Northwest Fisheries Science Center

Fish Ecology Programs


Dr. Richard Zabel
Division Director
Dr. Sandra Downing
Division Coordinator
Org Chart
Staff Directory

Watershed Program Glossary


Adaptive management
An iterative decision–making process involving a cycle of planning, implementing, monitoring, evaluating, and, subsequently, reexamining and altering management decisions based on monitoring results. 
Aggradation is a rise in grade or level of a stream–bed elevation through deposit of detritus, sediment. 
Alluvial groundwater (water table)
Water within the alluvium, or loose rock, gravel, soil, and sediment surrounding a channel.  This groundwater is linked hydrologically with water in the channel and strongly influences the channel, its riparian vegetation, and its connection with the floodplain.
Anastomosing channel
channel that branches and departs from the main channel, sometimes running parallel for several kilometers before rejoining the main channel.
Bankfull width
Channel width between the tops of banks on either side of a stream; tops of banks are the points at which water overflows its channel at bankfull discharge.  Contrast wetted width.
Basal area
Square feet of total base area of trees (usual at breast height) per unit area (typically acre or hectare).
Baseline monitoring
Characterizing existing biota, chemical or physical conditions for planning or future comparisons.  Compare status, trend, implementation, effectiveness, and validation monitoring.
Entire land–drainage area of a river.  Also called watershed, drainage basin, or catchment.
Bed load
Sediment particles resting on the channel bottom that are pushed or rolled along by the flow of water.  Note that sediment can move between bed load and suspended load as the stream discharge changes.  Compare suspended load and wash load.
Of, related to, or living in the soil–water interface of a lake or stream.
Community of microorganisms attached to a solid surface.
Vegetated channel commonly used to remove pollutants in storm water runoff.
Brush bundles
Groups of trees and branches placed into a lake or stream to create habitat and cover for fish.  Often used in conjunction with other habitat rehabilitation techniques.
Brush park
Submerged or partially submerged structures made of brush, branches, and aquatic vegetation secured in place with poles or fences.  They are designed to provide fish rearing areas, fishing opportunity, or refuge for fish.  They vary in size from a few square meters to several hectares and are used in lakes, streams, and brackish waters.
Biological activities, such as burrowing and feeding in, at, or near the sediment surface, that occur and cause the sediment to become resuspended and mixed.
Trees uprooted and felled, or branches broken and felled by strong gusts of wind. Also called windthrow.
Entire land–drainage area of a river.  Also called watershed, basin, or drainage basin.
Channel bifurcation ratio
Number of first–order channels divided by the number of second–order channels, the number of second order divided by third order, etc.  Bifurcation ratios provide insight into the maturity of tidal channel development.  Compare stream order.
Straightening, narrowing, and deepening of a stream channel.  Channelization may be deliberate to improve navigation, move water faster, or prevent flooding of human infrastructure.  It often includes removal of debris and channel obstructions that may impede flow.
Channel unit
See habitat unit.
Coarse sediment
Generally, greater than 2–mm diameter, which is gravel, cobbles, or boulders.  Compare fine sediment.
Control site
A study location nearly identical to the treated location, with the exception that no treatment occurs.  See also reference site.
Forest regeneration from vegetative sprouts from stumps, branches, or roots.
Core area
For a species, part of its range that is typified by high and frequent use or that provides high–quality habitat for breeding, rearing, feeding, and other key functions necessary for survival.
Creation (habitat)
Construction of a new habitat or ecosystem where it did not previously exist.  This is often part of mitigation activities
A transverse pipe or totally enclosed drain under a road or railway.  Typically used to convey stream flow under a road or other manmade construction.
Cross section
Profile of elevations perpendicular to the stream channel.
DBH (diameter at breast height)
A measurement of tree diameter taken at breast height.
