NPDP Dam Dictionary

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Term AKA Definition
Dam A barrier built across a watercourse to impound or divert water. See arch dam, afterbay dam, buttress dam, check dam, coffer dam, concrete dam, detention dam, embankment dam, gabion dam, gravity dam, masonry dam, multipurpose dam, precast dam, prestressed dam, regulating dam, rubble dam, or saddle dam.
Dam Failure Breach and uncontrolled release of the reservoir.
Dam Failure Detection Provide a description how the dam failure or the early signs of the failure were initially detected/identified.
Dam foundation The excavated surface or undisturbed material upon which a dam is placed.
Dam Height The height of the dam in feet to the nearest foot. It is defined as the vertical distance between the lowest point on the crest of the dam and the lowest point in the original streambed.
Dam Name The official name of the dam. For dams that do not have an official name the popular name is used.
Dam tender The person responsible for the daily or routine operation and maintenance activities of a dam and its appurtenant structures. The dam tender commonly resides at or near the dam.
Dam Type The type of the dam could be one or more of the following: 1. Earth 2. Rockfill 3. Gravity 4. Buttress 5. Arch 6. Multi-Arch 7. Concrete 8. Masonry 9. Stone 10. Timber Crib 11. Other
Damage to Cultural, or Historical Effects Description Describe the damage to cultural or historical structures, artifacts, etc.
Damping Resistance which reduces vibration by energy absorption.
Damping ratio The ratio of the actual damping to the critical damping, critical damping being the minimum amount of damping which prevents free oscillatory vibration.
Datum Any level surface taken as a plane of reference from which to measure elevations.
Dead capacity Dead storage The reservoir capacity from which stored water cannot be evacuated by gravity.
Debris fan Sloping mass of boulders, sand, silt and clay formed at the mouth of a stream valley.
Decking Separating charges of explosives by inert material which prevents passing of concussion, and placing a primer in each charge.
Deed covenant A term used in association with the sale of excess lands. In order for an eligible buyer of excess land to receive Reclamation irrigation water on such land, a covenant controlling the sale price of the land must be placed in the deed transferring the land to the buyer.
Deep percolation Percolation of irrigation water past the plant root zone to regions of deeper groundwater aquifers.
Deflagration To burn with sudden and startling combustion. Describes explosion of black powder, as opposed to the more rapid detonation of dynamite.
Deflation The force of wind erosion, e.g., blowouts.
Deflect A decrease in the vertical diameter of a flexible pipe.
Deflection Upstream or downstream movement of a dam or dike.
Deformation Change in shape or size.
Degradation Process wherein the elevation of streambeds, sandbars, and flood plains is lowered by erosion. The opposite of aggradation.
Delay A device used to obtain detonation of charges at separate times. An electric blasting cap which explodes at a set interval after current is passed through it.
Delay pattern Order of firing charges obtained by arranging delays to fire separate holes or series of holes at different times.
Delta An alluvial sediment deposit normally formed where a river or stream enters a lake or estuary. Sediment deltas are usually triangular in plan view, narrow at the upstream end and relatively wide at the downstream end. The sediment particles deposit because the river velocity and gradient are too low to keep the particles in motion. Active deltas contain diverging multiple channels that continually deposit sediment and migrate back and forth across the delta surface. The sediment particles of the delta deposit are usually well sorted such that the coarser particles (gravel and sand) deposit first at the upstream end, while finer particles (silt and clay) deposit farther downstream.
Demand Rate at which electric energy is used, expressed in kilowatts, whether at a given instant, or averaged over any designated period of time. Maximum water use under a specified condition.
Demersal Fish eggs or organisms that hatch on the bottom of a lake or stream.
Demographics Relating to the statistical study of human populations.
Dendritic Channel pattern of streams with tributaries that branch to form a tree-like pattern.