NPDP Dam Dictionary

Browse by Letter:
All  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  


Term AKA Definition
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.
Cubic foot 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.
Cubic foot per second cfs; ft3/s As a rate of streamflow, a cubic foot of water passing a reference section in one second of time. A measure of a moving volume of water (1 cfs = 0.0283 m3/s).
Cultural patrimony Ancestral heritage and entitlement.
Cultural resource(s) Any building, site, district, structure, or object significant in history, architecture, archeology, culture, or science.
Culvert A pipe or small bridge for drainage under a road or structure.
Current I The movement of electrons through a conductor, measured in amperes.
Curtain grouting The process of pressure grouting deep holes under a dam or in an abutment to form a watertight barrier and effectively seal seams, fissures, fault zones, or fill cavities in the foundation or abutment.
Curved gravity dam A gravity dam which is curved in plan.
Cut To lower an existing grade or surface level, or an area where this has been done. Gross cut is the total amount of excavation in a road or a road section, without regard to fill requirements. Net cut is the amount of excavated material to be removed from a road section, after completing fills in that section.
Cutoff An impervious construction by means of which water is prevented from passing through foundation material.
Cutoff trench Keyway An excavation in the foundation of an embankment dam, usually located upstream of the dam axis or centerline crest which extends to bedrock or to an impervious stratum. The excavation is backfilled with impervious material to form a cutoff and reduce percolation under the dam. See foundation trench.
Cutoff wall A wall of impervious material (e.g., concrete, asphaltic concrete, timber, steel sheet piling, or impervious grout curtain) located in the foundation beneath an embankment dam and which forms a water barrier and reduces seepage under a dam or spillway.