Saltation is the process by which sediment generally

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Unformatted text preview: altation is the process by which sediment, generally of sand size and coarser, bounces along the stream bed by the impact of the flow of water or of other moving particles; saltation can also occur by the movement of wind . Salt water is water on or beneath a land (or water) surface that accumulates as a result of natural processes of precipitation and which contains concentrations of dissolved solids (mostly salts) typical of normal sea water or of other small water bodies such as the Dead Sea or the Great Salt Lake; the concentration of dissolved solids in salt water is sufficient to cause deleterious effects by ingestion of living organisms adapted to a dependency on fresh water or brackish water. Sample, relative to the needs and activities of the natural sciences, is a small part or quantity that is randomly obtained to represent the whole of a larger mass, volume, group, or population; it is limited in size to be easily analyzed, studied, characterized, and stored, large enough to be typical of the larger feature, element, or landscape process, and has a degree of permanence. In general, a sample (such as a small volume of sand from a selected part of a dune field) has properties that allow it or a derivative (such as a known volume of water, snow, or ice that is evaporated but all solid residue is retained) to be preserved without employing measures that are destructive to the properties that characterize the sample as representative. Relative to statistical measures of hydrology, a sample is a value or element within a larger population of values; as an example, an annual flood discharge from a gage site is a sample of the entire list of floods for an annual series. Sand, as fluvial sediment, is sediment defined to be of particle diameter between 0.062 and 2.0 mm in diameter (b-axis). 37 Sand splay is a low ridge or rounded length of deposits of sand to fine gravel on a flood plain or low terrace; sand splays typically are flood sediment extending from the lee, or downstream, side of an obstacle (most typically large trees) to the flood flow. Sapping, or ground-water sapping, is a process of steady sediment removal by the laminar flow to and release of ground water as seepage at the saturated base of an escarpment, arroyo, or similar erosional feature, above which the soil, subsoil, alluvium, or bedrock is unsaturated. Sapping results in the separation at the seepage site of sand and silt particles from the rock or sediment through which the ground-water movement occurs; coupled with sediment-particle separation due to evaporation and precipitation of salts, the process causes erosion, undercutting, over-steepening of slope at the base of the landform, and eventually slope failure and cliff retreat. Sawyer, a channel snag, is a tree extending from the bed of a stream and having branches that project above the water surface; the term may be the source of the name for the Mark Twain novel, Tom Sawyer. Schmutzdecke is a German term meaning dirty cover, or filth cover; as applied to stream beds, it is a gelatinous complex, formed in the uppermost few centimeters of the channel alluvium, of variable proportions of bacteria, fungi, protozoa, rotifera, and aquatic insect lavae. For influent (loosing) streams, schmutzdecke reduces the potential for transmission loss of discharge by acting as an interstitial seal in the sand and gravel of the bed material, thereby minimizing the ability of water to flow through the schmutzdecke layer to underlying horizons of the unsaturated zone. Sediment is detached fragmental material that originates from either chemical or physical weathering of rocks and minerals and is transported by, suspended in, or deposited by water or air or is accumulated in beds by other natural agencies. Sedimentation is the process by which sediment is mechanically deposited from suspension within a fluid, generally water, or ice, thereby accumulating as layers of sediment that are segregated owing to differences in size, shape, and composition of the sediment particles. Sediment budget is an accounting, or inventory, of sediment-transport rate, generally as components based on particle-size ranges entering and leaving a specified area or stream reach; when the fluxes of sediment that enter and leave are unequal, the assumption follows that the differences signify the net amounts of sediment that are stored or taken from storage within the area or reach. Sediment concentration of streamflow is the amount of sediment, generally as a dry weight, that is entrained in a specified volume of water; sediment concentration is typically expressed in milligrams of sediment per liter of the water/sediment mixture. Sediment delivery is the sum of hydrologic and geomorphic processes resulting in the availability of sediment for transport in a stream network; sediment-delivery processes range from entrainment in overland flow to rapid mobilization by bank failure to much slower movement as soil creep. 38 Sediment-delivery ratio is the ratio, expressed as a percent, of sediment yield of a drainage basin to the total amount of sediment moved downslope by denudational processes during a specified period of time; over long time periods, mass balance must be maintained and the mean sediment-delivery ratio must approach 1.0. Sed...
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