Source of the glossary of river management terms: Geomorphic Investigation of Quinault River, Washington (18 Km Reach of Quinault River Upstream from Lake Quinault)


Active channel - The unvegetated channel that conveys the majority of the river's bedmaterial load. Does not include overflow or side channels.

Active floodplain - The zone of active channel, side channels, overflow channels and intervening surfaces that receive some flow at annual intervals and have been reworked by the active channel at least once within approximately the last century. It is synonymous with the boundaries of the 2002 historical channel migration zone (HCMZ).

Aggradation - The building up by a stream by deposition of sediment in order to establish or maintain uniformity of grade or slope (Bates and Jackson, 1987, p. 11).

Allogenic - An ecologic succession that resulted from factors that arise from outside the natural community and alter its habitat, such as an allogenic drought of prolonged duration.

Alluvium - A general term for clay, silt, sand, gravel, or similar unconsolidated detrital material, deposited during comparatively recent geologic time by a stream or other body of running water, as a sorted or semisorted sediment in the bed of the stream or on its flood plain or delta (Bates and Jackson, 1987, p. 18).

Alluvial fan - A low, outspread, relatively flat to gently sloping mass of loose rock material, shaped lake an open fan or a segment of a cone, deposited by a stream at the place where it issues from a narrow mountain valley upon a plain or broad valley, or where a tributary stream is near or at its junction with the main stream, or wherever a constriction in a valley abruptly ceases or the gradient of the stream suddenly decreases; it is steepest near the mouth of the valley where its apex points upstream, and it slopes gently and convexly outward with a gradually decreasing gradient (Bates and Jackson, 1987, p. 17).

Anadromous fish species - Anadromous fish, such as salmon and steelhead, migrate or swim from their freshwater place of birth to the saltwater ocean and then return to their freshwater home stream as an adult to breed.

Autogenic - An ecologic succession that resulted from factors originating within the natural community and altering its habitat.

Bar - Accumulations of bed load (sand, gravel, and cobble) that are deposited along or adjacent to a river as flow velocity decreases. If the sediment is reworked frequently, the deposits will remain free of vegetation. If the surface of the bar becomes higher than the largest flows, vegetation stabilizes the surface making further movement of the sediment in the bar difficult.

Base level - The level below which a stream cannot erode its bed. The general or ultimate base level for the land surface is sea level, but temporary base levels may exist locally. [From p. 57 in Bates, F.L., and Jackson, J.A. eds., 1987, Glossary of Geology (Third Edition): Alexandria, Virginia, American Geological Institute, 788 p.]

Bed material - Sediment that is preserved along the channel bottom and in adjacent bars; it may originally have been material in the suspended load or in the bed load.

Bedload - The sediment that is transported intermittently along the bed of the river channel by creeping, rolling, sliding, or bouncing along the bed. Typically includes sizes of sediment ranging between coarse sand to boulders (the larger or heavier sediment).

Bedrock - Areas where rock is present; includes Core and Peripheral rocks (Tabor and Cady, 1978), which are igneous, sedimentary, and metasedimentary rocks (basalt, sandstone, conglomerate, siltstone, argillite); hard and resistant to fluvial erosion.

Braided - A channel that contains, within one active channel segment, several channel paths that are separated by bars or islands.

Center line - A line drawn along the center of the active or unvegetated channel; visually placed to be at the center of all channel paths.

Channel deposits - Sediment that is deposited in the channel as flow subsides; usually consists of gravel and sand.

Channel Migration Zone (CMZ) - the valley area susceptible to reoccupation by the river through channel erosion and reworking processes. The CMZ encompasses the HCMZ (area of historical occupation over a given timeframe) and adjacent areas that may currently be terrace, glacial deposits, lake-bed deposits, or man-made surfaces but are at risk for being eroded by the river.

Channel planform - Characteristics of the river channel that determine its twodimensional pattern as viewed on the ground surface, aerial photograph, or map.

Channel sinuosity - The ratio between the length of the channel, as measured along the centerline of the channel, and the centerline length of the valley. For this study, the ratio was measured between the length of the channel and the centerline of the future channel migration zone. The higher the sinuosity value, the more curving the channel pattern.

Channel width - The average channel width calculated for the active and unvegetated channels by dividing the channel area by the length of the channel center line.

Cleared - Areas within the HCMZ where it appears that the vegetation has been artificially removed by human activity (e.g., logging, clearing for residential property, roads); areas are often covered with grass.

Coarse sediment - Boulders to coarse sand (2 to 4096 mm); sizes that are usually transported as bed load and are too large to be deposited outside of the channel on the flood plain by overbank flow.

