Glossary of Restoration Terminology

1.58-Year Return Period Discharge (Q1.5) The discharge with a return period of 1.58 years, derived from the observed annual maximum flow series. [Watson et al. 1999]. 2-Year Return Period Discharge (Q2) The discharge with a return period of 2 years, derived from the observed annual maximum flow series. [Watson et al. 1999]. Abatement Reducing the degree or intensity of, or eliminating, pollution. Abiotic Not living, refers to the non-living components of an ecosystem; also refers to non-biological processes (e.g., sediment deposition). Ablation The process by which ice and snow waste away as a result of melting and/or evaporation. Abrasion (1) Removal of streambank soil as a result of sediment-laden water, ice, or debris rubbing against the bank. (2) The process of wearing down, or wearing away, stream bed and bank material by friction of solid particles moved by gravity, water, ice, or wind. Absolute time Geologic time measured in years. Compare to relative time. Absorption The process by which substances in gaseous, liquid, or solid form are assimilated or taken up by other substances. Accretion The process of sediment accumulation due to flowing water. Acid Has a pH of water less than 5.5; pH modifier used in the U.S. Fish and Wildlife Service wetland classification system; in common usage, acidic water has a pH less than 7. Acidic (1) The condition of water or soil in which the amount of acid substances are sufficient to lower the pH below 7.0. (2) A material with a pH of less than 7.0 (opposite of alkaline). Soil nutrients are generally less soluble and less available to plants in moderately or strongly acid soils. Agricultural lime is commonly applied to acidic soils to increase the pH. Acid rain Rainfall with a pH of less than 7.0. Long-term deposition of these acids is linked to adverse effects on aquatic organisms and plant life in areas with poor neutralizing (buffering) capacity. Accretion Vertical accumulation of inorganic or organic material.

Acre A measure of area equal to 43,560 ft2 (4, 046.87 m2). One square mile equals 640 acres. Acre-foot (acre-ft., or af) The volume of water needed to cover an acre of land to a depth of one foot; equivalent to 43,560 cubic feet (ft3) or 325,851 gallons. Active Channel Width The portion of the channel where sediment actively moves and\or permanent vegetation generally does not become established. Active floodplain A floodplain in which the 1-3 year flood reaches bankfull capacity. Floodplains become active or inactive through channel change or through changes in annual flood frequency (i.e., upland watershed condition). Active storage capacity The total usable reservoir capacity available for seasonal or cyclic water storage. It is gross reservoir capacity minus inactive storage capacity. Adaptation (1) The condition of showing fitness for a particular environment, as applied to characteristics of a structure, function or entire organism; also, the process by which such fitness is acquired. (2) A modification of a species that makes it more fit for reproduction and/or existence under the conditions of its environment. Adfluvial Refers to fish that hatch in streams, migrate to a lake or shore to mature, and return to their natal stream to spawn. Adsorption The adherence of gas molecules, ions, or molecules in solution to the surface of solids. Aeolian Sediment deposited by wind. Derived from Greek mythology; Aeolus was god of the winds. Aeration Any active or passive process by which intimate contact between air and liquid is assured, generally by spraying liquid in the air, bubbling air through water, or mechanical agitation of the liquid to promote surface absorption of air. Aerobic (1) Occurring only in the presence of molecular oxygen (said of certain chemical or biochemical processes, such as aerobic decomposition); (2) Characterizing organisms able to live or be active only in the presence of free oxygen or air, and conditions that exist only in the presence of air or free oxygen. Contrast with Anaerobic. Affluent (stream) A stream or river that flows into a larger one; a tributary. Afterbay A reservoir that regulates fluctuating discharges from a hydroelectric power plant or a pumping plant. Aggradation

(1) A long-term, persistent rise in the elevation of a streambed caused by sediment deposition. (2) A progressive buildup or raising of the channel bed and floodplain due to sediment deposition. (3) The geological process by which streambeds, floodplains, and the bottoms of other water bodies are raised in elevation by the deposition of material eroded and transported from other areas. Typically a stream that is undergoing aggradation over a long section of its length has an excess supply of sediment. (4) Aggradation indicates that stream discharge and/or bed-load characteristics are changing. Opposite of Degradation. Aggrading Accumulating sediment or deposition; in reference to stream beds. Aggregate Sand, gravel, crushed stone, or slag, usually having a known range of particle sizes. Used either with a cementing medium to form concrete, or alone as in a roadway bed or for railroad ballast. Agricultural pollution Liquid and solid wastes from all types of farming, including runoff from pesticides, fertilizers, and feedlots; erosion and dust from plowing; animal manure and carcasses; and crop residues and debris. "A" horizon Organic soil zone immediately below the surface of the ground, from which soluble material and fine- grained particles have been moved downward by water seeping through the soil. Varying amounts of organic matter can give the "A" horizon varying colors, usually ranging from gray to black. Sometimes called topsoil. A-Jacks (E-SenSS) A proprietary product for scour protection, consisting of precast concrete units. Each unit has six legs, which interlock with other A-Jacks when the units are placed in the stream, thus providing greater stability. The units are available in various sizes from Armortec, Inc., Bowling Green , KY. Algae Microscopic plants that grow in sunlit water containing phosphates, nitrates, and other nutrients. Algae, like all aquatic plants, add oxygen to the water and are important in the fish food chain. Alevin The life stage of salmon and trout immediately following the egg stage. Hatchlings still have their yolk sacs attached to them, and they live within the spaces in the gravel. Algal bloom The rapid proliferation of passively floating, simple plant life, such as blue-green algae, in and on a body of water. Alkaline (1) Material with a pH greater than 7 (opposite of acidic); (2) pH modifier in the U.S. Fish and Wildlife Service wetland classification system; (3) in common usage, a pH of water greater than 7.4. Allochthonous Material originating offsite that is subsequently transported onsite through the action of water, gravity, or other mechanisms. Alluvial (1) Deposited by running water; (2) Refers to the transport of material by flowing water normally in a river or stream. (3) Referring to deposits of silts, sands, gravels and similar detrital material, which have been transported by running water.

Alluvial aquifer A water-bearing deposit of unconsolidated material (sand and gravel) left behind by a river or other flow water. Alluvial deposit Clay, silt, sand, gravel or other sediment deposited by the action of running, ponded, or receding water. Alluvial fan Depositional landforms whose surface forms a segment of a cone that radiates downslope from the point where the stream moves from a steep gradient to a flatter gradient and suddenly loses some sediment transport capacity. Typical of arid and semiarid climates, but not confined to these areas. Alluvial plain Flood plains produced by the filling of the valley bottom with alluvium. Alluvial plains are usually composed of fine mud, sand and gravel, but can include cobbles, boulders and organic material. Alluvial stream (1) Self-formed channels composed of silts, clays, sands, gravel, or cobble, and characterized by the ability to alter their boundaries and patterns in response to changes in discharge and sediment supply. (2) A stream whose channel boundaries are composed of appreciable quantities of the sediments transported by the stream flow. An alluvial stream is free to adjust its dimensions of size, shape, pattern, and slope in response to changes in flow and sediment. Alluvium (1) A general term for all deposits (gravel, sand, silt, clay, or other particulate rock material) resulting directly or indirectly from the sediment transport of streams, including the sediments collected in riverbeds, floodplains, lakes, fans, and estuaries; (2) Sediments transported by the flowing water of a river or stream; (3) A general term for detrital deposits made by streams on riverbeds, floodplains, and alluvial fans, especially a deposit of silt or silty clay laid down during times of flood. The term applies to stream deposits of recent time. It does not include subaqueous sediments of seas or lakes. (4) A general term for all material deposited by a modern stream anywhere along its course. Alluvium would include sediments laid down in river beds, flood plains, lakes, fans, and estuaries. Alpine snow glade A marshy clearing between slopes above the timberline in mountains. Alternate bars Depositional features on opposite sides of the channel formed when the low-water channel of a stream meanders within the banks of a straight section of the stream. Ammonia A compound of nitrogen and hydrogen (NH3) that is a common by-product of animal waste. Ammonia readily converts to nitrate in soils and streams. Anabranch A diverging branch of a river that re-enters the main stream. Anadromous Migratory fish that are born in freshwater, spend a portion of their lives in salt water (in estuaries and oceans) and return to spawn in freshwater rivers and streams. Anaerobic

Pertaining to, taking place in, or caused by the absence of oxygen. (2) An organism that can live without oxygen, or a process that takes place in the absence of oxygen. See anoxic. Anastomosing channel A channel that is divided into several smaller channels, which successively meet and then redivide. Synonymous with braided channel. Anchor point Either natural (e.g., tree or rock outcroppings) or man-made hard structures (e.g., rock or log trenches) at the upstream and/or downstream end of an isolated scour hole. Angler-day The time spent fishing for any part of a day by one person. Angle of repose The maximum slope or angle (measured from the horizontal) at which granular noncohesive material (such as soil, gravel, or loose stone) comes to rest. Also called slope of natural repose (SONR). Approximately equal to the angle of internal friction of a cohesionless, dry sand in a loose condition. Annual High Water (AHW) The lower limit suitable for establishing permanent woody vegetation on a given streambank. Note that in some stable streams systems, AHW may be equivalent to bankfull discharge (Qbf). The AHW may or may not represent the average annual peak discharge or the elevation for the one-year event. Annual Low Water (ALW) The elevation roots must be able to penetrate down to in order to have access to water during the dry season. Related to the "base flow" of a stream. ALW approximates the depth of the vadose zone in a streambank soil profile. The elevation of the vadose zone is increasingly dictated by soil type as distance from the stream lengthens. Anomalies As related to fish, externally visible skin or subcutaneous disorders, including deformities, eroded fins, lesions, and tumors. Anoxic The absence of oxygen, usually referring to zones of a lake that are devoid of oxygen. Anthropogenic Having to do with or caused by humans. Apex of a bend The area near the center of a bend. Usually measured by dividing the total arc angle of the bend by two; e.g., in a 90 degree bend the apex would be the section of the arc near 45 degrees. Application rate The quantity (mass, volume, or thickness) of material applied per unit area or along a lineal distance (one ton per ft of stone as an example). Aqueduct A pipe or conduit made to bring water from a source. Aquatic Living or growing in or on water. Aquatic bed wetlands

Wetland and deep water habitats class dominated by plants (e.g. rockweed, eelgrass, and water hyacinth) that grow principally on or below the surface of the water for most of the growing season in most years. Aquatic ecosystem Any body of water, such as a stream, lake, or estuary, and all organisms and nonliving components within it, functioning as a natural system. Aquatic guidelines Specific levels of water quality which, if reached, may adversely affect aquatic life. These are nonenforceable guidelines issued by a governmental agency or other institution. Aquatic habitat Habitat that occurs in free water. Aquatic-life criteria Water quality guidelines for protection of aquatic life. Commonly refers to criteria established by the U.S. Environmental Protection Agency. See also Water-quality guidelines, Water-quality criteria, and Freshwater chronic criteria. Aquatic life use A beneficial use designation (in state water quality standards) in which the waterbody provides suitable habitat for survival and reproduction of desirable fish, shellfish, and other aquatic organisms. Aquatic Plants Plants growing in or near the water that have true roots, stems, and leaves. Aquifer (1) A water-bearing rock or sediment formation, group of formations, or part of a formation that contains sufficient saturated permeable material that is capable of storing water, allowing water to pass through it, and yield significant quantities of water to springs and wells. (2) A permeable geological unit of sediment or rock within which groundwater is stored and can be transported relatively easily under a hydraulic gradient. The opposite of aquiclude. Arc A segment or section of a curve. Arc Angle In degrees, the angle associated with a segment of a curve or circle. In river engineering usually associated with the degree of curvature of a bend. Areal cover A measure of dominance that defines the degree to which above-ground portions of plants cover the ground surface. It is possible for the total areal cover for all strata combined in a community or for a single stratum to exceed 100 percent because (a) most plant communities consist of two or more vegetative strata; (b) areal cover is estimated by vegetative layer; and (c) foliage within a single layer may overlap. Arid A term describing a climate or region in which precipitation is so deficient in quantity or occurs so infrequently that intensive agricultural production is not possible without irrigation. Armoring, Armor

(1) Artificial surfacing of bed, banks, shore or embankment to resist erosion or scour; (2) Placement of a covering on a streambank that prevents erosion. (3) A natural process where an erosion-resistant layer of relatively large particles is established on the surface of the streambed through removal of finer particles by stream flow. A properly armored streambed generally resists movement of bed material at discharges up to approximately ¾ bankfull depth. (4) Natural process whereby an erosion-resistant layer of relatively large particles is formed on a streambank or stream bed due to the removal of finer particles by streamflow. This layer inhibits the transportation of underlying finer material until such time that a flow of sufficient magnitude occurs and destroys the armor layer. (5) The development of a coarse surface layer in a stream bottom. The gradual removal of fines from a stream, leaving only the large substrate particles, cause by a reduction in the sediment load. This is sometimes referred to as pavement. Arroyo (also wadi or wash) A small, deep flat-floored channel or gully cut by an intermittent or ephemeral stream, usually with nearly vertical banks cut into unconsolidated material. A term commonly used in the arid and semiarid regions of the Southwestern United States. (2) Flat-floored, vertically - walled channel of an ephemeral stream typical of semiarid climates. Artesian A term referring to water existing under hydrostatic pressure in a confined aquifer. The water level in a borehole penetrating an artesian aquifer will usually rise well above the upper boundary of the water bearing rocks and may even flow out of the borehole at the surface, in which case it is known as a flowing artesian well. Artesian aquifer A subsurface water mass that would discharge its water at the surface if a permeable layer were connected to the surface. Articulating Concrete Mattress or Mats (ACM) Systems of individual concrete blocks (called elements) approximately four feet long by 1.5 feet wide, connected together with corrosion-resistant cables or ultraviolet-stabilized rope that are placed on a streambank or streambed to prevent erosion. If required, filter fabric can be placed before mattress installation. The cavities between elements permit bank drainage and can allow growth of either volunteer or planted vegetation. This technique has been used extensively to protect pipelines since it can be easily removed, the pipeline can be repaired, and the ACM replaced. These mats are primarily placed for bank protection on the lower Mississippi River by the U.S. Army Corps of Engineers using the Mat Sinking Unit, the only one of its type in the world. Articulated Concrete Blocks (ACBs) Concrete blocks that are designed to interlock together but which can still move independently of one another to some extent. Normally placed on streambanks and used as form of flexible, hard armor. Plants can be grown in the open interstices between blocks. Artificial recharge (1) Augmentation of natural replenishment of groundwater storage by some method of construction, spreading of water, or by pumping water directly into an aquifer. (2) Addition of surface water to a groundwater reservoir by human activity, such as putting surface water into spreading basins. See also Groundwater recharge, recharge basin. "As-built" The size, location, and condition of river training structures or bank protection works immediately after construction has been completed. Typically a survey of the structures is taken (referred to as "as-builts") and compared to the original construction plans to determine whether the project was built correctly.

However, the most useful aspect of as-builts may be in future inspection and monitoring as an aid to determine how the protection is functioning and whether maintenance or reinforcement is required. Asphalt block Precast or broken pieces of asphalt that can be hand-placed or dumped on a streambank or filter for protection against erosion. The introduction of asphalt into a waterway may be environmentally unacceptable because of water quality concerns. Assemblage An association of interacting populations of organisms in a given waterbody. Assessment reach Assessment reach is that stream segment of interest, and can be based on ecological, erosional, or property length considerations. Atmospheric pressure The pressure exerted by the atmosphere on any surface beneath or within it; equal to 14.7 pounds per square inch at sea level. Augmentation (of stream flow) Increasing stream flow under normal conditions, by releasing storage water from reservoirs. Autochthonous (1) Indigenous (2) Substances, materials, or organisms native to or formed in the place where found (for example, a particular stream). Average annual runoff For a specified area, it is the average value of annual runoff amounts calculated for a whole hydrologic cycle of record that represents average hydrologic conditions. Average depth (d) Calculated by dividing the cross-sectional area of the channel by the channel width. Average discharge As used by the U.S. Geological Survey, the arithmetic average of all complete water years of record of surface water discharge whether consecutive or not. The term “average” generally is reserved for average of record and “mean” is used for averages of shorter periods, namely, daily, monthly, or annual mean discharges. See also “Mean”. Average year supply The average annual supply of a water development system over a whole hydrologic cycle. Average year water demand Demand for water under average hydrologic conditions for a defined level of development. Avulsion A change in channel course that occurs when a stream suddenly breaks through its banks, typically bisecting an overextended meander arc. (2) An abrupt change in channel course that occurs when a stream suddenly changes its course, usually associated with a flood or even a more catastrophic event. The legal interpretations of whether an "avulsion" has occurred is often the subject of bitter and prolonged legal dispute. The decision usually rests upon judicial precedent in a particular jurisdiction. When used in a geological rather than an engineering or geomorphological context, "avulsion" may refer to the stream changing meander belts within a valley, or even breaking through into another valley.

B Backfill (1) n. The material used to refill a ditch, trench, or other excavated area. (2) v. The process of replacing excavated material back into the original excavated area. Background concentration A concentration of a substance in a particular environment that is indicative of minimal influence by human (anthropogenic) sources. Backswamp A landform deposited over time in a slow moving or ponded backwater section of a waterway. Backwater (1) A pool type formed by an eddy along channel margins downstream from obstructions, such as bars, root wads, or boulders, or as a result of back flooding upstream from a blockage; sometimes separated from the channel by a sand/gravel bar; (2) A body of water, the stage of which is controlled by some feature of the channel downstream from the backwater, or in coves or covering low-lying areas and having access to the main body of water; (3) A body of water in which the flow is slowed or turned back by an obstruction such as a bridge or dam, an opposing current, or the movement of the tide; (4) A small, generally shallow body of water attached to the main channel, with little or no current of its own, or (5) A condition in subcritical flow where the water surface elevation is raised by downstream flow impediments. Backwater bars Gravel bars that form upstream due to backwater conditions. Backwater channel Side channels that do not carry appreciable flows, even at high stages. Backwater effect An increase in water surface elevation upstream of an obstruction. The obstruction may be either permanent (such as a roadway embankment or dam), semi-permanent (such as a landslide, beaver dam, or debris accumulation), or temporary (such as a flood in a downstream channel or an ice jam.) Backwater pool A pool that formed as a result of an obstruction like a large tree, weir, dam, or boulder. Bacteria Single-celled microscopic organisms. Bank (1) The sloping ground that borders a stream and confines the water in the natural channel when the water level, or flow, is normal; (2) Steep ascending slope of land of any height raised above the adjacent shore that can experience undercutting if it is in contact with water. (3) The side slopes of a channel between which the streamflow is normally confined at flows up to and including bankfull discharge. (4) The side of the stream on the observer's right or left when facing downstream, either "right bank" or "left bank", sometimes called "right descending bank" or "left descending bank". Unfortunately, cross- sections of the channel are sometimes recorded, plotted, and entered into hydraulic computational programs without regard to this convention. Therefore, one must be certain of the convention being used in a particular case. Bank barbs

Also known as deflectors, groins, wing dikes, transverse dikes, permeable dikes, hard points, or jetties. Two to five structures, usually rock, are placed in series along straight or convex bank lines in order to deflect the flow lines away from the bank. Bank barbs and vanes are distinctly different. Vanes point upstream 20 to 30 degrees. They dip down such that the instream tips of the structures are typically low enough to be overtopped by all flows and crests slope upward to reach bankfull stage elevation at the bank. Bank erosion The process by which water loosens and wears away soil and rock from the edge of a body of water, usually resulting in an enlargement of the body of water and a corresponding reduction in the size of the land. Bank fill Any material used to construct a streambank. Bank fill is usually composed mostly of mineral content, as opposed to topsoil. Bank protection Revetment, or other armor protecting a bank of a stream from erosion, includes devices used to deflect the forces of erosion away from the bank. Bank stability The ability of a streambank to counteract erosion or gravity forces. Bank storage (1) The temporary increase in groundwater levels near the stream channel during a period of flooding. As stage decreases the groundwater levels return to pre-flood levels. (2) Water absorbed by the bed and banks of a stream, reservoir, or channel and returned in whole or in part as the water level falls; (3) The change in the amount of water stored in an aquifer adjacent to a surface-water body resulting from a change in stage of the surface-water body. Bank zone That portion of the bank that is usually above the normal high-water level but is still exposed periodically to wave-wash, erosive river currents, ice and debris movement, and traffic by animals and man. The water table is often close to the soil surface due to its proximity to the normal river level. See zones, bank. Bankfull (1) Term describing peak flow; the stage at which the channel is nearly full. The term, "Bankfull" modifies stage, width, channel, and discharge. See bankfull discharge, bankfull elevation, bankfull stage, and bankfull width for definitions of these terms. (2) The full capacity of the channel clear up to the top of the channel bank on either side (the transition point between the bank and the floodplain). Bankfull channel depth The maximum depth of a channel within a riffle segment when flowing at a bankfull discharge. Bankfull channel width The top surface width of a stream channel when flowing at a bankfull discharge. Bankfull discharge (1) The expression, "bankfull discharge," Qbf, should be used to refer to the maximum discharge that the channel can convey without overflow onto the floodplain. Although this definition, proposed by Copeland et al. (2001), differs from that used by others (e.g., Rosgen, 1996), it eliminates confusion. Theoretically Qbf and Qeff are generally equivalent in channels that have remained stable for a period of time, thus allowing the channel morphology to adjust to the current hydrologic and sediment regime of the

watershed (e.g., Pickup, 1976, Andrews, 1980, Soar, 2000, but see Emmitt & Wolman, 2001). In such a channel, the bankfull discharge corresponds to a sharp change in the slope of the rating curve. It must be noted, however, that in an unstable channel that is adjusting its morphology to changes in the hydrologic or sediment regime, Qbf can vary markedly from Qeff. Therefore, the expression "bankfull discharge" should never be used to refer to Qri or Qeff. The relationship of Qbf to Qri and Qeff is useful as an indicator of channel stability and evolution (Schumm et al., 1984; Simon, 1989, Thorne et al., 1996). The Qbf from ‘template’ or ‘reference’ reaches (stable reaches from similar watersheds) has been used as a guideline for relevant dimensions of the restored channel (Rosgen, 1996). Field indicators of Qbf are often unreliable (Williams, 1978). Problems associated with basing design on Qbf are discussed by FISRWG (1998) and Biedenharn et al. (2000) [E-SenSS] (2) Bankfull Discharge (Qb) The maximum discharge which can be contained within the channel without over-topping the banks. Leopold et al. (1964) proposed that it is this flow which is responsible for forming and maintaining the morphology of the channel. Bankfull stage refers to the water surface elevation during bankfull flow and can be identified from various criteria. [Watson et al. 1999]. Bankfull stage/elevation (1) Same as bankfull elevation, the stage or water surface elevation at which water overflows the bankfull channel, and begins to spill onto a stream's active floodplain. The bankfull channel just conveys the bankfull, or channel forming discharge. In many streams the bankfull discharge has a recurrence interval of 1.5 to years. Indicators of the bankfull stage/elevation may include the top of a point bar, a change in vegetation, a change in the slope, the top of an undercut slope, a change in particle size, drift lines and water marks. One of the best indicators of bankfull stage is the floodplain. (2) The water surface elevation attained by the stream when flowing at the bankfull discharge, when it is at the point of overtopping the banks at a given location. The local gage may be referenced to an arbitrary datum (see Stage.) Bankfull width (1) The width of a river or stream's bankfull channel. The bankfull channel just conveys the bankfull, or channel forming discharge. In many streams the bankfull discharge has a recurrence interval of approximately 1.5-2 years. Indicators of the bankfull width may include the top of point bars, changes in vegetation, changes in slope, the top of undercut slopes, changes in particle size, drift lines, and water marks. (2) The width of a river or stream channel between the highest banks on either side of a stream. (3) The width of the water surface when a stream is at bankfull stage. Bar (1) Accumulation of sand, gravel, or other alluvial material found in the channel, along the banks, or at the mouth of a stream where a decrease in velocity induces deposition; bars are often exposed only during low-water periods. Diagonal – Elongated bodies with long axes oriented obliquely to the flow. They are roughly triangular in cross-section and often terminate in riffles. Longitudinal – Elongated bodies parallel to local flow, of different shape, but typically with convex surfaces. Common to gravelly braided streams. Point bar – Found on the inside of meander bends. They are typically attached to the streambank and terminate in pools. Transverse bar – Typically solitary lobate features that extend over much of the active stream width but may also occur in sequence down a given reach of river. They are produced in areas of local flow divergence and are always associated with local deposition. Flow is distributed radially over the bar. Common to sandy braided streams.

(2) An alluvial deposit or erosion feature composed of sand, gravel, or other materials, which obstructs flow. (3) An accumulation of alluvium (usually gravel or sand) caused by a decrease in sediment transport capacity on the inside of meander bends or in the center of an over wide channel. (4) A sand, gravel, or cobble deposit found on the bed of a stream that is often exposed only during low-water periods. (5) An elongated deposit of alluvium within a channel or across its mouth. Barbs Structures, usually rock, projecting from a bank to redirect flow away from a streambank, thereby controlling erosion of the streambank. Barrier A physical block or impediment to the movement or migration of fish, such as a waterfall (natural barrier) or a dam (man-made barrier). (2) A low dam or rack built to control flow of debris. Barrier bar An elongate offshore ridge, submerged at least at high tide, built up by the action of waves or currents. Barrier beach A narrow, elongate sandy ridge rising slightly above the high-tide level and extending generally parallel with the mainland shore, but separated from it by a lagoon. Base flood The flood or tide having a 1 percent chance of being exceeded in any given year (100-year flood); the “base flood” is commonly used as the “standard flood” in Federal flood insurance studies. Base floodplain The area subject to flooding by the base flood. Base flow (1) The sustained low flow of a stream, usually by groundwater inflow to the stream channel. During dry periods, base flow constitutes the majority of stream flow. (2) The sustained portion of stream discharge that is drawn from natural storage sources, and not affected by human activity or regulation. (3) The portion of the stream discharge that is derived from natural storage, i.e., groundwater outflow and the draining of large lakes and swamps or other source outside the net rainfall that creates surface runoff. Discharge sustained in a stream channel, not a result of direct runoff and without the effects of regulation, diversion, or other works of man. (4) The discharge of the stream derived from natural storage. Typically the average stream discharge during low flow conditions. Base flow width The width of the water surface when the stream is at base flow discharge. Base level (1) The level or elevation to which a stream-channel profile has developed. (2) The elevation below which a river can no longer erode, i.e., the level of its mouth. (3) Level below which the bed of the stream cannot erode. Usually considered to be the elevation of the water surface of the stream or water body that the stream in question flows into for a given hydrologic condition. Ultimate base level for all streams is sea level. In the framework of engineering time, a non-erodible grade control structure or geologic formation may also serve as a base level. Base level of a stream The elevation below which a river can no longer erode, i.e., the level of its mouth. Basic The opposite of acidic; water that has a pH of greater than 7.

Basic fixed sites Sites on streams in the U.S. Geological Survey’s National Water-Quality Assessment Program (NAWQA) Study Units at which streamflow is measured and samples are collected for analysis of temperature, salinity, suspended sediment, major ions and metals, nutrients, and organic carbon to assess the broad- scale spatial and temporal character and transport of inorganic constituents of streamwater in relation to hydrologic conditions and environmental settings. Basin (1) A large or small depression in the surface of the land. (2) The entire area drained by a river and its tributaries. (3) A broad area of the earth beneath which the strata dip, usually from the sides toward the center. See Drainage basin. Batter The receding, upward slope of a wall or the face of a structure. To give a structure or wall a receding, upward slope. Bayou A creek or stream that is usually slow-moving; most often used in reference to water courses in Louisiana and adjacent states along the upper Gulf Coast. (2) Term used mainly in southern gulf states to describe a stationary or sluggishly moving body of water that was once part of a lake, river or gulf. Bed (1) The bottom of a channel. (2) The floor or bottom on which any body of water rests. (3) In geology, a seam or deposit of mineral, also the smallest division of a stratified series. Bedload (also Bed Load) (1) The part of a stream’s sediment load that is moved on or immediately above the stream bed, such as the larger or heavier particles (boulders, cobbles, gravel) rolled along the bottom; the part of the load that is not continuously in suspension or solution. (2) The part of the sediment load that is transported by sliding, rolling, or bounding on or very near the streambed; sediment moved mainly by tractive or gravitational forces or both, but at velocities less than the surrounding flow; sediment particles resting on or near the channel bottom (in almost continuous contact with the bed) pushed or rolled along by the flow of water. (3) Sediment moving on or near the streambed and transported by jumping, rolling, or sliding on the bed layer of a stream. See also Suspended load. (4) Sediment moving on or near the stream bed by saltation (jumping), rolling, or sliding. (5) A component of the total sediment load made up of sediment particles moving in frequent, successive contact with the bed . Transport occurs at or near the bed, with the submerged weight of particles supported by the bed. Bed load movement takes place by gravitational processes of rolling, sliding, or saltation. Bedload discharge The quantity of bedload passing a cross-section in a unit of time. Bedload driven A severely overwidened stream with an oversupply of sediment where the roughness of the bed material causes the stream to partially abandon its main course and distribute flow toward one or both banks, causing increased bank erosion and continued widening. Basically, an aggrading, braided stream. Bedload sampler See Bed material sampler. Bed erosion The process by which water loosens and wears away soil and rock from the bottom of a body of water, usually resulting in a deepening of the body of water.

Bed material (1) The sediment mixture composing the streambed. (2) The material of which a streambed is composed. (3) The sediment mixture of which the bed is composed. In alluvial streams, bed material is transported in varying quantities depending upon the flow. Bed material discharge The quantity of bed material passing a cross-section in a unit of time, either in suspension or as bedload. Bed material load (1) That portion of the total sediment load with sediments of a size found in the streambed. (2) Synonymous with bed material discharge. (3) A portion of the total sediment load composed of grain sizes found in appreciable quantities in the stream bed. In gravel-bed rivers the bed material load moves as bed load, but in sand-bed streams significant quantities of bed material load move as suspended load. Bedload material The heavier portion of river sediment which is not suspended in the water but moves along the river bottom in the direction of flow. Bed material sampler A device for obtaining samples of the bed material for analysis of its composition. Bedforms Ripples, waves, dunes, and related forms that develop under various flow conditions on the beds of alluvial streams with significant bedload transport. Bedrock A general term used for solid rock that underlies soils or other unconsolidated material. (2) The solid rock underlying gravel, sand, and soils and overlying the mantle rock, ranging from surface exposure to depths of several hundred feet. Bedrock – Confined Channel A stream channel that has as its bottom the bedrock which is normally undergoing downcutting. Bedslope The inclination of the channel bottom, measured as the elevation drop per unit length of channel. Bed roughness (1) A measure of irregularity of the streambed as it contributes to flow resistance, commonly measured in terms of the Darcy-Weisbach roughness coefficient; (2) A measure of the irregularity of the streambed as it contributes to flow resistance. Commonly expressed as a Manning “n” value. (3) The unevenness of streambed material (e.g., gravel, cobbles) that contributes resistance to stream flow. The degree of roughness is commonly expressed using " Manning's roughness coefficient." Bed sediment The material that temporarily is stationary in the bottom of a stream or other watercourse. Bed slope The longitudinal inclination of the channel bottom. Bench (1) A strip of relatively level earth or rock breaking the continuity of a declivity (slope). See Berm. (2) A horizontal surface or step in a slope. Bend

The change in direction of a stream channel. Bendway Weir Bendway weirs are discontinuous, redirective, structures usually constructed of rock, designed to capture and then safely direct the flow through a meander bend. A minimum of five structures are typically placed in series (the series are known as “weir fields”) along straight or convex bank lines. Bendway weirs differ from spurs and vanes in that they form a control system that captures and directs the streamflow through the weir field, usually all the way through the bend (hence the name bendway weirs). Bendway weirs are generally longer (1/3 – 1/2 stream width) and lower than barbs or spurs, flat crested and are designed to be continuously submerged or at least be overtopped by the design flows. Transverse river training structures often provide pool habitat and physical diversity. Weirs can be constructed of stone, tree trunks, or geotextile tubes or bags filled with grout or streambed material. Benthic Of, pertaining to, or related to the bottom of a stream or other body of water; living on the bottom of a body of water. Benthic invertebrates Aquatic animals such as insects, mollusks, crustaceans, worms, clams, crayfish, and other organisms without a backbone that live in, on, or near the bottom of lakes, streams, or oceans. Benthos (1) The organisms living on river, sea or lake bottoms. (2) Aquatic plants and animals that live in or on the bottom of a water body; the plant and animal life whose habitat is the bottom of a sea, lake, river, etc. (3) The deepest part of sea, lake, or ocean. Benthic drift The downstream movement of bottom-dwelling plants and invertebrates, accomplished by floating in the current. Berm (1) A nearly horizontal portion of the beach or backshore formed by the deposit of material by wave action. (2) A terrace or ledge formed within a channel at the base of the streambank. (3) A terrace or ledge cut on a slope or embankment to divert water or intercept sliding earth. (4) A shelf that breaks the continuity of a slope. (5) A horizontal depositional feature located along the bank of a stream. (6) A ridge of earth constructed to direct the flow of surface water. (7) The embankment of a pit or pond which may be wide and solid enough for vehicular traffic. (8) A surcharge of earth or other material added to a levee to increase geotechnical stability and to reduce seepage during floods. Best management practice (BMP) (1) Conservation measures intended to minimize or mitigate impacts from a variety of land-use activities; (2) An agricultural practice that has been determined to be an effective, practical means of preventing or reducing nonpoint-source pollution. (3) The preferred methods and/or products that will correct or control erosion or sedimentation on a specific site for particular site conditions. (4) A measure that is implemented to protect water quality and reduce the potential for pollution associated with storm water runoff; (5) any program, technology, process, siting criteria, operating method, measure, or device that controls, prevents, removes, or reduces pollution. "B" horizon Soil zone below the "A" horizon. Tends to be clayey and usually contains some material moved down from the A horizon. Sometimes called subsoil. Bight of the bend

See apex of a bend. Binder (Also emulsion, tackifier) - Natural or synthetic additive that causes an otherwise noncohesive material to bond together into a cohesive matrix. Used to reduce soil erosion and retain seeds, which allows germination and growth. Bioassessment Evaluation of the biological conditions of a waterbody that uses biological surveys of the resident plants, animals, and other living organisms that depend upon the aquatic resource. Biochemical oxygen demand (BOD) The amount of oxygen, expressed in milligrams per liter, that is removed from aquatic environments by the life processes of microorganisms. Biodegradation Transformation of a substance into new compounds through biochemical reactions or the actions of microorganisms such as bacteria. Biodiversity (1) The variety of life forms, the ecological roles they perform, and the genetic diversity they contain; (2) The quality of an ecosystem based on the sum of all species of plants and animals present; (3) Genetic diversity within the individuals and populations of a species; (4) Diversity of ecosystems within a landscape. Bioengineering (1) The science of using living materials (plants and biota) to stabilize an eroding bank of a stream. See also soil bioengineering. (2) The integration of living woody and herbaceous materials along with organic and inorganic materials to increase the strength and structure of soil. Biological assessment Information prepared by or under the direction of a federal agency using specific procedures concerning listed and proposed species and designated and proposed critical habitat that may be present in an action area and the evaluation of potential effects of the action on such species and habitat. Biological assemblages A group of phylogenetically or ecologically related organisms that are part of an aquatic community. Biological criteria Under the Clean Water Act, numerical values or narrative statements that define a desired biological condition for a waterbody and are part of the water quality standards. Biological diversity The variety and variability among living organisms and the ecosystems in which they occur. Biodiversity includes the numbers of different items and their relative frequencies, these items are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, biodiversity encompasses expressions of the relative abundances of different ecosystems, species, and genes. Biomass The amount of living matter, in the form of organisms, present in a particular habitat, usually expressed as weight-per-unit area. Bioregion

Homogeneous areas defined by similarity of climate, landforms, soil, potential natural vegetation, hydrology, or other relevant physical, chemical, or biological variables. Biota All living organisms of a region, as in a stream or other body of water. Biotechnical stabilization Use of natural inclusions, living or inert, in combination with structural components in a mutually reinforcing manner to reinforce soil, protect streambanks and stabilize slopes. Biotechnical slope stabilization Integrated or combined use of living vegetation and inert structural components in a mutually reinforcing manner Biotechnical structures usually get stronger with time as the vegetative components grow. Bituminous mattress An impermeable rock-, mesh-, or metal-reinforced layer of asphalt or other bituminous material placed on a streambank to prevent erosion. Blackwater streams Streams common in the southeastern United States that have high concentrations of DOC and lignins, resulting in a dark stain. Blanket (1) Material covering all or a portion of a streambank to prevent erosion. (2) Also pertains to a large group of rolled erosion control products consisting of coir (coconut fiber), jute, straw, wood fiber, or various synthetic materials used to prevent erosion, trap sediment, protect seed, and promote the growth of vegetation. These mats can either be permanent or biodegradable. Blockage Any material in the stream channel that causes a backwater effect. Blowdown Trees felled by high winds. Bog (1) A nutrient-poor, acidic wetland dominated by a waterlogged, spongy mat of sphagnum moss that ultimately forms a thick layer of acidic peat; generally has no inflow or outflow; fed primarily by rain water. (2) Freshwater wetlands that are poorly drained and characterized by a buildup of peat. Bole The trunk or stem of a tree, without root wad. Bolson An extensive, flat, saucer-shaped, alluvium-floored basin or depression, almost or completely surrounded by mountains and from which drainage has no surface outlet; a term used in the desert regions of the Southwestern United States. Border dikes Earth ridges built to guide or hold irrigation water within prescribed limits in a field; a small levee. Bosque (1) A dense growth of trees and underbrush; (2) Term referring to riparian woodlands in portions of the Southwest. Bottomland