Mechanical site–preparation technique used to break up soil and plow existing vegetation into the soil.  It usually is performed by towing a disc (a trailer on wheels with numerous sharp rotating discs that cut into the soil) behind a tractor.
Branch of a river or a stream that flows away from the main channel and does not rejoin it.  Also called distributary channel.
Drainage basin
Entire land–drainage area of a river.  Also called watershed, basin, or catchment.
In restoration ecology, it refers to acquiring a portion of the rights to a land to allow for, or protect from, a specific use.  Technically defined as the nonpossessory interest granted in the lands of another, established to obtain certain limited rights granted in perpetuity or for set periods.  For example, development rights, but never the right to "quiet enjoyment."  Compare acquisition.
Area determined by similar land–surface form, potential natural vegetation, land use, and soil; it may contain few or many geological districts.
Dynamic and holistic system of all the living and dead organisms in an area and the physical and climatic features that are interrelated in the transfer of energy and material.
Effectiveness monitoring
Evaluating whether actions had the desired effects on physical processes, habitat, or biota.  Compare baseline, status, trend, implementation, and validation monitoring.
Composed of the variable, the sampling unit, and the statistic together.  Often used to establish a quantifiable measure of success.  For example, a water–quality endpoint might be a mean daily maximum temperature of 16°C.
To improve the quality of a habitat through direct manipulation.  It does not necessarily seek to restore processes or conditions to some predisturbed state.  Some practitioners call this partial restoration.  Compare rehabilitation and restoration.
Fencing an area to prevent (exclude) access of livestock or other ungulates.
Fine sediment
Generally, less than 2–mm diameter, typically composed of clay, silt, or sand.  Compare coarse sediment.
Decrease in mean substrate particle size.
A flat depositional feature of a river valley adjoining the channel, the floodplain is formed by climate and hydrological conditions and is subject to periodic flooding.
Wire rectangular or round basket placed in a stream channel and filled with gravel, gobbles, boulders or other hard material to serve as bank protection or to create a weir to trap gravel, create a pool, and improve fish habitat.
Removing the layer of bark and cambium around the circumference of a tree, usually performed in an attempt to kill the tree.
A jetty extending from the bank into the channel designed to protect or stabilize a bank or trap gravel and sediment sands.
A shallow stream section (habitat unit or mesohabitat) with even laminar flow and little or no turbulence or obstructions.
First perennial vegetation that forms a lineal grouping of community types on or near the water′s edge, most often at or below the bankfull stage.
Field measurement of specific attributes that have been predicted from models, maps, or remotely sensed data for the purpose of assessing accuracy and precision of predictions.
Erosion of soil by formation or extension of channels (gullies) from surface runoff.
Habitat complexity
Determined by survey of physical structures such as large woody debris, sediment types, number and depth of pools, bars, etc.  Complexity is a measures of habitat quality and has been correlated with survival and recruitement of fish.
Habitat unit
Distinct geomorphically defined area within a stream reach, such as a pool, a riffle, a glide, etc.  Sometimes called a mesohabitat.
Hydraulic head
Water elevation and water pressure.
Hyporheic zone
The saturated interstitial areas below the streambed and into the streambanks (or floodplain), where stream water and deep groundwater intermix and where a number of important chemical, hydrological, and biological processes take place.
Implementation monitoring
Evaluating whether the restoration project was constructed (implemented) as planned.  Compare baseline, status, trend, effectiveness, and validation monitoring.
Incised channel
An incised stream channel is one in which the stream bed is deepened to a point where flow is no longer connected the surrounding floodplain but cuts through the stream bed, resulting in further erosion and instability.  Incised channels are caused by erosion, usually resulting from an imbalance between sediment transport capacity and sediment supply to the stream. 
Large woody debris (LWD)
Large piece of woody material such as a log or stump that intrudes into or lies entirely within a stream channel; LWD typically is defined as wood greater than 10 cm in diameter and 1 m in length, but other minimum size criteria also are used.