Control point - A survey station that provides horizontal or vertical position data, or both, that can be identified on aerial photographs and used to ortho-rectify the photographs or to correlate data.

Cubic meter per second (m3/s) - The rate of water flow passing any point equal to a volume of one cubic meter of water every second.

D50- The median particle-size diameter for a sediment sample, such that 50 percent of the sample is larger than this value.

Debris flow - A moving mass of rock fragments, soil, and mud, more than half of the particles being larger than sand size.

Delta - A low, nearly flat, alluvial tract of land at or near the mouth of a river (in this study the delta is at Lake Quinault), commonly forming a triangular or fan-shaped plain crossed by many distributaries of the river, and resulting from the accumulation of sediment supplied by the river; delta sedimentation is partly subaerial and partly below water.

Discharge - The volume of water in a river that flows through a given cross section of the river channel per unit time. In the United States, it is usually measured in cubic feet per second (ft3/s).

Engineered Log Jam (ELJ) - Interconnected pile of large logs engineered to mimic natural log jams in a river system; usually creates a hard point in the channel and provides habitat for salmon; may be designed to be temporary or relatively permanent depending upon the size of the logs and the amount and type of anchors.

Fine sediment - Fine sand, silt, and clay (< 2 mm); sizes that can be transported as suspended sediment and are often deposited outside of the active channel in areas of low velocity and on the floodplain by overbank flow.

Floodplain - The zone interpreted to include the active floodplain and additional surfaces outside the active floodplain that are inundated by peak river flows, tributary channel flows, and backwater flooding from Lake Quinault.

Fluvial geomorphology - The study of river channel geometry and planform, and how it changes over time.

Forset bed - A bed of unconsolidated sand and (or) gravel that is part of a set of inclined (gently dipping) layers that are usually crossbedded; sediment is deposited along an advancing or relatively steep slope, such as the outer margin of a delta, and progressively buries the lower beds; the sediment is, in turn, buried and truncated by younger beds as deposition continues.

GIS - Geographical information system. An organized collection of computer hardware, software, and geographic data designed to capture, store, update, manipulate, analyze, and display all forms of geographically referenced information (McCoy and Johnston, 2002).

Grass vegetation - Areas outside of the HCMZ where the canopy is homogeneous in appearance, open, and of very low relief; areas have been cleared artificially by human disturbances; mainly on low surfaces (Holocene) adjacent to the HCMZ.

Hillshade - A hypothetical illumination of a surface that is created in Arc using x, y, and z values for an area.

Historical channel migration zone (HCMZ) - An area where the main river channel occupies and transports sediment and woody debris within a specified timeframe.

Holocene - The geologic time interval between about 10,000 years ago and the present. Hydraulics - The physical laws governing water movement.

Immature vegetation - Area outside of the HCMZ where the canopy is homogeneous in appearance, single-storied, and of low to moderate relief ; consists of either conifers or deciduous trees; areas are present on all surfaces and bedrock.

Incision - The process by which a downward-eroding stream deepens its channel or produces a relatively narrow, steep-walled valley (Bates and Jackson, 1987, p. 331). Intermediate Holocene surface - Surface that is outside of the HCMZ, but is commonly inundated by overbank flow; composed of surfaces of several heights, but most are between about 1 and 2 m above the active channel of the Quinault River; surfaces are commonly dissected by side channels that convey flow all or part of the year (terrace channels); surfaces are commonly covered by alders and spruce with diameters up to 1 ft and Sitka spruce with diameters up to 2 ft; associated deposits may include delta deposits below thin (usually < 1 m) of overbank deposits; late Holocene.

Key member - An individual piece of wood that is large enough to become stable within the channel.

Lacustrine - Sediment deposited in a lake; usually very fine (silt and clay); often dark gray because of the organic material present in the sediment

Large woody debris (LWD) - Large downed trees that are transported by the river during high flows and are often deposited on gravel bars or at the heads of side channels as flow velocity decreases. The trees can be downed through river erosion, wind, fire, or human induced activities.

Late-successional forest - A forest stand usually less than 150 years old that has had natural or anthropogenic disturbances and generally has a high canopy closure. These forests contain a relatively high density of large trees but do not exhibit the many oldgrowth characteristics including an advanced state of decadence or diverse species composition.

Levee - A natural or artificial embankment that is built along a river channel margin; often constructed to protect an area from flooding or confine water to a channel. Often referred to as a dike.

Loess - A deposit of wind-blown silt.

Longitudinal bar - An elongated gravel bar that extends along and roughly parallel to a relatively straight section of river channel. It grows in a downstream direction, with its steep side toward the channel bank and with a narrow trough between the bar and the bank.