See floodplain. Bottom-land forest Low-lying forested wetland found along streams and rivers usually alluvial floodplains. Bottomset bed Layer of fine sediment deposited in a body of standing water beyond the advancing edge of a growing delta. As the delta grows, it covers the bottomset bed with additional sediment. Boulder (1) A large substrate particle that is larger than a cobble, 256 mm (10 inches) in diameter. (2) A large, naturally occurring stone, which is transported by a stream only during high flows. (3) Technically, any bed material particle with a diameter greater than 256 mm; the largest bed material size, larger than a cobble. Brackish water (1) Water with a salinity intermediate between seawater and freshwater (containing from 1,000 to 10,000 milligrams per liter of dissolved solids). (2) Generally, water containing dissolved minerals in amounts that exceed normally acceptable standards for municipal, domestic, and irrigation uses. Considerably less saline than seawater. Also, marine and estuarine waters with mixohaline salinity (0.5 to 17 ppt due to ocean salts). Water containing between 500-17,000 parts per million (ppm) total dissolved solids (TDS). The term, “brakish water” is frequently interchangeable with saline water. The term should not be applied to inland waters. Braided channel A stream characterized by flow within several channels, which successively meet and divide. Braiding may be an adjustment to a sediment load too large to be carried by a single channel. Braiding often occurs when sediment loading is too large to be carried by a single channel. Braided channels often occur in deltas of rivers or in the outflow from a glacier. Braided stream A stream characterized by flow within several channels that successively meet and redivide. Braiding may be an adjustment to a sediment load too large to be carried by a single channel. Braided channels often occur on deltas or in the outflow from a glacier. Braided river A wide and shallow river whose flow passes through a number of interlaced branches that divide and rejoin and are separated by bars and shoals. Bridge scour Scour of the streambed at highway or railroad bridges; caused by the localized hydraulic contraction of the bridge piers, abutments, or approach fills, and not by system wide erosional processes. Such scour may result in catastrophic failure of the bridge and is difficult to predict and protect against, although research continues. Brine Water that contains more than 35,000 milligrams per liter of dissolved solids. Broadcast The application of material scattered or sprayed on the soil surface. E.g., broadcast seeding is the uniform distribution of seeds over the entire planted area. Brush mattress

A live brush mattress is a thick blanket (15-30 cm (6-12 in)) of live brushy cuttings and soil fill. The mattresses are usually constructed from live willow branches or other species that easily root from cuttings. Brush mattresses are used to simultaneously revegetate and armor the bank. The dense layer of brush increases roughness, reducing velocities at the bank face, and protecting it from scour, while trapping sediment and providing habitat directly along the waters' edge. Brush mattresses are an excellent candidate for combining with structural techniques such as rock toe protection. Buffer, Buffer strip (1) A vegetated area of grass, shrubs, or trees designed to capture and filter runoff from surrounding land uses. (2) A barrier of permanent vegetation, either forest or other vegetation, between waterways and land uses such as agriculture or urban development, designed to intercept and filter out pollution before it reaches the surface water resource. Buffer zone (1) As applied to streams, a narrow strip of natural vegetation along streambanks to reduce the possibility of adverse impacts from land use on water quality. (2) An area situated between two zones which have conflicting interests. As applied to streams, a strip of natural vegetation along streambanks to reduce the possibility of adverse impacts by adjacent land uses, and to increase beneficial stream effects such as shading, cover, erosion control, and organic inputs. (3) Areas of trees, grass, or other vegetation located between top bank and adjacent pastures or cultivated fields (also called greenbelts or riparian buffer zones). Bulkhead A vertical or nearly vertical retaining wall or structure supporting a natural or artificial embankment. Buttress A lateral restraint against slope movement. In geotechnical applications a buttress consists of a large mass of rock or earth placed at the toe of slope to increase stability. Buttressing Lateral restraint provided by earth or rock masses and embedded structural columns. Bypass channel A short flood diversion channel constructed to bypass a tortuous reach of natural stream or features of special interest such as wetlands. Bypass channels may be constructed to convey all flows or flood discharges only. C Canal A constructed open channel for transporting water. Candidate species Plant and animal taxa reviewed for possible inclusion on a Federal or State list of Endangered or Threatened species. A candidate species is not protected by law. See also Endangered species and Threatened species. Canopy (1) The overhead branches and leaves of vegetation; (2) A layer of foliage in a forest stand. This most often refers to the uppermost layer of foliage, but it can be used to describe lower layers in a multistoried stand. Leaves, branches and vegetation that are above ground and/or water that provide shade and cover for fish and wildlife. (3) The foliage of a tree, shrub, or herbaceous plant. Canopy angle

Generally, a measure of the openness of a stream to sunlight. Specifically, the angle formed by an imaginary line from the highest structure (for example, tree, shrub, or bluff) on one bank to eye level at midchannel to the highest structure on the other bank. Canopy cover The vegetation that projects over the stream. Can arbitrarily be divided into two levels: Crown cover is more than 1 m (3.33 ft) above the water surface. Overhand cover for fish is less than 0.31 m (1 ft) above the water surface. Cap out The addition of rock to a river training structure, either to reinforce and bring permanence to a short-lived permeable structure, such as a timber pile dike, or to restore a structure to the original elevation in the event of settlement or scour. Capacity (of a stream) The ability of a stream current to transport water, in terms of quantity. Capillary fringe (1) A zone immediately above the water table (zero gauge pressure) in which water is drawn upward from the water table by capillary action; (2) The zone immediately above the water table, where water is drawn up by capillary forces. Cascade (1) Habitat type characterized by swift current, exposed rocks and boulders, high gradient and considerable turbulence and surface agitation, and consisting of a stepped series of drops; (2) A short, steep drop in streambed elevation often marked by boulders and agitated white water. Catadromous Adjective describing fish that migrate from fresh water to spawn in the sea. Catchment (1) An area above a specific point on a stream from which water drains towards the stream; (2) The catching or collecting of water, especially rainfall. (3) A reservoir or other basin for catching water; (4) The water thus caught; (5) A watershed. Caving (1) The collapse of a streambank by undercutting due to wearing away of the toe or an erodible soil layer above the toe. (2) The collapse of a bank following undercutting due to flow or wave erosion of the toe or an erodible soil layer above the toe. Cellular-block mattress See Articulated Concrete Block Mattress. Cellular confinement system A synthetic grid matrix with open spaces filled with soil, sand, gravel, or concrete. The matrix mechanically stabilizes these materials and is used for erosion control and/or load support. See also geocellular confinement system (GCS). Channel (1) An open conduit either naturally or artificially created which periodically or continuously contains moving water, or which forms a connecting link between two bodies of standing water. (2) Deepest portion of a river body in which the main current flows. (3) An area that contains continuously or periodically flowing water that is confined by banks and a streambed. (4) A natural or artificial waterway

of perceptible extent that periodically or continuously contains moving water. It has a definite bed and banks which serve to confine the water. Channel bed slope A channel's vertical change over distance (the gradient). Channel bed width The width of the bankfull channel. In some channels, there is not a floodplain or a bench present to define bankfull width. In those cases, bankfull width is determined by features that do not depend on a floodplain; features similar to those used in the description of an active channel and ordinary high water. Channel blocks See valley plug and backwater effect. Channel confinement Lateral constriction of a stream channel. Channel depth The vertical distance from the bankfull elevation to the channel bed. Typically measured in riffle sections to obtain an average depth of the stream channel. Channel Evolution Model (CEM) A conceptual classification system designed to determine the status of a stream as the effects of downstream base level lowering move upstream. When streambanks exceed a critical geotechnical threshold, bank failure results in rapid widening of the stream cross-section on both banks. As the bed degrades, and a stable bed slope is restored, a compound channel feature forms, with a low-flow channel flanked by one or two stable berms. The CEM can be useful in predicting the changes that can be expected to occur in a disturbed stream in the future, by substituting space (distance along the stream channel) for time. Channel fills Accumulations of sediment in abandoned or aggrading channel segments, ranging from relatively coarse bedload to plugs of clay and organic mud. Channel flanking See Flanking Channel forming discharge The discharge that most efficiently drives the fluvial processes responsible for forming and maintaining the main morphological features and dimensions of the channel. This concept is based on the idea that even though channel width, depth, and slope vary along a stream and through time, average values of width, depth and slope tend to be constant for a reach with a given drainage area if the stream bed and banks are alluvial; there have not been any extreme floods, droughts, earthquakes, forest fires, or other catastrophic events in the recent past; the watershed is largely free of human-caused disturbances, such as land use changes, grazing, mining, road building, dams, or channelization, and furthermore, the channel geometry is such that the greatest discharge the channel will carry without overflowing is not a rare flood (which moves tremendous amounts of sediment, but occurs only rarely) or a low flow (which occurs frequently, but has relatively little erosive power), but is an intermediate magnitude, such as the one- or two-year flood. This characteristic discharge is referred to as the “channel-forming” or “dominant” discharge, Qcf.. Synonymous with dominant discharge. Channel scour

Erosion by flowing water and sediment on a stream channel; results in removal of mud, silt, and sand on the outside curve of a stream bend and the bed material of a stream channel. Channel scour and fill (1) Words used to define erosion and sedimentation during relatively short periods of time, whereas aggradation and degradation apply to similar processes that occur over a longer period of time. Scour and fill applies to events measured in minutes, hours, days, perhaps even seasons, whereas aggradation and degradation apply to persistent trends over a period of years or decades. (2) Terms used to define erosion and sedimentation processes during relatively short periods of time (minutes, hours, days, or seasons), whereas “degradation” and “aggradation” apply to similar process that occur over a longer period of time (years or decades). Channel stability A relative measure of the resistance of a stream to aggradation or degradation. Stable streams do not change appreciably from year to year. An assessment of stability helps determine how well a stream will adjust to and recover from mild to moderate changes in flow or sediment transport. Channel top width The horizontal distance along a transect line from top of bank to top of bank, measured at right angles to the direction of flow. Channel width (1) The horizontal distance along a transect line from bank to bank at the high water marks, measured at right angles to the direction of the flow. (2) The horizontal distance along a transect line from bank to bank at the bankfull elevation, measured at right angles to the direction of flow. Channelization (1) Straightening and deepening of a stream or the dredging of a new channel to which the stream is diverted; (2) The process of changing (usually straightening) the natural path of a waterway. (3) The straightening of a stream, usually performed to increase hydraulic conveyance or to ease navigation. Char Char belong to the Family "Salmonidae" genus "Salvelinus," and are described as having a body with light spots on a darker background, very fine and embedded scales, and the absence of teeth on the shaft of the vomer. Char include bull trout, Dolly Varden, eastern brook trout and lake trout. Check dam (1) A control structure placed in the channel downstream from a small headcut. (2) Small barriers constructed across a swale or drainage ditch to reduce flow velocities. See also grade control structure. Chemical stabilization Streambank protection technique involving the application of chemical substances to increase particle cohesiveness and to shift the size distribution toward the coarser fraction. The net effect is to improve the erosion resistance of the treated material. Chemical weathering Weathering or decomposition of rock material by chemical processes (e.g., oxidation, hydrolysis, etc.) that transform original material into new chemical combinations. Opposite of physical weathering which results in size reduction or disintegration of rock but without a change in composition. Chevron A redirective structure spanning the streambed, keyed into both banks, with equal legs angled upstream at approximately 30 degrees, with a lower crest elevation near the center of the channel. Chevrons can

act as both a grade control structure (bed armoring) and bank protection by redirecting currents away from the banks and toward the center of the channel. More commonly known as Cross Vanes. Chimney drain Vertical drains that typically feed into a collection drain at their base. Normally placed behind earthen slope retention (e.g., buttresses) to intercept seepage and prevent saturation of the buttress structures. "C" horizon Soil zone with a sandy texture that contains partially disintegrated and decomposed parent material. Lies directly under the "B" horizon and grades downward into unweathered (parent) material. May contain “relict structures” or vestiges of the parent rock, e.g., bedding planes, joints, and foliation surfaces. Chute A secondary channel, usually on the inside of a bend in a meandering stream, or a minor channel in a braided stream. Chute cutoff The process of a chute becoming the main channel, either in terms of the amount of flow it carries or the depth or area of flow. The process can be gradual or relatively dramatic. Cienega An area where the water table is at or near the surface of the ground, and/or the ground is wet due to the presence of seepage or springs; standing water occurs in depressions in the area, and it is covered with grass or sometimes with dense vegetation. Circumneutral Said of water with a pH between 5.5 and 7.4; pH modifier used in the U.S. Fish and Wildlife Service wetland classification system. Clay (1) Substrate particles that are smaller than silt and generally less than 0.003 mm (0.00012 inches) in diameter. (2) Material passing the No. 200 (0.074 mm) U. S. Standard Sieve that exhibits plasticity (putty- like properties) within a range of water contents and has considerable strength when air-dry (Unified Soil Classification System). Clay is typically comprised of the finest (smallest) particles in a soil and is composed primarily of clay minerals, e.g., kaolinite, illite, and chlorite. Clay blanket Layer of compacted clay placed over noncohesive bank soils to protect them against erosive streamflow. Clay plug Cohesive sediment with much organic muck deposited in a cutoff river meander. (See channel fill). Clean Water Act Federal law that sets maximum permissible levels of pollution in waters of the United States. This law requires that a permit be issued before performance of any activities that could possibly impact the quality of any waters of the United States. This law is administered by the Environmental Protection Agency. The permitting process is administered by the U.S. Army Corps of Engineers. Climax plant community The final species diversity or community composition following a period of plant succession found in a matured vegetated area. Closed basin

A basin whose topography prevents surface outflow of water. It is considered to be hydrologically closed if neither surface nor underground outflow of water can occur. Coarse woody debris (CWD) Portion of a tree that has fallen or been cut and left in the woods. Usually refers to pieces at least 20 inches (50.8 cm) in diameter. Cobble Substrate particles that are smaller than boulders and larger than gravels, and are generally 64-256 mm (2.5-10 in.) in diameter. Can be further classified as small and large cobble. Cobbles A rock fragment between 64 and 256 mm in diameter, thus larger than gravel and smaller than a boulder. Cobble streambed A watercourse predominately lines with naturally rounded stones, they are shaped by the water’s action. Cofferdam A temporary watertight enclosure built in the water and pumped dry to expose the channel bottom so that construction (locks, dams, river training structures) can be undertaken. Cohesion The capability of sticking or adhering together. Property exhibited by clays, silty clays, and clayey silts. Cohesive sediments Sediments whose resistance to initial movement or erosion is affected mostly by the cohesive bonds between the particles. Coir fiber Organic fibrous tissue obtained from the fruit of the coconut palm (Cocos Nucifera L.). Coir fiber lies between the exocarp (tough outer covering) and the endocarp (hard shell that covers the kernel). Coir fiber can be used as a mulch, as a soil substrate mixture, and in the manufacture of erosion control blankets, woven geotextiles, coir tubes and logs, and other manufactured erosion control products. Coir log (1) A coir log is made of usually made of interwoven coconut fibers (or other sturdy biodegradable materials) bound together with biodegradable netting. They provide substrate for plant growth and temporary physical protection until vegetation is established. (2) Cylindrical objects constructed from coconut fiber (coir) and bound by mesh. Coldwater stream Headwater stream located at an elevation or latitude sufficient to produce water temperatures low enough to support salmonid fishes. Colluvial (1) Pertaining to material or processes associated with transportation and/or deposition by mass movement (gravity) and runoff on side slopes and/or at the base of slopes. (2) A general term for loose deposits of soil and rock moved by gravity. (3) A general term applied to loose and unsorted deposits, usually at the toe of a bank or slope, brought from the upper bank chiefly by gravity. Talus and cliff debris are forms of colluvium. Colonization The habitation by natural invasion of any site by generally highly adaptable and opportunistic species, e.g., smartweeds colonizing a newly exposed mudflat in a lake, river, or reservoir.

Colonization stability Ability to reside in a semi-permanent status; not transient. Community In ecology, the species that interact in a common area. Community (plant) Particular assembling of plant species reflecting the prevailing environment, soil type and management. Complex response A series of interrelated responses by a stream to an alteration or change. Composite Aggregate of more than one sampling effort. Concave Curved like the inner surface of a sphere. Concave bank (of a bend) The outer bank of a sinuous channel. Concentration The ratio of the quantity of any substance present in a sample of a given volume or a given weight compared to the volume or weight of the sample. Concrete block Precast concrete material placed on a streambank to prevent erosion. Conductivity The measure of the ionic strength or concentration in water. Confined aquifer (artesian aquifer) (1) An aquifer that is completely filled with water under pressure and that is overlain by material that restricts the movement of water. (2) A water-bearing subsurface stratum that is bounded above and below by formations of impermeable, or relatively impermeable, soil or rock. Confining layer A body of impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers that restricts the movement of water into and out of the aquifers. Confluence (1) The flowing together of two or more streams; the place where a tributary joins the main stream. (2) The act of flowing together; the meeting or junction of two or more streams; also, the place where these streams meet. (3) The stream or body of water formed by the junction of two or more streams; a combined flood. (4) The junction of two or more streams, or rivers, or the junction of a tributary to a river or stream. Conifer (1) A tree belonging to the order Gymnospermae, comprising a wide range of trees that are mostly evergreens. Conifers bear cones (hence, coniferous) and have needle-shaped or scale like leaves. (2) Any of a large family of evergreen shrubs and trees, characterized by needle-shaped leaves and cones, such as pines, firs, hemlocks and spruces. Conjunctive use

The operation of a groundwater basin in combination with a surface water storage and conveyance system. Water is stored in the groundwater basin for later use by intentionally recharging the basin during years of above average water supply. Conservation The process or means of achieving recovery of viable populations. Conservation area Designated land where conservation strategies are applied for the purpose of attaining a viable plant or animal population. Conservation recommendations Suggestions by conservation agencies regarding discretionary measures to minimize or avoid adverse effects on a proposed action of federally listed threatened or endangered species or designated critical habitat. Conservation strategy A management plan for a species, group of species, or ecosystem that prescribes standards and guidelines that, if implemented, provide a high likelihood that the species, groups of species, or ecosystem, with its full complement of species and processes, will continue to exist well-distributed throughout a planning area, i.e., a viable population. Constituent A chemical or biological substance in water, sediment, or biota that can be measured by an analytical method. Constriction (flow) A reduction in the channel cross-sectional area that results in greater average stream velocities within the constricted area. Construction stake See dead stout stake Container plant Seeded or pot-raised plants in containers of different sizes and materials; non-degradable containers are to be removed before planting. Contaminate To make impure or unclean by contact or mixture. Contamination Degradation of water quality compared to original or natural conditions due to human activity. Contiguous habitat Habitat suitable to support the life needs of a species that is distributed continuously or nearly continuously across the landscape. Continuous Bank Protection A bank protection technique that covers the entire longitudinal length of eroding bank in an unbroken manner. Opposite of Discontinuous Bank Protection. Contour (1) An imaginary line on the surface of the earth connecting points of the same elevation. (2) A line on a survey or map connecting points of the same elevation.

Contraction dikes Dikes opposite each other, extending from both banks, designed to widen and/or deepen the navigable section of the channel. Usually constructed in crossings or relatively straight sections of the river. Contributing area The area in a drainage basin that contributes water to streamflow or recharge to an aquifer. Controlled river or stream See regulated river or stream. Conventional engineering (Hard construction) Engineered construction incorporating inert building materials such as aggregates, rock, concrete, steel, lumber, etc. without live vegetation (apart from incidental landscape planting). Convex Having a surface or boundary that curves or bulges outward, like the surface of a sphere. Convex bank (of a bend) The inner bank of a sinuous channel. Conveyance The ability of the stream to transport water. Often expressed numerically, with the most well-known relationships being Manning's formula or Chezy's formula, which both use an estimated value of channel "roughness" along with the cross-sectional area of flow and the hydraulic radius to obtain a numerical value for a given location. Core area The area of habitat essential in the breeding, nesting, and rearing of young, up to the point of dispersal of the young. Creel census survey The collection of data concerning the number of fish caught by sport fishers on a particular stream or in a particular area. Creep (1) The slow gravity driven downslope mass movement of rock or soil that is usually not perceptible except to observations of long duration. (2) The slow change in length or thickness of a material under prolonged stress. Crest elevation (1) The maximum elevation of a water surface during a specific period of time. (2) The highest elevation of a structure. Crib A frame structure, filled with earth or stone ballast, designed to retain earth masses and to protect streambanks against erosion. Cribs can be vegetated to improve stability, reduce near-structure stream velocities, improve aesthetics and/or ecological values. Cribwall A structure built of logs laid horizontally and separated by smaller wooden spacers placed at right angles. Cribwalls are designed to resist lateral earth forces and sometimes are used to protect streambanks from the erosive effects of channel flow. Critical depth

A theoretical hydraulics term which has little application to alluvial channels. It is the depth in a culvert or channel at which, for a given discharge, flow changes from subcritical to supercritical or vice versa. Flow in an alluvial channel is always subcritical, except in rare circumstances such as a levee break. Supercritical flow is characterized by such high velocities that a moveable bed channel will scour to such an extent that subcritical flow is soon restored. (See hydraulic jump). Critical flow That flow in open channels at which the energy content of the fluid is at a minimum; also, that flow which has a Froude number of one. Critical habitat Under the Endangered Species Act, critical habitat is defined as (1) the specific areas within the geographic area occupied by a federally listed species on which are found physical and biological features essential to the conservation of the species, and that may require special management considerations or protections; and (2) specific areas outside the geographic area occupied by a listed species, when it is determined that such areas are essential for the conservation of the species. (3) Specific areas within a geographical area occupied by an endangered or threatened species that when adversely impacted could be detrimental to species survival or recovery. Critical shear stress The minimum amount of shear stress exerted by stream currents required to initiate soil particle motion. Because gravity also contributes to streambank particle movement but not on streambeds, critical shear stress along streambanks is less than for streambeds. (2) The amount of shear stress adjacent a fluid/bed boundary required to initiate particle motion, as exerted by streamflow on the channel boundary. Critical slope That slope at which the maximum flow will occur at the minimum velocity; the slope or grade that is exactly equal to the loss of head per meter resulting from flow at a depth that will give uniform flow at critical depth; the slope of a conduit which will produce critical flow. Critical velocity Mean velocity of flow when flow is at critical depth. Crossing The relatively short and shallow reach of a stream where the thalweg crosses from one bank to the other, either between bends or between pools in a straight reach. Crossover (1) The point of inflection in a meander. The point where the thalweg intersects the center line of the stream in crossing from near the outside of the next bend. (2) The point of inflection in a meander where the thalweg intersects the centerline of the stream. Also known as a riffle. Crossover or crossover point Same as crossing. Cross-section (1) A line across a stream perpendicular to the flow along which measurements are taken, so that morphological and flow characteristics of that section are described from bank to bank. (2) A diagram or drawing of a channel, made approximately perpendicular to the channel and/or flow direction that defines the banks, bed, and water surface. Also may refer to the physical location of the cross-section on the ground. Cross-sectional area

The area of a stream channel taken perpendicular to the channel centerline. Usually taken at the bankfull elevation or top of bank for channel capacity. Cross sectional survey A stream survey conducted across the stream perpendicular to the flow to assess the channel configuration, flood prone width, water surface elevation, maximum depth elevation, bankfull elevation, bankfull width, floodplain and floodplain width. These parameters can be used for future geomorphological assessments, to calculate maximum flows, stream classification, and to document channel characteristics. Cross vane Cross vanes (aka. vortex weirs) are "V" shaped, upstream pointing, rock structures stretching across the width of the stream. Cross vanes redirect water away from the streambanks, and into the center of the channel. This serves to decrease shear stress on unstable banks, as well as create aquatic habitat in the scour pools formed by the redirected flow. Cross vanes are designed to be overtopped at all flows. The lowest part of the structure is the vortex of the "V", which is at the point farthest upstream. The crests are sloped 3-5% with the ends of the vanes keyed into the streambanks at an elevation approximate to annual high water or bankfull stage. This shape forms a scour pool inside of the "V". Cross vanes are particularly useful for modifying flow patterns, enhancing in-stream habitat, substrate complexity and providing in grade control. Double cross vanes (W weirs) are a variation suitable for wider channels. Crown The upper part of a tree or other woody plant that carries the main system of branches and the foliage. Crown cover The degree to which the crowns of trees are nearing general contact with one another. Cubic feet per second (cfs, or ft3/s) (1) A unit of stream discharge, representing one cubic foot of water moving past a given point in one second, equivalent to approximately 7.48 gallons per second or 448.8 gallons per minute or 0.02832 cubic meter per second. (2) In a stream channel, the rate of discharge of a stream at a rectangular cross section, whose channel is 1 square foot in cross-sectional area and whose average velocity is 1 foot per second). (3) A unit used to measure water flow. One cubic foot per second is equal to 449 gallons per minute. Culvert A buried pipe, conduit, drain or channel crossing under a road through which a stream passes. Current (1) The flow of water through a stream channel. (2) The flow of water (velocity) through a waterway channel. (3) Flow of water, both as a phenomenon and as a vector. Usually qualified by adjectives like downward, littoral, tidal, etc. to show relation to a pattern of movement. Current set A term originated by river pilots to describe the direction of the current as it affects navigation at a specific location, especially approaching a bridge, navigation structure, sharp bend, or other critical point. Cut bank (1) The concave bend of a stream channel undergoing erosion due to lateral migration of the stream channel. The outside bank of a bend, across the stream from a point bar and often eroding. (2) The eroding bank of a meandering stream, usually the outside (concave bank) of the bend. The cut bank is often steep and actively eroding and is located directly opposite the point bar.

Cut slope The open, steep face of an excavated slope. Cutoff A channel formed when a stream cuts, or is artificially realigned, through the neck of a bend or through a chute, thereby shortening its channel. See chute cutoff and neck cutoff. Cutting A branch or stem pruned from a living plant. Cypress dome Small, isolated, circular, depressional, forested wetlands, in which cypress predominates, that have convex silhouettes when viewed from a distance. D D50 Median size particle measured in the alluvial channel. 50% of the material is greater and 50% is smaller in size. D50 , D100 The particle size for which 50 and 100 percent of the sample is finer, respectively, based on a mechanical (sieve) and/or sedimentation (hydrometer) analysis. Datum plane A horizontal plane to which ground elevations or water surface elevations are referenced. Deadman A log or block of concrete buried in the bank or bed of a stream that is used as an anchoring system for tree trunks or other bank stabilization structures. Dead Stout Stake A type of wooden stake used to anchor any of a number of different types of bioengineering materials. The dead stout stake is a 2-in by 4-in by 2 to 4-ft long wooden board sawn from dimensioned lumber along a diagonal and ending in a point. Debris Includes gravel, cobble, rubble, and boulder-sized sediments as well as trees and other organic material scattered about by either natural processes or human influences. See Large Woody Debris Debris flow A rapidly moving mass of rock fragments, soil, and mud, with more than half of the particles being larger than sand size. Debris jam Log jam – Accumulation of logs and other organic debris. Debris slide Small, rapid movement of largely unconsolidated material that slides or rolls downward to produce irregular topography. Debris torrent Rapid movement of a large quantity of materials (wood and sediment) down a stream channel during storms or floods. This generally occurs in smaller streams and results in scouring of the streambed.

Deciduous (1) Any of a large family of trees and shrubs that shed their leaves each year, such as maple, birch, cottonwood and alder. (2) Tree or shrub that retains its leaves for one growing season only, dropping them before the following winter. Declivity A descending slope. Decomposer Any of various organisms (as many bacteria and fungi) that feed on and break down organic substances (such as dead plants and animals). Decomposition (1) The breakdown of matter by bacteria and fungi, changing the chemical makeup and physical appearance of materials. (2) The breakdown of organic matter under both aerobic and anaerobic conditions into constitutive or elemental compounds. See also chemical weathering. Deep percolation The percolation of water through the ground and beyond the lower limit of the root zone of plants into a groundwater aquifer. Deepwater habitat Permanently flooded lands lying below the deepwater boundary of wetlands. Deflector Any object that redirects near-field currents away from a streambank. The patterns of deposition and scour in the immediate vicinity can be quite complex, varying with time and flow. A "shadow" of fine sediment usually settles on the streambed immediately downstream of the deflector, and bed scour will usually occur at the point of maximum flow constriction, that is, at the end of the deflector. Degraded Condition of the quality of water that has been made unfit for some specified purpose. Degradation (1) The geological process by which streambeds and floodplains are lowered in elevation by the removal of material; the opposite of Aggradation. (2) The geological process by which streambeds are lowered in elevation and streams are detached from their floodplain. Also referred to as entrenched or incised streams. (3) A progressive lowering of the channel bed due to scour. Degradation is an indicator that the stream’s discharge and/or sediment load is changing. (4) A decrease in value for a designated use. (5) The lowering of a relatively long reach of channel bed due to scour, usually caused by a lowering of the base level, a reduction in the size or quantity of sediment entering the reach, or, more rarely, a long-term increase in discharge. Degradation can occur along an entire stream length, a certain reach of a stream, (i.e. downstream of a dam, reservoir, or other sediment retention structure), or system wide (every stream in the watershed is undergoing degradation). Degree of Curvature See arc angle. Delta A low-lying plain, usually triangular in shape, composed of sediments deposited by a river at its mouth as it enters a sea or estuary, in such quantities that it is not removed by tides, waves, or currents; also, such a plain between diverging branches of a river mouth.

Delta A deposit of alluvium, usually flat and fan-shaped, formed where moving water is slowed by a body of standing water. Typical examples are found where a river flows into a bay, where a river flows into a lake or reservoir, or where a tributary flows into a larger stream or river. Dendritic drainage pattern A drainage pattern in which the streams branch randomly in all directions and at almost any angle, resembling in plan view the branching habit of certain trees. This pattern is produced where a consequent stream receives several tributaries which in turn are fed by smaller tributaries. It is indicative of streams flowing across horizontal and homogeneous strata offering uniform resistance to erosion. Density The mass of a substance per unit volume. Density current A highly turbid mixture of water and very fine grained sediment which flows into and along the bottom of a reservoir because its density is greater than that of the standing water in the reservoir. Denuded Land stripped of vegetation. Dependable supply The annual average quantity of water that can be delivered during a drought period. Depletion A water use term. The water consumed within a service area and no longer available as a source of supply. For agriculture and wetlands, it is evapotranspiration of applied water (ETAW) and evapotranspiration (ET) of flooded wetlands, plus irrecoverable losses. For urban water use, it is ETAW (water applied to landscaping or home gardens), sewage effluent that flows to a salt sink, and incidental ET losses. For instream use, it is the amount of dedicated flow that becomes groundwater and is not available for reuse. Deposit Earth material of any type that has accumulated by natural processes. Deposition The settlement or accumulation of material out of the water column and onto the stream bed or floodplain. Occurs when the energy of flowing water is unable to transport sediment load. Deposition The mechanical or chemical processes through which sediments settle and accumulate. Depositional stream reaches Low gradient streams, beds and banks comprised of alluvial sediment deposits (predominantly silts, sands, and gravels), subdued topographic relief, laterally unconstrained channels (stream can migrate across valley bottom), and relatively large riparian areas. Desiccation To lose moisture and dry up. Desiccation cracks The phenomenon which occurs in fine grained soils or dredged material (usually containing some clay) in which cracks form as the material dewaters and shrinks.

Design discharge (1) A quantity of flow that is expected at a certain location as a result of a design storm or flood frequency; usually expressed as a rate of flow in cubic meters per second. The tractive force or velocities associated with the design discharge are commonly used to compute the size and thickness of stone riprap for protection works. (2) The steady discharge used in the engineering design of a stable channel or flood defense scheme to define the upper boundary of the operating range of discharges for the project. Design frequency The reoccurrence interval for hydrologic events used for design purposes. E.g., a design frequency of 50 years (Q50) means a storm of a magnitude that would be expected to occur on the average of once in every 50 years (2 percent chance of occurrence during a particular year). Design life The length of time for which it is economically sound to require a structure or project to successfully function without major repairs or replacement. Design storm A selected rainfall pattern of specified amount, duration, intensity, and frequency that is used to calculate the volume of water runoff and peak discharge rate. Detritus (1) Minute fragments of plant parts found on the soil surface. When fused together by algae or soil particles, this is an indicator that surface water was recently present. (2) Organic matter undergoing decomposition, with attendant protists, protozoans, and other organisms that serve as food for detritus feeders. Dewater The removal of surface or subsurface water. Can apply to the permanent removal of water behind a large dam, or to the temporary emptying of a dammed section of a river or stream for construction purposes, i.e. pumping water from an area enclosed by a coffer dam. Diagonal bar An elongated alluvial deposit that has its long axes orientated obliquely to the flow; roughly triangular in cross-section and often terminating in riffles. Diatoms Single-celled, colonial, or filamentous algae with siliceous cell walls constructed of two overlapping parts. Dike (1) (Engineering) An embankment (usually earthen) constructed to control or confine water, especially one built along the banks of a river to prevent overflow of lowlands; a levee; (2) A low wall that can act as a barrier to prevent a spill from spreading; (3) A structure designed (a) to reduce the water velocity as streamflow passes through the dike so that sediment deposition occurs instead of erosion (permeable dike) or (b) to deflect erosive currents away from the streambank (impermeable dike). (4) A structure attached to and extending from the streambank into the channel that is designed to (a) reduce the stream velocity as the current passes through the dike, thus encouraging sediment deposition along the bank (permeable dike) or (b) deflect erosive currents away from the streambank (impermeable dike) or (c) improve the depth and/or alignment of the navigation channel (contraction dike). Usually more than one structure is built at a given location; the aggregate is called a "dike field". A dike is sometimes referred to as a groin, jetty, spur, or wing dam. (5) A levee (esp. European). (6) (Geology) A tabular body of igneous (formed by volcanic action) rock that cuts across the structure of adjacent rocks or cuts massive rocks. Dike notching

Removal of a short section of the crest of a dike to concentrate flow and decrease sedimentation between dikes, ideally increasing habitat diversity in the area downstream of the dike or within a field of dikes. Direct runoff The runoff entering stream channels promptly after rainfall or snowmelt. Discharge (1) Discharge or streamflow, is the rate at which a volume of water flows past a point over some unit of time. In SI system, it is expressed in m3/s. It is normally symbolized by Q. Also expressed by ft3/s, million gallons/day, gallons/minute, or seconds/minute/day. (2) Rate of flow expressed in volume per unit of time, for instance, in cubic feet per second or liters per second. Discharge is the product of the mean velocity and the cross-sectional area of flow. Also, see stream discharge or sediment discharge. (3) The volume of water passing through a cross-section in a stream per unit time. It is usually expressed in cubic meters or cubic feet per second. Discharge area (groundwater) Area where subsurface water is discharged to the land surface, to surface water, or to the atmosphere. Discontinuous bank protection Redirective or indirect bank protection methods spaced at intervals along an eroding bank. The sections of the bank between structures are not treated or disturbed. Discount rate The interest rate used in evaluating water (and other) projects to calculate the present value of future benefits and future costs or to convert benefits and costs to a common time basis. Dispersion The extent to which a liquid substance introduced into a groundwater system spreads as it moves through the system. Dissolved constituent Operationally defined as a constituent that passes through a 0.45-micrometer filter. Dissolved gas concentrations The amount of chemicals normally occurring as gases, such as nitrogen and oxygen, that are held in solution in water, expressed in units such s milligrams of the gas per liter of liquid. Supersaturation occurs when these solutions exceed the saturation level of the water (beyond 100 percent). Dissolved load (1) The material in the stream that is transported in solution. (2) The chemical load contained in stream water; that acquired by solution or by decomposition of rocks followed by solution. (3) The part of the stream load that is carried in solution, such as chemical ions (e.g., sodium, calcium, or bicarbonate ions) yielded by weathering and erosion of the land mass. Dissolved organic compounds Carbon substances dissolved in water. Dissolved oxygen (DO) (1) Oxygen dissolved in water and available for fish and other aquatic organisms to use for respiration. Generally, a DO level under 5 mg/L is stressful to most vertebrates and causes mortality to some invertebrates. One of the most important indicators of the condition of a water body. (2) The amount of free (not chemically combined) oxygen dissolved in water, wastewater, or other liquid, usually expressed in milligrams per liter, parts per million, or percent of saturation.