An embankment or dike constructed of earth, rock or other material to prevent a river from overflowing.
LIDAR (light detection and ranging)
 Using a principle similar to radar, the LIDAR instrument transmits light to a target and receives reflected or scattered light back for analysis.  Change in the properties of light enable measurment of various properties of the target, such as distance, speed, rotation, or chemical composition and concentration.
Limiting factor
Factor that confines (limits) the growth of an ecosystem element.
Long profile (longitudinal profile)
Longitudinal plot of elevation versus distance (gradient), typically along the thalweg of a stream.
Main stem
Principle stream or channel of a stream network.
Mass wasting
Downslope movement of earth materials under gravity, including such processes as rockfalls, landslides, and debris flows.
Benthic animals that can fit a mesh size of 1 mm and be retained on a mesh size of 42 Âμm.
Surrogate for a real ecosystem that meets the requirement of being of sufficient size to contain all the components of interest while allowing "natural" behavior.  In aquatic ecology, it often is an enclosed portion of a stream or other body of water or artificial stream channel, and may range from a few to several hundred square meters, depending on the ecosystem and organisms being studied.
Distinct geomorphically defined habitat area within a stream reach such as a pool, a riffle, a glide, etc.  Often called a habitat unit.
Network of semi–isolated populations, with some level of regular or intermittent migration and gene flow among them, in which individual populations may go extinct but then the habitat they occupied can become recolonized from remaining populations.
Standard of measurement or combination of parameters used as a standard of measurement.  See also parameter and variable.
Specific locations where organisms live that contain combinations of habitat characteristics that directly influence the organism′s physiology or energetics in a small or restricted area.  In fisheries and aquatic ecology, this typically is at a scale smaller than a mesohabitat or a habitat unit and may include preferences for substrate, velocity, depth, etc.
Action taken to alleviate or compensate for potentially adverse effects on an aquatic habitat that has been modified or lost by human activity.
Systematically checking or scrutinizing something for the purpose of collecting specific categories of data, especially on a recurring basis.  In ecology, it generally refers to systematically sampling something in an effort to detect or evaluate a change or lack of change in a physical, a chemical, or a biological parameter.  Compare baseline, status, trend, implementation, effectiveness, and validation monitoring.
Nutrient enrichment
Addition of organic or inorganic compounds to a water body to increase background levels of nutrients (e.g., phosphorous, nitrogen).
Uppermost layer of foliage that forms a forest canopy.  Compare understory.
Photic zone
Upper layers of bodies of water into which sunlight penetrates sufficiently to influence the growth of plants and animals.
Primary production
Creation of organic matter (biomass) by photosynthesis or chemosynthesis.
Primary productivity
Rate at which organic matter (biomass) produced by photosynthesis or chemosynthesis is stored in an ecological community or group of communities.  Compare secondary productivity.
Rainsplash erosion
Transport of sediment by movement of water from precipitation, which typically causes soil particles to be splashed more on the downhill than on the uphill side of a slope.
A geomorphically similar stream section or a section of stream as defined by two selected points.
Reference site
Site in a relatively natural state, representative of conditions before human disturbance.  See also control.
Returning an area to its previous habitat type but not necessarily fully restore all functions.
A spawning nest constructed in the substrate of a lake or stream by a fish.
To restore or improve some aspects or an ecosystem but not fully restore all components. A general restoration term that can include habitat improvement, enhancement, or reclamation. Some practitioners call this partial restoration. Compare enhancement and restoration.
Remote sensing
Gathering data from a remote station or platform, as in satellite or aerial photography.
1. Return of an ecosystem to its predisturbed condition.  Also called full restoration.

