMONT NORTH CAROLINA Geologic Hydrogeologic Number Average Yield Rock Classification Rock Classification of Wells m Metamorphosed Granitic Felsic Metaigneous 791 19.1 Felsic Metavolcanic Felsic Metavolcanic 280 13.0 Intermediate Metavolcanic Intermediate Metavolcanic 43 16.8 Mafic Metavolcanic Mafic Metavolcanic 63 11.9 Metamorphosed Gabbro & Intermediate Metaigneous 284 18.4 Diorite Ph litte& Schist Ph litte 127 20.3 Metavolcanic E iclastic Metavolcanic E iclastic 95 16.9 Metasmudstone& Argillite 319 14.6 Meta-Argillite Chatham Group, Triassic Sedimentary 269 11.6 Undivided Rocks Source: Adapted from Statistical Analysis Relating to Well Yield to Construction Practices and Siting of Wells in the Piedmont and Blue Ridge Provinces of North Carolina, U.S. Geological Survey, 1987. The geologic rock units listed in the table are shown on the Geology Map. Although not shown in the table, well yields were generally greater where wells were located in draws and valleys, and lowest on hills and ridges. Floodplains The riparian zone of a river, stream or other body of water is the land adjacent to that body of water that is, at least periodically, influenced by flooding. In general terms, riparian ecosystems are found wherever streams or rivers at least occasionally cause flooding beyond their channel confines. Such ecosystems can be broad alluvial valleys or narrow strips of streambank vegetation The flooding of the riparian ecosystem is important for the maintenance of that system for several reasons. The flooding water and subsequent ground water levels are the main determinants of the type and productivity of vegetation found in the riparian zone. Flooding waters also bring nutrient-rich sediments to the floodplain, export organic and inorganic material from the floodplam, and serve as a primary agent for long-term aggradation(deposition of alluvial material)and degradation(downcutting of surface geology)of the floodplain. 100-Year Floodplain.The precise boundaries of riparian ecosystems, particularly on the upland edge, are difficult to determine because of seasonal and yearly changes in flooding levels, soil moisture, and