(3) Oxygen molecules dissolved into a body of water that are necessary for the respiration of most aquatic organisms. High concentrations of DO are usually present in free-flowing, tumbling water, but can be provided artificially by aerator pumps or constructed riffles or falls. Dissolved solids (1) Minerals and organic matter dissolved in water. (2) The mass of dissolved constituents in water determined by evaporating a sample to dryness, heating to 103-105 C for two hours, desiccating, and weighing. Distressed streambank A bank that has experienced, or is currently experiencing, erosion or failure. Distributary Any channel, waterway, or outlet that conveys water away from a stream. Opposite of tributary. Disturbances Human (e.g., dams, streambank armoring) or natural (e.g., floods, landslides) activities that disrupt the natural dynamic equilibrium of the stream ecosystem. In this protocol, human-caused disturbances are assessed. Disturbed area Areas that have been purposefully cleared, grubbed, excavated, or graded by the contractor; ground surface that has been disrupted by construction activities, including construction access/roads, producing significant areas of exposed soil and soil piles; staging and storage sites are considered as part. Ditch A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line. Diversion (1) A turning aside or alteration of the natural course of a flow of water, normally considered physically to leave the natural channel. In some states, this can be a consumptive use direct from another stream, such as by livestock watering. In others, a diversion must consist of such actions as taking water through a canal, pipe, or conduit. (2) The transfer of water from a stream, lake, aquifer, or other source of water by a canal, pipe, well, or other conduit to another watercourse or to the land, as in the case of an irrigation system. (3) The change in character, location, direction, or quantity of flow of a natural drainage course (a deflection of flood water is not a diversion); (4) Draft of water from one channel to another; (5) Interception of runoff by works which discharge it through unnatural channels. Diversion channel (1) An artificial channel constructed around a town or other point of high potential flood damages to diver floodwater from the main channel to minimize flood damages. (2) A channel carrying water from a diversion dam. Diversion dam A barrier built to divert part or all of the water from a stream into a different course. Divided Flow The situation where streamflow is divided into two or more channels, separated by bars or islands. The channel which normally carries the most discharge is called the "main channel"; and the channel(s) which carry the remainder of the flow are "secondary channel(s)". The division of flow often varies with the total amount of streamflow, since the conveyance of each channel changes as the water level in the stream changes. Domestic withdrawals

Water used for normal household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens. The water may be obtained from a public supplier or self-supplied. Also called residential water use. Dominant discharge (1) A term developed in an attempt to quantify a single flow which governs the long term behavior of a stream. An abstract quantity, since a single flow cannot create precisely the same channel as a continually varying range of flows over a long period of time. Often considered to approximate a bankfull discharge in a stream that is neither aggrading or degrading, but may also be viewed as the flow that over many hydrologic cycles transports the most total bed material sediment. Also called "channel-forming" discharge. (2) The single, steady discharge which would produce the same cross-sectional morphology, alluvial features, planform geometry, and dimensions as those generated by the actual flow regime. Dominant plant The plant species controlling the environment. Dormancy or dormant season The season of the year when plants no longer grow. For deciduous plants, the time between leaf shedding and when the leaf buds appear. Roughly between late fall and early spring, dependent on weather and species. Drainage Interception and removal of ground or surface water by artificial means, such as excavating channels or placing pipes. Drainage area (1) The drainage area of a stream at a specified location is that area, measured in a horizontal plane, which is enclosed by a drainage divide. (2) The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds. Drainage basin (1) That area so enclosed by a topographic divide (the drainage divide) that surface runoff from precipitation drains into a stream above the point specified. (The term “watershed” is commonly misapplied to the drainage area.) The drainage area can be contained within a single watershed or include a number of watersheds. (2) The land area drained by a river or stream. (3) The total area of land from which water drains to a specific river. Drainage area or basin (1) The area so enclosed by a topographic divide that surface runoff from precipitation drains into a stream above the point specified. The term “watershed” is commonly misapplied to the drainage area. A drainage area can be contained within a single watershed or include a number of watersheds. (2) An area confined by drainage divides, often having only one outlet for discharge. Sometimes (esp. U.S. ) called a watershed (not to be confused with U.K. usage of watershed, which is a drainage divide). Drainage divide Boundary between adjoining drainage basins. Drainage pattern The configuration or arrangement in plan view of the natural stream courses in an area. Usually strongly related to the local geologic and geomorphologic features and history. Drawdown

Difference between the water level in a well before pumping and the water level in the well during pumping. Also, for flowing wells, the reduction of the pressure head as a result of the discharge of water. (2) See rapid drawdown. Dredge spoil Dredged material. Dredging (1) Removing material (usually sediments) from wetlands or waterways, usually to make them deeper or wider. (2) The process of excavating sediment from a watercourse, reservoir, or wetland. Dredging window That period of time when it is environmentally safe to dredge and deposit dredged material in an area occupied by a species of concern, such as the non-breeding season in areas with important water bird colonies, or non-spawning season for locally important fish species. Drift line An accumulation of water-carried debris along a contour or at the base of vegetation that provides direct evidence of prior inundation and often indicates the directional flow of flood waters. Drop inlet A structure in which water drops (1) through a vertical riser connected to a discharge conduit or (2) over the crest of a vertical wall to a lower elevation. Drop pipe A vertical pipe designed to convey water from an overbank area into the stream without detrimental effects. Drop structure A structure in a channel or conduit which permits water to drop to a lower level. In open channel hydraulics it is usually associated with efforts to control the grade (bed elevation) of the stream. Drop / weir scour Scour resulting from an increase in flow velocity through a weir or due to hydraulic forces associated with a drop in water-surface elevation. Drought (1) A prolonged period of less-than-normal precipitation such that the lack of water causes a serious hydrologic imbalance. (2) Generally, the term is applied to periods of less than average or normal precipitation over a certain period of time sufficiently prolonged to cause a serious hydrological imbalance resulting in biological losses (impact flora and fauna ecosystems) and/or economic losses (affecting man). In a less precise sense, it can also signify nature’s failure to fulfill the water wants and needs of man. Dry wash A streambed that carries water only during and immediately following rainstorms. Dunes Bed forms with triangular profile that advance downstream due to net deposition of particles on the steep downstream slope. Dunes move downstream at velocities that are slow when compared to the stream flow velocity. Duration of flow See flow duration.

Dynamic equilibrium A stream that has adjusted its width, depth, and slope such that the channel is neither aggrading nor degrading. However, change may be occurring in the streambanks due to natural meandering, erosion may result, and bank stabilization may be necessary in critical areas. E Ecological community See ecosystem. Ecological integrity The condition of the biotic (aquatic community) and Abiotic (water chemistry and habitat) components of unimpaired water bodies as measured by assemblage (an association of interacting populations of organisms in a given waterbody, e.g., fish assemblage) structure and function, water chemistry, and habitat measures of a site.

Ecological studies Studies of biological communities and habitat characteristics in U.S. Geological Survey’s National Water- Quality Assessment Program (NAWQA) Study Units to evaluate the effects of physical and chemical characteristics of water and hydrologic conditions on aquatic biota and to determine how biological and habitat characteristics differ among environmental settings. Ecology The study of the interrelationships of living organisms to one another and to their surroundings. Economic demand The consumer’s willingness and ability to purchase some quantity of a commodity based on the price of that commodity. Ecological stage A specific period of growth or development of an ecological community; e.g., grassland could be an intermediate stage in the developmental process of a disturbed site that will ultimately become a forest. Ecological succession The progression of a site from early growth stages to climax; e.g., on a cleared site the stages of succession over time could be bare ground, sparse herbaceous cover, dense herbaceous cover, shrub/grasses, shrub/trees, and finally, forest. Succession in the riparian zone can be disturbed by channel migration, hydraulic events, or human disturbance. Ecology blocks Concrete blocks. Ecoregion An area of similar climate, landform, soil, potential natural vegetation, hydrology, or other ecologically relevant variables. Ecosystem (1) A community of organisms considered together with the nonliving factors of its environment; (2) Recognizable, relatively homogeneous units, including the organisms they contain, their environment, and all the interactions among them. (3) All of the organisms (community) in a given area interacting with the physical environment; the interaction between living organisms and their non-living environment. Ecosystem management

A strategy of plan to manage ecosystems to provide for all associated organisms, as opposed to a strategy or plan for managing individual species. Ecotone (1) The zone where two or more different plant communities meet and intergrade; a transition zone between two or more diverse communities. (2) The transition zone between two ecological communities. The ecotone has some of the ecological features of both communities, but has its own distinct ecological structure, and can include species unique to the area. Ecotype Naturally occurring variant of a species which is adapted to a particular set of ecological or environmental conditions. Edaphoecotropism The ability of plant stems and roots to avoid or adapt to stress full conditions, e.g., light, gravity, lack of soil moisture, confinement, and mechanical obstacles. Also called Bio-Adaptive Plant Response. Eddy A circular current of water, sometimes quite strong, diverging from and initially flowing contrary to the main current; it is usually formed at a point at which the flow passes some obstruction or on the inside of river bends; often forms backwater pools or pocket water in riffles. Eddy current A vortex-type motion of a fluid flowing contrary to the main current, such as the circular water movement that occurs when the main flow becomes separated from the bank. Effective discharge (1) Discharges as determined from measured or calculated flow and sediment records. If available, a time series of discharge records may be used to construct a frequency histogram. The mass of sediment transported by each discharge increment may be computed using a sediment rating curve or sediment transport formula. The effective discharge, Qeff, is the increment of discharge that transports the largest sediment load over a period of years (Wolman and Miller, 1960; Andrews, 1980; Emmett & Wolman, 2001). Thus, Qeff integrates the magnitude and frequency of flow events, and is the best starting point for design because it links sediment load with channel geometry. However, there are several problems associated with Qeff, (Biedenharn et al., 2000 and 2001; Soar & Thorne, 2001). Key among these is the high level of uncertainty in sediment transport computations. The effective discharge is useful in comparing the competence of alternative channel geometries to transport the incoming sediment load. Results of effective discharge analysis are also useful when predicting the impact of alteration of watershed conditions with respect to sediment loads (e.g., upstream dam removal) or hydrology (e.g., urbanization) on channel stability. (2) Discharge class responsible for transporting the largest fraction of the bed material load in a stable channel over a period of years. Defined by the peak in a histogram of bed material load (tons) versus discharge (cumecs) developed using the principles of magnitude and frequency analysis. Effluent (1) Outflow from a particular source, such as a stream that flows from a lake or liquid waste that flows from a factory or sewage-treatment plant. (2) Something that flows out or forth, especially a stream flowing out of a body of water. (3) (Water Quality) Discharged wastewater such as the treated wastes from municipal sewage plants, brine wastewater from desalting operations, and coolant waters from a nuclear power plant. (4) A material which flows out from the point of concern. e.g., sewage water or other waste liquids flowing out of a reservoir basin or treatment plant. Elevation

The vertical distance from a datum to a specific point or object on the earth's surface or water surface. Embankment An artificial deposit of material that is raised above the natural surface of the land and used to contain, divert, or store water, support roads or railways, or for some other similar purposes. Embeddedness (1) The degree that larger particles, such as boulders, rubble, or gravel, are surrounded or covered by fine sediment; usually measured in classes according to percentage of coverage of larger particles by fine sediments. (2) The degree to which boulders, cobble, or gravel are surrounded by fine sediment – this indicates the suitability of stream substrate as habitat for benthic macroinvertebrates and for fish spawning and egg incubation. Evaluated by visual observation of the degree (percent) to which larger particles are surrounded by fine sediment. (3) The degree to which an object is buried in surrounding stream sediment. Emergent plants Erect, rooted, herbaceous plants that may be temporarily or permanently flooded at the base but do not tolerate prolonged inundation of the entire plant. Emulsion See binder. Encroachment Extending beyond the original, or customary limits, such as by occupancy of the river and/or flood plain by earth fill embankment. Endangered species (1) A species that is in imminent danger of becoming extinct. (2) A plant or animal species of such limited and declining population (in danger of extinction throughout all or a significant portion of its range) that the species has been legally placed on a Federal or State Endangered Species list. Federally listed species and their needs are published in the Federal Register. Species that decline to endangered status usually do so as a result of degradation or destruction of preferred habitat. By law the listed species and its habitat is protected from destruction. See also Candidate and Threatened species. Endangered Species Act of 1973 A Federal law to designed to prevent the extinction of endangered or threatened species of plants or animals. Sections of the law describe how to identify and list threatened and endangered species; identifying, designating, and revising critical habitat; developing and revising recovery plans; and monitoring species removed from the list of threatened or endangered species. Energy base Basis for organizing of trophic levels, or feeding strategies, in the system. Energy can be derived from within (e.g., photosynthesis) or outside (e.g., leaf fall) of the aquatic system. Energy dissipator (1) Any object or structure installed at the outlet of a channel, drop structure, or conduit designed to reduce the effects, or absorb the force of high-velocity and high-energy flow. It may consist of a wide variety of materials and designs, such as riprap, boulders, linings, baffles, staggered blocks, or end sills. (2) A structure for the purpose of slowing the flow of water and reducing the erosive forces present in any rapidly flowing body of water. Energy dissipation

(1) The loss of kinetic energy of moving water due to internal turbulence, bottom friction, large rocks, debris, or other obstacles that impede flow. (2) The loss of kinetic energy of moving water due to internal turbulence, channel boundary friction, large rock and debris, meanders, and any other obstacles that impede flow. Energy grade slope An inclined line representing the total energy of a stream flowing from a higher to a lower elevation. For open-channel flow the energy grade slope is located a distance of U2/2g above the water surface (U = velocity and g = acceleration due to gravity). Energy sink A scour pool formed by flow in the corner of a tight-radius bend that dissipates the energy of the entire momentum of the flow. Engineered log jam Constructed collections of large woody debris that redirect stream flow. Engineering fabric See geotextile Enhancement Emphasis on improving the value of particular aspects of water and related land resources. Entrain To detach and transport an object in suspension due to the velocity of a moving fluid. Entrainment The incidental trapping of fish and other aquatic organisms in waters being diverted for other purposes. Sediment entrainment refers to sediment transported by flows. Entrenched A channel in which the width of the flood prone stage is the same as or only slightly larger than the width of the bankfull stage. Entrenchment (1) The vertical containment of a river and the degree to which it is incised in the valley floor. (2) Qualitatively defined as the vertical containment of a river and the degree in which it is incised in the valley floor. A stream may also be entrenched by the use of dikes or other structures. Entrenchment ratio Measurement of entrenchment. It is the floodprone width divided by the surface bankfull discharge width. The lower the entrenchment ratio the more vertical containment of flood flows exist. Higher entrenchment ratios depict more floodplain development. Environment (1) The sum of all external conditions and influences affecting the life and development of an organism or ecological community; (2) The total social and cultural conditions. Environmental analysis An analysis of alternative actions and their predictable short-term and long-term environmental effects, incorporating physical, biological, economic, and social considerations. Environmental Assessment (EA)

A systematic analysis of site-specific activities used to determine whether such activities have a significant effect on the quality of the human environment and whether a formal environmental impact statement is required; and to aid an agency’s compliance with the National Environmental Policy Act when no environmental impact statement is necessary. Environmental impact The positive or negative effect of any action upon a given area or resource. Environmental Impact Statement (EIS) A formal document to be filed with the Environmental Protection Agency that considers significant environmental impacts expected from implementation of a major federal action. Environmental sample A water sample collected from an aquifer or stream for the purpose of chemical, physical, or biological characterization of the sampled resource. Environmental setting Land area characterized by a unique combination of natural and human-related factors, such as row-crop cultivation or glacial-till soils. Environmentally sustainable development See Sustainable development. Eolian Same as Aeolian. Ephemeral Of brief duration, as the flow of a stream in an arid region. Ephemeral stream (1) A watercourse that flows briefly only in direct response to precipitation in the immediate locality, and whose channel is at all times above the water table. It receives little or no water from springs, melting snow, or other sources. (2) A stream that flows only in direct response to precipitation and receives little or no sustained supply from snowmelt, groundwater, or other sources. An ephemeral stream's channel is at all times above the water table. (3) Watercourse in which channel processes and morphology are significantly affected by the fact that the discharge of water is intermittent. To be comparable with the definition of a perennial stream, this may be taken as a water course which exhibits a measurable surface discharge less than 80% of the time. EPT richness index An index based on the sum of the number of taxa in three insect orders, Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies), that are composed primarily of species considered to be relatively intolerant to environmental alterations. Equal-width increment (EWI) sample A composite sample of water collected across a section of stream with equal spacing between verticals and equal transit rates within each vertical that yields a representative sample of stream conditions. Erodible Capable of undergoing erosion. Fine grained soils with little or no cohesion (e.g., silts, silty sands, and fine sands) are the most erodible. Erosion

(1) Removal and wearing away of surface soils and rock by the gradual detachment of soil or rock fragments by water, wind, ice, and extreme sun/heat, and other mechanical, chemical, or biological forces, and by human activities. Internal erosion leads to change of the earth structure and piping; closed vegetation is the best safeguard against erosion. Can be classified by degree (e.g., slight, severe); by type (e.g., natural or geological erosion or accelerated erosion, which is primarily caused by human activities); by the kind of erosion process and the resulting surface characteristics (e.g., sheet and rill, gully or ephemeral), or by the rate at which soil is eroding. Closed vegetation is the best safeguard against erosion. (2) The wearing away of the land surface by detachment of soil and rock fragments through the action of moving water, wind, and other geological agents. Erosion and accretion Loss and gain of land, respectively, by the gradual action of a stream in shifting its channel by cutting one bank while it builds on the opposite bank; property is lost by erosion and gained by accretion but not by avulsion when the shift from one channel to another is sudden; property is gained by reliction when a lake recedes. Erosion control (1) The prevention and/or reduction of soil particle movement. Erosion control reduces soil detachment and transport and promotes deposition. (2) Vegetation, such as grasses and wildflowers, and other materials, such as straw, fiber, stabilizing emulsion, protective blankets, etc., placed to stabilize areas disturbed by grading operations, reduce loss of soil due to the action of water or wind, and prevent water pollution. Erosion control blanket (ECB) A degradable material placed on a bank for the purpose of preventing erosion or providing temporary stabilization until vegetation is established. Sometimes called "Rolled erosion control product", or RECP. Composed of processed natural or polymer fibers bound together structurally, chemically, or mechanically to form a continuous blanket. Erosion control matting Fibrous matting (e.g., jute, paper, fiberglass, etc.) Placed or sprayed on a streambank to prevent erosion or to provide temporary stabilization until vegetation is established. Erosion control netting (ECN) A woven mesh of natural fiber or geosynthetic material used either as a component of "Rolled erosion control product" (RECP), or as a separate degradable cover for mulch e.g., jute or coir netting. Erosion control revegetation mat (ECRM) A permanent blanket made of synthetic material used for long term protection against soil movement. Placed over a prepared, seeded or hydroseeded surface. Escarpment (1) A steep slope or long cliff resulting from erosion or faulting and separating two relatively level areas. (2) Number of returning adult fish surviving past a point in their migration, e.g., "spawning escapement" denotes the number of fish arriving at the spawning grounds. Essential habitat Habitat needed by a species to survive or recover, but not officially designated as "critical habitat". Establishment Measures which enable fast and good rooting growth of artificially started vegetation. Establishment period

(1) Time between sowing of the seed and the stage at which the plant is no longer reliant on the nutrient supply in the seed; (2) time between planting and the stage at which special care is not required to ensure that all parts of the plant are functioning normally. Estuarine Refers to deepwater tidal habitats and adjacent tidal wetlands that are usually semi-enclosed by land but have open, partly obstructed, or sporadic access to the open ocean, and in which ocean water is at least occasionally diluted by freshwater runoff from the land (Cowardin et al. 1979). Estuarine wetlands Tidal wetlands in low-wave-energy environments where the salinity of the water is greater than 0.5 parts per thousand and is variable owing to evaporation and the mixing of seawater and freshwater; tidal wetlands of coastal rivers and embayments, salty tidal marshes, mangrove swamps, and tidal flats. Estuary (1) The seaward widened end or the funnel-shaped tidal mouth of a river valley where fresh water comes into contact with seawater and where tidal effects are evident; an arm of the ocean at the lower end of a river. (2) A coastal body of water that is semi-enclosed, openly connected with the ocean, and mixes with freshwater drainage from land. Eutrophic Usually refers to a nutrient-enriched, highly productive body of water. Eutrophication The process of enrichment of water bodies by plant nutrients, most commonly phosphorus and nitrogen. Evaporation (1) The physical process by which water is changed to gas or vapor; occurs directly from water surfaces and from the soil. (2) The physical process by which a liquid (or a solid) is transformed to the gaseous state. In hydrology, evaporation is vaporization that takes place at a temperature below the boiling point. Evapotranspiration (ET) (1) The process by which water is discharged to the atmosphere as a result of evaporation from the soil and surface-water bodies, and transpiration by plants. (2) The quantity of water transpired (given off), retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. Quantitatively, it is usually expressed in terms of depth of water per unit area during a specified period of time. (3) The diffusion of water vapor into the atmosphere from a vegetated surface. Evapotranspiration of applied water (ETAW) The portion of the total evapotranspiration provided by irrigation. Existing Vegetation Any vegetated area that has not already been cleared and grubbed. Exotic (1) An organism or species that is not native to the region; a foreign species artificially introduced by man. Exotic species usually have few natural enemies or diseases, are extremely adaptable, and often become dominant at a site. (2) An organism or species that is not native to the region; a foreign species artificially introduced by man. Exotic species usually have few natural enemies or diseases, are extremely adaptable, and often become dominant at a site. Expansion

A rapid or abrupt increase in the width of a stream. This expansion usually results in slower average velocities and deposition of sediment within the expansion area, but local bank scour may occur if the expansion is abrupt. Eyed Eggs Incubating fish eggs at the stage where the eyes of the developing embryo become visible through the transparent shell membrane. F Fabric See geotextile. Fabric-formed concrete systems Geotextile tubes, bags, or mattresses filled with grout or concrete. Used for "armor" bank protection. Face The outer layer of slope revetment. Face planting Planting live cuttings and other vegetation in the front openings of retaining structures. Failure Collapse or slippage of a large mass of bank material into a stream. Failure plane See slip plane. Fall line Imaginary line marking the boundary between the ancient, resistant crystalline rocks of the Piedmont province of the Appalachian Mountains, and the younger, softer sediments of the Atlantic Coastal Plain province in the Eastern United States. Along rivers, this line commonly is reflected by waterfalls. Fall velocity The falling or settling rate of a particle in a given medium. Family A taxonomic level of organization containing several genera and multiple species. Fan An accumulation of debris brought down by a stream on a steep gradient and debouching on a gently sloping plain in the shape of a fan, forming a section of a very low cone. Fascine Elongated, cigar-shaped bundles of tree or shrub branch cuttings tied tightly together and anchored into trenches using either live stakes or dead stout stakes. Within the bundle all tips of the branches are at one end of the bundle and the butt ends are at the other end of the bundle. Fascines are installed on a slope with the butt ends of all branches at the lower elevation. The butt ends are usually covered with soil to promote root growth. Fascines are used for a wide variety of slope stabilization projects. Sometimes called a "live fascine". See also Wattle. The bundles of branch cuttings are placed in long rows in shallow trenches across the slope on contour or at an angle. Fascines are intended to grow vegetatively while the terraces formed will trap sediment and detritus, promoting vegetative establishment. Fascines can be utilized as a resistive measure at the stream edge and for erosion control on long bank slopes above annual high water. Fascines are also an effective way to anchor Erosion Control Blankets (ECBs) and Turf Reinforcement Mats (TRMs).

Fault (1) The relative displacement of formerly adjacent points on opposite sides of the fault, measured in the fault surface. (2) A smooth joint or crack where the strata have moved upon each other. Fecal bacteria Microscopic single-celled organisms (primarily fecal coliform and fecal streptococci) found in the wastes of warm-blooded animals. Their presence in water is used to assess the sanitary quality of water for body-contact recreation or for consumption. Their presence indicates contamination by the wastes of warm-blooded animals and the possible presence of pathogenic (disease-producing) organisms. Fecal coliform See fecal bacteria Fen Peat-accumulating wetland that generally receives water from surface runoff and/or seepage from mineral soils in addition to direct precipitation; generally alkaline; or slightly acidic. Fence A streambank protection technique consisting of wire mesh or timber attached to a series of posts, sometimes in double rows; the space between the rows may be filled with rock, branches, brush, hay bales, or other materials. Fences may be placed either parallel to the bank or extended into the stream; in either case these structures decrease the flow velocity and encourage sediment deposition within the area protected by the fence. Fertilizer Any of a large number of natural or synthetic materials, including manure and nitrogen, phosphorus, and potassium compounds, spread on or worked into soil to increase its fertility. Fetch The area in which waves are generated by wind having a rather constant direction and speed; sometimes used synonymously with fetch length. Fetch length The horizontal distance (in the direction of the wind) over which wind generates waves and wind setup. See fetch. Fill (1) (Geology) Any sediment deposited by any agent such as water so as to fill or partly fill a channel, valley, sink, or other depression. (2) (Engineering) Soil or other material placed as part of a construction activity. Fill material Soil that is placed at a specified location to bring the ground surface up to a desired elevation. Filter A layer of fabric, sand, gravel, or graded rock placed, or developed naturally where suitable in-place materials exist, between the bank revetment or other river training structure and the underlying soil for one or more of three purposes: to prevent the soil from moving through the revetment by piping, extrusion, or erosion; to prevent the structure from sinking into the soil; and to permit natural seepage from the streambank, thus preventing the buildup of excessive hydrostatic pressure. Filter cloth See geotextile.

Filter strip A belt of vegetation engineered to provide infiltration, intercept sediment and other pollutants, and reduce stormwater flow and velocities. Designed to accept an even distribution of surface runoff; effectiveness is reduced if a channel forms, or if high velocity flows occur. Filtrate Liquid that has passed through a filter. Filtration The process of passing a liquid through a filter to remove suspended matter that usually cannot be removed by settling. Final environmental impact statement (FEIS) The final report of environmental effects of proposed action on an area of land. This is required for major federal actions under Section 102 of the National Environmental Policy Act. It is a revision of the draft environmental impact statement to include public and agency responses to the draft. Fine material Particles of a size finer than the particles present in appreciable quantities in the bed material; normally silt and clay particles (particles finer than 0.074mm). Fine material load (1)That part of the total sediment load that is composed of particles smaller than the particles present in appreciable quantities in the stream bed. Normally composed of sediment particles smaller than 0.074mm (silts and clays). [E-SenSS] (2) A portion of the total sediment load composed of particles finer than those found in the stream bed, and usually the fraction finer than 0.062 mm. Often synonymous with wash load. [Watson et. al 1999] Fine sediment Clay, silt, and sand-sized particles. Fingerling A juvenile fish; arbitrarily, a fish between 3 and 6 inches total length. Fixed-bed physical model A hydraulic model in which the bed and bank materials are non-erodible. Current directions, velocities, or water surface elevations for a specific flow, bed bathymetry, or hydraulic structural configuration can be measured and scaled to the prototype. This information is then used to evaluate structural performance, navigability, or flood heights. Flanking Erosion resulting from streamflow between the bank and the landward end of a river-training or grade- control structure. Severe flanking can result in the structure becoming completely disconnected from the streambank, the function of the structure may be compromised, and accelerated local bank erosion may occur. Flanking may also occur at the ends of revetment. Flash flood A sudden flood of great volume, usually caused by heavy rain. Also, a flood that crests in a short length of time and is often characterized by high velocity flows. Flashy stream Stream with a relatively high flood peak of short duration. Flood

(1)Any relatively high streamflow that overflows the natural or artificial banks of a stream. (2) Any relatively high streamflow which overtops the natural banks in any reach of a stream. Flood attenuation A weakening or reduction in the force or intensity of a flood. Flood control measures or works See non-structural flood control measures and structural flood control measures. Flood duration The percent of time over the period of study that a stream overflows its banks at a given location. See flow duration. Flood frequency (1) Also referred to as exceedence interval, recurrence interval or return period; the average time interval between actual occurrences of a hydrological event of a given or greater magnitude; the percent chance of occurrence is the reciprocal of flood frequency, e.g., a 2 percent change of occurrence is the reciprocal statement of a 50-year flood; (See probability of exceedence); (2)Usually used interchangeably with the return interval of a specific magnitude flood; e.g., a flood event with a 2-year recurrence interval (frequency) is called the Q-2 event. See recurrence interval. There are hydrologic and probabilistic distinctions in the ways that the values of flood frequencies can be computed, but the distinctions are of little relevance to most applications. The most relevant fact is that a flood of a given frequency or recurrence interval can and often does occur more often than that, analogous to a coin flip turning up the same side several times in a row. Flood irrigation The application of irrigation water whereby the entire surface of the soil is covered by ponded water. Flood stage (1) The stage at which a stream overtops its natural banks. Synonymous with bankfull stage. It is not the stage at which flood control measures are overtopped. (2) The elevation at which overflow of the natural banks of a stream begins to run uncontrolled in the reach in which the elevation is measured. Flooded A condition in which the soil surface is temporarily covered with flowing water from any source, such as streams overflowing their banks, runoff from adjacent or surrounding slopes, inflow from high tides, or any combination of sources. Floodplain (1) A strip of relatively smooth land bordering a stream channel that is typically overflowed (inundated) during periods of high water. Although a floodplain is generally composed of finer material near the surface than at the base, the particle size gradation is not universal. Floodplains are generally formed by the progressive channel migration and deposition from overbank flows and are built and rebuilt by the stream in its present hydrologic regime. (2) Land built of sediment that is regularly covered with water as a result of the flooding of a nearby stream. (3) The flat area adjoining a river channel constructed by the river in the present climate and overflows during moderate flow events. (4) Low-lying areas of land adjacent to the stream that are inundated by water from the stream whenever the stream overflows its banks. Floodplains are sometimes delineated by the areas inundated during a flood with a specific reoccurrence interval, e.g. the 100-year floodplain. Floodplain (100-year) The area adjacent to a stream that is on average inundated once a century. Floodplain roughness

Any objects on the floodplain that, through friction, reduce flow velocity over the floodplain. Floodplain width The width of (1) any flat, or nearly flat, lowland that borders a stream and is covered by its waters at flood stage; (2) the land adjacent to a stream that is inundated when stream discharge exceeds channel capacity. Note: It can be difficult to distinguish between a terrace and a floodplain. Look for depositional features and relatively flat surfaces for the floodplain. Floodprone area Generally includes the active floodplain and the low terrace. The elevation of the floodprone is qualitatively defined as 2 times the max. bankfull depth. Flood prone width The width of the floodplain and active channel that is subjected to regular (every ~2-5 years) flooding, as indicated by topography, soil/substrate, and vegetation community. Changes in vegetation types, flood deposits of fine woody materials, and change in slope are often good indicators of the flood prone width. Changes in vegetation are typically presented as a transition from riparian vegetation to upland grasses and/or other mesic species that have lesser water requirements. Floodway A natural or constructed channel that conveys flood waters; a channel constructed to carry flood water overflowing from a stream channel and deliver it to some other body of water or to a downstream reach of the same stream; sometimes considered to be the transitional area between the active channel and the floodplain. Flow (1) The movement of a stream of water and/or other mobile substances from place to place; Synonymous with Discharge. (2) The movement of water, and the moving water itself; (3) The volume of water passing a given point per unit of time. (4) The amount of water passing a particular point in a stream or river, usually expressed in cubic feet per second (cfs). (4) A term used to define the movement of water, silt, sand, etc.; discharge; total quantity carried by a stream. Flow augmentation Increased flow from release of water from storage dams. Flow channels Natural drainage ways in arid and semiarid environments usually with steep banks and intermittent flow. Examples are arroyos and coulees. Flow Doing Most Work A steady discharge which performs the most geomorphic work, where work is defined in terms of sediment transport (Wolman and Miller, 1960). [Watson et al 1999] Flow duration The percent of time that a given discharge was equaled or exceeded during the period of record, often presented as a "flow duration curve", from which the converse can also be derived, the percent of time that flow was equal to or less than a given discharge. Flow duration curve A graphical representation of the relationship between streamflow and the percentage of time it is exceeded. (2) A graphical representation of the percent of time (x-axis) that a specific discharge (y-axis) is equaled or exceeded during the period of record for which the curve was developed.

Flow line The idealized path followed by particles of water. Flow path An underground route for groundwater movement, extending from a recharge (intake) zone to a discharge (output) zone such as a shallow stream. Flow rate See stream discharge. Flow regime (1) Amount of streamflow in terms of magnitude, duration, and frequency. Flow regime controls the forces governing the appearance and water supply of most riparian systems. The supply of water is controlled by precipitation and regulated through interactions among geology, soils, and vegetation. (2) The system or order characteristic of streamflow with respect to velocity, depth, and specific energy. Flow slide Saturation of a bank to the point where the soil material behaves more like a liquid than a solid; the soil/water mixture may then move downslope resulting in a bank failure. Such failures may be sudden and dramatic, extending well behind top bank, and are often triggered by toe scour. Fluvial (1) Migrating between main rivers and tributaries; (2) Of or pertaining to streams or rivers or produced by stream action. (3)(a) Pertaining to streams or rivers. (b) Of, relating to, or living in a stream or river. (c) Caused by the action of flowing water. Fluvial deposit A sedimentary deposit consisting of material transported by suspension or laid down by a river or stream. Fluvial Geomorphology (1) The study of water-shaped landforms; focuses on trends and descriptions rather than precise predictions and is more qualitative than quantitative. (2) The scientific study of the form and structure of the geology of an area as affected by flowing water. (3) The study of land forms created by and pertaining to the fluvial process. Fluvial Processes Depositional, transportation, and erosional processes associated with a river environment. Fluvial sediment Particles derived from rocks or biological materials which are transported by, suspended in, or deposited by flowing water. Flyway A specific air route taken by birds during migration. Forbe A broad-leafed herb or herbaceous plant other than grass. Ford A shallow place in a body of water, such as a river, where one can cross by walking or riding on an animal or in a vehicle. Forebay

A reservoir or pond situated at the intake of a pumping plant or power plant to stabilize water levels; also a storage basin for regulating water for percolation into groundwater basins. Foreshore (1) Lower shore zone, between ordinary low and ordinary high water levels. (2) (esp. southern U.S. ) the land lying between top bank of the stream and a flood control levee; i.e. batture. Freeflowing stream A stream or a portion of a stream that is unmodified by the works of man, or if modified, still retains its natural scenic qualities and recreational opportunities. Freshet (1) A rapid, temporary rise in stream discharge and level caused by heavy rains or rapid melting of snow and ice. (2) Rapid, temporary rise in stream flow caused by snow melt or rain. Freshwater Water that contains less than 1,000 milligrams per liter of dissolved solids. Freshwater chronic criteria Term used by USGS: the highest concentration of a contaminant that freshwater aquatic organisms can be exposed to for an extended period of time (4 days) without adverse effects. See also Water quality criteria. Frost heave The raising of a surface or object due to the accumulation of ice in the underlying soil. Froude Number (1) A dimensionless expression of the ratio of inertia forces to gravity forces, used as an index to characterize the type of flow in a hydraulic structure in which gravity is the force producing motion and inertia is the resisting force; it is equal to a characteristic flow velocity (mean, surface, or maximum) of the system divided by the square root of the product of a characteristic dimension (as diameter of depth) and the gravity constant (acceleration due to gravity) all expressed in consistent units. Fr = V/(gD)1/2, where V is the mean velocity (m/s), g the acceleration due to gravity (m/s2) and D the hydraulic depth (m). (2) A dimensionless number related to the ratio of inertia force to gravitational force. It is the velocity squared divided by length times the acceleration due to gravity. In open channels the numerical value of 1, termed critical flow, distinguishes between subcritical and supercritical flow. Fry (1) Fish up to the time when the yolk sac has been absorbed. (2) A recently hatched fish. Furrow irrigation A type of surface irrigation whereby water is applied at the upper (higher) end of a field and flows in furrows to the lower end. Gabions (1) Wire baskets filled with stone (gravel or cobble) or other material, wired together to form a continuous bank stabilization structure; used to stabilize streambanks. (2) A wickerwork or wire mesh basket or cage filled with stone or other materials, placed against a streambank to resist lateral earth forces or across the stream to act as a grade control structure. Gabion Mattress Relatively flat gabions that are linked together to armor streambanks and channels against scour and erosion. Also known as a "Reno mattress".

