NPDP Dam Dictionary

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Term AKA Definition
Saddle dam A subsidiary dam of any type constructed across a saddle or low point on the perimeter of a reservoir.
Saline sodic land Soil that contains soluble salts in amounts that impair plant growth but not an excess of exchangeable sodium.
Salmonids Family of fish that includes salmon and steelhead.
Sample error Random variation reflecting the inherent variability within a population being counted.
Sand Mineral grains whose particle size vary from a No. 4 sieve to a No. 200 sieve.
Sand backfill Material which has a particle size which varies from a No. 4 sieve to a No. 200 sieve and is used for refilling an excavation.
Sand boil Seepage characterized by a boiling action at the surface surrounded by a cone of material from deposition of foundation and/or embankment material carried by the seepage. A swirling upheaval of sand or soil on the surface of or downstream from an embankment caused by water leaking through the embankment. The ejection of sand and water resulting from piping.
Saturation (and internal vibration) A method of compacting soil using water added to soil and internal vibrators (such as a concrete vibrator) are worked down through the depth of soil placed.
Scatter A concentration of artifacts.
Scheduled outage Shutdown of a generating unit, or other facility, for inspection or maintenance, in accordance with an advance schedule.
Scrape A nest made from scratching in the ground.
Seasonal stream See intermittent stream.
Secchi depth A measure of water clarity.
Second foot sec-ft Shortened term for cubic foot per second (cfs or ft3/s).
Sediment Any finely divided organic and/or mineral matter deposited by air or water in nonturbulent areas. Unconsolidated solid material that comes from weathering of rock and is carried by, suspended in, or deposited by water or wind.
Sediment discharge Rate at which sediment passes a stream cross-section in a given period of time, expressed in millions of tons per day (mtd).
Sediment load Mass of sediment passing through a stream cross section in a given period of time, expressed in millions of tons (mt).
Sediment yield Amount of mineral or organic soil material that is in suspension, is being transported, or has been moved from its site of origin. The portion of eroded material that does travel through the drainage network to a downstream measuring or control point. The sediment yield per unit of drainage area is the sediment yield rate.
Seep A spot where groundwater oozes slowly to the surface, usually forming a pool.
Seepage The slow movement or percolation of water through soil or rock.
Seepage collar A projecting collar of concrete built around the outside of a tunnel or conduit, within an embankment dam, to reduce seepage along the outer surface of the conduit.
Seepage force The force transmitted to the soil or rock grains by seepage.
Seepage loss Water loss by capillary action and slow percolation.
Seepage velocity The rate of discharge of seepage water through a porous medium per unit area of void space perpendicular to the direction of the flow.
Seiche wave A wave generated by either a landslide into a reservoir or by a sudden displacement or deformation of a fault line in a reservoir floor during a major earthquake.
Seismic Of or related to movement in the earth's crust caused by natural relief of rock stresses.
Seismic evaluation criteria A guideline for determining which faults or seismic sources need to be assigned MCE's. For high hazard structures, faults with Holocene or latest Pleistocene displacement are included and probabilistic assessments are based on an annual probability of occurrence of 2 x 10-5. For significant hazard structures, faults with Holocene displacement are included and probabilistic assessments are based on an annual probability of occurrence of 1 x 10-4.
Seismic intensity Subjective measurement of the degree of shaking at a specified place by an experienced observer using a descriptive scale. See intensity scale.
Seismic parameters Descriptors of earthquake loading or earthquake size, such as magnitude, peak acceleration, location (distance and focal depth), spectrum intensity, or any of many other parameters useful in characterizing earthquake loadings.
Seismo Pertains to earthquakes.