Low-flow channel - The channel that carries water during times of low flow. It tends to follow the deepest part of the channel.

Lower Holocene surface - Surface that is frequently inundated with flow (at least on nearly a yearly basis); includes surfaces of several heights, but the highest ones included in the lower surface are about 1 m above the active channel of the Quinault River; commonly covered with alder, willow, and small conifer; synonymous with the HCMZ.

Mass wasting - General term for the dislodgement and downslope transport of soil and rock under the influence of gravitational stress (mass movement). Often referred to as shallow-rapid landslide, deep-seated failure, or debris flow.

Mature forest - Area where the canopy is generally heterogeneous in appearance, multistoried, and of high relief (tall) consisting predominantly of conifers; although small remnants remain on the lower surfaces (Holocene), the most expansive areas are found on bedrock and Pleistocene surfaces.

Mid-channel bar - A ridge-shaped or somewhat arcuate gravel bar that is preserved between branches of a low-flow channel.

Mixed vegetation - Vegetation within or outside of the HCMZ that includes both shrubby vegetation and scattered trees; may include small areas of dense or nearly continuous trees; trees appear to be mostly deciduous; vegetation often appears to follow old channels that receive little or no flow.

Moraine - A mound or ridge composed of unsorted, unstratified glacial drift, predominantly till, deposited chiefly by direct action of glacier ice (Bates and Jackson, 1987, p. 433).

Old channel - Channel that is essentially covered with vegetation, but is still recognizable as a channel; it does not convey enough flow to disrupt vegetation, and may no longer receive surface flow from the Quinault River.

Old growth forest - A forest stand usually at least 180-220 years old with moderate to high canopy closure; a multilayered, multispecies canopy dominated by large overstory trees; high incidence of large trees, some with broken tops and other indications of old and decaying wood (decadence); numerous large snags; and heavy accumulations of wood, including large logs on the ground. Any evidences of man's activities may be present, but do not significantly alter the other characteristics and would be a subordinate factor in a description of such a stand (USDA, 1998).

Ortho-rectified photograph - An aerial photograph that has been corrected for the geometries and tilt angles of the camera when the image was taken and for topographic relief using a digital elevation model, flight information, and surveyed control points on the ground.

Overbank deposits - Fine sediment (fine sand, silt, and clay) that is deposited outside of the channel on the floodplain or terrace by overbank flow.

Overflow channel - A channel, often adjacent to the active channel, that carries water only during high flows (floods). The channel can be dry for much of a year, but receives flow frequently enough that it is generally unvegetated. It is synonymous with floodflow channel.

Partially cleared and (or) regrowth - Areas within the HCMZ where it appears that the vegetation has been partially cleared artificially by human activity; areas often include several types of vegetation in artificially appearing patterns (e.g., linear sections of a different vegetation type that appear to follow old roads); includes areas that were once entirely cleared artificially, but vegetation has begun to regrow.

Pleistocene - The geologic time interval between 1.6 million years ago and 10,000 years ago.

Pleistocene surface - Surface that is not inundated by overbank flow; composed of surface of several heights and ages, but most are greater than 5 m above the active channel of the Quinault River; commonly covered by mature ferns, and large-diameter (4 ft or larger) Sitka spruce, Douglas fir, and bigleaf maple; large-diameter stumps are present in some areas; surface are interpreted to be Pleistocene on the basis of their relationship to glacial deposits.

Point bar - A sand or gravel bar that is deposited at the inside of a meander bend as a result of secondary currents related to changes in velocity at a bend in the channel. It is usually found where sediment is supplied from upstream, so that the bar grows in the downstream direction as sediment continues to be added to the inside of the bend. Potential habitat - Narrow or wide overflow or side channel of the Quinault River that flows through an area with some vegetation, usually riparian; for wide channels, water is usually visible; water source may be a surface connection to the Quinault River or groundwater; at least some vegetation is present to protect the channel and habitat conditions. This is potential habitat as it is not known whether the channel was actually used for reproduction or rearing; the presence of riparian or mixed riparian vegetation and trees suggests that the channel has not received large flows from the Quinault River in the recent past.

Quaternary - The geologic time interval between 1.6 million years ago and the present. It includes both the Pleistocene and the Holocene.

Raster - A file that uses a grid structure to store geographical information; represents information as an array of equally sized square cells (or pixels) arranged in rows and columns; each grid cell is referenced by its geographic x, y location (McCoy and Johnston, 2002).

Raster calculator - A function in Spatial Analyst in Arc that performs mathematical calculations and queries on raster files using numeric values assigned to each pixel.