Gage height See Stage Gaging station (Gage Station) (1) A selected section of a stream channel equipped with a gage, recorder, or other facilities for determining stream discharge, or systematic observations of hydrologic data are obtained. (2) A particular site in a stream, lake, reservoir, etc., where hydrologic data are obtained. (3) A selected cross-section of a stream channel where one or more variables are measured continuously or periodically to index discharge, stage, sediment concentrations and yield, and/or other parameters. Gaining stream A stream or reach of stream that receives water from the zone of saturation. Gallons per minute (gpm) A unit used to measure water flow. Gap Analysis (1) The process of identifying and classifying components of biodiversity to determine which components already occur on (protected) areas and, conversely, which are un- or under-represented. (2) A representation of existing versus desired conditions. Genus An associated group of species. Geocellular Confinement System (GCS) A series of long, narrow sheets of polymer welded or bonded together at regular intervals . When expanded and placed in position on a slope these sheets form a continuous, three-dimensional web of cells that can be infilled with concrete, gravel, or soil. Used primarily to armor and protect streambanks or slopes against erosion. Also known as geocells. Geocomposite A manufactured material using geotextiles, geogrids, and/or geomembranes in laminated or composite form. Geographic Information System (GIS) A set of computer hardware and software for analyzing and displaying spatially referenced features (i.e., points, lines, and polygons) with non-geographic attributes such as species and age. Geogrid An extruded net-like polymeric material, used to reinforce, stabilize, and/or contain soil rock, earth, other material in a wide variety of applications including internally reinforced soil walls, segmental retaining walls, or steep slopes. Geologic column Chronological arrangement of rock units in columnar form, with oldest units on the bottom and youngest at top. Geologic control Natural geologic formation (erosion-resistant clay, stone, bedrock) that either temporarily or permanently controls the grade of a stream. Geologic time A length of time usually expressed in thousands or millions of years. In this time scale only major geologic activity (formation of mountain ranges, changes in sea level, climate change) would be significant.

Geology The science which analyzes the earth, the rocks of which it is composed, and the changes which it has undergone, or is currently undergoing. Geomembrane A synthetic impermeable membrane used to contain liquids and/or sediment. Geomorphic Pertaining to the form or general configuration of the Earth or of its surface features. Geomorphic equilibrium The "sediment-transport continuity” of a stream, wherein the quantity and size of sediment transported into the reach is approximately the same as the quantity and size of sediment transported out of the reach. If a stream is in geomorphic equilibrium, the processes of bank erosion and channel migration will be stable or occur only gradually. Geomorphic threshold A progressive change in one variable that results in an abrupt change in the system. Geomorphology (1) The branch of geology that deals with the origin and nature of landforms. The active forces that shape landforms are water, ice, wind, and gravity. (2) A branch of both physiography and geology that deals with the form of the earth, the general configuration of its surface, and the changes that take place due to erosion of the primary elements and the buildup of erosional debris. (3) That branch of both physiography and geology that deals with the form of the earth, the general configuration of its surface, and changes in the landscape that take place due to erosion, mass wasting, glaciation, subsidence, and other surficial processes. Geosynthetic Any synthetic material, including geotextiles and geomembranes, or any combination thereof, used with foundation, soil, rock, or any other geotechnical engineering related material, as an integral part of a structure or system. Geotechnical engineering The application of the laws and principles of science and mathematics to solve problems related to the materials of the earth's crust. It includes the fields of soil mechanics, rock mechanics, and many of the engineering aspects of geology, geophysics, hydrology, fluvial geomorphology, and related sciences. Geotextile (1) Durable high tensile strength synthetic construction fabrics used for separation, filtration, drainage, reinforcement and erosion control of soils and crushed aggregates; biodegradable fabrics are made from natural fibers such as coir, jute, flax, ramie, etc. and are used primarily for erosion control; also used as soil reinforcement in conjunction with brush layering (live gabions) as short-term subsurface filters, or as separators holding back soil behind geogrids in steep slopes pending establishment of vegetation. (2) A water permeable material, either natural or synthetic, used to filter liquids, prevent the movement of sediment, separate different materials, or reinforce or strengthen materials. Geotextiles may be constructed from natural fibers (e.g., sisal, jute, coconut or coir) or synthetics such as polypropylene or nylon. The synthetic forms are also called engineering fabric or filter cloth, and are available in either 1) woven forms , which use different diameter and shape threads that can be precisely designed for opening size, or 2) non-woven forms, which have either a felt like, bulky texture or alternatively are manufactured in thin, melt-bonded sheets or mats. Each form has advantages for different applications. Geothermal

Relating to the Earth’s internal heat; commonly applied to springs or vents discharging hot water or steam. Geotube Woven or non-woven geotextiles sewn into a cylindrical tube-like configuration. Sludge or slurried material is pumped into the tube, which traps the solids and releases the liquid. Typically used for containment of dredged material itself, sludge dewatering, construction of dredged material containment areas, and stream or shoreline protection. See Longard Tubing. Glacial Of or relating to the presence and activities of ice or glaciers. Glacial till Material deposited by glaciers, usually composed of a wide range of particle sizes, which has not been subjected to the sorting action of water. Glacial drift A general term for rock material transported by glaciers or icebergs and deposited directly on land or in the sea. Glacial lake A lake that derives its water, or much of its water, from the melting of glacial ice; also a lake that occupies a basin produced by glacial erosion. Glacial outwash Stratified detritus (chiefly sand and gravel) “washed out” from a glacier by meltwater streams and deposited in front of or beyond the end moraine or the margin of an active glacier. Glide (1) A slow-moving, relatively shallow type of run; calm water flowing smoothly and gently, with moderately low velocities (10 to 20 cm/sec), and little or no surface turbulence. (2) A section of stream that has little or no turbulence. Gobi Block A proprietary precast cellular block mattress used as a substitute for riprap. One of the first such products. Gradation curve See particle-size distribution. Grade (1) The continuous descending curve of a stream channel just steep enough for current to flow and transport its load of sediment. (2) To level off to a smooth horizontal or sloping surface. (3) Measure of inclination expressed in percent. (4) The slope of a plane. (5) A reference elevation. (6) A position in a scale of size. Grade control structure A structure placed across a stream channel from bank to bank (usually approximately perpendicular to flow) for the purpose of controlling the stream slope and preventing bed degradation upstream. Depending upon the design of the structure and the stream flow, it does this by discharging water from a higher to a lower elevation in a controlled fashion, and/or by armoring the bed at the site. In small channels, may be called a sill or check dam. Grade stabilization

The maintenance of a gentle, noneroding gradient on a watercourse or land surface; usually accomplished by means of structural measures or be regarding (lengthening) the slope. Grade stabilization structure See grade control structure. Graded stream See dynamic equilibrium. Gradient (1) The rate of ascent or descent expressed as a percent or as a decimal as determined by the ratio of the change in elevation to the length. (2) Vertical drop per unit of horizontal distance. (3) Degree of inclination of a stream channel parallel to stream flow; it may be represented as a ratio, fraction, percentage, or angle. (4) Slope, particularly of a stream or a land surface. Grading Degree of mixing of size classes in sedimentary material. For sediments, well-graded implies a relatively continuous size distribution ranging from coarse to fine. For stone, well-graded implies a relatively continuous distribution of sizes from gravel to the maximum weight of stone specified. Poorly graded implies a uniformity in size or a lack of continuous distribution. Grass/forb Herbaceous vegetation. Grassed waterway A natural or constructed watercourse or outlet that is shaped or graded and established in suitable vegetation for the disposal of runoff water without erosion. Grassed waterways The practice of conserving soil on runoff ditches on slopes by gently sloping the ditch sides and perpetually maintaining them in mowed (turf) grass to trap sediment and reduce erosion. Gravel (1) An unconsolidated natural accumulation of rounded rock fragments, mostly of particles larger than sand (diameter greater than 2 mm), such as boulders, cobbles, pebbles, granules, or any combination of these. (2) Rounded or semi-round particles of stone that can pass a 3-in. (76.2 mm) and be retained on a No. 4 (4.76 mm) U.S. Standard Sieve (Unified Soil Classification System). Gravel is smaller than cobbles and larger than course sand. (3) Rock larger than sand and smaller than cobble, arbitrarily ranging in diameter from 5 to 50 mm. Gray water Wastewater from a household or small commercial establishment that specifically excludes water from a toilet, kitchen sink, dishwasher, or water used for washing diapers. Greenbelt Strip of trees and shrubs growing parallel to stream that prevents overuse of the top bank area by man, animals, and machinery. This strip of vegetation also retards rainfall runoff down the bank slope and provides a root system which binds soil particles together. A linear park, usually located along a stream corridor or other right-of-way. Greenbelt See riparian corridor. Greenline

First perennial vegetation above the stable low water flow. Grid (computational) Network of points covering the space, or time-space domain of a numerical model. Grizzly A large screen, usually constructed of iron bars, which is used to sort quarried stone into appropriate size classifications, e.g. an 18 to 24 in stone size classification refers to the "b" axis length of the graded stones. The "b" axis is the middle axis (not the longest, not the shortest) of the stone. Groin See dike. Ground bioengineering A general term for all categories of application of plant materials for soil protection and slope stabilization either on its own or in combination with mechanical methods. Ground cover Any vegetation producing a protective mat on or just above the soil surface. Usually refers to low-growing herbaceous plants Groundwater (1) In the broadest sense, all subsurface water; more commonly that part of the subsurface water in the saturated zone. (2) Subsurface water and underground streams that can be collected with wells, or that flow naturally to the earth’s surface through springs. Groundwater basin A groundwater reservoir, defined by an overlying land surface and the underlying aquifers that contain water stored in the reservoir. In some cases, the boundaries of successively deeper aquifers may differ and make it difficult to define the limits of the basin. Groundwater discharge The movement of groundwater from an aquifer to the surface of the earth. Groundwater flow Water that moves through the subsurface soil and rocks. Groundwater lubricating an existing failure plane or causing a buildup of pore water pressure can lead to geotechnical failure. Groundwater seeping out of or “daylighting” at a streambank can cause seepage erosion and piping. Groundwater flow system The underground pathway by which groundwater moves from areas of recharge to areas of discharge. Groundwater table See water table. Groundwater overdraft The condition of a groundwater basin in which the amount of water withdrawn by pumping exceeds the amount of water that recharges the basin over a period of years during which water supply conditions approximate average. Groundwater prime supply Long-term average annual percolation into major groundwater basins from precipitation falling on the land and from flows in rivers and streams. Groundwater recharge

Increases in groundwater storage by natural conditions or by human activity. See also Artificial recharge. Groundwater storage capacity The space or voids contained in any given volume of soil and rock deposits. Groundwater table (1) The depth below the surface where the soil is saturated; that is the open spaces between the individual soil particles are filled with water. Above the groundwater table and below the ground surface the soil either has no water between the particles or is partially saturated. (2) The upper surface of the zone of saturation, except where the surface is formed by an impermeable body. Grout A fluid mixture of cement and water, or sand, water and fly ash or other cementing agents that can be poured and pumped easily. Used to (1) fill voids between riprap, culverts, or other structures in channels or slopes to prevent or reduce erosion or inadvertent water flow, or (2) to fill geotubes or other fabric- formed structures. Growth habitat The physical form and geometry of a plant – its above ground components. Gully A channel or miniature valley cut by concentrated runoff but through which water commonly flows only during and immediately after heavy rains or during the melting of snow; may be dendritic or branching or it may be linear rather than long, narrow, and of uniform width. The distinction between gully and rill is one of depth. A gully is sufficiently deep that it would not be obliterated by normal tillage operations, whereas a rill is of lesser depth and would be smoothed by ordinary farm tillage. H Habitat (1) The place where an animal or plant usually lives, often characterized by a dominant plant form or physical characteristics. (2) The environment occupied by individuals of a particular species, population, or community. (3) The local environment in which organisms normally live and grow. (4) The environment in which an organism or biological population lives or grows. Habitat assessment The evaluation of the structure of the surrounding habitat that influences the quality of the water resource and the condition of the aquatic community. Habitat attribute (Fisheries) - A single element, such as velocity, depth, cover, etc. of the habitat or environment in which a fish or other aquatic species or population may live or occur. Synonymous with “component”. Habitat conservation plan (HCP) An agreement between the Secretary of the Interior and either a private entity or a state that specifies conservation measures that will be implemented in exchange for a permit that would allow taking of a threatened or endangered species. Habitat diversity (1) The number of different types of habitat within a given area. (2) The variability of parameters within a specific habitat. For aquatic habitats this would include variations of depth, flow, velocity, substrate, substrate size, and cover. Generally, the more diversity contained within a habitat, the greater the likelihood that the habitat requirements are met for a larger number of species, or that the requirements are met for the different life stages of a single species.

Habitat evaluation procedures (HEP) A habitat evaluation methodology developed by the U.S. Fish and Wildlife Service that can be used to document the quality of available habitat for selected wildlife species or communities. HEP is commonly used as a decision-making tool in federally-funded projects to assess baseline conditions and project habitat gains and losses over the life of the project. Habitat fragmentation (1) The fragmentation of a large area of habitat into isolated patches that are not linked through corridors. (2) The breaking up of habitat into discrete islands through modification or conversion of habitat by management activities. Habitat management A planned sequence of activities that creates or augments various habitats needed to maintain or enhance the abundance of specified species. Habitat niche The peculiar arrangement of food, cover, and water that meets the requirements of a particular species. Habitat suitability index (HSI) A component of the U.S. Fish and Wildlife Service Habitat Evaluation Procedures (HEP). A value ranging from 0.0-1.0, assigned on the basis of known food and cover requirements of a species. HSI is multiplied by the area of habitat (in hectares or acres) to determine the habitat units available for each species in the area. This method is often used in determining mitigation requirements. Habitat unit (HU) In Habitat Evaluation Procedures HEP, used by the U.S. Fish and Wildlife Service, the HSI x the area available with that HSI. "Hard" bank protection methods Refers to the use of stone, block, jacks, concrete bags or any of a myriad number of solid materials that are used as bank protection. Hard point A streambank protection technique whereby erodible materials are excavated from a streambank at intervals along the channel and replaced by stone or other inert non-erodible material. Some hard points protrude a short distance into the channel to direct erosive currents away from the bank, in which case they may be referred to as dikes. Hard points also occur naturally along streambanks as passing currents remove erodible materials leaving non-erodible materials exposed. In some Corps of Engineers districts hard points and transverse dikes are interchangeable terms. Hardness A property of water that causes the formation of an insoluble residue when the water is used with soap and a scale in vessels in which water has been allowed to evaporate. It is due primarily to the presence of ions of calcium and magnesium. Generally expressed in milligrams per liter as calcium carbonate (CaCO3). General hardness scale – Soft (0-60); Moderately hard (61-120); Hard (121-180); Very hard (more than 180). Hardpan A layer of nearly impermeable soil beneath a more permeable soil, formed by natural chemical cementing of the soil particles. Hard water

Water high in multivalent cations, such as calcium and magnesium. This type of water does not lather easily when used with soap and forms a scale in containers when allowed to evaporate. Hatch box A device used to incubate relatively small numbers of fish eggs. The hatch box is usually located adjacent to a stream, which supplies the box with water. Hazardous materials Anything that poses a substantive present or potential hazard to human health or the environment when improperly treated, stored, transported, disposed of, or otherwise managed. Head Pressure measured as an equivalent height of water. Headcut A point of abrupt change in the longitudinal profile of a stream. Headcuts typically migrate upstream through time. Synonymous with Nick point or Knickpoint. Headcutting (1) The action of an upstream moving waterfall or locally steep channel bottom with rapidly flowing water through an otherwise placid stream. These conditions often indicate that a readjustment of a stream’s discharge and sediment load characteristics is taking place. (2) Channel bottom erosion moving upstream through a basin indicating that a readjustment of the basin slope and its stream discharge and sediment load characteristics is taking place. Headcutting is evidenced by the presence of waterfalls or rapidly moving water through an otherwise placid stream, and often leaves streambanks in an unstable condition (oversteepened) as it progresses through a reach. See degradation. (3) The cutting of the streambed to a lower elevation; progressive scouring and degrading of a streambed at a relatively rapid rate in the upstream direction, usually characterized by one or a series of vertical falls. Headwaters The source and upper part of a stream or river. Heavy metals Metallic elements with high atomic weights, e.g., mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain. Helical flow Three-dimensional movement of water particles along a spiral path in the general direction of flow. This type of current is of most significance as flow passes through a bend, but also occurs in multiple cells in relatively wide straight reaches as well. The vector of flow nearest the bed is referred to as "secondary current", and its net effect is to move bank and bed material from the cut bank and deposit it on the point bar or middle bar. Herbaceous With characteristics of an herb; a plant with no persistent woody stem above ground. Herbaceous vegetation Plants without woody stems such as grasses, most legumes, forbs, and wildflowers. Can be annual or perennial. High-Density Polyethylene (HDPE) A synthetic polymer used for geomembranes and pond liners. High gradient streams

Streams in moderately to highly sloping landscapes having substrate primarily composed of course sediment particles or frequent course particulate aggregations along stream reaches. Holding areas Areas in a stream that are protected from the current, where salmon can rest while migrating, usually upstream. Horizon See soil horizon. Humus See organic matter. Hydrarch succession The sequence of community changes that occurs as an aquatic ecosystem fills with sediment and eventually, through mostly extrinsic factors, develops into a terrestrial ecosystem. Hydraulic conductivity The capacity of a rock to transmit water. Expressed as the volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction of flow. Hydraulic control point The top of an obstruction to which stream flow must rise before passing over, or a point in the stream where the flow is constricted. Hydraulic constriction Flow around a small-radius bend that due to centrifugal force results in higher velocities and a narrowed channel width (relative to upstream and downstream channel widths). See constriction. Hydraulic geometry (1) A quantitative way of describing the channel changes in width, depth, and velocity relative to discharge. (2) A geomorphic expression introduced by Leopold and Maddock (1953) to describe the morphology of an alluvial river as a function of dominant discharge. The concept is similar to regime theory, but differs in the way that the dominant discharge is expressed. With respect to the hydraulic geometry of an alluvial river, the dominant discharge is the single flow event which is representative of the natural sequence of events which actually occur. Regime theory was developed for canals, which do not experience a range of flows. Hence, the dominant discharge for regime theory is the steady, operating discharge. [Watson et al. 1999]. Hydraulic gradient (1) The slope of the water surface; (2) The drop in head per length in the direction of stream flow. See also Streambed gradient. (3)A line which represents the relative force available due to the potential energy available. This is a combination of energy due to the height of the water and internal pressure. In an open channel, the hydraulic gradient is equal to the water surface. In a closed conduit, if several openings were placed along the top of the pipe and open tubes inserted, a line connecting the water surface in each of these tubes would represent the hydraulic grade line. Hydraulic jump (or jump) (1) Transition of flow from the rapid to the tranquil state. A varied flow phenomenon producing a rise in elevation of water surface. A sudden transition from supercritical flow to the complementary subcritical flow, conserving momentum and dissipating energy. (2) An abrupt, turbulent rise in the water level of a flowing stream, normally occurring at the transition from shallow, fast flow to deeper and slower flow. (3)

In fluid flow, a change in flow conditions accompanied by a stationary, abrupt turbulent rise in water level in the direction of flow. Hydraulic mean depth The area of the flow cross section divided by the water surface width. Hydraulic mulch Processed materials such as wood and paper products, cotton or straw fibers that are applied by special equipment utilizing a water-based slurry which is sprayed on the soil surface to stabilize the surface and promote the growth of seeded plants. Hydraulic radius (1) The cross sectional area of a stream divided by the wetted perimeter. For practical purposes in natural streams, equivalent to average depth unless the stream is unusually deep and narrow. (2) The cross sectional area of a stream of water divided by the length of that part of its periphery in contact with its containing conduit. Hydraulics Refers to water, or other liquids, in motion and their action. Hydric – Wet. Hydric soil (1) Soil that is wet long enough to periodically produce anaerobic conditions, thereby influencing the growth of plants. (2) Soils that are in a wetted condition for a long enough duration to periodically produce anaerobic conditions, thereby influencing the growth of plants. Usually associated with wetland areas. Hydrograph (1) A graph showing stage, flow, velocity, or other property of water with respect to time. (2) A curve showing stream discharge over time. (3) A graph showing the stage or discharge of a waterway with respect to time. Hydrographic survey The measurement of water depths and the charting of the bottom topography of rivers, streams, and lakes. Refers to surveying and mapping that part of the water body which is underwater at the time of the survey. Hydrologic, hydrological Pertaining to the cyclic phenomena of waters of the earth; successively as precipitation, runoff, storage and evaporation, and quantitatively as to distribution and concentration. Hydrologic balance An accounting of all water inflow to, water outflow from, and changes in water storage within a hydrologic unit over a specified period of time. Hydrologic regime The characteristic behavior and sum total of water that occurs in an area or drainage basin on average during a given period. Hydrologic region A study area, consisting of one or more planning subareas, that has a common hydrologic character. Hydrologic unit A distinct watershed or river basin defined by an 8-digit code.

Hydrology (1) The science of hydrology deals with the occurrence and movement of water upon and beneath the land areas of the earth. (2) The science that deals with water as it occurs in the atmosphere, on the surface of the ground, and underground. (3) The scientific study of the water of the earth, its occurrence, circulation and distribution, its chemical and physical properties, and its interaction with its environment, including its relationship to living things. (4) The properties, distribution, circulation and storage of water in streams, lakes, oceans, glaciers, and groundwater. (5) Overlaps and includes portions of other sciences such as meteorology and geology. The particular branch of Hydrology that a design engineer is generally interested in is surface runoff that is the result of excessive precipitation. Hydroperiod (1) The seasonal pattern of water abundance in a wetland; varies regionally, locally, and by wetland type. (2) The depth, duration, seasonality, and frequency of flooding. In its simplest form, it refers to the time period of inundation of the land surface. Hydrophobic Not capable of uniting with or absorbing water. Hydrophyte (1) Water-loving vegetation found almost exclusively in wetlands under natural conditions. (2) Any macrophyte that grows in water or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content; (3) Plants typically found in wet habitats. Hydroriparian Wetlands with hydric soils or whose substrates are never dry or are dry for only a short period; usually associated with perennial or intermittent water; vegetation, when present, consists of a predominance of obligate and preferential wet riparian plants. Term proposed by Johnson et al. (1984) to be added as a subsystem to the Palustrine System of Cowardin et al. (1979). See Mesoriparian and Xeroriparian. Hydroseeding Spreading of seed hydraulically in a water medium. Mulch, lime, and fertilizer can also be incorporated into the sprayed mixture. Hydrostatic pressure The pressure exerted by the water at any given point in a body of water at rest. Hyporheic flow See Subsurface flow Hyporheic zone The area under the stream channel and floodplain where groundwater and the surface waters of the stream are exchanged freely. Ice jam Fragments of broken river ice lodged in a narrow portion of the river channel. Can be associated with a difference in head resulting in backwater effects. Ice types Anchor Ice – Ice formed on the streambed materials when, due to outward radiation in evening, they become colder than the water flowing over them. Frazil Ice – Needle-like crystals of ice that are slightly lighter than water, but carried below the surface due to turbulence. This causes a milky mixture of ice and water. When these crystals touch a surface that is

even a fraction of a degree below freezing, they instantly adhere and form a spongy, often rapidly growing, mass. Hinge Ice – A marginal sheet of surface ice attached to the bank materials and extending toward the center of a stream but not spanning it completely. Impaired Condition of the quality of water that has been adversely affected for a specific use by contamination or pollution. Impermeable Not permitting the passage of a fluid. Can be a manufactured membrane, a natural material such as rock or clay, or an engineered structure. Often applied to stone dikes; even though a stone dike may allow a limited amount of flow through it, the amount is insignificant relative to total streamflow. Impervious Not capable of being passed through; soil which is resistant to the entrance of water, air, or plant roots. Impinging flow Flow attacking a streambank at an angle oriented close to perpendicular to the bank of the stream. Incised channel (1) Those channels which have been cut relatively deep into underlying formations by natural processes; characteristics include relatively straight alignment and high, steep banks such that overflow rarely occurs, if ever. (2) A stream channel that has deepened and as a result is disconnected from its floodplain. Incised river A river that erodes its channel by the process of degradation to a lower base level than existed previously or is consistent with the current hydrology. Incised stream A stream or channel that has become hydraulically disconnected from its original or previous floodplain due to bed degradation. A flow which previously overtopped the floodplain will now be contained well within top bank, e.g. the 5-yr flow event, or even the 100-year flow event, is confined within the main channel. Incision of the main channel usually results in the eventual base lowering of all tributaries, which can result in destabilization of the entire watershed. See degradation. Incision The change in channel cross section resulting from the process of degradation. Index A usually dimensionless, numeric combination of scores derived from biological measures called metrics. Index of Biotic Integrity (IBI) An aggregated number, or index, based on several attributes or metrics of a fish community that provides an assessment of biological conditions. Indicators (1) Those parameters assessed to measure a stream's health. (2) Indicator plants or species are those species that are symptomatic or representative of some specific characteristic of a certain locality. Indicator sites (in USGS NAWQA Study Units)

Stream sampling sites (in U.S. Geological Survey’s National Water-Quality Assessment Program [NAWQA] Study Units) located at outlets of drainage basins with relatively homogeneous land use and physiographic conditions; most indicator-site basins have drainage areas ranging from 20 to 200 square miles. Indirect bank protection A structure, or group of structures, that extend into the stream channel in order to redirect the flow so that hydraulic forces at the channel boundary (bank) are reduced to a non-erosive level, usually accompanied by deposition within the structure(s). Also known as redirective bank protection. See dike, rock vane, J- Hook vane, and bendway weir. Infiltration That portion of rainfall or surface runoff that moves downward into the subsurface rock and soil. Infiltration (soil) The movement of water through the soil surface into the soil. Inflow Water that flows into a stream, lake, reservoir, or Forebay during a specified period. Inoculation Method of artificially infecting shrubs and trees or herbaceous legumes with, respectively, mychorrhizae or rhizobium bacteria that normally live in symbiosis with them. Inorganic (1) Containing no carbon; matter other than plant or animal. (2) Composed of mineral matter that is not of plant or animal origin. Inorganic soil Soil with less than 20 percent organic matter in the upper 16 inches. In-situ Material in its natural position or place. Said specifically of a rock, soil, or fossil when found in the situation in which it was originally formed or deposited. Instant shade theory A restoration technique designed to quickly provide vegetative shade and cover over the channel of a stream by planting long branches or trunks of plant materials, or container plants at angles from near horizontal to 45 degrees. Instantaneous discharge The volume of water that passes a point at a particular instant of time. Instantaneous flow The discharge measured at any instant in time. Instream cover (1) Areas of shelter in a stream channel that provide aquatic organisms protection from predators or competitors and/or a place in which to rest and conserve energy due to a reduction in the force of the current. (2) The layers of vegetation, like trees, shrubs, and overhanging vegetation, that are in the stream or immediately adjacent to the wetted channel. Instream flow

(1) Portion of a flood flow that is contained by the channel. (2) A minimum flow requirement to maintain ecological health in a stream. Instream use (1) Water use taking place within the stream channel for such purposes as hydroelectric power generation, navigation, water-quality improvement, fish propagation, and recreation. Sometimes called nonwithdrawal use or in-channel use. (2) Use of water that does not require diversion from its natural watercourse. For example, the use of water for navigation, recreation, fish and wildlife, aesthetics, and scenic enjoyment. Insulated stream A stream or reach of stream that neither contributes to nor receives water from the zone of saturation. It is separated from the zones of saturation by an impermeable bed. Integrated drainage Drainage developed during geomorphic maturity in an arid region, characterized by coalescence of drainage basins as a result of headward erosion in the lower basins or spilling over from the upper basins. Interception Part of the moisture remaining in the vegetation layer which evaporates; depends on the meteorological conditions and the vegetation. Interdisciplinary team A group of people, each possessing expert knowledge in a different field (e.g. hydraulic engineering, soils and geology, biology, hydrology, fish and wildlife.) working together as a team to create hydraulically successful and environmentally compatible projects. Interface In hydrology, the contact zone between two fluids of different chemical or physical makeup. Interfluve The region of higher land between two rivers that are in the same drainage system. Intermittent stream (1) A stream that flows only when it receives water from rainfall runoff or springs, or from some surface source such as melting snow. (2) Any nonpermanent flowing drainage feature having a definable channel and evidence of scour or deposition. This includes what are sometimes referred to as ephemeral streams if they meet these two criteria. (3) A stream that has the potential for continuous flow, but at times the entire flow is absorbed by the bed material. Sometimes used interchangeably with "ephemeral stream". Intermontane Situated between or surrounded by mountains, mountain ranges, or mountainous regions. Internal drainage Surface drainage whereby the water does not reach the ocean, such as drainage toward the lowermost or central part of an interior basin or closed depression. Interrupted stream One that contains alternating reaches that are either perennial, intermittent, or ephemeral. Interstices A space, especially a small or narrow one, between things or parts, e.g. voids between rocks.

Interstitial flow (1) See intragravel flow. (2) That portion of the surface water that infiltrates the stream bed and moves through the substrate pores. Intolerant organisms Organisms that are not adaptable to human alterations to the environment and thus decline in numbers where alterations occur. See also Tolerant species. Intragravel flow The portion of the surface water that infiltrates the stream bed and moves through the substrate pores. Inundation A condition in which water from any source temporarily or permanently covers a land surface. Invert Refers to the bottom, inside surface of a pipe, log, or other object. Occasionally used to refer to the bottom or base elevation of a structure. (3) The lowest point on a cross-section (usually called thalweg point in natural streams). (4) The lowest elevation of the inside of a culvert or pipe. Invertebrate An animal that does not have a backbone or spinal column. See also Benthic invertebrate. Invertebrate drift Streams and terrestrial invertebrates that float with the current. Irrigation Controlled application of water to arable land to supply requirements of crops not satisfied by rainfall. Irrigation diversion Generally, a ditch or channel that deflects water from a stream channel for irrigation purposes. Irrigation efficiency The efficiency of water application and use. Computed by dividing evapotranspiration of applied water by applied water and converting the result to a percentage. Efficiency can be computed at three levels: farm, district, or basin. Irrigation return flow (1) The part of irrigation applied to the surface that is not consumed by evapotranspiration or uptake by plants and that migrates to an aquifer or surface-water body. (2) Applied water that is not transpired, evaporated, or deep-percolated into a groundwater basin but returns to a surface water supply. Irrigation withdrawals Withdrawals of water for application on land to assist in the growing of crops and pastures or to maintain recreational lands. J J-Hook or J-Hook Vane Vanes with J-Hooks are actually rock vanes modified to enhance the instream habitat benefits. They are redirective, upstream-pointing deflection structures whose tip is placed in a “J” configuration and partially embedded in the streambed so that they are submerged even during low flows. The rock vanes have demonstrated effectiveness in reducing near-bank velocities by redirecting the thalweg toward the center of the channel. The “J” structures are intended to create scour pools and thereby improve substrate complexity. The scour usually results in a “tail out” deposition of gravel (riffle) which may provide spawning habitat.

Jack (1) A type of river training structure consisting of wire or cable strung on three mutually perpendicular metal, wooden, or concrete struts. (jackstraw, tetrahedron jack, Kellner jack, Kellner jetty). Usually constructed in groups called "jack fields", with the individual jacks cabled together. Can be oriented either longitudinally (acting as a retard) or perpendicular to flow (a type of permeable dike). (2) Smaller units without wire or cable, usually used as scour protection (see A-jack). Jams Large accumulations of debris partially or completely blocking the stream channel, creating major obstructions to flow. Jet scour Scour resulting as a jet of flow enters the stream (similar to flow ejecting from the nozzle of a hose). Joint A surface of actual or potential fracture or parting in a rock, without displacement. Common in granitic rocks. Joint planting The insertion of live branch cuttings between openings or interstices of rocks, blocks, or other inert armor units and into the natural ground. K Karst (1) A type of topography that results from dissolution and collapse of carbonate rocks such as limestone, dolomite, and gypsum, and that is characterized by closed depressions or sinkholes, caves, and underground drainage. (2) Topography with sinkholes, caves, and underground drainage that is formed in limestone, gypsum, or other rocks by dissolution. Kellner jack See jack. Kettle A steep-sided hole or depression, commonly without surface drainage, formed by the melting of a large detached block of stagnant ice that had been buried in the glacial drift. Kettle lake A body of water occupying a kettle, as in a pitted outwash plain or in a kettle moraine. Key The portion of a river training or bank stabilization structure placed on, or excavated into, the riverbank. Designed to prevent flanking. Sometimes called a "root" or bankhead when applied to a dike. Key watershed As defined by National Forest and Bureau of Land Management District fish biologists, a watershed containing (1) habitat for potentially threatened species or stocks of anadromous salmonids or other potentially threatened fish, or (2) greater than 6 square miles with high-quality water and fish habitat. Kicker A dike, usually located at the downstream end of a bend, intended to improve and stabilize the navigation crossing to the opposite bank. Used extensively on the Missouri River, the Red River, and other regulated streams to control crossings between bends.

Kill Dutch term for stream or creek. Knickpoint (also known as Nick Point) (1) A location on the thalweg where there is an abrupt change of elevation and slope, usually referring to a vertical overfall. (2) The point at which a stream is actively eroding the streambed downward to a new base level. (3) A break in slope along a stream profile which indicates an area of active erosion. Niagara Falls is an example of a very large nick point. Synonymous with Head cut. Knickzone A steep reach of channel where a headward migrating zone of degradation is occurring. L Lacustrine Pertaining to, produced by, or formed in a lake. Lacustrine system Wetlands and deepwater habitats with all of the following characteristics: (1) situated in a topographic depression or a dammed river channel; (2) lacking trees, shrubs, persistent emergents, emergent mosses or lichens with greater than 30 percent area coverage; and (3) total area exceeds 8 ha (20 acres). Lacustrine wetlands Wetlands within a lake or reservoir greater than 20 acres or within a lake or reservoir less than 20 acres if the water is greater than 2 meters deep in the deepest part of the basin; ocean-derived salinity is less than 0.5 parts per thousand. Lagoon A shallow stretch of seawater or lakewater near or communicating with the sea (or lake) and partly or completely separated from it by a low, narrow, elongate strip of land. Lake An inland body of standing water deeper than a pond, an expanded part of a river, a reservoir behind a dam. Laminar flow (1) A smooth pattern of flow in which fluid moves in parallel “layers” which slide past each other at differing speeds but in the same direction; can be characterized by the appearance of a flat ripple free surface, or a thin coating over solid surfaces, or where flow moves through the small openings between rocks in a streambed and through dense stands of aquatic weeds. (2) A flow in which all particles or filaments of water move in parallel paths, characterized by the appearance of a flat, ripple free surface. Does not occur in nature. (3) Motion of fluids where the fluid moves in distinct and separate lines. Typical of most groundwater seepage. Seldom occurs in natural channels except in sluggish, backwater areas. (4) That type of flow in which each particle moves in a direction parallel to every other particle and in which the head loss is approximately proportional to the velocity (as opposed to turbulent flow).] Landscape A heterogeneous land area with interacting ecosystems that are repeated in similar form throughout. Landscape diversity The size, shape, and connectivity of different ecosystems across a large area. Landscape features The land, water, vegetation, and structures that compose the characteristic landscape.

Landslide A movement of earth mass down a steep slope. Large organic (woody) debris (LWD), Log (1) Pieces of wood larger than 10 ft long and 6 in. in diameter, in a stream channel. (2) Any large piece of relatively stable woody material having a least diameter greater than 10 cm and a length greater than 1 m that intrudes into the stream channel. Large woody debris is often abbreviated, LWD. Large woody debris (LWD) Trees or large branches of trees that have fallen or been eroded into a stream. Lateral earth pressure The horizontal pressure exerted by soil against a retaining structure. Lateral roots Shallow roots running out sideways from stem. Lateral scour Formed by the scouring action of the flow as it is directed laterally or obliquely to one side of the stream by a partial channel obstruction, such as a gravel bar or wing deflector. Launching Self-adjusting ability of undercut material (stone riprap, rubble, slag, etc.) to roll downslope. If sufficient material self-adjusts or accumulates on the streambank face and scoured sections of the toe, the slope can remain effectively armored and scour will be arrested. Layering The development of a new individual plant from a branch or stem that has rooted in the ground. Leaching (1) The flushing of minerals or pollutants from the soil or other material by the percolation of applied water. (2) The removal in solution of soluble materials by percolating water. Generally refers to the movement of soil nutrients to a deeper soil horizon, making them unavailable for plant growth. Leaf area index A measure of the total area of leaves, twigs, stems, etc. relative to the area of the canopy in forest. Left bank or left descending bank When looking in a downstream direction, the streambank on the left. See bank. Legumes Herbs, shrubs, and trees of the pulse family, as nitrogen gatherer because of a specific root clad bacteria; good ground improvers; many form specially strong and deep-reaching roots and are good ground stabilizers; an important part of seed mixes. Lens A non-continuous layer of material that is different in composition than adjacent material. Lentic (1) Pertaining to still waters, such as a lake, pond, swamp, or bog; lakelike. (2) Of, relating to, or living in still water. Opposite of lotic. Levee

(1) An embankment to prevent inundation, usually on or along the bank of a stream or lake to protect outer lowlands (dike). (2) An embankment constructed to prevent a river from overflowing (flooding). (3) An embankment or structure built to contain periodic floodwater in river systems within specific areas of the floodplain, thus preventing overflow into adjacent lowlands. Life zone Major area of plant and animal life; region characterized by particular plants and animals and distinguished by temperature differences. Lift An applied and/or compacted layer of soil, waste, gravel, or stone. Also referred to as a course. Most dikes on the Mississippi River , and many reinforced soil projects, are constructed in "lifts". Limiting factor A requirement such as food, cover, or another physical, chemical, or biological factor that is in shortest supply with respect to all resources necessary to sustain life and thus “limits” the size or retards production of a population. Limnetic The deepwater zone (greater than 2 meters deep); a subsystem of the Lacustrine System of the US Fish and Wildlife Service wetland classification system. Limnology The study of life in lakes, ponds, and streams. Line transect A sampling route through a surveyed area that is followed by an observer counting, for example, contacts over a measured distance Liner A layer of emplaced materials which serves to restrict the escape of liquids or solids placed within an impoundment. Liners can include reworked or compacted soil or clay, asphaltic and concrete materials, spray-on membranes, polymeric membranes, or any substance that serves the above stated purpose. Live fascines Bound, elongated sausage-like bundles of live cut branches that are placed in shallow trenches, partly covered with soil, and staked in place to arrest erosion and shallow mass wasting. Listed species Any species of fish, wildlife, or plant which has been determined to be endangered or threatened under the Endangered Species Act of 1973. Lithology The description of rocks or earth materials on the basis of color, composition and grain size. Littoral The shallow-water zone (less than 2 meters deep); a subsystem of the Lacustrine System of the US Fish and Wildlife Service wetland classification system. Live pole planting Ground bioengineering technique comprising the installation by driving, or insertion into pre-drilled holes, of long live stakes, rods or poles of 1-2.5m length of poplar or willow (or any plant which propagates from cuttings) at close centers for slope stabilization purposes as a form of live soil nailing.

