NPDP Dam Dictionary

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Term AKA Definition
Coordinated operation Generally, the operation of two or more interconnected electrical systems to achieve greater reliability and economy. As applied to hydropower resources, the operation of a group of hydropower plants to obtain optimal power benefits with due consideration to all other uses.
Corduroy A road made of logs laid crosswise on the ground or on other logs.
Core Impervious core; Impervious zone A zone of material of low permeability in an embankment dam. Hence the expressions central core inclined core puddle clay core and rolled clay core." A cylindrical piece of an underground formation cut and raised by a rotary drill with a hollow bit."
Core drill A rotary drill, usually a diamond drill, equipped with a hollow bit and a core lifter.
Core wall A wall of substantial thickness built of impervious material, usually of concrete or asphaltic concrete in the body of an embankment dam to prevent leakage. See membrane.
Correlation The relation between two or more variables. A statistical test that sets a numerical value to the amount of interdependence.
Corridor Narrow strip of land reserved for location of transmission lines, pipelines, and service roads.
Corrosion Wear or dissolving away through chemical action as by rusting, or acids.
Cost effectiveness Economic efficiency, obtaining the best method for the least amount of money.
Coulees Small streams or dry streambeds.
County The name of the county in which the dam is located.
Coyote holes Horizontal tunnels in which explosives are packed for blasting a high rock face.
Crazing A network pattern of fine cracks in concrete that do not penetrate much below the surface. Crazing cracks are very fine and are barely visible, except when the concrete is drying after it has become wet
Creep Slow movement of rock debris or soil usually imperceptible except to observations of long duration. Time- dependent strain or deformation, for example, continuing strain with sustained stress.
Crest The top surface of the dam. A roadway may be constructed across the crest to permit vehicular traffic or facilitate operation, maintenance, and examination of the dam. Also, the high point of the spillway control section.
Crest elevation Crest of dam; Top of dam; Dam crest The elevation of the uppermost surface of a dam, usually a road or walkway, excluding any parapet wall, railing, curb. etc. The crown of the roadway or the level of the walkway which crosses the dam. On embankment dams, the crest of the dam is the top of the embankment, not including camber, crown, or roadway surfacing.
Crest length Length of dam The distance, measured along the axis or centerline crest of the dam at the top level of the main body of the dam or of the roadway surface on the crest, from abutment contact to abutment contact exclusive of an abutment spillway; provided that, if the spillway lies wholly within the dam and not in any area especially excavated for the spillway, the length includes the spillway.
Crest structure Portion of spillway between the inlet channel and the chute, tunnel or conduit, which does not contain gates.
Crest width Top thickness The thickness or width of a dam at the level of the top of dam (excluding corbels or parapets). In general, the term thickness is used for gravity and arch dams, and width is used for other dams.
Crib dam A gravity dam built up of boxes, cribs, crossed timbers or gabions, filled with earth or rock.
Critical depth The depth of flow when the Froude number equals one.
Critical flow When the Froude number is equal to one, the flow is critical and surface waves remain stationary in the flow.
Critical habitat Defined in Section 3(5)(A) of the Endangered Species Act as: (1) The specific areas within the geographical area occupied by the species at the time it is listed, on which are found those physical and biological features (a) essential to the conservation of the species and (b) which may require special management considerations for protection; and (2) Specific areas outside the geographical area occupied by a species at the time it is listed upon a determination by the Secretary of the Department of Interior that such areas are essential for the conservation of the species. These areas have been legally designated via Federal Register notices.
Crop rotation A pattern of changing the crops grown in a specific field from year to year in order to control pests and maintain soil fertility.
Crop subsidy Price support paid by the government to farmers.
Crown The highest point of the interior of a circular conduit, pipe, or tunnel. The point in an arch dam which generally corresponds with where the height of the dam is a maximum. The elevation of a road center above its sides.
Crushed gravel Gravel which has been produced by a machine.
Crushed rock Rock which has been reduced in size by a machine.
Crusher A machine which reduces rocks to smaller and more uniform sizes.
Cubic feet per second CFS; FT3/s) A unit of discharge for measurement of a flowing liguid equal to a flow of 1 cubic foot per second (448.8 gallons per minute, or 1.98 acre-feet per day). A rate of streamflow; the number of cubic feet of water passing a reference point in 1 second.