Redd - Also known as spawning beds, or nests, redds are areas in the stream bottom dug out by female salmon in preparation for spawning. After fanning out a redd with her tail, a female will deposit her eggs and then cover them with more gravel.

Regime equation - An equation developed by comparing channel discharge (typically bankfull) to average slope of several measured rivers. The equation is generally used to classify rivers in a common geomorphic context, such as meandering or braided.

Riparian - Pertaining to areas of land directly influenced by water. Riparian areas usually have visible vegetative or physical characteristics reflecting this water influence. Stream sides, lake borders, or marshes are typical riparian areas (USDA, 1998).

Riprap - Large angular rocks that are placed along a river bank to prevent or slow erosion.

River kilometer (RK) - The distance in kilometers measured along the centerline of the river channel upstream from the mouth or other established point of origin (e.g., confluence).

Scattered vegetation - Areas outside of the HCMZ where the canopy is heterogeneous in appearance, partially open, and has low to moderate relief; areas generally have deciduous trees, but conifers can be numerous; areas are mainly on low surfaces (Holocene) adjacent to the HCMZ.

Scour - Local erosion of sediment from the channel bed during high-velocity flows. Scrub vegetation - Areas outside of the HCMZ where the canopy can be heterogeneous or homogeneous in appearance, predominantly open, and of low relief; includes areas where vegetation has regrown after timber harvesting; common on low surfaces (Holocene) adjacent to the HCMZ.

Shapefile - A format for vector data for storing the location, shape, and attributes of geographic information (McCoy and Johnston, 2002)

Shrubby vegetation - Low vegetation within the HCMZ where individual plants are not visible on the aerial photographs; often appears to follow old channels, which receive little or no flow so that vegetation has become established.

Side channel - A secondary channel that nearly always carries flow and is located in the active flood plain and may be fed from groundwater or tributaries much of the time.

Slightly vegetated channel - A channel that has scattered vegetation, but is still recognizable as a channel; it is an overflow channel that may still receives some flow, but not often enough for it to remain free of vegetation; it carries water only at the highest flows.

Smolts - The point in a juvenile salmon's lifecycle when their bodies are changing in preparation for surviving in salt water, enabling them to migrate from freshwater to the sea.

Stage - The height of the water surface above the channel bed; referenced either by depth or to a vertical datum.

Suspended-sediment load - The fine sediment (fine sand, silt, and clay) that is transported in suspension above the channel bed. It is the sediment that is light enough or small enough to be transported in suspension much of the time, in contrast to the bed load that is primarily moved along the bed.

Terrace - A relatively stable, flat surface formed when the river abandons the floodplain that it had previously deposited. It often parallels the river channel, but is high enough above the channel that it rarely, if ever, is covered by water and sediment. The deposits underlying the terrace surface are alluvial, either channel or overbank deposits, or both. Because a terrace represents a former floodplain, it can be used to interpret the history of the river.

Terrace channel - Side channel or overflow channel that is incised into a terrace surface; incision ranges between <0.5 m to 5 m; channel widths are a few meters to tens of meters; banks reveal alternating beds of gravelly (channel deposits) and fine (overbank deposits) alluvium; unvegetated bars of gravelly alluvium may be present along the channel; may include LWD; the channel usually, but not always, connects to the main channel at its upstream and downstream ends, either directly or through a network of terrace channels; channels may be quite sinuous and complexly interconnected.

Transverse bar - A gravel bar that extends roughly perpendicular across the direction of flow. It is often associated with split, branching flow and can create steps in the channel bed.

Tree vegetation - Areas within the HCMZ that are covered nearly continuously with trees, either deciduous or conifer, or both; little other vegetation is visible on the aerial photographs; on surfaces that have not been part of the unvegetated channel recently, so that they have stabilized and revegetated.

Tributary channel - The channel of a stream feeding, joining, or flowing into a larger stream (e.g., the Quinault River); same as tributary; referred to as a tributary channel to distinguish it from the main, side, or overflow channels of the Quinault River.

Unvegetated channel - The unvegetated area adjacent to the active channel; it includes the active channel and unvegetated bars adjacent to it; it includes overflow channels that are unvegetated; it is the area that conveys flow at higher discharges often enough to remain unvegetated; it probably receives flow at least once, but probably several times, a year.

Upper Holocene surface - Surface that is infrequently inundated by overbank flow; composed of surfaces of several heights, but most are between 3 and 5 m above the active channel of the Quinault River; commonly dissected by mostly ephemeral and perennial channels (terrace channels); commonly covered by mature ferns, and large-diameter (4 ft or larger) Sitka spruce, Douglas fir, and bigleaf maple; large-diameter stumps are present in some areas; Holocene.