Live stake Cuttings from living branches that are tamped or inserted into the earth; the stakes eventually root and leaf out. Load (1) Material that is moved or carried by streams, reported as weight of material transported during a specific time period, such as tons per year. (2) See sediment load. Loading (1) The influx of pollutants to a selected water body. (2) The total amount of material entering a system from all sources. Loam A soil textural classification in which the proportions of sand, silt, and clay are well balanced. Loams have the best properties for cultivation of plants. Local scour Discrete, tight scallops along the bankline or as depressions in the streambed resulting from erosion. It is generated by flow patterns that form around an obstruction in a stream and spill off to either side of the obstruction, forming a horseshoe-shaped scour pattern in the streambed. Loess Material transported and deposited by wind and consisting predominantly of silt-sized particles. Loess deposits can stand at nearly vertical slopes because of weak cementation at grain contacts, but these contacts are soluble and loess is easily eroded by surface runoff and subsurface seepage. Log toe A structure installed at the base of a bank slope constructed of log materials to protect the base of the bank from erosive forces. Long or Pole Cutting Ends of branches of tree willows and poplars, with end buds, 1-2.5m long. Longard tubing Sand-filled synthetic tubes placed on a streambank, lake bank, or beach for erosion protection. See geotube. Longitudinal The direction parallel with stream flow or a section of streambank, or parallel with the general downvalley direction of the stream. Longitudinal Fill Stone Toe Protection (LFSTP) A resistive streambank protection method consisting of a continuous trapezoidal windrow of stone placed at, or slightly streamward of, the toe of a streambank. The LFSTP is keyed into the bank at its upstream and downstream limits, often with intermittent keys or tiebacks extending back into the bank along its length. Sometimes used in conjunction with bank grading and vegetative treatments, or a constructed vegetated bench or floodplain. LFSTP is usually constructed of a self-launching stone (see launching) to control localized scour on the stream side of the LPSTP. When designed and constructed correctly, LFSTP provides enough self-launching stone to maintain its original height of protection even in areas experiencing considerable localized scour. The LFSTP can also be designed to act as a roadway during construction in areas of limited access. Longitudinal Peaked Stone Toe Protection (LPSTP) (aka: Longitudinal Stone Toe)

A triangular section of stone placed parallel to, or slightly streamward of, the toe of an eroding streambank (at the natural angle of repose of the stone) to prevent erosion of the toe and induce sediment deposition landward of the LPSTP. The LPSTP is keyed into the bank at the upstream and downstream limits, with intermittent keys or tiebacks extending back into the bank along its length. Typically used where the streambank either is already vegetated (existing vegetation not disturbed during construction) or the protected bank can be expected to vegetate once the toe is stabilized. Is usually constructed with a minimal disturbance to the existing bank, and does not require precise design and control. The controlling specification is usually expressed in tons of stone per linear ft of bank, rather than by structural dimensions (e.g., 2 tons/ft), although a crest elevation can also be specified. LPSTP is usually constructed of a self-launching stone (see launching) to control localized scour on the stream side of the LPSTP. Long-term monitoring The collection of data over a period of years or decades to assess changes in selected hydrologic conditions. Longitudinal bar An elongated alluvial deposit parallel to the local flow, of different shape, but typically with convex structures. Common to gravelly braided streams. Longitudinal profile (1) A graph of the vertical fall of the stream bed or water surface measured along the course of the stream; a graphical presentation of the elevation versus distance, as in channel cross sections and longitudinal sections; in open-channel hydraulics, a plot of water-surface elevation against channel distance. (2) A profile of a stream or valley, drawn along its length from source to mouth; it is the straightened out, upper edge of a vertical section that follows the winding of the stream or valley. (3) A graph of the bed (thalweg) elevation (y-axis) of a stream versus the length of the stream (x-axis). Losing stream A stream or reach of stream that contributes water to the zone of saturation. Lotic Of, relating to, or living in moving water, as in a stream, spring, or river. Opposite of lentic. Low gradient streams Streams in low to moderately sloping landscapes having substrates of fine sediment or infrequent aggregations of coarse particulate aggregations along stream reaches. Lower bank That portion of a streambank which is usually underwater. See also upper bank, middle bank, and zones. Low flow The lowest discharge recorded over a specified period of time; also called minimum flow. Lower bank That portion of the streambank below the elevation of the average water level of the stream. Lower streambank The periodically submerged portion of the channel cross-section from the normal high water line to the water’s edge during the summer low flow period. LUNKERS (or LUNKER structure, an acronym for Little Underwater Neighborhood Keeper Encompassing Rheotactic Salmonids)

An engineered structure employing a roof and having an open front and ends, designed to replicate an undercut bank thus functioning to improve aquatic habitat for rheotactic fishes (species that prefer to face into the current) while providing streambank protection. Can be constructed of concrete, wood, or "synthetic wood". M Macroinvertebrates Invertebrates large enough to be visible to the naked eye, such as insect larvae and crayfish. Benthic macroinvertebrates are animals without backbones, living in or on sediments or other substrates, of a size large enough to be seen with the unaided eye, and which can be retained by a U.S. Standard No. 30 sieve (28 openings per inch, 0.595-mm openings). Macrophytes Aquatic plants large enough to be seen with the naked eye. Main channel See Divided flow. Main stem (1) The principal trunk of a river or a stream. (2) The principal channel of a drainage system into which other smaller streams or rivers flow. Management The process of setting goals, defining objectives, identifying problems, implementing actions to address problems, and evaluating actions to determine if objectives and functions have been achieved. Manning's roughness coefficient A coefficient that represents the degree of channel roughness and resulting drag on hydraulic flow in a channel. The coefficient appears in the denominator of Manning's equation which quantifies flow in open channels. Manufactured retention system Manufactured elements and materials made and installed to retain earth masses, armor stream banks, and stabilize channel beds, usually consisting of interlocking or connected units. Marine wetland Wetlands that are exposed to waves and currents of the open ocean and to water having a salinity greater than 30 parts per thousand; present along the coastlines of the open ocean. Marsh A water-saturated, poorly drained area, intermittently or permanently water covered, having aquatic and grasslike vegetation. Mass failure The sudden breaking away and downward movement of a portion of the land surface, e.g. hillside or streambank, usually along a well defined slip surface, as opposed to the gradual erosion of soil. Mass movement (1) The downslope movement of earth caused by gravity. Includes but is not limited to landslides, rock falls, debris avalanches, and creep. It does not however, include surface erosion by running water. It may be caused by natural erosional processes, or by natural disturbances (e.g., earthquakes or fire events) or human disturbances (e.g., mining or road construction). (2) Movement of a relatively large portion of the land surface under direct gravitational stress, as in creep, landslide, rock slides and falls,

earthflows, debris flows, and avalanches. Opposite of surficial erosion. (3) The movement of large, relatively intact masses of earth and/or rock along a well-defined shearing surface as a result of gravity and seepage. Mass wasting A general term for a variety of processes by which large masses of earth material are moved by gravity either slowly or quickly from one place to another . Synonymous with mass movement or mass erosion. Mathematical model A model that uses mathematical relationships to represent the prototype. Sometimes used interchangeably with "numerical model", but can more accurately be considered the basis for a numerical model, in which the basic equations can realistically only be solved approximately. See numerical model. Mattress A covering of concrete, wood, stone, or other material used to protect a streambank against erosion. Maturity A stage in the evolutionary erosion of land areas in which the flat uplands have been widely dissected by deep river valleys. Maturity (stream) The stage in the development of a stream at which it has reached its maximum efficiency, when velocity is just sufficient to carry the sediment delivered to it by tributaries; characterized by broad, open, flat-floored valleys having a moderate gradient and gentle slope. Maximum contaminant level (MCL) (1) Maximum permissible level of a contaminant in water that is delivered to any user of a public water system. MCLs are enforceable standards established by the U.S. Environmental Protection Agency. (2) The highest concentration of a constituent in drinking water permitted under federal and State Safe Drinking Water Act regulations. Maximum flow See Peak flow. Maximum historical flood The maximum flood that has been recorded or experienced at any particular highway location. Mean (1) The arithmetic average of a set of observations, unless otherwise specified. (2) The average value of a group of numbers. Mean annual discharge (1) Daily mean discharge in units per second averaged over a period of years. Mean annual discharge usually fills a river channel to about one-third of its bankfull depth. (2) Yearly-averaged discharge. [Watson et al. 1999] Mean annual discharge/mean annual flow The averaging of the daily mean discharge over a period of years. Mean annual flood (Q2.33) Discharge corresponding to the probability of exceedence of the mean annual flood event in a Gumbel extreme value type 1 probability distribution (EV1) derived from the observed annual maximum flow series. This event has a recurrence interval of 2.33 years. [Watson et al. 1999]. Mean depth For a stream at any stage, the wetted normal section divided by the surface width. Hydraulic mean depth.

Mean discharge The arithmetic mean of individual daily mean discharges of a stream during a specific period, usually daily, monthly, or annually. Mean flow The average discharge at a given stream location, usually expressed in cubic feet per second (cfs), computed for the period of record by dividing the total volume of flow by the number of days, months, or years in the specified period. Mean high flow The mean of the highest flows over a period of time. Mean high water The highest level of inundation that occurs under "normal" hydrologic conditions. The term is too imprecise to be useful for engineering or scientific purposes, but is often the subject of intense regulatory and legal debate. Mean low water The lowest elevation of the water surface under "normal" hydrologic conditions. As with mean high water, it must be accompanied by a more scientific definition to be useful in practice. Mean Sea Level, MSL Mean Sea Level, referring to the datum established in 1929. Another, more current, version is referred to as National Geodetic Vertical Datum (NGVD). The two terms can be considered to be interchangeable for most purposes. Mean velocity (1) The average velocity of water in one vertical segment of a cross section of a stream. Surface velocity is usually much stronger than bottom velocity. Also refers to the general velocity of the channel as a whole. (2) The average cross-sectional velocity of water in a stream channel. Surface values typically are much higher than bottom velocities. May be approximated in the field by multiplying the surface velocity, as determined with a float, times 0.8. Meander (1) A winding stream channel, usually in an erodible alluvial valley; (2) a reverse of an S-shaped curve or series of curves formed by erosion of the concave bank, especially at the downstream end, characterized by curved flow and alternating shoals and bank erosions. Meandering is a stage in the migratory movement of the channel, as a whole, down the valley. (3) A series of sine-generated curves characterized by curved flow and alternating banks and shoals. (4) A reach of stream with a ratio of channel length to valley length greater than 1.5. By definition, any value exceeding unity can be taken as evidence of meandering, but 1.5 has been widely accepted by convention. (5) n. One of a series of sinuous curves, bends, or loops, developed in a flood plain by flowing water. (6) v. To change course in a sinuous, and somewhat systemic, pattern. Meander amplitude The distance between points of maximum curvature of successive meanders of opposite phase in a direction normal to the general course of the meander belt, measured between center lines of channels. Meander belt (1) The part of a flood plain encompassed between two lines tangent to the outer bends of all the meanders.

(2) The zone within which channel migration has historically occurred. Within the meander belt, channel migration is indicated by abandoned channels, accretion topography (scrolling), and oxbow lakes. Meander belt deposits Sands, silts, and clays that have been deposited in a river valley by a meandering stream. Meander belt width The distance between lines drawn tangential to the extreme limits of fully developed meanders. Not to be confused with meander amplitude. Meander length The lineal distance downvalley between two corresponding points of successive meanders of the same phase. Meander pattern (1) A series of sinuous curves or loops in the course of a stream that are produced as a stream swings from side to side in flowing across its floodplain. (2) A series of sinuous curves or loops in the course of a stream that are produced as a stream swings from one side of its floodplain to the other. Meander ratio The length of a river or stream channel from an upstream point to a downstream point divided by the straight line distance between the same two points. Meander scroll (1) One of a series of long, parallel, close fitting, crescent-shaped ridges and troughs formed along the inner bank of a stream meander as the channel migrated laterally and/or downvalley. (2) Evidence of historical meander patterns in the form of lines visible on the inside of meander bends (particularly on aerial photographs) which resemble a spiral or convoluted form in ornamental design. These lines are concentric and regular forms in high sinuosity channels and are largely absent in poorly developed braided channels. Meandering stream A stream which has a basically sinuous pattern characterized by alternating changes in direction (bends). Measured Load A portion of the total sediment load measured by conventional suspended load samplers. Includes a large proportion of the suspended load but excludes that portion of the suspended load moving very near the bed (that is, below the sampler nozzle) and all of the bed load. [Watson et al. 1999] Mechanism of failure The physical processes of mass and surficial erosion respectively. Mass failure occurs when shear stresses equal or exceed shear strength along a critical surface. Erosion failure is initiated when drag or tractive forces on particles at a fluid bed boundary exceed cohesion and inertial forces between particles. Median The middle or central value in a distribution of data ranked in order of magnitude. The median is also known as the 50th percentile. Mesic (1) Characterized by a moderate amount of moisture. (2) Moderately wet. Mesophyte Any plant growing where moisture and aeration conditions lie between the extremes of “wet” and “dry.”

Mesoriparian Wetlands with nonhydric soils and whose substrate is dry seasonally; usually associated with intermittent water or high-elevation ephemeral wetlands; vegetation, when present, consists of a mixture of obligate, preferential, and facultative riparian plants. See “Hydroriparian” and “Xeroriparian”. Metric A measurable characteristic of the biota that changes in some predictable way with increased human influence. Microclimate Climate of small area, ranging from a few square centimeters to a slope or valley bottom. Micrograms per liter (μg/L) A unit expressing the concentration of constituents in solution as weight (micrograms) of solute per unit volume (liter) of water; equivalent to one part per billion in most streamwater and groundwater. One thousand micrograms per liter equals one milligram per liter. Midden A mound or stratum of refuse (broken pots, ashes, food remains) normally found on the site of an ancient settlement. Middle bank The ill-defined zone of transition between the lower bank and upper bank. See also lower bank, upper bank, and zones. Middle bar An area of deposition lying within the channel of the stream but not connected to the banks. Midge A small fly in the family Chironomidae. The larval (juvenile) life stages are aquatic. Migration rate Distance a stream moves laterally over a specific unit of time. Usually determined by comparison of aerial photographs or surveys taken at different times, and reported as an average distance per year over that period of time. Milligram A mass equal to 10-3 grams. Milligrams per liter (mg/L) (1) A unit expressing the concentration of chemical constituents in solution as weight (milligrams) of solute per unit volume (liter) of water; equivalent to one part per million in most streamwater and groundwater. (2) The weight in milligrams of any substance dissolved in 1 liter of liquid; nearly the same as parts per million by weight. Mineralization The process whereby concentrations of minerals, such as salts, increase in water, often a natural process resulting from water dissolving minerals found in rocks and soils through which it flows. Minimum flow The lowest discharge recorded over a specified period of time. Mitigation

(1) Actions taken to avoid, reduce, or compensate for the effects of human-induced environmental damage. (2) The process of reducing the negative environmental impacts of a project. Sometimes takes the form of replacement or substitution of a habitat in repayment for habitat that has been degraded or destroyed. Modern time A period of time spanning anywhere from tens of years to several hundreds of years, depending upon the context. Moisture stress A condition of physiological stress in a plant caused by lack of water. Monitoring (1) Repeated observation, measurement, or sampling at a site, on a scheduled or event basis, for a particular purpose. (2) The process of collecting physical, chemical, and environmental data to determine the impacts of an action undertaken on a waterway, ideally before, during, and after the action. Monoculture Artificial plant community (sown or planted) which is composed of a single species. Morphology (1) The form, shape, or structure of a stream or organism. (2) A scientific study of changes in form and structure. Morphological Morphology refers to the form, shape, or structure of a stream or organism. The characteristics of a stream’s form and structure are, thus, described as “morphological”. Most Probable Annual Flood (Q1.58) The discharge corresponding to the probability of exceedence of the modal annual flood event in a Gumbel extreme value type 1 (EV1) derived from the observed annual maximum flow series. This event has a recurrence interval of 1.58 years. [Watson et al. 1999]. Mouth The place where a stream discharges to a larger stream, a lake, or the sea. Movable-bed physical model A model in which the bed or bank materials, or both, are erodible and are transported in a manner similar to the prototype. Usually designed to determine the effects of various river training structures on the bathymetry or planform of a reach of river. Muck Dark, finely divided, well-decomposed, organic matter forming a surface deposit in some poorly drained areas. Mulch (1) A natural or artificial layer of material or plant residue covering the land surface which reduces the rainfall impact and tractive forces of water on the soil surface (thereby reducing erosion), conserves moisture, improves soil structure, and aids in the establishment of plant cover. Straw, hay, wood chips, leaf litter, compost, paper, etc. can all be used as a mulch. Mulch also holds soil in place and reduces temperature fluctuations. Multimetric approach Analysis techniques using several measurable characteristics of a biological assemblage.

Multimetric index A dimensionless numeric combination of scores derived from biological measures called metrics. A metric is a characteristic of the biota that changes in some predictable way with increased human influence and can therefore be scored according to conditions. Multipurpose project A project designed to serve more than one purpose. For example, one that provides water for irrigation, recreation, fish and wildlife, and, at the same time, controls floods or generates electric power. Multivariate approach Statistical methods (e.g., ordination or discriminate analysis) for analyzing physical and biological community data using multiple variables. Muskeg Large expanses of peatlands or bogs in subarctic zones. Mychorrhizae A family of fungi that colonize some species of plant roots, effectively extending the root system into the surrounding soil, assisting the plant in the uptake of nutrients and increasing disease resistance, resulting in superior growth and survival of the plant. N “n” Value The roughness coefficient in the Manning formula for determination of the discharge coefficient in the Chezy formula, V=C(RS)1/2 where C=(1/n)R1/6. National Geodetic Vertical Datum of 1929 Geodetic datum derived from a general adjustment of first-order level nets of the United States and Canada; formerly called “Sea Level Datum of 1929.” National Pollution Discharge Elimination System (NPDES) Federal legislation that requires cities with populations over 100,000 to establish a permit process to control sediment pollution. A permit is also required for developments 5 acres or larger. Permits are authorized and enforced by the Environmental Protection Agency or a designated state agency as directed by the Clean Water Act. [E-SenSS] (2) A provision of Section 402 of the Federal Clean Water Act of 1972 that established a permitting system for discharges of waste materials to watercourses.[Fischenich] Native vegetation Vegetation that is indigenous to a certain area and is adapted to that area's environmental conditions (climate, rainfall, soils, etc.) Natural flow The flow past a specified point on a natural stream that is unaffected by stream diversion, storage, import, export, return flow, or change in use caused by modifications in land use. Natural levee (1) Levees that form at the edge of stream channels as a result of sediment deposition that occurs as the velocity of floodwater is reduced after it leaves the stream channel. (2) A long, broad, low ridge built by a stream on its floodplain along one or both banks of its channel in time of flood. (3) A low, alluvial ridge adjoining the channel of a stream, formed by sediment deposited by floodwaters that have overflowed the channel banks. Deposits in a natural levee usually graduate from coarse to fine in the direction away from the stream.

Natural Resources Conservation Service (NRCS) A federal agency, formerly called the Soil Conservation Service (SCS), that provides technical assistance on natural resource management issues. Navigable stream (1) A waterway of sufficient depth and width to handle specified navigation traffic. (2) A waterway which has been officially designated as "navigable" for legal and regulatory purposes. Near bank region Sometimes referred to as the terrace side of the stream or the concave bank side or the top of the meander wave. This bank is opposite the point bar and most susceptible to erosion. This area is referred to sometimes as the near bank region because it is the location in the channel where the thalweg comes closest to the bank. Neck cutoff Breakthrough of a river across a narrow neck separating two meanders, where downstream migration has been slowed and the next meander upstream has overtaken it. Compare with chute cutoff. Net water demand (net water use) The amount of water needed in a water service area to meet all requirements. It is the sum of evapotranspiration of applied water (ETAW) in an area, the irrecoverable losses from the distribution system, and the outflow leaving the service area; does not include reuse of water within a service area (such as reuse of deep-percolated applied water or use of tailwater). Newbury Rock Riffles Newbury Rock Riffles are ramps or low weirs with long aprons made from riprap or small boulders that are constructed at intervals along a channel approaching natural riffle spacing (5 to 7 channel widths). The structures are built by placing rock fill within an existing channel. The upstream slope of the rock fill is typically much steeper than the downstream slope, which creates a longitudinal profile quite similar to natural riffles. These structures provide limited grade control, pool and riffle habitat, and visual diversity in otherwise uniform channels. NGVD See mean sea level. Niche space The position of a particular species or population in an ecological community. Nickpoint (see Knickpoint or Headcut) Nitrate An ion consisting of nitrogen and oxygen (NO3-). Nitrate is a plant nutrient and is very mobile in soils. Noncohesive sediments Sediments consisting of discrete particles. For given erosive forces, the movement of such particles depends only on the properties of shape, size, and density, and on the position of the particle with respect to surrounding particles. Examples include: sand, gravel, and cobble. Nonpersistent emergent plants Emergent plants whose leaves and stems break down at the end of the growing season from decay or by the physical forces of waves and ice; at certain seasons, there are no visible traces of the plants above the surface of the water. Nonpoint source

Nutrients or contaminants that enter wetland and aquatic ecosystems across a wide expanse in contrast to a point source of entering from a discrete point. Common nonpoint sources are agricultural and urban landscapes. Non-point source pollution (NPS) (1) Pollution that does not originate from a clear or discrete source. (2) Pollution that enters a water body from diffuse and indistinct sources. NPS pollution occurs when water runs over land or through the ground, picks up pollutants, and deposits them in surface waters or introduces them onto groundwater. The most common NPS pollutants are sediment and nutrients that wash into water bodies from agricultural land, construction sites, urban areas, or disturbed areas. Compare to point source pollution. Non-structural flood control measures Measures taken to reduce flood damage without altering the stream or its overflow characteristics. Non- structural measures may include, but are not limited to: land use regulation, land acquisition, providing for the maintenance of aquatic areas, floodplain zoning, flood-proofing of existing buildings, flood forecasting, flood warning, providing flood hazard information, flood insurance, tax adjustments, emergency assistance, and relocation of properties and people. Non-uniform flow The depth and velocity of flow changes along the length of the channel. Typical of natural channels. Normal Perpendicular. Usually applied to the angle of a dike relative to the direction of flow, e.g., a dike oriented normal to flow. Normalization The mathematical manipulation of a variable to allow comparisons with an otherwise different variable. Normalized demand The process of adjusting actual water use in a given year to account for unusual events such as dry weather conditions, government interventions for agriculture, rationing programs, or other irregularities. Noxious plant Sometimes termed "noxious weed". (1) A plant that is undesirable at a given site because it conflicts with management objectives. (2) A plant that has been legally declared "noxious". Noxious species (1) Non-native plant species, as identified by local, state, and/or federal agencies, found in the riparian zone and adjacent upland area that are considered noxious, and that outcompete native plants for available resources, reproduce prolifically, and potentially dominate regions and ecosystems. (2) A plant that is undesirable because it conflicts, restricts, or otherwise causes problems under management objectives. Nuisance species Undesirable plants and animals, commonly exotic species. Numerical model A mathematical model in which the governing equations are not solved analytically; using discrete numerical values to represent the variables involved and using iterative arithmetic operations. The governing equations are solved approximately. Nutrient Any inorganic or organic compound needed to sustain plant life.

Nutrient depletion Detrimental changes at a site in the total amount of nutrients and/or their rates of input, uptake, release, movement, transformation, or export. O Obligate Wetland Species A species that is nearly always found in wetlands. Obstruction Any material in the stream that causes flow to be retarded or diverted. Off-channel area Any relatively calm portion of a stream outside of the main flow. Off-site enhancement The improvement in conditions for fish or wildlife species away from the site or development activities that may have detrimental effects on fish and/or wildlife, as part or total compensation for those effects. Offstream use Water withdrawn or diverted from a ground- or surface-water source for use. See also Withdrawal. Open channel A waterway or drainage course which has no restrictive top. Open Weave Textile (OWT) A degradable rolled erosion control product (RECP) composed of processed natural or polymer yarns woven into a matrix and used to provide erosion control and facilitate establishment of vegetation. Optical opacity An expression for the amount of light absorbed and scattered by a suspension. Reported as: (1) extinction coefficient, (2) percent of incident light scattered at 90 degrees, and/or (3) percent of incident light transmitted at 180 degrees over a standard distance. Order See Stream order. Ordinary high water elevation Generally, the lowest point at which perennial vegetation grows on the streambank. Legal definitions of the ordinary high water elevation describe erosion and sediment characteristics as well. The ordinary high water elevation can usually be identified by physical scarring along the bank or shore, or by other distinctive signs. This scarring is the mark along the bank where the action of water is so common as to leave a natural line impressed on the bank. That line may be indicated by erosion, shelving, changes in soil characteristics, destruction of terrestrial vegetation, the presence of litter or debris or other distinctive physical characteristics. The legal definition of ordinary high water elevation per WAC 220-110-020(31) is: “Ordinary high water line means the mark on the shores of all waters that will be found by examining the bed and banks and ascertaining where the presence and action of waters are so common and usual and so long continued in ordinary years, as to mark upon the soil or vegetation a character distinct from that of the abutting upland: Provided, that in any area where the ordinary high water line cannot be found the ordinary high water line adjoining saltwater shall be the line of mean higher high water and the ordinary high water line adjoining freshwater shall be the elevation of the mean annual flood.” Considerable judgment is required to identify representative ordinary high water marks. It may be difficult to identify the mark on cut banks. In warm months, grasses or hanging vegetation may obscure the mark. Artificial structures (culverts, bridges or other constrictions) can affect the mark in their vicinity by creating marks

on the shore that are consistent with ordinary high water marks, but they are above the elevation that is usually found in undisturbed river reaches. Where the ordinary high water mark cannot be determined reliably, the surveyor should move to a location where the channel section will allow for a more precise measurement. At a location beyond the influence of artificial structures, measure the indicators at five different places (spaced about five channel widths apart straight channel sections), and take the average of these distances. Ordinary high water mark. The line on the shore established by the fluctuation of water and physically indicated on the bank (1.5 + years return period). Organic Containing carbon, but possibly also containing hydrogen, oxygen, chlorine, nitrogen, and other elements. Organic detritus Any loose organic material in streams, such as leaves, bark, or twigs, removed and transported by mechanical means, such as disintegration or abrasion. Organic matter (humus) That portion of soil, usually dark in color, resulting from the decomposition of plant and animal materials. Organic mixtures and mulches Any of a number of agents (e.g. petrochemicals or vegetative matter) used to stabilize a streambank against erosion by providing protection and nutrients while vegetation becomes established. These agents, which may be in the form of liquids, emulsions, or slurries, are normally applied by mechanical broadcasters. Organic soil Soil that contains more than 20 percent organic matter in the upper 16 inches. Orographic Pertaining to mountains, in regard to their location and distribution; said of the precipitation caused by the lifting of moisture-laden air over mountains. Outcrop (a) The part of a geologic formation or structure that appears on the surface of the earth. (b) An exposure of bedrock at or above the ground surface. Outfall (1) Point where water flows from a conduit, stream, or drain. (2) The mouth or outlet of a river, stream, lake, drain, or sewer. Outlet Point of water disposal from a stream, river, lake, tidewater, or artificial drain. Outlet channel A waterway constructed or altered primarily to carry water from man-made structures, such as terraces, tile lines, and diversions. Outwash Soil material washed down a hillside by rainwater and deposited upon more gently sloping land. Overbank See floodplain.

Overbank deposits Sediment deposited on the floodplain when a river or stream overflows its banks. Overbank drainage Water from the floodplain that flows over the top bank, down the bank slope, and into the waterway. Overbank flooding Any situation in which inundation occurs as a result of the water level of a river or stream rising above bank level. Overbank flow Water movement above top bank elevation either due to a high stream stage or to inland surface-water runoff. Overburden (1) The material (soil, sand, silt, gravel, clay) that overlies bedrock. (2) All material overlying an underground excavation. (3) Material placed over a buried pipeline or cable to protect it from stream forces (sometimes called backfill). Overfall (1) Abrupt change in stream channel elevation; the part of a dam or weir over which the water flows. (2) A sudden drop in grade, as in a gully or the upper edge of a steep bank. Overflow Discharge of a stream outside its banks; the parallel channels carrying such discharge. Overhead cover Material (organic or inorganic) that provides protection to fish or other aquatic animals from above; generally includes material overhanging the stream less than a particular distance above the water surface. Oversteepened bank A streambank that has been steepened beyond the angle of repose or beyond the point to which soil cohesion and internal friction supports the bank. Overland flow The flow of rainwater or snowmelt over the land surface toward stream channels. Oxbow (1) An abandoned meander in a river or stream, caused by cutoff. Used to describe the U-shaped bend in the river of the land within such a bend of a river. (2) An abandoned meander caused by a neck cutoff (see oxbow lake). (3) An extremely curved active channel meander with only a narrow neck between adjacent reaches. (4) The land within an oxbow reach. Oxbow lake (1) Small lake located in an abandoned meander loop of a river channel. It is formed as a river cuts through a meander loop to shorten its course, blocks off the old channel, and then migrates away from the lake. (2) A lake, usually curved, crescent, or horseshoe-shaped in planform, occupying a cut-off channel reach that has been abandoned by the main watercourse. P Palisades A proprietary technique, developed by Erkon, Inc. (formerly Hold That River, Inc.), consisting of steel pipe pilings connected by webs of nylon netting to form a permeable dike (usually deployed in system fashion),

typically oriented normal to flow. Palisades are designed to protect a streambank by reducing near-bank velocities, thereby encouraging deposition of sediment within the Palisade field. Palustrine wetland (1) Freshwater wetlands including open water bodies of less than 20 acres in which water is less than 2 meters deep; includes marshes, wet meadows, fens, playas, potholes, pocosins, bogs, swamps, and shallow ponds; most wetlands are in the Palustrine system. (2) All nontidal wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to oceanic-derived salts is below 0.5%. Parallel flow Flow in a direction roughly parallel to the bank of a stream. Parameter A determining characteristic or factor Particle size A linear dimension, usually designated as "diameter", used to characterize the size of a particle. The dimension may be determined by any of several different techniques, including sedimentation sieving, micrometric measurement, or direct measurement. Particle size classification See sediment grade scale. Particle size distribution (1) The composition of the material along the streambed is sampled; from this sample a plot of particle size or weight versus frequency in percent is plotted. (2) The frequency distribution of the relative amounts of particles in a sample that are within specified size ranges, or a cumulative frequency distribution of the relative amounts of particles coarser or finer than specified sizes. Relative amounts are usually expressed as percentages by weight. Particle size intermediate axis The size of a rock or sediment particle determined by the direct measurement of the axis normal to a plane representing the longest and shortest axes. This dimension is typically the quoted size of stone when graded at the quarry, i.e. a 12 in maximum diameter stone would have a maximum B-axis length of 12 inches. Basically, the width of a stone. Also called the B-axis. Parr A juvenile anadromous fish during the freshwater rearing phase of its life cycle. Part per million (ppm) Unit of concentration equal to one milligram per kilogram or one milligram per liter. Pathogen (1) Any living organisms that causes disease. (2) Any viruses, bacteria, or fungi that cause disease. Pavement Streambank surface covering, usually impermeable, designed to serve as protection against erosion. Common pavements used on streambanks are concrete, compacted asphalt, and soil-cement, although asphalt may not meet current environmental standards. Peak discharge The maximum instantaneous flow from a given storm condition at a specific location.

Peak flow (1) The highest discharge recorded over a specified period of time. Often thought of in terms of spring snowmelt, summer, fall, or winter rainy season flow. Also called maximum flow. (2) Maximum momentary stage or discharge of a stream in flood; Design discharge. Peak stage Maximum height of a water surface above an established datum plane. Same as peak gage height. Peat (1) A highly organic soil, composed of partially decomposed vegetable matter. (2) Partially decomposed plants and other organic material that build up in poorly drained wetland habitats. Pebble Stone 10 to 75 mm in diameter, including coarse gravel and small cobble. Per capita water use The water produced by or introduced into the system of a water supplier divided by the total residential population; normally expressed in gallons per capita per day (gpcd). Percent open area The net area of a fabric that is not occupied by fabric filaments, normally determinable only for geotextiles having distinct visible and measurable openings that continue directly through the fabric (i.e., woven fabric). See geotextile. Perched floodplain A terrace. A floodplain surface that, because the streambed has degraded, becomes high enough above the channel that it is no longer inundated by the current hydrologic regime. Perched groundwater, perched water (1) Unconfined groundwater separated from an underlying main body of groundwater by an unsaturated zone. (2) Groundwater supported by a zone of material of low permeability located above an underlying main body of groundwater with which it is not hydrostatically connected. (3) Ground water located above the level of the water table and separated from it by a zone of impermeable material. Percolation (1) The movement, under hydrostatic pressure, of water through interstices of a rock or soil (except the movement through large openings such as caves). (2) The downward movement of water through the soil or alluvium to a groundwater table. (3) The downward movement of water through the soil horizons. The percolation rate of a soil is usually expressed as inches per hour. Perched stream Either a losing stream or an insulated stream that is separated from the underlying groundwater by a zone of aeration Perennial Term for plants which grown and reproduce for many years; perennial plants are usually woody. Perennial flows Water flows year-round. Perennial stream A natural or artificial watercourse, ranging from a small creek to a major river, that normally flows continuously; a permanent stream; one that flows continuously throughout the year. (2) A channel that

has continuous flow at all times. (3) A stream which exhibits a measurable surface discharge more than 80% of the time. Perennial yields The maximum quantity of water that can be annually withdrawn from a groundwater basin over a long period of time (during which water supply conditions approximate average conditions) without developing an overdraft condition. Sometimes referred to as sustained yield. Periphyton (1) Microorganisms that coat rocks, plants, and other surfaces on lake bottoms. (2) A broad organismal assemblage composed of attached algae, bacteria, their secretions, associated detritus, and various species of microinvertebrates. Permeability (1) The capacity of a rock for transmitting a fluid; a measure of the relative ease with which a porous medium can transmit a liquid. (2) The capability of soil or other geologic formations to transmit water. (3) The ease with which water can move or pass through a structure ((e.g., a dike) or material (e.g., soils, filters) under a hydraulic gradient. Used interchangeably with hydraulic conductivity. Permit Written authorization from a regulated agency authorizing work in waters of the United States . Some activities requiring a permit (not an all-inclusive list) include: diversion of water, construction of a bank protection project, a dock, bridge, dam, culvert, or irrigation project; mining; dredging; replacement or maintenance of existing structures; debris removal; channel widening, relocation, filling, excavation, or reshaping. More than one permit might have to be obtained for a single activity. The public and several agencies might review or comment on a single permit. There are over 50 nationwide permits. For example, a nationwide "Section 13" permit can usually be issued for construction of bank stabilization works if the project is less than 500 ft long, and there is less than 1 cu. yd. of fill material introduced into the stream per linear ft of stream length. An individual permit is issued for projects not meeting nationwide guidelines. Permittivity An alternative expression for flow rate of water through a geotextile. Pervious Allowing fluid passage through interconnected openings or interstices, e.g. ease of water flow through a sandy soil or aggregate filter. pH (1) A measure of the acidity (less than 7) or alkalinity (greater than 7) of a solution; a pH of 7 is considered neutral. pH values between 7.0 and 8.0 are optimal for supporting a diverse aquatic ecosystem; pH between 6.5 and 8.5 is generally suitable. (2) The negative logarithm of the molar concentration of the hydrogen ion, or, more simply, acidity. Phosphorus A nutrient essential for growth that can play a key role in stimulating aquatic growth in lakes and streams. Photo degradable The ability of a material to break down due to exposure to ultraviolet light. Phreatic line The upper boundary of the seepage water surface landward of a streambank. Phreatophyte

(1) Plants growing on or near the stream bank with their roots in the ground water and decreasing streamflow by transpiration during their growing season; (2) A plant capable of maintaining a high rate of transpiration by virtue of a taproot that extends to the water table. Physical model A scale model that uses the physical properties and behavior of modeling materials to represent the prototype. See movable-bed physical model and fixed-bed physical model. Physiography A description of the surface features of the Earth, with an emphasis on the origin of landforms. Physiographic region A geographic area whose patterns of landform differ significantly from that of adjacent regions. Phytoplankton (1) See Plankton (2) Minute plants, usually algae, that live suspended in bodies of water and that drift about because they cannot move by themselves or because they are too small or too weak to swim effectively against a current. Piedmont Lying or formed at the base of a mountain or mountain range. In the United States the Piedmont (noun) is a low plateau extending from New Jersey to Alabama and lying east of the Appalachian Mountains. Piezometer An instrument used to measure hydraulic head or water pressure above a point in the ground. May consist of a simple standpipe which measures head directly or a pneumatic device which uses air back pressure. Pile An elongated member, installed vertically, usually made of timber, concrete, or steel, that serves as a structural component of a river-training structure. Pile dike A permeable dike usually constructed of timber, steel, or pre-cast concrete pilings designed to trap sediment within the dike field in order to protect the bank or improve the navigation channel. See dike. Pioneer species or plant Early successional stage plant species that are the first species to colonize a disturbed site; herbaceous annual and seedling perennial plants that colonize bare areas as a first stage in secondary succession. Pioneer vegetation (1) The first several species of plants to become established in a disturbed area that has been stabilized. Sometimes called volunteer vegetation. (2) early or young stage of a naturally developed or artificially started vegetation. Piping (1) Erosion by percolating water in a layer of subsoil, resulting in caving and in the formation of narrow conduits, tunnels, or “pipes” through which soluble or granular soil material is removed. (2) Flow of groundwater through subsurface conduits in the bank. (3) The entrainment and movement of soil particles by subsurface flow (seepage) through a soil, leading to the development of voids, tunnels, or pipe-like cavities within a soil bank. Planform

(1) The contour of the stream, as viewed from above. (2) The pattern formed by a waterway as viewed from above. The primary types of planform are meandering, braided, and straight. Planning The selection and prearrangement of events for the attainment of an objective. Plan view Viewing an object or stream from above, i.e. a birds eye view. Plankton Floating or weakly swimming organisms at the mercy of the waves and currents. Animals of the group are called zooplankton and the plants are called phytoplankton. Plasticity The property of a material that enables it to undergo permanent deformation (putty like) without appreciable volume change or elastic rebound, and without rupture. Playa A dry, flat area at the lowest part of an undrained desert basin in which water accumulates and is quick evaporated; underlain by stratified clay, silt, or sand and commonly by soluble salts; term used in the Southwestern United States. Playa lake A shallow, temporary lake in an arid or semiarid region, covering or occupying a playa in the wet season but drying up in summer; temporary lake that upon evaporation leaves or forms a playa. Plunge pool A pool created by water passing over or through a complete or nearly complete channel obstruction, and dropping vertically, scouring out a basin in which the flow radiates from the part of water entry; also called Falls pool or Plunge basin. Pocket Water (1) A series of small pools surrounded by swiftly flowing water, usually caused by eddies behind boulders, rubble, or logs, or by potholes in the streambed. (2) Similar to “runs”, however, the flow is blocked by numerous partial obstructions, usually boulders, and is fairly turbulent. Pocosin A local term along the Atlantic coastal plain, from Virginia south, for a shrub-scrub wetland located on a relatively flat terrain, commonly between streams. Point bar (1) The convex side of a meander bend (inside of a stream bend) that is built up due to suspended and bed load sediment deposition; can cause some obstruction of flow. (2) Usually the side opposite the concave bank. The point bar is an important pattern. The point bar is the depositional feature that facilitates the movement of bedload from one meander to the next. The point bar extends at the loss of the near bank region. (3) Sediments laid down on the inside (convex side) of a meander bend. Compare to alternate bar and middle bar. Point count method Count of contacts recorded by an observer from a fixed observation point and over a specified time interval: fixed distance (radius) point count is limited to individuals within a single fixed distance; variable distance (radius) point count is limited to individuals within distances varying according to species- characteristic detection distances (synonymous with variable circular plot); and unlimited distance point

count includes all individuals without limits, that is, all detections recorded regardless of distance. Synonymous with Station count method. Point of concentration That point at which the water flowing from a given drainage area concentrates. With reference to a highway, this would generally be either a culvert entrance or some point in a roadway drainage system. Point source (1) Originating at any discrete source. (2) A stationary or clearly identifiable source of a large individual water or air pollution emission, generally of an industrial nature. (3) Any discernible, confined, or discrete conveyance from which pollutants are or may be discharged, including (but not limited to) pipes, ditches, channels, tunnels, conduits, wells, containers, rolling stock, concentrated animal feeding operations, or vessels. Point source is also legally and more precisely defined in federal regulations. Contrast with nonpoint source (NPS) pollution. Point source contaminant (1) Any substance (pollutant) that degrades water quality and originates from discrete locations such as discharge pipes, drainage ditches, wells, concentrated livestock operations, channels, sewers, tunnels, containers, and floating craft. (2) A stationary or clearly identifiable source of an individual water or air pollution emission, generally of an industrial nature. Point source (PS) pollution Pollutants discharged from any identifiable point, including pipes, ditches, channels, sewers, tunnels, and containers of various types. See non-point source (NPS) pollution. (2) Pollution discharged into a water body at a single distinct location, such as an industrial discharge or a sewer pipe. Point transect A transect along which the point count method is used. No recordings are made between stations (as opposed to strip transects with continuous recordings). Poised stream A term used by river engineers applying to a stream that over a period of time is neither degrading or aggrading its channel, and is nearly in equilibrium as to sediment transport and supply. Pollutant (1) Any substance that, when present in a hydrologic system at sufficient concentration, degrades water quality in ways that are or could become harmful to human and/or ecological health or that impair the use of water for recreation, agriculture, industry, commerce, or domestic purposes. (2) Something that pollutes, especially a waste material that contaminates air, soil, or water. (3) Any solute or cause of change in physical, chemical, or biological properties that renders water unfit for a given use. Pollution A condition caused by the presence of substances of such character and in such quantities that the quality of the environment is impaired. Water pollution is generally divided into point source and non-point source. See point source pollution and non-point source pollution. Pollution (of water) The alteration of the physical, chemical, or biological properties of water by the introduction of any substance into water that adversely affects any beneficial use of water. Polymer

A macromolecular material formed by the chemical combination of monomers. Plastics, rubbers, and textile fibers are all high molecular weight polymers . Synthetic polymers are used to make geosynthetic s products such as geomembranes and geogrids. Polyvinylchloride (PVC) A synthetic thermoplastic polymer prepared from vinyl chloride. In erosion control applications PVC can be compounded into rigid forms used in pipe manufacture and coatings for the wire in gabion baskets, or into flexible forms used in the manufacture of geotextiles. Pond A body of water smaller than a lake, often artificially formed. Ponding See backwater effects. Pool (1) A reach of stream that is characterized by deep, low-velocity water and a smooth surface; frequently used by fish for resting and cover. (2) A portion of the stream with reduced current velocity (during base flow), with water deeper than the adjacent areas. (3) A relatively deep section of a stream or river marked by slower velocities and finer bed materials. Pool/riffle ratio The ratio of surface area or length of pools to the surface area or length of riffles in a given stream reach; frequently expressed as the relative percentage of each category. Used to describe fish habitat rearing quality. Pool tailout The downstream end of a pool where the bed surface gradually rises and the water depth decreases. The tailout of a pool may vary in length and usually occurs immediately upstream of a riffle. Poorly graded Same as well sorted. See grading. Poorly sorted Same as well graded. See sorting. Population A collection of individuals of one species or mixed species making up the residents of a prescribed area. Porosity (1) The ratio of the volume of voids in a rock or soil to the total volume. (2) The percentage by volume of voids of a given material with respect to the total volume of the material. Porous pavement A permeable surface material which provides support for traffic without deformation and allows for stormwater and surface runoff to gradually infiltrate into the subbase or subsoil. Porous weir A low-profile structure consisting of loosely consolidated boulders that span the width of the channel. Potable water Water suitable for human consumption. Potential evapotranspiration

The amount of moisture which, if available, would be removed from a given land area by evapotranspiration; expressed in units of water depth. Potentiometric surface An imaginary surface that represents the total head in an aquifer. It represents the height above a datum plane at which the water level stands in tightly cased wells that penetrate the aquifer. Practicable Capable of being done within reasonable natural, social, and economic constraints. Prairie pothole A shallow depression, generally containing wetlands, occurring in an outwash plain, a recessional moraine, or a till plain; usually the result of melted blocks of covered glacial ice; occur most commonly in the North-Central United States and in States west of the Great Lakes from Wisconsin to eastern Montana. Precipitation (1) Any or all forms of water particles that fall from the atmosphere, such as rain, snow, hail, and sleet, measured in depth of fall or in terms of intensity of fall in unit time. (2) The process by which water in a liquid or solid state (rain, sleet, snow) is discharged out of the atmosphere onto a land or water surface. (3) The act or process of producing a solid phase within a liquid medium. Present time Encompassing a period of current time spanning from one to ten years. Primary producers Organisms capable of producing their own food, e.g., algae. Primary succession The sequence of communities developing in a newly exposed site devoid of life. Prior converted wetland Wetlands that before 23 Dec 1985, were drained, dredged, filled, leveled, or otherwise manipulated for the purpose, or to have the effect of, making the production of an agricultural commodity possible. Pristine The earliest condition of the quality of a water body; unaffected by human activities. Probability The chance of occurrence or recurrence of a specified event within a unit of time, commonly expressed in 3 ways. Thus a 10-year flood has a chance of 0.1 per year and is also called a 10%-chance flood. Probability of exceedence (1) The statistical probability, expressed as a percentage, of a hydrologic event occurring or being exceeded in any given year. The probability (p) of a storm or flood is the reciprocal of the average recurrence interval (N). (2) The probability that a random flood will exceed a specified magnitude in a given period of time. Probable maximum flood The flood discharge that may be expected from the most severe combination of critical meteorological and hydrological conditions reasonably possible in the region. Profile

A depiction of certain characteristics, usually depth, bed configuration, substrate, and velocity, of the cross section of a stream. Profile view A cross-sectional depiction of certain characteristics; with streams, these usually include depth, bed configuration, substrate and velocity. Project life The period of time a project is designed to function as originally planned. Proposed species Any species of fish, wildlife, or plant that is proposed in the Federal Register to be listed as endangered or threatened under the guidelines of the Endangered Species Act of 1973. Prototype The full-sized structure, system process, or phenomenon. Usually used in connection with modeling; the actual situation as opposed to the model. Public supply withdrawals Water withdrawn by public and private water suppliers for use within a general community. Water is used for a variety of purposes such as domestic, commercial, industrial, and public water use. Pulsed monitoring When an existing project or reach of stream is monitored on a long-term schedule with varying levels of effort. As an example a project could be photographed and analyzed at six month intervals but comprehensively surveyed only once every several years. Pumped storage project A hydroelectric power plant and reservoir system in which water released for generating energy during peak load periods is stored and pumped back into the upper reservoir, usually during periods of reduced power demand. Q Quality assurance Evaluation of quality-control data to allow quantitative determination of the quality of chemical data collected during a study. Techniques used to collect, process, and analyze water samples are evaluated. Quarry-run stone Natural material used for streambank protection as received from a quarry without regard to gradation requirements with only an upper size limit specified. Also termed "shot rock". Quiescent zone A calm zone of water in a stream; opposite of turbulent. R Radial drainage Arrangement of stream courses in which streams radiate outward in all directions from a central zone. Typical drainage pattern in volcanic and some mountainous areas. Radius (of a circle) The distance from the center to any point on the circumference of a circle. Radius of curvature

The radius of a circle defining the curvature of an individual bend measured between adjacent inflection points. Rapid drawdown Lowering the elevation of water against a streambank more quickly than the bank can drain, which can leave the bank in a saturated condition with positive pore pressure that may cause bank return flows (see piping) and/or bank failure. Rain shadow A dry region on the lee side of a topographic obstacle, usually a mountain range, where rainfall is noticeably less than on the windward side. Rainfall Point precipitation: that which registers at a single gauge. Area Precipitation: Adjusted point rainfall for area size. Rainwash The creep of soil lubricated by rain. Ramaderos In South Texas, riparian strips of dense brush that provide important habitat for various wildlife species as well as access routes to riparian brush along the Rio Grande. Rapids (1) Those parts of large streams and rivers which are relatively swift and shallow with a bed of boulders. Analogous to riffles of a smaller stream. (2) A reach of stream that is characterized by small falls and turbulent, high-velocity water. Ravine A small stream channel, narrow, steep-sided, and commonly V-shaped in cross-section, larger than a gully. Also called a gulch. Reach (1) A section of stream between two defined points [Fischenich]; (2) the length of a channel uniform with respect to discharge, depth area, and slope; (3) more generally, any length of a river or drainage course. [(2) and (3) RiverWorks 2004; (4a) Any specified length of stream. (4b) A relatively homogeneous section of a stream having a repetitious sequence of physical characteristics and habitat features. (4c) A regime of hydraulic units whose overall profile is different from another reach. [4a-c from Fischer and Selected Terms Commonly Used in Stream Geomorphology glossary]; (5) (a) A selected portion of a channel's length between any defined limits. (5b) A relatively long, straight section of river (river pilot term). [(5a and b) from E-SenSS] Reaeration The replenishment of oxygen in water from which oxygen has been removed. Real-time data As defined by the U.S. Geological Survey, data collected by automated instrumentation and telemetered and analyzed quickly enough to influence a decision that affects the monitored stream. Rearing The process by which young fish spend up to two years (depending upon the species) in small streams, back channels and lakes where they feed and grow. Juvenile salmon may rear in different streams than they were born in, including intermittent or seasonally wetted watercourses.

Rearing habitat Areas in rivers or streams where juvenile fish find food and shelter to live and grow. Rearing pond An artificial impoundment in which juvenile fish are raised prior to release into the natural habitat. Receiving waters All distinct bodies of water that receive runoff such as streams, rivers, ponds, lakes, and estuaries. Also, all navigable surface waters and, in certain instances, groundwater, if there is a direct connection; waters of a watercourse or water body that receive waters from overland flow or other watercourses. Recharge (1) Water that is added to the groundwater reservoir, for instance, that part of infiltration which reaches the groundwater table. (2) The process involved in the absorption and addition of water to the zone of saturation; also, the amount of water added. Recharge area An area within which water infiltrates the ground and reaches the zone of saturation. Recharge basin A surface facility, often a large pond, used to increase the percolation of surface water into a groundwater basin. Reclamation (1) The process of restoring and revegetating a disturbed site to, or near to, its previous habitat quality. (2) (rarely now) The conversion of wetland, desert, or other "non-productive" land to a form suitable for agriculture or human settlement. Recreational rivers Rivers or sections of rivers that are readily accessible by road or railroad, that may have some development along their shoreline, and that may have undergone some impoundment or diversion in the past. Recreation-day Participation in a recreational activity, such as skiing, biking, hiking, fishing, boating, and/or camping, for any part of a day by one person. Recurrence interval (1) The average interval of time within which the magnitude of a given event, such as a storm or flood, will be equaled or exceeded once. (2) Interchangeably used with “return period”; a statistic based on frequency analysis derived from annual or partial duration peak flow series that describes the average interval (in years) between events equaling or exceeding a given magnitude. (3) The average time interval between occurrences of a hydrological event of a given or greater magnitude. It is important to realize that the computation is based on an average over a period of record, so events of a given recurrence interval may, and often do, occur more often than that over the short term. It is not a forecast. Recycled water Urban wastewater that becomes suitable, as a result of treatment, for a specific direct beneficial use. See also water recycling. Redd A nest in a stream, excavated by spawning fish, where they deposit their eggs. Excavation is accomplished by whipping their tails back and forth in the gravel.

Redirective Bank Protection Methods Any of a number of bank protection techniques designed to vector energy away from the eroding bank and toward an area where the energy will not cause adverse effects. Some examples include bendway weirs, rock vanes, J-Hooks, and upstream and downstream kickers or deflectors. See indirect bank protection. Reference conditions Expectations on the state of aquatic biological communities in the absence of human disturbance and pollution. Reference site (1) A sampling site selected for its relatively undisturbed conditions. (2) Real sites that are used for characterizing reference conditions. These sites should be minimally impaired by human disturbance and pollution. Reference site (stream geomorphology context) The reference site is the stable morphological stream type in the system. This type may – or may not be – in a pristine state. The majority of time it is not pristine; however, the important geomorphologic, and most likely vegetative components, are there to sustain a long-term stable stream type. The reference site would fall within the range of natural variability for geomorphic type and bedload transport. Reforestation The natural or artificial restocking of an area with forest trees. Refugia An area protected from disturbance where fish or other animals can find shelter from bad weather, sudden flow surges or other short-duration disturbances. Refusal (1) Erosion resistant material placed in a trench (excavated landward) at the stream end of a revetment to prevent flanking. Sometimes used interchangeably with "key". (2) The point at which a piling, sheet pile, or other object cannot be driven any deeper into the ground. Regime theory (1) A theory of channel formation that applies to streams that make a part of their boundaries from their transported sediment load and a portion of their transported sediment load from their boundaries. Channels are considered in regime or equilibrium when bank erosion and bank formation are equal. (2) The application of the idea that the width, depth, slope, and planform of a river are adjusted to a channel- forming discharge. See dominant discharge. [E-SenSS]; (3) A self-formed alluvial channel is in regime if there are no net changes in discharge capacity or morphology over a period of years. The concept was originally developed by engineers designing canals to convey a steady discharge with neither erosion nor siltation in India and Pakistan [Watson et al. 1999]. Regression (as in channel-regression equations) Equations that define the mathematical relationship among channel attributes and other variables. Regulated river or stream A section of stream or river where the stage and duration of flow are at least partially changed or affected by upstream dams, reservoirs, or grade control structures. The upstream structures must have at least some retention capacity and/or the ability to control flow releases. This typically results in lower peak flows and higher minimal flows, both of longer duration than what occurred naturally prior to regulation. Rehabilitation

Partial restoration of a structure or a river or stream to as near its original condition and function as functional. See restoration.

Reinforced-earth bulkhead (1) Strengthening of a soil fill by utilizing tensile inclusions, such as metal strips, woody fibers, wire mesh or fabric. (2) A retaining structure consisting of vertical panels and attached to reinforcing elements embedded in compacted backfill for supporting a natural or artificial streambank (a specific type of retaining wall). Reinforcement (1) To strengthen by the addition of materials or support; e.g., the strengthening of a soil by the contributions of the geosynthetic inclusions. (2) The addition of structural components to a stabilization structure in order to strengthen it. (3) The introduction of living plants whereby the plant roots act as tensile inclusions that increase soil shear strength and assist in holding the soil matrix together. Relative abundance The number of organisms of a particular kind present in a sample relative to the total number of organisms in the sample. Relative time Dating of events by place in chronological order of occurrence rather than in years. Replacement planting Planting to replace planting (installed by others) that is damaged or removed during highway construction activity, including irrigation modification and/or replacement. Reservoir An impounded body of water or controlled lake where water is collected and stored. Reservoir capacity The storage capacity available in a reservoir for all purposes, from the streambed to the normal maximum operating level. Includes dead (or inactive) storage, but usually excludes surcharge (water temporarily stored above the elevation of the top of the spillway). Resistances to flow Internal Distortion Resistance: The resistance to streamflow caused by turbulence and secondary circulations. Bars, bends, boulders, undulations of the bed, protuberances and sheerflow energy affect this measure of resistance. Skin Resistance: Resistance to flow due to roughness of the stream bed and banks. Also depends on the discharge. Spill Resistance: Caused when water impacts an obstruction and causes an abrupt reduction in velocity. Redd An area of streambed dug out by a female trout before spawning and in which she buries her eggs after spawning. Reference site Sites that can be used for characterizing conditions that match expectations on the state of aquatic biological communities in the absence of human disturbance and pollution.

Residential water use See Domestic withdrawals. Restoration (1) The return of an ecosystem to a close approximation of its condition prior to disturbance. (2) Return of a stream, river, waterway corridor, or ecosystem to as close an approximation of its original condition and functions prior to disturbance. In many instances, true restoration is not possible due to extreme changes in basin hydrology and topography. Retaining wall (1) A structure used to resist unbalance lateral earth forces, retain earthen masses, and protect against scour and undermining. (2) A vertical structure used to maintain an elevation differential between the water surface and top bank while at the same time preventing bank erosion and instability. Retard Structure placed parallel to a streambank to prevent erosive currents from attacking the bank. See indirect bank protection. Return flow (1) That part of irrigation water that is not consumed by evapotranspiration and that returns to its source or another body of water. (2) The portion of withdrawn water not consumed by evapotranspiration or system losses that returns to its source or to another body of water. Return period See recurrence interval. Reuse The additional use of previously used water. Revegetation (1) The process of reestablishing vegetation cover on any disturbed or newly formed site. (2) Planting of indigenous plants to replace natural vegetation that is damaged or removed as a result of highway construction projects or permit requirements. This work may include provisions for irrigation. Revegetative Techniques The use of various vegetative establishment methods to repair or restore vegetative cover to a slope (or streambank) that is unstable and/or undergoing accelerated erosion. Used in conjunction with "landform" grading to produce a vegetated, topographic surface that mimics stable, natural slopes. Also used in conjunction with more "robust" vegetative establishment aids and/or slope armor, e.g., TRMs, GCSs, ACBs etc. Most soil bioengineering methods that employ live cuttings, e.g., live fascines, brushlayers, brush mattresses, etc., would also fall into this category. Distinct from Vegetative Techniques. Revetment (1) A force-abating structure commonly used in bank stabilization–constructed from a variety of hard materials and placed horizontal to the bank on the “toe” of a normal discharge beads; a sloped facing built to protect existing land or newly created embankments against erosion by wave action, currents, or weather. Revetments are usually placed parallel to the natural shoreline. (2) Cover of erosion-resistant material placed to protect the bank of a stream, river, or channel. Revised Universal Soil Loss Equation (RUSLE) An updated, computerized method of estimating soil losses due to rainfall erosion. RUSLE incorporates the updated climate, soil erodibility, and vegetative cover factors of the Universal Soil Loss Equation. Rhizobium

The nitrogen fixing bacteria capable of living in symbiotic relationship with leguminous plants in nodules on the roots. Rhizome Stem growth which creeps beneath the soil surface; rooting at nodes to form new individuals; found in many grasses and herbs. Riffle (1) A region of the stream characterized by partially or completely submerged coarser bed materials and shallower faster-moving water. Riffle areas tend to support higher densities of benthic invertebrates (important for fish). (2) A reach of stream that is characterized by shallow, fast-moving water broken by the presence of rocks and boulders. (3) A shallow, rapid section of stream where the water surface is broken into waves by obstructions that are wholly or partly submerged. (4) A shallow section of a stream where the stream flows at relatively greater velocities over coarse bed material or bedrock, resulting in a rapids of comparatively little fall. Rift A shallow or rocky place in a stream, forming either a ford or a rapid. Right bank or right descending bank When looking in a downstream direction, the streambank to the right. See bank. Right-of-way Legal permission from a landowner that allows a person or agency personnel ingress and egress to a project site to perform site reconnaissance, construction, monitoring, and maintenance activities. Rill Shallow downslope erosion feature normally les than 0.3m wide and 0.6m deep. Rill erosion (1) Removal of soil particles from a bank slope by surface runoff moving through relatively small channels. (2) Land erosion forming small, well-defined incisions in the land surface that are less than 1 ft (30 centimeters) in depth. Riparian (1) Pertaining to or situated on the bank of a natural body of flowing water. (2) Located on the banks of a stream or other body of water. (3) Relating to or living on or near the bank of a watercourse. These zones range in width from narrow bands in desert or mountainous areas to wide bands which occur in low gradient valleys and more humid regions. (4) Pertaining to anything connected with, adjacent to, or influenced by a stream, river, lake, reservoir, or other water body. Riparian area, zone (1) An area of land and vegetation adjacent to a stream that has a direct effect on the stream. This includes woodlands, vegetation, and floodplains. (2) The land surrounding a stream, river, or other body of water that is, at least periodically, influenced by flooding. This undisturbed corridor of trees and shrubs growing parallel to a stream provides several benefits, including: preventing overuse of the top bank area by man, animals, and machinery; naturally filtering pesticides, nutrients and other chemicals; retarding rainfall runoff; providing habitat, food, shelter, and vegetative cover for wildlife; and providing a root system which binds soil particles together helping to prevent streambank and overbank erosion. Sometimes called "riparian buffer zone" or "greenbelt". (3) Term denoting an ecosystem situated between aquatic and upland environments that is at least periodically influenced by flooding and is distinctly different from the surrounding lands because of unique soil and/or vegetational characteristics

that are strongly influenced by free or unbound water in the soil. The riparian area includes wetlands and those portions of floodplains and valley bottoms that support riparian vegetation. Riparian corridor A continuous, unbroken riparian zone conducive to the movement of fauna between two or more riparian areas Riparian habitat The aquatic and terrestrial habitat adjacent to streams, lakes, estuaries, or other waterways. Riparian vegetation The plants that grow adjacent to a wetland area such as a river, stream, reservoir, pond, spring, marsh, bog, meadow, etc., and that rely upon the hydrology of the associated water body.

Ripple (1) A specific undulated bed form found in sand bed streams. (2) Undulations or waves on the surface of flowing water. (3) Small, roughly triangular, bed forms that are similar to dunes but have much smaller heights and lengths of 0.3 m or less. Ripples develop when the Froude number is less than approximately 0.3. See dunes. Riprap (1) A layer, facing, or protective mound of broken concrete, sacked concrete, rock, rubble, or stones randomly placed to prevent erosion, scour, or sloughing of a structure or embankment; also, the stone used for this purpose. (2) Rock or other material with a specific mixture of sizes referred to as a “gradation,” used to stabilize streambanks or riverbanks from erosion or to create habitat features in a stream. See stone riprap. Riser pipe A vertical outlet pipe used to control the discharge rate from a pond or basin. Rithron zone Stream reach at higher elevations characterized by rapid flow, low temperature and high dissolved oxygen levels. River A large stream, usually active when any streams are flowing in the region. River basin A major water source region. The United States has been divided in 20 river basin areas. River channels Large natural or artificial open streams that continuously or periodically contain moving water, or which form a connection between two bodies of water. River miles Generally, miles from the mouth of a river to a specific destination or, for upstream tributaries, from the confluence with the main river to a specific destination. River reach Any defined length of a river. River stage The elevation of the water surface at a specified station above some arbitrary zero datum (level).

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River training structure Any configuration constructed in a stream, or placed on, adjacent to, or in the vicinity of a streambank that is intended to deflect currents, induce sediment deposition, induce scour, or in some other way alter the flow and sediment regimes of the river or stream. River training works Structures placed in a stream to direct the current in a predetermined channel. River wash A miscellaneous area of unstabilized sandy, silty, clayey, or gravelly sediment that is flooded and washed and reworked frequently by rivers. Riverine (1) Of flowing waters; refers to the channels, vegetated shallows, and bank associated with rivers, streams, and flowages. (2) Relating to, formed by, or resembling a river including tributaries, streams, brooks, etc. (3) The area along or near the banks of a river or stream which was produced by the waterway and is still influenced by it. Riverine habitat The aquatic habitat within streams and rivers. Riverine wetland (1) Wetlands within river and stream channels; ocean-derived salinity is less than 0.5 part per thousand; (2) Wetland system that includes all wetlands and deepwater habitats within a channel. Riverward In a direction towards a river. Riverworks Engineering works involving construction of or repairs to banks of streams, rivers, canals and edges of ponds, shorelines of lakes and sheltered portions of estuaries. Rock (1) Any naturally formed, consolidated or unconsolidated material (but not soil) consisting of two or more minerals. (2) Cobble, boulder or quarry stone as a construction material; hard natural mineral, in formation as in piles of talus. (3) Strictly, any naturally formed aggregate or mass of mineral material, whether or not coherent, constituting an essential and appreciable part of the earth's crust. Sometimes used interchangeably with "stone". Rock-and-wire mattress A flat or cylindrical wire cage or basket filled with stone or other suitable material placed on a streambank as protection against erosion. Rock check structures See check dam. Rock toe A structure composed of rock materials, installed at the base of a bank slope to protect the base of the bank from the erosive forces of stream flow. Rock vanes Rock vanes are discontinuous, redirective structures angled upstream 20 to 30 degrees. Generally, two or three vanes are constructed along the outer bank of a bend in order to redirect flows near the bank to the center of the channel. Typically, vanes project 1/3 of the stream width. The riverward tips are at

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channel grade, and the crests slope upward to reach bankfull stage elevation at the key. Rock vanes can preclude the need for rock armor and increase vegetative techniques as the high flows are redirected away from the bank. Vanes can increase cover, backwater area, edge or shoreline length, and the diversity of depth, velocity and substrate. Variations include Cross Vanes and Rock Vanes with J-hooks. Rolled Erosion Control Product (RECP) A general term applied to manufactured materials, which may be synthetic or organic, fabricated into a mat or blanket, designed to be placed over a prepared surface and fastened to the soil in order to stabilize the soil until vegetation is established. Usually furnished in rolls, thus sometimes called "rolled goods". There are four categories of RECP: erosion control netting (ECN), open weave textile (OWT), erosion control blanket (ECB), and turf reinforcement Mat (TRM). See separate listings for each. Rolling drainage dip An inverted water bar. Rookery The breeding place of a colony of gregarious birds; generally used in reference to colonial water birds.

Root When used in context with "dike", that portion of the dike that is excavated into the streambank. See key. When used in context with plant, the underground part of the plant that serves as support, draws water and nutrients from the surrounding soil, and stores food. Root cutting Root piece which through sprouting shoots vegetatively increases. Root hairs Fine structures at tips of young roots, through which water and mineral salts are absorbed from soil. Root pads Large clumps of shrubbery planted, where practical, to assist with erosion control in splash, bank, and terrace zones of the bank. Root-shoot ratio The ratio of root growth to the branches and other aerial parts of a plant. Rootwad The mass of roots associated with a tree adjacent to or in a stream that provides refuge for fish and other aquatic life. (2) Root wad – The root mass of a tree. Root zone The portion of a soil profile in which plant roots occur (Environmental Laboratory 1987). Rooted Expression indicating that a bank has been excavated and the end structure (check dam, dike, etc.) Has been placed in the cavity, thus retarding future streamflow around the end of the structure (flanking). Rotational slip or rotational failure A deep seated soil failure along a well-defined curved shear surface that results in back-tilting of the failed mass toward the bank. Roughness

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A measure of the irregularity of streambed materials as they contribute to resistance to flow. Commonly measured in terms of Manning's Roughness Coefficient. Roughness element Large obstacles in a channel that deflect flow and affect a local increase in shear stress that causes scour and deposition. Roughness trees Trees anchored to a channel margin or within the floodplain to increase roughness, or the resistance to flow. Their function is to slow stream flow. Rubble (1) Stones larger than gravel, but smaller than boulders. Rough, irregular fragments of random size placed on a streambank to retard erosion; the fragments may consist of broken concrete slabs, masonry, or other suitable refuse. (2) Rough, irregular fragments of random size placed on a streambank to retard erosion. The fragments may consist of broken concrete slabs, masonry, or other suitable refuse. Run (in stream or river) (1) A reach of stream characterized by fast-flowing, low-turbulence water. (2) Deep areas in a stream where water flows fast with little or no turbulence. Runoff Surface Runoff or Overland Flow: Runoff water flowing over the land surface. Subsurface Runoff: Runoff water flowing beneath the land surface. (1) Overland flow that is discharged from an interfluve area to a stream channel. (2) The surface waters that exceed the soil’s infiltration rate and depression storage; (3) The portion of precipitation that appears as flow in streams; drainage or flood discharge which leaves an area as surface flow or a pipeline flow, having reached a channel or pipeline by either surface or subsurface routes. (4) Water that flows over the ground and reaches a stream as a result of rainfall or snowmelt. (5) Water from precipitation flowing above or below ground to a stream or surface water body without entering the groundwater table. Rural withdrawals Water used in suburban or farm areas for domestic and livestock needs. The water generally is self- supplied and includes domestic use, drinking water for livestock, and other uses such as dairy sanitation, evaporation from stock-watering ponds, and cleaning and waste disposal. S Sack revetment Streambank protection consisting of sacks (e.g. burlap, paper, or nylon) filled with mortar, concrete, sand, stone, or other available material placed on a bank to serve as protection against erosion. Saline water Water that is considered unsuitable for human consumption or for irrigation because of its high content of dissolved solids; generally expressed as milligrams per liter (mg/L) of dissolved solids; seawater is generally considered to contain more than 35,000 mg/L of dissolved solids. Slightly saline: 1,000-3,000 mg/L; Moderately saline: 3,000-10,000 mg/L; Very saline: 10,000-35,000 mg/L; Brine: More than 35,000 mg/L. Salinity The concentration of mineral salts dissolved in water. Salinity may be measured by weight (total dissolved solids), electrical conductivity, or osmotic pressure. Where seawater is known to be the major source of salt, salinity is often used to refer to the concentration of chlorides in the water.

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Salinity intrusion The movement of salt water into a body of fresh water. It can occur in either surface water or groundwater bodies. Salmonid A fish of the family Salmonidae, including trout, char, salmon, grayling, and whitefish. Salt marsh Saltwater wetlands that occur along many coasts. Saltation Mechanism by which a particle moves by jumping from one point to another along a streambed due to flow. Saltwater barrier A physical facility or method of operation designed to prevent the intrusion of salt water into a body of fresh water. Sand (1) Small substrate particles, generally from 0.06 to 2 mm in diameter. Sand is larger than silt and smaller than gravel. [Fischenich]. (2) Mineral particles that can pass the No. 4 (4.76 mm) U. S. Standard Sieve and be retained on the No. 200 (0.075 mm) sieve. (3) A loose, granular material that results from the weathering and disintegration of rocks, consisting of particles smaller than gravel and larger than silt. (4) A soil containing 85 percent or more of sand and 10 percent or less of clay size material respectively. [(2- 4 E-SenSS]; (5) Granular sand coarser than silt and finer than gravel, ranging in diameter from 0.05 to 5 mm [2004 RiverWorks].

Sandbar A depositional area composed primarily of sand, within the channel of a river, either attached to the bank or in midstream. See also bar. Sapping The disintegration and entrainment of a section of bank due to piping and seepage flow. Sapling Strong, young tree plant, the stem of which has normal branch development from the bottom up. Saturated zone A subsurface zone in which all the interstices or voids are filled with water under pressure greater than that of the atmosphere. See also Water table. Saturation The point at which all the voids (interstices) between soil particles are filled with water. Scale of particle sizes See sediment grade scale. Scalp To remove a layer of sand and gravel from a gravel bar. Scarify

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(1) To loosen or till the ground surface in preparation for seeding or other operations. (2) To abrade the coating of a seed to improve germination. Scarp (1) A steep descent. (2) An escarpment, cliff, or steep slope of some extent along the margin of a plateau, mesa, terrace, bench, or overbank of a stream. Scattered debris Single pieces of debris at irregularly spaced intervals along the channel (Hunter 1991). Scenic rivers Rivers or sections of rivers that are free of impoundments, with shorelines or watersheds still largely primitive, and shorelines largely undeveloped, but accessible in places by roads. Scour (1) The erosive act of flowing (running) water in streams that removes (excavates) and carries away material from the bed and banks; wearing away by abrasive action. Scour may occur in both earth and solid rock material and can be classed as general, contraction, or local scour. (2) Erosion due to flowing water; usually considered as being localized as opposed to general bed degradation. See also bridge scour. Scrub In ecology, an area dominated by shrubs, possibly as a stage in succession to high forest; in forestry, an area of unproductive woodland. Scrub-shrub wetland A wetland class dominated by woody vegetation less than 6 m (20 ft) tall (e.g. alder, tamarack, leucothoe, Atlantic white cedar). Sea level Long-term average position of the sea surface. Sea level varies from place to place and with the time period for which the average is calculated. For the coterminous United States, sea level is most commonly referenced to the National Geodetic Vertical Datum of 1929. Seasonal application efficiency (SAE) The sum of evapotranspiration of applied water (ETAW) and leaching requirement (LR) divided by the total applied water (AW), expressed as a percentage: SAE = (ETAW + LR)/AW. Secchi depth A relatively crude measurement of the turbidity (cloudiness) of surface water. The depth at which a Secchi disc (disk), which is about 10-12 in. in diameter and with a black and white pattern, can no longer be seen. Secchi disc A circular plate, generally about 10-12 in. (25.4-30.5 cm) in diameter, used to measure the transparency or clarity of water by noting the greatest depth at which it can be visually detected. Its primary use is in the study of lakes. Secondary channel See divided flow. Secondary currents Currents flowing in a helical pattern on a path parallel to the main downstream flow direction. See helical flow.

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Secondary maximum contaminant level (SMCL) The maximum level of a contaminant or undesirable constituent in public water systems that, in the judgment of the U.S. Environmental Protection Agency, is required to protect the public welfare. SMCLs are secondary (nonenforceable) drinking water regulations established by the USEPA for contaminants that may adversely affect the odor or appearance of such water. Secondary treatment In sewage, the biological process of reducing suspended, colloidal, and dissolved organic matter in effluent from primary treatment systems. Secondary treatment usually involves the use of trickling filters or the activated sludge process. Second crop The Land Cover/Use cropland category for the second crop of double cropped sites. Secondary Channel Relatively small, sometimes isolated pools in a smaller braid of the main stem and usually associated with gravel bars. See Side Channel. Secondary Succession Progression of communities in habitats where the climax community has been disturbed or removed entirely. Section 404 Permit Permit issued by the Corps of Engineers authorizing activities regulated under authority of Section 404 of the Clean Water Act (33 U.S.C. 1341 et seq.). Most commonly thought of as a permit to place fill in wetlands but also issued for other waters of the United States where the jurisdictional boundary is otherwise defined, usually by the high water mark or mean high water line. Section depth When used in context with a structure, the vertical measurement of stone or other material used in a dike, weir, or key. Sediment (1) Particles derived from rocks or biological materials that have been transported by a fluid; (2) Fragmentary material that originates from weathering of rocks and is transported by, suspended in, or deposited by water. (3) Solid material suspended in or settled from water. (4) It includes chemical and biochemical precipitates and decomposed organic materials such as humus, or alternatively, an assemblage of individual mineral grains that were deposited by some geological agent such as water, wind, ice, or gravity. (5) Soil or mineral material transported by water or wind and deposited in streams or other bodies of water. (6) Any mineral or organic matter of any size in a stream channel. Name Millimeters Inches Boulder > 256 >10 Cobble 64-256 2.5 – 10 Gravel 2 – 64 0.08 – 2.5 Sand 0.062 – 2 Silt 0.004 – 0.062 Clay < 0.004

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Sediment budget The quantification of the incoming and outgoing sediment within the area under study. Usually used in connection with mathematical or numerical modeling. Sediment concentration Concentration of sediment in the stream represented by the ratio of sediment discharge to the water discharge. Usually expressed in terms of milligrams per liter or parts per million (ppm). It is normally assumed that the density of the water-sediment mixture is approximately equivalent to the density of the water. Sediment deposition The accumulation of soil particles on the channel bed and banks. See deposition. Sediment discharge (1) Rate of flow of sediment contained in a stream, expressed as volume or weight per unit time. Sediment discharge includes “suspended load discharge” and “bed load discharge”. Suspended load discharge is the product of streamflow discharge and concentration of suspended sediment. (2) The mass or volume of sediment passing a particular point on a stream during a unit of time. Technically, "sediment discharge rate". (3) Mass of sediment that passes through a cross-section in a stream per unit time. Usually expressed in kilograms per second or tons per day. Sediment grade scale The grouping of sediment particles into size classes based on particle diameters using the American Geophysical Union size classification scale of 1947. Sediment load (1) The amount of sediment transported by a particular watercourse; a function of the flow velocity patterns produced by the hydraulic characteristics of the water body and particle size. The sediment load includes both suspended sediment in the water column and bedload sediment transported by rolling, sliding, or skipping along the water bottom. (2) The mass or volume of sediment being moved by a stream past a given point in a given unit of time. The total of bed load plus suspended load. For practical purposes, interchangeable with sediment discharge. Sediment rating curve Graphical representation of the non-linear relationship between discharge (x-axis) and sediment discharge (y-axis). [Watson et al. 1999] Sediment sample A quantity of water sediment mixture or deposited sediment that is collected to characterize some property or properties of the sediment. Sediment transport The rate of sediment movement through a given reach of stream. Sediment transport (rate) See sediment discharge. Sediment-transport continuity The condition wherein the volume of material transported into and out of a reach of river is roughly equal. Sediment yield

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The total sediment outflow from a drainage basin during a specific period of time. Usually used in context with studies of an entire watershed; sometimes used interchangeably with "sediment discharge" or "sediment load". Sedimentation (1) The combined processes of soil erosion, entrainment, transport, deposition, and consolidation. (2) Deposition of sediment. (3) A broad term that embodies the process of erosion, entrainment, transportation, deposition, and the compaction of sediment. (4) Gravitational deposit of transported material in flowing or standing water. Seed bank The store of dormant seed in the soil. Seep A small area where water percolates slowly to the land surface. Seepage (1) Groundwater emerging on the face of a streambank; flow of water in the pores of soil under influence of gravity or capillary action. (2) The gradual movement of a fluid into, through, or from a porous medium. (3) The slow movement or percolation of water through soil, rock, embankments, or pervious structures. Seepage profile A graph showing discharge at various points along a stream’s course (ideally on one given day). From this can be seen the downstream increase (or decrease) in volume of streamflow. Seepage run The process of measuring discharge at various points to obtain a “seepage profile”. Self-adjusting stone See Launching. Self-launching stone See Launching. Seiche A sudden oscillation of the water in a moderate-size body of water, caused by wind. Separation The function of a geotextile or other product used as a partition between two adjacent dissimilar materials to prevent mixing of the two materials. Seral Stage Refers to various plant communities, one replaced by another, during the process of succession. Sere (1) A series of stages of community change in a particular area leading toward a stable state; (2) The stages that follow one another in an ecologic succession. Sewage The liquid waste from domestic, commercial, and industrial establishments. Shallow A term applied to a shallow place or area in a body of water; a shoal. Shallow mass movement

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Near-surface sliding or movement of earth and/or rock masses usually along planar failure surfaces parallel to the slope face. Shear (1) Force parallel to a surface as opposed to directly on the surface. An example of shear would be the tractive force that removes particles from a streambank as flow moves over the surface of the slope; on the other hand, a floating log that directly strikes the bank would not be shear force. (2) A force acting parallel to a surface as opposed to at some angle to the surface. Shear strength The characteristic of soil and rocks that resists the sliding or shearing of one internal surface against another. Soils and earthen materials fail when shear stress exceeds shear strength along a critical surface. Shear stress (1) Results from the tangential pull of flowing water on the streambed and banks. The energy expended on the wetted boundary of the stream increases proportionally with the energy slope and water depth. (2) A force per unit area that acts tangentially to either an internal surface or external boundary. (3) A measure of the erosive force acting on and parallel to a channel boundary. In a channel, shear stress is created by water flowing parallel to the boundaries of the channel; bank shear is a combined function of the flow magnitude and duration, as well as the shape of the bend and channel cross section. Shear stress force The shear stress or tractive force results from the tangential pull of flowing water on the stream bed and banks, and is expressed in pounds per square foot or n/m². The energy expended on the wetted boundary of the stream increases proportionally with the energy slope and water depth. The transition zone between an area of low and high shear stress is incorrectly called a “shear zone.” Instream structures that tend to increase the difference between such low and high shear stress areas have been called, also incorrectly, “shear structures”. Sheet drain A planar, surface-formed drain that separates the native bank material (or fill) from the surface bank treatment. A sheet drain intercepts and diverts seepage water away from the bank treatment. Sheet erosion (1) The removal by surface runoff of a fairly uniform layer of soil from a bank slope. (2) The more or less uniform removal of soil from an area by raindrop splash and/or overland flow without the development of water channels. Included with sheet erosion, however, are the numerous conspicuous small rills that are caused by minor concentrations of runoff. (3) Erosion of thin layers of soil by sheets of flowing water. Sheet flow (1) Unchanneled flow of water over a sloped surface. Sometimes called sheet wash. (2) Any flow spread out and not confined; i.e., flow across a flat open field.

Shelters, log and brush Logs and brush cuttings placed or staked along eroding banks to provide streambank protection and overhead cover; a variety of brush matting and layering techniques are available. Shoal A relatively shallow place in a stream, lake, or sea. Shoaling

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Deposition of alluvial material resulting in areas with relatively shallow depth. Shotcrete Mortar or concrete conveyed through a hose and pneumatically projected at high velocity onto a surface. Used to stabilize the surface. Can be applied by either a "wet" or "dry" mix method. Shot Rock See quarry run stone. Shrink-swell The volume change of soil associated with changes in moisture content. Soils that shrink when dry and swell when wet can damage plant roots, roads, dams, and building foundations. Shrub Woody growth whose main and side shoots form multiple branches from main stock baseline or form below-ground side shoots or on which, instead of only one stem (main stem), several stems are grown. Shrub land Land covered predominantly with shrubs. Side channel A lateral channel with an axis of flow roughly parallel to the main stem, which is fed by water from the main stem; a braid of river with flow appreciably lower than the main channel. Side channel habitat may exist either in well-defined secondary (overflow) channels or in poorly defined watercourses flowing through particularly submerged gravel bars and islands along the margins of the main stem. Sidecast The act of moving and depositing excavated material to either side of an excavated area. Sideslope gradient The representative change in elevation in a given horizontal distance (usually about 300 yards) perpendicular to a stream; the valley slope along a line perpendicular to the stream (near a water-quality or biological sampling point). Sieve A wire mesh utensil used to separate and size materials ranging in size from silt to gravel. Separation and sizing between silt and clay size fractions requires a sedimentation (hydrometer) analysis. Sieve analysis The action of sieving and analyzing soils and rock and classifying said materials by size, usually conforming to the Unified Soil Classification System…the most widely used and adopted system in the world. Sieve diameter The smallest standard sieve opening size through which a given particle of sediment will pass. Sill A structure built across the bed of a stream to prevent scour or head-cutting; see also grade-control structure. Silt (1) Noncohesive soil whose individual particles are not visible to the unaided human eye. Soil will crumble when rolled into a ball. In common usage, silt degrades sediments finer than sand. Technically, however, silt is a specific grain size, finer than sand but courser than clay.[Fischer] (2) Substrate particles

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smaller than sand and larger than clay (3 to 60 μm). [Fischenich](3) Material passing No. 200 (0.074 mm) U. S. Standard Sieve that is nonplastic or very slightly plastic and exhibits little or no strength when air- dried (Unified Soil Classification System). Silt is smaller than fine sand and larger than clay. [E-SenSS] (4) Water-Borne Sediment. Detritus carried in suspension or deposited by flowing water, ranging in diameter from 0.005 to 0.05 mm. The term is generally confined to fine earth, sand, or mud, but is sometimes both suspended and bedload. (5) Deposits of Water-Borne Material. As in a reservoir, on a delta, or on floodplains. [(4-5) 2004 RiverWorks] Siltation (1) The deposition or accumulation of silt (or small-grained material) in a body of water. (2) The deposition of accumulation of fine soil particles. Silvicultural Activities All forest management activities, including logging, log transport, and forest roads. Sinuous (1) Slight curvature as seen from above within a belt of less than approximately two channel widths. (2) Refers to a meandering stream planform pattern. Sinuosity (1) The ratio of the length of the river thalweg to the length of the valley proper. (2) The ratio of the channel length between two points on a channel to the straight-line distance between the same two points; a measure of meandering. (3) The ratio of channel length to direct down-valley distance. Also may be expressed as the ratio of down-valley slope to channel slope. When measured accurately from aerial photos, channel sinuosity may also be used to estimate channel slope (valley slope/sinuosity). (4) The ratio of the distance measured along the thalweg of the stream divided by the downvalley length of the drainage basin where the stream flows. In other words, the distance a fish swims divided by the distance a crow flies. The sinuosity of a perfectly straight stream would equal one. A stream with a sinuosity of less than 1.2 is generally considered straight. Typically this is an unnatural (altered) condition where the stream has been straightened by man. Sinuosity greater than 1.3 is considered meandering. Slack water Pool-like depressions along the stream margin and on the floodplain that contain water only during high flow or after floodwaters recede; more transient in nature than secondary-channel pools, they may contain water for only a few days or weeks. Slag (1) Cinders resulting from steel-making. (2) Rough, cindery lava from a volcano. Slide (1) A landslide. (2) Gravitational movement of an unstable mass of earth from its natural position. (3) The landform produced by mass movement under the influence of gravity. Slip (1) Rooted, trimmed stem of grass used for vegetative propagation. (2) See fault. Slipout Gravitational movement of an unstable mass of earth from its constructed position. Applied to embankments and other man-made earthworks. Slip plane Closely spaced surfaces along which differential movement takes place in rock or soil. Slope

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(1) The ratio of the change in elevation over distance. (2) Degree of deviation from horizontal; expressed either as a percentage, as a numerical ratio, in degrees, or as rise or fall per unit distance of stream length. As a percentage, the number of meters (feet) of rise or fall in 100 m (100 ft) of horizontal distance. As a ratio, it is the number of feet of horizontal(H) to the number of feet vertical(V). E.g., a 25 percent slope is equal to a 4H:1V slope, is equal to a slope of approximately 14 degrees, and is equal to 0.25 ft per ft. Slope is sometimes described by the phrase "the rise over the run". (3) Gradient of a stream. (4) Inclination of the face of an embankment, expressed as the ratio of horizontal to vertical projection; or (5) The face of an inclined embankment or cut slope. In hydraulics it is expressed as percent or in decimal form. Slope flattening Reduction in slope angle by excavation and regarding in order to achieve a more stable slope. Slope of natural repose (SONR) See angle of repose. Slope stability The resistance of a natural or artificial slope or other inclined surface to failure by mass movement. Slough (1) A small marshy tract lying in a swale or other local shallow, undrained depression; a sluggish creek or channel in a wetland. (2) A shallow backwater inlet that is commonly exposed at low flow or tide. Sloughing, Sloughing off Movement of a mass of soil down a bank into the channel (also called slumping). Sloughing is similar to a landslide. Sloughing See Slumping. Slumping Shallow movement of a soil mass down a streambank as the result of an instability condition at or near the surface. Conditions leading to slumping are: bed degradation, attack at the bank toe, rapid drawdown, and slope erosion to an angle greater than the angle of repose of the material. Sometimes called "slope failure" or "sloughing". Slurry A thick, but watery, mixture of suspended matter. Small streams Perennial streams less than 200 m (660 ft.) wide. Small water bodies Inland bodies of water with a water surface area of less than 40 acres. This distinction is made by the U.S. Bureau of the Census. Small Woody Debris (SWD) Small trunks or branches of trees (and leaves) that have fallen in the floodplain, or fallen or have been eroded into a stream or river. Often overlooked in "restoration projects" in addition to many important environmental values, SWD can provide many hydraulic values as well (dissipation of energy, scour and deposition of sediment). In some observed low-energy systems (along with leaf litter and leaf packs), SWD provides most of the channel diversity and complexity. Snag

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(1) A standing dead tree > 6.1-m (20 ft) tall from which the leaves and most of the limbs have fallen; (2) A standing dead tree; sometimes a submerged fallen tree in large streams, the top of which is exposed or only slightly submerged. (3) Any standing dead, partially dead, or defective (cull) tree at least 10 in. in diameter at breast height and at least 6 ft tall. Snags are important riparian habitat features. Snagging The removal of material that is obstructing the flow of the stream or interfering with navigation. Socioeconomic considerations Social and economic conditions and opinions which must be evaluated for any project to determine project cost: benefit ratios, as well as the project good to the community. "Soft" bank protection methods Usually refers to the use of living plant (bioengineering), or combinations of bioengineering and coir fiber rolls or mats for bank protection. Soft water Water that contains low concentrations of multivalent cations, such as calcium and magnesium. This type of water does not precipitate soaps and detergents. Soil (1) The layer of material at the land surface that supports plant growth. (2) Unconsolidated mineral and organic surface material that has been sufficiently modified and acted upon by physical, chemical, and biological agents so that it will support plant growth. Soil arching Restraint of soil movement through an opening or gap as a result of transfer of shear stress from the deforming (or moving) soil mass to adjacent stationary (nonyielding) portions of the soil. Soil bioengineering (1) The science of using living materials (plants) and some compatible solid (hard) materials to stabilize an eroding bank of a stream. See also bioengineering. (2) Use of live, woody vegetative cuttings to repair slope failures and increase slope stability; the cuttings serve as primary structural components, drains, and barriers to earth movement. Soil-cement A designed mixture of soil and Portland cement compacted at a proper water content to form a veneer or structure that can prevent streambank erosion. Soil Conservation Service See Natural Resource Conservation Service. Soil horizon A layer of soil that is distinguishable from adjacent layers by characteristic physical and chemical composition. Soil horizons are commonly referred to as topsoil, subsoil, and parent material, or as the "A" horizon, "B" horizon, and "C" horizon, respectively. See "A" horizon, "B" horizon, and "C" horizon. Soil liquefaction Loss of strength of a saturated soil resulting from the combined effects of vibration and hydraulic forces, thereby causing the material to flow. Soil mechanics The application of the laws and principles of mechanics and hydraulics to engineering problems dealing with soil as an engineering material.

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Soil moisture Water occurring in the pore spaces between the soil particles in the unsaturated zone from which water is discharged by the transpiration of plants or by evaporation from the soil. Soil profile Vertical section of the soil from the surface through all horizons. Soil sealants See binder. Soil stabilization Chemical or mechanical treatment designed to increase or maintain the stability of a mass of soil or otherwise to improve its engineering properties. Soil test The process to determine the soil pH and the nutrient-supplying capability of a specific soil for a specific crop or plant species. Used to determine recommended fertilization and liming rates. Sole-source aquifer As defined by the U.S. Environmental Protection Agency, an aquifer that supplies 50 percent or more of the drinking water of an area. Soluble minerals Naturally occurring substances capable of being dissolved. Solution Formed when a solid, gas, or another liquid in contact with a liquid becomes dispersed homogeneously throughout the liquid. The substance, called a solute, is said to dissolve. The liquid is called the solvent. Sorption General term for the interaction (binding or association) of a solute ion or molecule with a solid. Sorting (1) In a descriptive sense, the degree of similarity, in respect to some particular characteristic, of the component parts in a mass of material. (2) In reference to size distribution, poorly sorted implies a wide distribution of material sizes. Well-sorted is the opposite of poorly sorted and would describe material of similar size and shape. Compare to grading. Spall (1) The breaking off of chips, fragments, or thin layers of rock due to physical and chemical forces, such as freeze-thaw cycles, weathering, or quarrying and handling operations. (2) A fragment of rock resulting from such forces, sometimes used in the context of riprap gradation specifications. Spatiotemporal heterogeneity Synonymous with habitat diversity and habitat complexity. Habitat diversity or complexity refers to the number of different types of habitats at a location. Different habitats at a location can support different life- cycle requirements for a single species, such as foraging, resting and breeding habitat. In addition, habitat diversity is also related to species richness (numbers of different kinds species) since habitats at a single location often can support different types of species. Spawn Used as a verb, the act of breeding in fish; also as a noun meaning the reproductive products of aquatic animals.

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Spawning The depositing and fertilizing of eggs (or roe) by fish and other aquatic life. Specialists Species with very narrow habitat tolerances, or predators that have coevolved with a specific prey species and thus rely on that species to survive. Species (1) Populations of organisms that may interbreed and produce fertile offspring having similar structure, habits, and functions. (2) A taxonomic designation assigned to a distinct group of plants or animals which can only breed with another like organism, and which is usually characterized by individual differences from any other species. Species diversity Refers to the number of different kinds of plants and/or animal species in a given area or biological community. Species recovery Improvement in the status of an endangered or threatened species to the point at which listing is no longer appropriate under the criteria set forth by the Endangered Species Act of 1973. Species (taxa) richness A measurement or expression of the number of species (taxa) of plants or animals present in an area; the more species present, the higher the degree of species richness. Specific capacity The yield of a well per unit of drawdown. Specific conductance A measure of the ability of a liquid to conduct an electrical current. Specific gage record A series of stage readings from a single gage, taken over a relatively long period of time, for a specific discharge, that are plotted to determine the long term trends in stage changes for the specific discharge. This information is then used to determine if the long-term tendency of the stream is to aggrade, degrade or remain stable. Specific gravity Ratio of the mass of any volume of a substance to the mass of an equal volume of water at 4 degrees centigrade. A substance with a specific gravity of less than 1.0 will float, specific gravity greater than 1.0 will sink. Specifications A detailed description of particulars, such as size, gradation and amounts of stone, quality of materials, contractor performance, terms, quality control, etc. Spillway (1) A channel for reservoir overflow. (2) Principal spillway - An open or closed channel or conduit used to convey excess water from a pond, reservoir, or basin. (3) Emergency spillway - A designed depression at one side of the embankment of a pond or basin that will pass peak discharges greater than the maximum design storm controlled by the principal spillway and detention storage.

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Spit A small point or low tongue or narrow embankment of land having one end attached to the mainland and the other terminating in open water. Splash pad A non-porous material placed at the outfall of a conduit, channel, or grade stabilization structure, designed to decrease the energy of water flow to a non-erosive velocity. Splash zone That portion of a stable bank between the normal high-water and normal low-water flow rates. The zone of highest stress–exposed frequently to wave-wash, erosive river currents, ice and debris movements, wet-dry cycles and freezing thawing cycles. The section of the bank would normally be inundated throughout most of the year–at least 6 months/yr. The water depths will fluctuate daily, seasonally and by location within the splash zone. Split channel Multiple channels or one with islands. Spoil (1) Overburden or other water material removed in mining, quarrying, dredging, or excavating. (2) Excess rock or soil material not needed after a project is constructed. Sometimes used in reference to material that has been dredged from a navigation or flood control channel. Sprig cuttings Sprigs that can be propagated vegetatively by cutting and planting them, e.g., reed planting. Spring Place where a concentrated discharge of groundwater flows at the ground surface. Spur dike Spur dikes, deflectors or groins are transverse structures that extend into the stream from the bank and reduce erosion by deflecting flows away from the bank. Transverse river training structures often provide pool habitat and physical diversity. Two to five structures are typically placed in series along straight or convex bank lines where flow lines are roughly parallel to the bank. Spurs, groins, and deflectors have no specific design criteria regarding crest height, crest slope or upstream angle and therefore differ from vanes and bendway weirs. Earthen core spur dikes are groins constructed with a soil core armored by a layer of stone. Deflectors can also be constructed from natural materials, such as large woody debris (LWD), or LWD embedded with rock, and designed to provide biologic benefits and habitat restoration. Stone spurs capped with a prism of earth reinforced with live fascines are referred to as "live booms." See dike. Stable channel A stream channel with the right balance of slope, planform, and cross section to transport both the water and sediment load without net long-term bed or bank sediment deposition or erosion throughout the stream segment. Stable channel or stable stream A condition that exists when a stream has developed the correct bed slope and cross section for its channel to transport the water and sediment delivered from the upstream watershed through the system without significant aggradation or degradation. Stage

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(1) Height of the water surface above an established datum plane, such as in a river above a predetermined point that may (or may not) be at the channel floor. (2) Elevation of water surface above any chosen reference plane. Also known as water level or gage height. (3) Water surface elevation of a stream, lake, reservoir, or other water body referenced to a datum plane, which may be MSL, NGVD, or an arbitrary datum plane, such as the average low water elevation at a given location, or an even more arbitrary value, such as a surveyor's estimate of the elevation of the river bed at some point in time. A given value for stage is meaningless for scientific or engineering purposes without a definition of the datum plane to which it is referenced (usually referred to as "zero" of the gage). Standard deviation Statistical measure of the dispersion or scatter of a series of values. It is the square root of the variance, which is calculated as the sum of the squares of the deviations from the arithmetic mean, divided by the number of values in the series minus 1. Stage discharge curve A graphical representation of the relationship between channel discharge at a given cross-section and the corresponding gage height (stage). Stage-discharge relationship Discharge plotted against corresponding stage (water surface elevation). Standing crop The number or weight of organisms present per unit space at a given point in time, e.g., trout/acre, pounds of trout/acre, trout per mile, pounds of trout/mile. Synonymous with “stock density”. Units involving weight are synonymous with “biomass”. Standing wave A highly turbulent condition in a stream which produces a fixed wave pattern at a specific location. Standing waves are caused by a change in the internal energy condition of the flow brought about by an abrupt channel transition. State climate division Geographic area in a state based primarily on crop-reporting districts. States can have 2 to 10 climate divisions. Station (1) The area within which observations made from a point are recorded by the observer (or often synonymous with "point." See point count method; (2) A monitoring station is an area of usually less than about 50 ha where intensive censuses, nest searching, and/or mist netting are conducted. Stem cutting(s) Cuttings made from shoots; according to the nature of the wood they can be divided into hardwood, semi- softwood, softwood, and herbaceous cuttings. Usually willow or poplar one or two years old, and straight- growing; the stems measure up to 2m long (long stem cuttings) and are cut without side branches. Stolon Stem growth which creeps over the ground surface, rooting at nodes to form new individuals; found in many grasses and herbs. Stone (1) Rock or rock fragments used for construction. (2) Concreted earthy or mineral matter. (3) A small piece of rock. (4) Rock, or rocklike material; a particle of such material, in any size from pebble to the

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largest quarried stone. Large, natural masses of stone are generally called rocks; small or quarried masses are called stones. Stone-filled dike A dike constructed entirely of stone. Seldom used now, because of possible confusion with "stone-filled pile dike" or other similar terms. The term "stone dike" is much preferred. Stone-filled pile dike An existing pile dike that has been filled in with stone to increase or maintain its effectiveness. Stone riprap Quarried rock placed on a sloped streambank as protection against erosion. Occasionally, natural cobbles or boulders may be used, if suitable for the erosive forces at the site. Storm surge An abnormal and sudden rise of the sea along a shore as a result of the winds of a storm. Strand (1) To lodge on bars, banks, or overflow plain, as for drift; (2) Bar of sediment connecting two regions of higher ground. Stratification (1) The formation, accumulation, or deposition of materials in layers. (2) Two or more horizontal layers of water of differing characteristics, especially the arrangement of the waters of a lake in layers of different densities. (3) The use of chemical and mechanical systems to break dormancy and increase germination. Stream (1) A general term for a body of water flowing by gravity; natural watercourse containing water at least part of the year. In hydrology, the term is generally applied to the water flowing in a natural narrow channel as distinct from a canal. (2) A natural watercourse containing flowing water at least part of the year, supporting a community of plants and animals within the stream channel and the riparian vegetation zone  Perennial: One that flows continuously throughout the year.  Ephemeral: One that flows briefly only in direct response to precipitation in the immediate locality and whose channel is at all times above the water table.  Intermittent or Seasonal: (1) One in contact with the groundwater table that flows only at certain times of the year as when the water table is high and/or when it receives water from springs or from some surface source, such as melting snow in mountainous areas. It ceases to flow above the streambed when losses from evaporation or seepage exceed the available stream flow. (2) One that flows only at certain times of the year, usually on a seasonal basis. (3) Any body of running water that moves under gravity to progressively lower levels, in a relatively narrow but clearly defined channel on the ground surface, in a subterranean cavern, or beneath or in a glacier. It is a mixture of water and dissolved, suspended, or entrained matter. (4) streams range in size from small creeks to large river. Stream-aquifer interactions Relations of water flow and chemistry between streams and aquifers that are hydraulically connected. Stream barbs See Rock vane.

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Stream channel A long narrow depression shaped by the concentrated flow of a stream and covered continuously or periodically by water. Stream competence The maximum size particle that a stream will move. Stream discharge (Q) The quantity of flow passing a channel cross-section in a unit of time, usually measured in cubic feet per second (cfs) or cubic meters per second (cms). The stream discharge can consist of water, dissolved solids, organic sediment, and inorganic sediment. The defining equation is Q=AV where the discharge Q (the flow rate) is equal to the cross-sectional area (A) multiplied by the average velocity (V). Stream gradient A general slope or rate of change in vertical elevation per unit of horizontal distance of the bed, water surface, or energy grade of a stream. Stream hydraulics The science and technology of water behavior in streams. Stream length The length of stream measured along the thalweg. Stream mile A distance of 1 mile along a line connecting the midpoints of the channel of a stream. Stream morphology The form and structure of streams. Stream order (1) A ranking of the relative sizes of streams within a watershed based on the nature of their tributaries. The smallest unbranched tributary is called first order, the stream receiving the tributary is called second order, and so on. (2) A hydrologic system of stream classification. Each small unbranched tributary is a first-order stream. Two first-order streams join to make a second-order stream. A third-order stream has only first- and second-order tributaries, and so forth. (3) A classification system designed to provide information on the relative size of a stream. A headwater stream with no tributaries is designated a first order stream, a stream with first order tributaries flowing into it is a second order stream, and so on. Lower (first and second) order streams are usually small and can be intermittent or ephemeral, even in temperate climates. Stream power (1) The rate of doing work, or a measure of the potential energy available for moving rock, sediment particles, or other debris in the stream channel, as determined by the product of discharge, water surface slope, and the specific weight of water, divided by the bottom width. Also equal to the product of shear stress and mean velocity. (2) An expression used in predicting bed forms and hence bed load transport in alluvial channels. It is the product of the mean velocity, the specific weight of the water-sediment mixture, the normal depth of flow and the slope. Stream reach (1) A continuous part of a stream between two specified points. (2) An individual segment of stream that has beginning and ending points defined by identifiable features such as where a tributary confluence changes the channel character or order. Stream response

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Changes in the dynamic equilibrium of a stream by any one, or combination of various causes. Stream restoration See restoration. Stream slope See slope. Stream stability See stable stream. Stream terrace See terrace. Stream waters Former surface waters which have entered and now flow in a well defined natural watercourse, together with other waters reaching the stream by direct precipitation or rising from springs in bed or banks of the watercourse. They continue as stream waters as long as they flow in the watercourse, including overflow and multiple channels as well as the ordinary or low-water channel. Streambank (1) The portion of the channel cross section that restricts lateral movement of water at normal water levels. The bank often has a gradient steeper than 45 degrees and exhibits a distinct break in slope from the stream bottom. An obvious change in substrate may be a reliable delineation of the bank. (2) The side slopes of a channel between which the streamflow is confined except during floods. Streambank erosion (1) Removal of soil particles from a bank slope primarily due to water action. Climatic conditions, ice and debris, chemical reactions, and changes in land and stream use may also lead to bank erosion. (2) Removal of soil particles or a mass of particles from a bank surface due primarily to water action. Other factors such as weathering, ice and debris abrasion, chemical reactions, and land-use changes may also directly or indirectly lead to streambank erosion. Streambank failure (1) Collapse or slippage of a large mass of bank material into the channel. (2) Collapse of a relatively large section of streambank that fails and slides into the channel. Streambank protection or streambank protection works Any technique used to prevent erosion or failure of a streambank. Streambank stabilization The lining of streambanks with riprap, matting, etc., or other measure intended to control erosion. Streambank undercut A situation occurring when the streambank overhangs the stream or river channel. This provides cover for fish and is a condition favorable to producing high fish biomass, especially in small streams. Undercut is a good indicator of how successfully streambanks are protected under alternative land uses, such as livestock grazing and road building. Streambed (1) The unvegetated portion of a channel boundary below the baseflow level. (2) The channel through which a natural stream or water runs or used to run, as a dry streambed. (3) The substrate plane, bounded by the stream banks, over which the water column moves. Synonymous with “Stream bottom”.

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Streambed gradient The vertical distance a stream falls per unit of distance it flows horizontally. Commonly expressed as feet of fall per mile or meters of fall per kilometer. Streamflow (1) The discharge of water in a natural channel. (2) The rate at which water passes a given point in a stream or river, usually expressed in cubic feet per second (cfs). (3) The movement of water and sediment through a channel. Streamline A line on a map that is parallel to the direction of fluid flow and shows flow patterns. Strip transect method A procedure using a strip of land, or water, of fixed direction that is sampled visually and/or aurally by an observer. Counts may be one of the following: fixed distance (width ) counts limited to a strip of set width for all or specially chosen species; variable distance (width) counts, with different, species-specific widths that are determined to reflect detection attenuation; or unlimited distance counts, in which all detections are recorded regardless of distance. Synonymous with “Belt transect”. Structure (1) Any object, usually large, in the stream channel that affects water and sediment movement; (2) The diversity of physical habitat within a stream; (3) When applied to a biological community, the organization of taxa into various functional or trophic groups. Structural flood control measures Artificial measures designed to reduce flood damages by altering the stream and/or its overflow characteristics. Examples include: channelization, reservoirs, floodways, dikes and other river training structures, levees, clearing of riparian areas to improve flood conveyance, floodwalls, pumping plants, and flow diversions. Structural heterogeneity Composed of parts of different kinds, or having widely dissimilar elements. Subaqueous Found or taking place under water. Subclimax A stage of succession along a sere prevented from progressing to the climatic climax (i.e., the steady- state community characteristic of a particular climate) by fire, grazing, and similar factors. Subcritical flow (1) Flow with a Froude number less than one. The usual state of alluvial streams. See Froude number, hydraulic jump. (2) In this state, inertia forces are dominant, so that flow has a high velocity and is usually described as rapid, shooting and torrential. Submergent plants Aquatic plants having all parts submerged beneath the water surface. Submersed plant A plant that lies entirely beneath the water surface, except for flowering parts in some species. Subsidence The gradual downward settling or sinking of the Earth’s surface with little or no horizontal motion.

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Subsoil (1) Soil below a subgrade or fill. (2) That part of the soil profile occurring below the "A" horizon. Substrate (1) The mineral and organic material that is from the bed of stream; (2) The surface beneath a wetland, lake, or stream in which organisms grow or to which organisms are attached. (3) The composition of a streambed, including either mineral or organic materials. (4) Material that forms an attachment medium for organisms. (5) The foundation upon which all things exist. E.g., soil is a substrate that supports plants, animals, buildings, roads, and other structures. The bed material that the stream rests on is also a substrate. This includes the layers of material underlying the bed surface layer. Substrate size The diameter of streambed particles such as clay, silt, sand, gravel, cobble and boulders. Subsurface drain A shallow drain installed in an irrigated field to intercept the rising groundwater level and maintain the water table at an acceptable depth below the land surface. Subsurface drainage Rainfall that is not evapotranspirated or does not become surface runoff. Subsurface flow That portion (part or all) of the water that infiltrates the stream bed and moves horizontally through and below it. It may or may not return to the stream channel at some point downstream. Synonymous with Hyporheic flow. Succession The orderly process of community change or replacement in a region where one plant community or population replaces another through time as it proceeds toward its highest and most stable ecological expression–the climax. Supercritical flow Flow with a Froude number greater than one. Rare in alluvial streams. See Froude number, hydraulic jump. Superfund list A list of the hazardous waste disposal sites most in need of cleanup. The list is updated annually by the U.S. Environmental Protection Agency (EPA) based primarily on how a site scores using the Hazard Ranking System. Also referred to as the National Priorities List (NPL). Supply augmentation Alternative water management programs – such as conjunctive use, water banking, or water project facility expansion – that increase supply. Surcharge (1) A weight on a slope that exerts a down-slope (destabilizing) stress and a perpendicular stress component, the combination of which tends to increase resistance to sliding. (2) This refers to a condition where the hydraulic capacity of a storm drain system is temporarily exceeded (e.g., during a storm event), and the amount of water that enters the system exceeds the conveyance capacity. Surface erosion The detachment and transport of soil particles by wind, water, or gravity. Or a group of processes whereby soil materials are removed by running water, waves and currents, moving ice, or wind.

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Surface runoff (1) That portion of rainfall that moves over the ground toward a lower elevation and does not infiltrate the soil; (2) Runoff that travels over the land surface to the nearest stream channel. (3) The movement of water on earth’s surface, whether flow is over surface of ground or in channels. Surface runoff That portion of rainfall that moves over the ground toward a lower elevation and does not infiltrate the soil. See runoff. Surface supply Water supply from streams, lakes, and reservoirs. Surface water All waters whose surface is naturally exposed to the atmosphere, for example, rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc., and all springs, wells, or other collectors directly influenced by surface water. Surplus water Developed water supplies in excess of contract entitlement or apportioned water. Survey (1) Sampling of a representative number of sites during a given hydrologic condition. (2) An enumeration or index of the number of individuals in an area from which inferences about the population can be made. (3) A map of the bed, banks, and/or the adjacent floodplain of a stream. Typically, elevations are taken along a series of cross-sections that are roughly perpendicular to the direction of stream flow, although recent innovations in surveying and mapping technology are less restrictive, and may allow more detailed coverage with less field work. Surveys made for special purposes may involve more or less detail or area of coverage, depending upon the specific need. Survey length The run or the stream distance (not the valley distance) over which you measure the stream gradient. Measured upstream and downstream from the mark at the bankfull width at the right edge of the steam (facing downstream). Suspended (As used in tables of chemical analyses) The amount (concentration) of undissolved material in a water- sediment mixture. Most commonly refers to that material retained on a 0.45-micrometer filter. Suspended bed material load A portion of the bed material load that is transported in suspension within the water column. [Watson et al. 1999] Suspended load That part of the sediment load whose immersed weight is carried by the fluid. See also “bed load”. (2) That part of a stream's total sediment load which is transported within the body of fluid and has very little, or no, contact with the bed. (3) A component of the total sediment load made up of sediment particles moving in continuous suspension within the water column. Transport occurs above the bed, with the submerged weight of particles supported by anisotropic turbulence within the body of the flowing water. Suspended sediment (1) Sediment that is transported in suspension by a stream. (2) Sediment suspended in a fluid by the upward components of turbulent currents, moving ice, or wind. (3) Sediment that is carried in suspension by the turbulent components of the fluid, both bed material and fine material.

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Suspended-sediment concentration The velocity-weighted concentration of suspended sediment in the sampled zone (from the water surface to a point approximately 0.3 foot above the bed); expressed as milligrams of dry sediment per liter of water-sediment mixture (mg/L). Suspended sediment discharge The quantity of suspended sediment passing a cross-section of the stream in a unit of time, both bed material and fine material. Suspended sediment load That portion of a stream’s total sediment load that is transported within a body of water and has very little contact with the streambed. Suspended solids (1) The composition of a streambed, including either mineral (e.g., soil particles) or organic (e.g., algae) materials. (2) Material that forms an attachment medium for organisms. A total suspended solids test measures the weight of material per volume of water. Suspended solids Soil particles and organic matter which remain suspended in the water column after agitation from dredging, or during movement downstream in river systems. Suspension The state of a substance when its particles are kept from falling or sinking. Sustainable development A project that works in harmony with the natural system to meet the needs of the present without compromising the ability to meet the needs of future generations. Swale (1) A slight depression, sometimes filled with water, in the midst of generally level land. (2) A natural or artificial low-lying, often wet, area of land. Typically results from irregular deposition patterns as a stream channel migrates, but artificial swales can be engineered to slow, store, route, or filter runoff. Swamp An area intermittently or permanently covered with water, and having trees and shrubs. Sweeper log Fallen tree whose bole or branches form an obstruction to floating subjects. Synthetic mattress, matting, or tubing A manufactured, semi-flexible casing placed on a streambank and filled with grout or sand to prevent erosion T Tackifier See binder. Tailings Rock that remains after processing ore to remove the valuable minerals. Tailout The downstream end of a pool where the bed surface gradually rises and the water depth decreases. It may vary in length, but usually occurs immediately upstream of a riffle.

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Tailspill The area of a redd where substrate excavated upstream by the female is deposited. Tailwater (1) The reach of stream immediately below a dam on a stream. (2) The area immediately downstream of a spillway. (3) Applied irrigation water that runs off the end of a field. Talus Fallen disintegrated material which has formed a slope at the foot of a steeper declivity. See colluvium. Talus slope A sloping mass of fragments which has been dislodged from a mountain side or cliff due to the process of weathering. The rock fragments accumulate faster than the forces of erosion are able to remove them or reduce them to smaller particles. Target species A desired species or group of species toward which habitat development and management are directed. Tarn A relatively small and deep, steep-sided lake or pool occupying an ice-gouged basin amid glaciated mountains. Taxa richness See Species richness Taxon Any identifiable group of taxonomically related organisms. Taxonomic composition The number and arrangement of distinct species that are found in an assemblage. Temporary construction site BMPs BMPs that are required only temporarily to address a short term storm water contamination threat. For example, silt fences are located near the base of newly graded slopes that have a substantial area of exposed soil. Then, during rainfall, the silt fences filter and collect sediment from runoff flowing off the slope. Tensile strength The maximum unit tensile force a material can bear without tearing apart. Units are reported as maximum stress (e.g. pounds per square inch) or force per unit length (e.g. pounds per inch width of geotextile). Tenting Separation of installed manufactured blankets from contact with the ground surface. Often is a symptom of underlying problems which may lead to partial failure of the protection. Terrace (1) An abandoned depositional surface floodplain unrelated to the current hydrologic regime, formed by climatic change, urbanization, historic agricultural practices, logging, etc. Note: Not to be confused with active floodplain. (2) A relatively level bench or step-like surface breaking the continuity of a slope; a previous floodplain which has been disconnected from a stream channel because of channel incision. (3) A flood plain that seldom, if ever, floods due to streambed degradation. (4) Also a level area or bench in a section of a formed or natural slope; can be several meters wide; small berms (up to 1 m wide) are also called terraces.

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Terrane Area or surface over which a particular rock type or group of rock types is prevalent. Terrestrial Pertaining to, consisting of, or representing the Earth. Tertiary treatment In sewage, the additional treatment of effluent beyond that of secondary treatment to obtain a very high quality of effluent for reuse. Tetrahedron jack A type of river-training structural component made of six steel or concrete struts fabricated in the shape of a pyramid, as opposed to being assembled as a jack. Tetrapod Bank-protection component of precast concrete consisting of four legs joined at a central joint, with each leg making an angle of 109.5 degrees with the other three. Texture (1) Refers to relative proportions of clay, silt, and sand in soil. (2) The percent of sand, silt, and clay in a soil. Thalweg (1) The lowest thread along the axial part of a valley or stream channel. (2) The middle, chief, or deepest part of a navigable channel or waterway. (3) A subsurface, groundwater stream percolating beneath and in the general direction of a surface stream course or valley. (4) The line connecting the lowest points along a streambed; the longitudinal profile. The path of maximum depth in a river or stream. (5) The line connecting the lowest or deepest points along a stream bed in the longitudinal direction. Thermal loading Amount of waste heat discharged to a water body. Thread The central element of a current, which is continuous along a stream. Threatened species A species of plant or animal that is not listed on the endangered species list, but if species population continues to decline in all or a significant portion of its habitat range, it will be listed as endangered. See also Endangered and Candidate species. Tidal flat (1) An extensive, nearly horizontal, tract of land that is alternately covered and uncovered by the tide and consists of unconsolidated sediment. (2) Saltwater wetland that are characterized by mud or sand and daily tidal fluctuations. Tieback Structure placed between longitudinal protection or longitudinal training works and the bank to prevent flanking. Tied in An expression used to indicate that a revetment or dike is constructed to prevent or minimize streamflow between the structure and the bank. Tier 1 sediment guideline

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(As defined by the U.S. Geological Survey) Threshold concentration above which there is a high probability of adverse effects on aquatic life from sediment contamination, determined using modified U.S. Environmental Protection Agency (1996) procedures. Tile drain A buried perforated pipe designed to remove excess water from soils. Till Predominantly unsorted and unstratified drift, deposited directly by and underneath a glacier without subsequently reworking by meltwater, and consisting of a heterogeneous mixture of clay, silt, sand, gravel, and boulders. Timber mattress A revetment made of brush, poles, logs, or lumber interwoven or otherwise lashed together. The completed mattress is then placed on the bank of a stream and weighted with ballast, usually stone. Time of concentration The time required for storm runoff to flow from the most remote point, in flow time, of a drainage area to the point under consideration; it is usually associated with the design storm. Tinaja A pocket of water developed below a waterfall; a term used in the Southwestern United States; used loosely to mean a temporary pool. Toe (1) The break in slope at the foot of a bank where the bank meets the bed. May not be well-defined; often the bank slope flattens as it nears the toe, and the horizontal location and elevation of the toe at a given location often changes with stream discharge. Toe erosion The erosion of particles from the streambank and/or bed which results in the undermining of the toe and subsequent gravity collapse or sliding of overlying layers. Toe zone Portion of a streambank between the streambed and the average normal river stage. Tolerant species Those species that are adaptable to (tolerant of) human alterations to the environment and often increase in number when alterations occur. Top bank (1) The break in slope between the bank and the surrounding terrain. (2) The usually well-defined break at the top of the bank slope, where the flood plain begins. Topsoil Upper, rooted through, live humus surface soil layer. See "A" horizon. Topographic map A map of contour lines showing differences in elevation. Topography (1) The general configuration of a land surface or any part of the Earth’s surface, including its relief and the position of its natural and man-made features. (2) Shape and physical features of land. Torrent

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(1) A turbulent, swift-flowing stream. (2) A heavy downpour; a deluge. Total concentration Refers to the concentration of a constituent regardless of its form (dissolved or bound) in a sample. Total dissolved solids A quantitative measure of the residual minerals dissolved in water that remain after evaporation of a solution. Usually expressed in milligrams per liter. Abbreviation: TDS. See also Salinity. Total head The height above a datum plane of a column of water. In a groundwater system, it is composed of elevation head and pressure head. Trace element A chemical element that is present in minute quantities in a substance. Total sediment load Total mass of granular sediment transported by the stream [Watson et al. 1999] Tractive force (1) The drag on a streambed or streambank caused by passing water which tends to pull soil particles along with the streamflow. (2) The force on a stream bed or bank caused by flowing water, which tends to pull or pluck soil particles along with the streamflow, or remove structural components of bank protection, such as riprap. Transect (1) A cross section of an area along which the observer moves in a given direction. (2) A predetermined line along which vegetation occurrence or other characteristics such as canopy density are counted for monitoring purposes. A channel cross section. Transitional stream reaches Reaches with intermediate characteristics, alternating channel erosion and aggradation, riparian areas of intermediate size. Transmissivity The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of an aquifer under a unit hydraulic gradient. It equals the hydraulic conductivity multiplied by the aquifer thickness. Transpiration (1) Process by which water vapor escapes from a living plant and enters the atmosphere. (2) An essential photosynthetic and physiological process by which plants release water into the air in the form of water vapor; the process in plants by which water is released into the gaseous environment (atmosphere), primarily through the stromata. Transport To carry solid material in a stream in solution, suspension, saltation, or entrainment. Transportation (sediment) The complex process of moving sediment particles from place to place. The principle transporting agents are flowing water, ice and wind. Transport capacity The ability of a stream to carry sediment.

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Transport velocity The velocity of flow required to maintain particles of a specific size and shape in motion along the stream bed. Also known as the critical velocity. Transverse Oriented perpendicular to the longitudinal direction of the river or stream. Transverse bar Typically solitary lobate features that extend over much of the active stream width but may also occur in sequence down a given reach of river; produced in areas of local flow divergence and are always associated with local deposition. Flow is distributed radially over the bar. Common to sandy braided streams. Transverse dike A dike that extends into the channel approximately perpendicular to the channel. Trap efficiency The proportion of the incoming sediment load that is deposited in a defined area, such as a sediment retention reservoir, reported in per cent. Trash rack A structural device used to prevent debris from entering a pipe, spillway, or other waterway. Trellis pattern Roughly rectilinear arrangement of stream courses in a pattern reminiscent of a garden trellis, developed in a region where rocks of differing resistance to erosion have been folded, beveled, and uplifted. Trench A pool characterized by a relatively long, slotlike depression in the streambed, often found in bedrock- dominated channels. Trenchfill revetment Trench fill revetments are constructed by excavating a trench along the top of the bank and placing stone riprap in the trench. As the bank erodes, the stone is undercut and “launches” down the bank line, resulting in a more gradual, protected slope. Earth removed for excavation of the trench may be used to cover the riprap, thus completely concealing it until it is launched. This technique might be chosen if access to the stream reach is restricted due to legal or environmental issues. Tributary (1) Any channel, waterway, or inlet that conveys water into a stream; (2) A river or stream flowing into a larger river, stream, or lake. Trophic Relating to the processes of energy and nutrient transfer from one or more organisms to others in an ecosystem. Trophic Level Position along food chain, or feeding level, measured as the number of steps from primary production. Tundra A vast, nearly level, treeless plain of the arctic and subarctic regions. It usually has a marshy surface which supports mosses, lichens, and low shrubs, underlain by mucky soils and permafrost. Turbidity

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(1) A measure of the amount of light scattered from a water sample (more suspended particles cause greater scattering). Suspended sediments, dissolved solids, natural or man-made chemicals, and algae may all contribute to the water's cloudiness/murkiness. (2) The state, condition, or quality of opaqueness or reduced clarity of a fluid due to the presence of suspended matter. (3) A measure of the content of suspended matter that interferes with the passage of light through the water or in which visual depth is restricted. Suspended sediments are only one component of turbidity. (4) The degree of cloudiness in water caused by suspended particles. Turbidity can be precisely measured and is often used as an indicator of pollution. Turbulence (1) The motion of water where local velocities fluctuate and the direction of flow changes abruptly and frequently at any particular location, resulting in disruption of laminar (smooth) flow; it causes surface disturbance and uneven surface level, and often masks subsurface areas because air bubbles are entrained in the water. (2) The motion of water where local velocities fluctuate wildly in all three dimensions, resulting in abrupt changes in flow directions. It causes surface disturbances and uneven surface levels, and often masks subsurface areas due to the entrainment of air. (3) Motion of fluids in which local velocities and pressures fluctuate irregularly in a random manner. Opposite of laminar flow. In general terms, the irregular motion of a flowing fluid. Open channel flow is almost always turbulent to some degree. (4) The state of flow wherein the water is agitated by cross-currents and eddies, as opposed to a condition of flow that is quiet and laminar. Turbulent flow That type of flow in which any particle may move in any direction with respect to any other particle, and in which the head loss is approximately proportional to the square of the velocity. Turf Reinforcement Mat (TRM) A relatively permanent rolled erosion control product (RECP) composed of ultraviolet stabilized synthetic fibers, netting, and/or filaments processed into a three-dimensional reinforcement matrix designed for critical hydraulic applications where design discharges exert velocities and shear stresses that exceed the limits of mature natural vegetation. Designed to provide sufficient thickness, strength. and void space to permit soil filling and/or retention and allow development of vegetation within the matrix of the mat. U Unconfined aquifer An aquifer whose upper surface is a water table free to fluctuate under atmospheric pressure. Unconsolidated Friable or loose material lacking internal cohesion. Unconsolidated deposit Deposit of loosely bound sediment that typically fills topographically low areas. Undercut bank A bank that has had its base cut away by the water or has been manmade and overhangs part of the stream. Underground water See groundwater. Undermining The removal of lateral support at the base of a slope by scour, piping erosion, or excavation. Understory

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A foliage layer lying beneath and shaded by the main canopy of a forest. Uniform flow Flow in which the depth, velocity, cross-sectional area, and discharge are all constant as flow moves downstream. Rare in natural channels. Un-ionized ammonia The neutral form of ammonia-nitrogen in water, usually occurring as NH4OH. Un-ionized ammonia is the principal form of ammonia that is toxic to aquatic life. The relative proportion of un-ionized to ionized ammonia (NH4+) is controlled by water temperature and pH. At temperatures and pH values typical of most natural waters, the ionized form is dominant. Univariate Statistical tests for comparing two or more groups; techniques include t-test, analysis of variance, sign test, Wilcoxan rank test, and the Mann-Whitney U-test. Universal Soil Loss Equation (USLE) An estimate of the amount of soil loss from an area due to rainfall erosion based upon five factors: climate, soil erodibility, length and steepness of slope, vegetative cover, and structural and/or management practices. See Revised USLE. Unmeasured Load A portion of the total sediment load that passes beneath the nozzle of a conventional suspended load sampler, by near-bed suspension and as bed load. Unravel To lose material from the edges of a revetment. Unsaturated zone A subsurface zone above the water table in which the pore spaces may contain a combination of air and water. Unsteady flow A flow in which the depth at a given location changes with respect to both space and time. Upgradient Of or pertaining to the place(s) from which groundwater originated or traveled through before reaching a given point in an aquifer. Upland (1) A general term for nonwetland; elevated land above low areas along streams or between hills; any elevated region from which rivers gather drainage. (2) The region of higher elevation above a floodplain, usually characterized by vegetation not tolerant of inundation, but can range from bare ground to mature forest. Uplift The hydrostatic force of water exerted on or underneath a structure, causing a displacement of the structure. Upper bank (1) That portion of the streambank above the elevation of the average water level of the stream. (2) The portion of a streambank which is normally above water. See also lower bank, middle bank, and zones. Urban runoff

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(1) Surface runoff from an urban area, including discharge of runoff collected in stormwater drainage systems and baseflow discharge from stormwater drains during dry weather; base flow may be composed of polluted and non-polluted components. (2) Storm water from city streets and gutters that usually carries a great deal of litter and organic and bacterial wastes into the sewer systems and receiving waters. V Vadose or Vadose zone The capillary area above the groundwater table where sufficient moisture exists but roots are not oxygen deprived. Valley length The straight line length of the valley along the same reach as the survey length is measured. This is usually obtained by topographic map, or by measuring the straight-line distance from the upstream extent of the longitudinal survey to the downstream extent. Valley length is measured over the exact same reach as the survey length and can be entered at the same time that gradient survey is measured. Valley plug Blockage of a stream channel by sediment or debris to the extent that flow is forced into overbank areas. Vanes Rock vanes are discontinuous, redirective structures angled upstream 20 to 30 degrees. Generally, two or three vanes are constructed along the outer bank of a bend in order to redirect flows near the bank to the center of the channel. Typically, vanes project 1/3 of the stream width. The riverward tips are at channel grade, and the crests slope upward to reach bankfull stage elevation at the key. Rock vanes can preclude the need for rock armor and increase vegetative techniques as the high flows are redirected away from the bank. Vanes can increase cover, backwater area, edge or shoreline length, and the diversity of depth, velocity and substrate. Variations include Cross Vanes and Rock Vanes with J-hooks. Variance A measure of the variability or precision of a set of observations. Vascular plant A plant composed of or provided with vessels or ducts that convey water or sap (example: a fern). Vascular system The tissues which conduct water and nutrients from one part of a plant to another – comprising xylem and phloem. Vector A quantity completely specified by a magnitude and a direction. Vegetated structures A retaining structure in which living plant materials, cuttings, or transplants have been integrated into the structure. Vegetated structural revetments Porous revetments, e.g., a gabion mattress or riprap, into which live plants or cuttings can be placed or inserted. Vegetation

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Plant life or total plant cover formed of many different plant types; the whole of the plant species of an area. Can be rooted, attached, or floating, deciduous or evergreen, woody or herbaceous, commercial or noncommercial. Vegetative cuttings Live, cut stems and branches of plants that will root when embedded or inserted in the ground. Vegetative measures The use of live cuttings, seeding, sodding, and transplanting in order to establish vegetation for erosion control and slope protection work. Vegetative propagation Reproduction by cuttings, layering and grafting; not involving fertilization. Vegetative succession See ecological succession. Vegetative techniques The standard (conventional) use of seeding, topsoiling, transplanting, and cuttings to establish a vegetative cover. Can be used in conjunction with vegetative establishment aids such as mulching, conditioning, fertilization, and watering. Distinct from Revegetative Techniques. Velocity (1) The speed of water flowing in a stream/river, calculated as distance/time (m/s or ft/s). (2) The speed that water travels in a given direction; expressed as a distance traveled during an interval of time, usually in feet per second (fps) or meters per second (m/s). Theoretically, velocity is a vector, and the value of speed would be accompanied by a precise direction, but for practical purposes it is usually assumed to be in the general direction of flow at the time and under the conditions under study. Vernal pool A small lake or pond that is filled with water for only a short time during the spring. Vertebrate A living organism that has a backbone or spinal column. Viscosity A measure of the resistance of a fluid to flow. For liquids, viscosity increases with decreasing temperature. Visitor-day See recreation-day. Void (1) Space within a soil or rock mass not occupied by solid mineral matter. (2) The open spaces in a geosynthetic material through which flow can occur. Volunteer A plant that invades a site, often after disturbance; usually represents an adjoining source of seed or other propagules. W Wadi See Arroyo.

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Warmwater stream A stream with water too warm to support salmonid fishes. Wash (1) To carry, erode, remove, or destroy by the action of moving water. To be carried away, removed, or drawn by the action of water. Removal of erosion of soil by the action of moving water. (2) A deposit of recently eroded debris. (3) Low or marshy ground washed by tidal waters. A stretch of shallow water. (4) (Western United States) The dry bed of a stream, particularly a watercourse associated with arid environments and are characterized by large, high-energy discharges with high bed-material load transport. Washes are often intermittent and their beds sparsely vegetated. (5) Turbulence in air or water caused by the motion or action of an oar, propeller, jet, or airfoil. Wash See Arroyo. Wash load (1) See fine-material load. (2) A portion of the total sediment load composed of grain sizes finer than those found in appreciable quantities in the stream bed. In sand-bed streams wash load moves as suspended load, but in boulder-bed rivers the wash load may include gravel which moves as bed load. The sum of bed material load and wash load makes up the total sediment load. Washout (1) Erosion of a relatively soft surface, such as a roadbed, by a sudden gush of water, as from a downpour or floods. (2) A channel produced by such erosion. (3) The failure of a culvert, bridge, embankment, or other structure resulting from the action of flowing water. Wastewater The used water, liquid waste, or drainage from a community, industry, or institution. Wasteway A waterway used to drain excess irrigation water dumped from the irrigation delivery system. Water bar A diversion ditch and/or hump in a trail or road built for the purpose of carrying runoff water into a ditch, a dispersion area or a vegetated area so the water does not gain sufficient volume and velocity to cause soil movement and erosion. Water body A type of (permanent open) water area which includes ponds, lakes, reservoirs, bays or gulfs, and estuaries. There are 3 size categories: (1) less than 2 acres; (2) 2-40 acres; and (3) at least 40 acres. Water budget An accounting of the inflow to, outflow from, and storage changes of water in a hydrologic unit. Water column An imaginary column extending through a water body from its floor to its surface. Water conservation Reduction in applied water due to more efficient water use such as implementation of Urban Best Management Practices or Agricultural Efficient Water Management Practices. The extent to which these actions actually create a savings in water supply depends on how they affect net water use and depletion. Water content of snow

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Amount of liquid water in the snow at the time of observation. Water equivalent of snow. Water demand Water requirements for a particular purpose, such as irrigation, power, municipal supply, plant transpiration, or storage. Water demand schedule A time distribution of the demand for prescribed quantities of water for specified purposes. It is usually a monthly tabulation of the total quantity of water that a particular water user intends to use during a specified year. Water discharge See stream discharge. Water exports or imports Artificial transfer (by pipes or canals) of freshwater from one region or subregion to another. Water gap A deep, narrow pass in a mountain ridge through which a stream flows. Water pollution Generally, the presence in water of enough harmful or objectionable material to damage the water’s quality. Water quality (1) A general term denoting a category of properties of water, commonly used in reference to chemical characteristics and temperature of the water. It can logically be the title of organization which deals with these aspects of water and can even serve as a general heading in a paper, but the term is often misused; for example, “Dog Creek lacks water quality” is an obscure way to say that it gets too hot in summer for trout. “Water quality” is a vague term and should be used sparingly. Instead, use “water temperature” or “chemical content” or “pollution”. (2) A term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose. Water-quality criteria Specific levels of water quality which, if reached, are expected to render a body of water unsuitable for its designated use. Commonly refers to criteria established by the U.S. Environmental Protection Agency. Water-quality criteria are based on specific levels of pollutants that would make the water harmful if used for drinking, swimming, fishing, farming, fish production, or industrial processes. Water-quality guidelines Specific levels of water quality which, if reached, may adversely affect human health or aquatic life. These are nonenforceable guidelines issued by a governmental agency or other institution. Water quality standard A law or regulation that consists of the beneficial designated use or uses of a water body, the numerical and narrative water-quality criteria that are necessary to protect the use or uses of that particular water body, and an antidegradation statement. Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use. (From Federal Clean Water Act). Water reclamation Includes water recycling, seawater desalting, groundwater reclamation, and desalting agricultural brackish water.

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Water recycling The treatment of urban wastewater to a level rendering it suitable for a specific, direct, beneficial use. Water resources region Natural drainage basin or hydrologic area that contains either the drainage area of a major river or the combined areas of a series of rivers. In the United States, there are 21 regions of which 18 are in the coterminous United States, and one each in Alaska, Hawaii, and the Caribbean. Water resources subregion Subdivision of a water-resources region. The 21 water-resources regions of the United States are subdivided into 222 subregions. Each subregion includes that area drained by a river system, a reach of a river and its tributaries in that reach, a closed basin(s), or a group of streams forming a coastal drainage area. Water rights (1) Legal rights to the use of water. (2) A legally protected right to take possession of water occurring in a natural waterway and to divert that water for beneficial use. Water supply A use of land and water category under Agricultural Production that includes all ponds, reservoirs, canals, ditches, streams, rivers, or other water bodies used for irrigation, and livestock water supplies. Water table (1) The upper surface of groundwater or that level below which the soil is saturated with water. It is at least 6 in. thick and persists in the soil for more than a few weeks. [Fischer] (2) The top water surface of an unconfined aquifer at atmospheric pressure. [USGS] (3) See groundwater table. [Fischenich] (4) The upper surface of the zone of permanent saturation in permeable rock or soil. This is typically an irregular surface with shape or slope determined by the quantity of groundwater and permeability of earth materials. In general, it is highest beneath hills and lowest beneath valleys.[E-SenSS] Water year A continuous 12-month period selected to present data relative to hydrologic or meteorological phenomena during which a complete annual hydrologic cycle normally occurs. The water year used by the U.S. Geological Survey runs from October 1 through September 30, and is designated by the year in which it ends. (2) A continuous 12-month period for which hydrologic records are compiled and summarized. In California, it begins on October 1 and ends September 30 of the following year. Water yield The quantity of water derived from a unit area of watershed. Waters of the United States Includes all dry land and water-covered areas below the ordinary high water marks on navigable and nonnavigable streams. Waterbar An angled depression or trough in a road surface placed to direct surface water off the road. Used to prevent erosion. Waterfall A sudden, nearly vertical drop in a stream, as it flows over rock. Watershed

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(1) The entire region or drainage that contributes to a water supply point; (2) An area of land whose total surface drainage flows to a single point in a stream; (3) Formerly most commonly used to refer to the divide separating one drainage basin from another. However, over the years, the use of the term to signify drainage basin or catchment area has come to predominate, although the term drainage basin is preferred. Drainage divide, or merely divide, is used to denote the boundary between one drainage area and another. Used alone, the term “watershed” is now ambiguous and should not be used unless the intended meaning is made clear. (4) U.S.Geological Survey uses “Drainage Basin”. (5) A convex surface such as a mountain or hill which sheds water from one high point or ridge into several streams which may form its boundary. (6) See drainage basin. (7) (esp. U.K.) The dividing line of highest elevations, or "divide", between drainage basins. (8) An area of land that drains into a particular river or stream, usually divided by topography. Watershed management (1) The administration and regulation of the aggregate resources of a drainage basin for the production of water and the control of erosion, streamflow, and floods. (2) The analysis, protection, development, operation, or maintenance of the land, vegetation, and water resources of a drainage basin for the conservation of all its resources for the benefit of its residents. Watershed project A comprehensive program of structural and nonstructural measures to preserve or restore a watershed to good hydrologic condition. These measures may include detention reservoirs, dikes, channels, contour trenches, terraces, furrows, gully plugs, revegetation, and possibly other practices to reduce flood peaks and sediment production. Watershed restoration Improving current conditions of watersheds to restore degraded habitat and provide long-term protection to aquatic and riparian resources. Waterway (1) That portion of a watercourse that is actually occupied by water; (2) A navigable inland body of water. Wattle Cigar-shaped bundles of tree or shrub branch cuttings tied tightly together and anchored in trenches using live stakes or dead stout stakes. Wattles are installed on contour (level), with cuttings oriented in both directions within the bundle. The butt ends and about one-half of the wattle should be covered with soil to promote root growth. Wattles are used for a wide variety of slope stabilization projects. Sometimes called a "live wattle". A variation is the "reinforced wattle" which uses either a small proprietary anchor or 5-ft sections of 1/2 in diameter rebar driven through and tied to the wattle as anchors. See fascine. Wave attack (1) Impact of waves on a streambank. (2) Impact of waves on a shoreline or riverbank. Weathering Physical disintegration or chemical decomposition of rock due to wind, rain, heat, freezing, or thawing. Wedge and “K” dams Small dams, usually constructed with logs or cut planks, which can be used to create pools and provide deeper areas in shallow streams. Weather State of the atmosphere at any particular time and place. Weathering

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(1) Process whereby earthy or rocky materials are changed in color, texture, composition, or form (with little or no transportation) by exposure to atmospheric agents. (2) Physical disintegration or chemical decomposition of rock due to wind, rain, heat, freezing, thawing, etc. Weephole (1) Opening left in a revetment or bulkhead to allow groundwater drainage. (2) Opening placed in a revetment or bulkhead to allow groundwater drainage. Weighted mean A value obtained by multiplying each of a series of values by its assigned weight and dividing the sum of these products by the sum of the weights. In the ordinary arithmetic mean, each value is assigned a weight of 1. Weir (1) A structure to control water levels in a stream. Depending upon the configuration, weirs can provide a specific “rating” for discharge as a function of the upstream water level. (2) A notch or depression in a levee, dam, embankment, or other barrier across or bordering a stream, through which the flow of water is measured or regulated; (3) A barrier constructed across a stream to divert fish into a trap; (4) A dam (usually small) in a stream to raise the water level or divert its flow. Stone weirs are structures that span the stream and produce a drop in the water surface elevation. These structures are frequently made of angular quarried stone, but logs, sheet piling, concrete, boulders and masonry are also quite common. Well-constructed stone weirs can prevent or retard channel bed erosion and upstream progression of "knickpoints" and headcuts, as well as providing pool habitats for aquatic biota. Stone weirs or similar grade control structures are often intended to raise or elevate the bottom of incised channels, with the ultimate goal of elevating a dropping water table. Variations on stone weirs that have additional habitat benefits are Newbury Rock Riffles and Cross Vanes. Weir (fish trap) Usually a barrier constructed to catch upstream migrating adult fish. Well-graded Same as poorly sorted. See grading. Well-sorted Same as poorly graded. See sorting. Wetland function A process or series of processes that take place within a wetland that are beneficial to the wetland itself, the surrounding ecosystems, and people. Wetlands (1) Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas. (2) "..... those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas" (Corps Regulation 33 CFR 328.3 and EPA Regulations 40 CFR 230.3). (3) Lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. [(1-3) Fischer] (4) A land area that is wet or flooded by surface or ground water often enough and long enough to develop characteristic hydric soil properties and to support vegetation that will grow in saturated soil conditions. Wetland types

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range from coastal intertidal marshes to freshwater swamps and bottomland hardwoods. Wetlands usually have quite distinctive vegetation communities. [(4) E-SenSS] Wetted perimeter The length of the wetted contact between a stream of flowing water and the stream bottom and banks in a vertical plane at right angles to the direction of flow. (2) Wetted perimeter (P) - The length of the wetted cross-section (i.e., bed and banks) measured normal to the direction of flow. The practical equivalent of channel width, except for channels that are relatively narrow and deep. Width to Depth ratio (w/d) The bankfull width divided by the average bankfull depth. This measurement is taken after determining the bankfull discharge height and choosing a representative cross section. (2) The channel width (w) divided by the average depth (d) of the channel. Wild rivers Rivers or sections of rivers that are free of impoundments and generally inaccessible except by trail, with watersheds or shorelines essentially primitive and waters unpolluted. Wildlife tree A live tree retained to become future snag habitat. Willow carr A pool, or wetland dominated by willow trees or shrubs. Willow curtain method A bioengineering streambank protection method whereby medium to large willow tree trunks are placed and anchored in shallow trenches oriented longitudinally to the direction of stream flow at elevations slightly above the base flow water surface elevation of the stream. Willow pole method A bioengineering streambank protection method whereby medium to large willow tree trunks are placed and anchored in shallow trenches oriented roughly perpendicular to the slope of the eroding bank. Willow post method A bioengineering protection technique whereby large willow tree trunks are systematically installed in augured and backfilled holes on a streambank. As with all such methods, most successful when installed during the plant's dormant season. Windfall Trees or parts of trees felled by high winds. Windrow revetment A row of stone (the windrow) placed on a relatively smooth alignment on the top bank landward of an eroding streambank. As erosion continues, the windrow is eventually undercut, launching the stone downslope, thus armoring the bank face and toe. Compare to trenchfill revetment, which is excavated into the bank. Windrow revetment has the advantage of being easier to construct, but the disadvantages of requiring more stone to accommodate a given scour depth and the presence of a mass of stone on the streambank for an indeterminate length of time. Windthrow A tree or trees uprooted or felled by the wind. Wing dam See dike.

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W-Weir Double Cross Vane designed to split a single channel into two channels for the purpose of protecting or reducing scour near a mid-channel resource (e.g. bridge piling). See Cross Vane. Withdrawal Water removed from the ground or diverted from a surface-water source for use. Also refers to the use itself; for example, public-supply withdrawals or public-supply use. Woody debris Referring to wood in streams. Woody plants Plants containing hard tissue made up of the remains of dead xylem cells in the stems; wood is made of mostly lignin and supports the plant and acts as a conduit for water and nutrients. X Xeric Referring to habitats in which plant production is limited by lack of water. Xerophyte Plant typically found in very dry habitats; any plant growing in a habitat in which appreciable portion of the rooting medium dries to the wilting coefficient at frequent intervals. Xeroriparian Mesic to xeric habitat-type with average annual moisture higher than surrounding uplands, but provided with surface moisture in excess of local rainfall only on infrequent occasions (usually for less than one month per year); vegetation, when present, consists of a mixture of preferential, facultative, and non- riparian plants. Term proposed by Johnson et al. (1984) to be added as a subsystem to the Palustrine System of Cowardin et al. (1979). See “Hydroriparian” and “Mesoriparian”. Xylem Tissue in the vascular system. Y Yazoo-type river Tributary unable to enter main stream due to natural levees along main stream. Usually flows along a back-swamp zone parallel to the main stream. Derived from the Native American and present-day, name for a stream in Mississippi which has such a relationship with the Mississippi River. Yield The mass of material or constituent transported by a river in a specified period of time divided by the drainage area of the river basin. Z Zone of aeration Zone immediately below the ground surface in which voids are partially filled with air and partially filled with water trapped by molecular attraction. Zone (of a streambank) A specific area of a streambank at a given location or reach of stream, distinguished by elevation, used to determine what vegetative species or structural techniques would be most successful for bioengineering protection applications. The specific terms may vary, but one useful approach is a division into four categories: terrace zone, bank zone, splash zone, and toe zone. Those designations graduate,

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respectively, from the flood plain down to or beyond the toe of the bank. For bioengineering, these terms are more useful than upper bank, middle bank, and lower bank. Usually, existing vegetation in the area is a better guide to zone distinction than an arbitrary hydrologic distinction. Zone of saturation Underground region within which all openings are filled with water. The top of the zone of saturation is called the water table. Water contained within the zone of saturation is groundwater. Zoogeographic Concerning geographic distribution of animal populations and assemblages. Zooplankton See Plankton.

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REFERENCE LITERATURE

1) USGS, (U.S. Geological Survey), “Water Basics Glossary”, as downloaded from URL: http://capp.water.usgs.gov/GIP/h2o_gloss/, and accessed on 12/11/2004. 2) Fischenich, Craig. 2000. “Glossary of Stream Restoration Terms,” USAE Research and Development Center, Environmental Laboratory, 3909 Halls Ferry Rd., Vicksburg, MS 39180, ERDC TN-EMRRP-SR-01 (filename: 4_22_0920b.pdf.) 3) “Selected Terms Commonly Used in Stream Geomorphology,” (sent via email to Michael Sprague, (filename: 4_22_0920c.pdf) 4) E-SenSS. E-Senss “Glossary of Stream Stabilization Terms”, as provided in E-SenSS software 2004. 5) Watson, Chester C., David S. Biedenharn, and Stephen H. Scott. 1999. Channel Rehabilitation: Processes, Design, and Implementation, Presented by US Army Engineer, Engineer Research and Development Center, Vicksburg, Mississippi, July 1999, Appendix II. Glossary, p. 294-296. 6) Gordon, Nancy D., Thomas A. McMahon, Brian L. Finlayson, Stream Hydrology: An Introduction for Ecologists, John Wiley & Sons, Chichester, 1992. 7) EPA, (Environmental Protection Agency) “Glossary for the Rapid Bioassessment Protocols Module,” from URL: http://www.epa.gov/watertrain/rbp/glossary.html, as accessed September 21, 2004. 8) 2004 RiverWorks, Inc. Glossary. 2004. 9) Fischer, Richard. “Glossary”, compiled by Richard Fischer, WES, US Army Corps of Engineers.

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