2. General term referring to various enhancement, improvement, and rehabilitation actions. 

Shallow section of a river or stream, with moderate to rapid flow and with surface turbulence.
One of the first and smallest channels formed by surface runoff.
Removal of soil by water from small, well–defined, visible channels or streamlets where there is substantial overland flow.
The banks of a river or the terrestrial aquatic interface.  That part of a terrestrial landscape that exerts a direct influence on stream channels or lake margins, and the water or aquatic ecosystems.
Layer of large, durable materials such as rock used to protect a streambank from erosion; also may refer to the materials used, such as rocks or broken concrete.
Rubble matt
The placement of rocks, boulders, or concrete into the stream channel to create diverse flow and velocities and create riffles or fast water habitats for fishes and other aquatic organisms.
Road prism
Road surface and fill, and its geometry. Road prism removal includes excavation of part or all of road fill to restore natural drainage patterns.
See brush park.
Secondary productivity
Rate at which primary (plant and organism) material is synthesized into animal tissue per unit area in a given time period.  Compare primary productivity.
Sediment budget
Accounting of sediment sources and transfer processes in a watershed. The complete budget quantifies sediment sources, transport, and storage within a watershed, usually tracking each process of sediment production or movement separately.
Sediment supply
Supply of sediment to a river system, where it is carried in suspension (see suspended load and wash load) or on the bottom (see bed load).
Surface erosion from water running off in sheets, distinct from channelized erosion in rills and gullies.
Side channel
a subsidiary or overflow channel branching from the primary stream channel, typically conveying a small fraction of the total stream flow.
A low weir partially buried in the stream bottom designed to aggrade or maintain the channel level and improve fish habitat.
In forestry or forest management, the care, cultivation, and harvest of trees. In restoration ecology, the term generally refers to planting, removing, or growing trees and other vegetation to restore certain forest characteristics.
Soil creep
Gradual downslope movement of the soil mantle.
Staking and layering (riparian planting)
A form of riparian replanting that involves both the vertical placement of live shoots or cuttings and the horizontal placement of larger cuttings or branches. Commonly used for establishing willows to stabilizing banks and soils.
Source–sink dynamics
Interplay between high–productivity (source) and low–productivity (sink) areas in which excess individuals produced in a source area help maintain populations in sink areas through immigration.
Status monitoring
Characterizing the condition (spatial variability) of physical or biological attributes across a given area. Compare baseline, trend, implementation, effectiveness, and validation monitoring.
Stream order
A method of classifying streams based on size and number of tributaries. Typically smallest streams are given smaller numbers. For example, a first–order stream would be the smallest detectable headwater stream, a second–order stream would be formed by the formation of two first–order streams, etc.
Changes in species composition of plants and animals in an ecosystem with time, often in a predictable order. More specifically, the gradual and natural progression of physical and biological changes, especially in the trophic structure of an ecosystem, toward a climax condition or stage.
Suspended load
Part of the total stream load that is carried for a considerable period of time in suspension, free from contact with the streambed; it mainly consists of clay, silt, and sand. Note that sediment can move between suspended load and bed load as the stream discharge changes. Compare bed load and wash load.
Exposed former floodplain deposit that results when a stream begins downcutting into its floodplain. 
Line defining the lowest (deepest) points along the length of a stream.
Removal of trees or other vegetation to allow for increased growth of other trees or vegetation.
Tidal prism
Volume of water between mean higher high water (MHHW) and mean lower low water (MLLW).
Trend monitoring
Monitoring changes in biota or physical conditions over time. Compare baseline, status, implementation, effectiveness, and validation monitoring.
Stream or river that flows into another stream or river.
Shrubs and smaller trees between the ground cover and the forest canopy. Compare overstory.
Any of a number of hoofed, typically herbivorous, quadruped mammals, superficially similar but not necessarily closely related taxonomically.
UTM (Universal Transverse Mercator) Grid
Briefly, a grid base on the UTM geographic coordinate system.  The UTM represents locations in terms of northing and easting values.  Earth is divided into 60 numbered zones with each zone covering 6° longitude.  Easting values represent distance in meters from the longitudinal center of a numbered zone, while northing values represent distance in meters from the equator.  For complete details, see U.S. Geological Survey Fact Sheet 077–01 .
Validation monitoring
Evaluating whether the hypothesized cause–and–effect relationship between restoration action or other treatment, and physical and biological response were correct. Sometimes considered a part of effectiveness monitoring. Compare baseline, status, trend, implementation, and effectiveness monitoring.
Water bar
Construction of small (generally less than 50 cm) mound of soil and associated ditch across dirt or gravel roads to transport water across the road onto forest floor or adjacent hill slope. They are typically constructed on roads in mountainous areas to prevent water from running down the road surface and cause erosion. Variable
Attribute that may assume any one of a range of values. See also metric and parameter.
Number of life cycles repeated annually.
Wash load
Relatively fine material in near–permanent suspension that is transported entirely through the system without deposition. Compare bed load and suspended load.
Entire land–drainage area of a river.  Also called a basin, drainage basin, or catchment.
1. A low dam constructed in a stream to divert or retain water for various human uses.

2. A low dam or obstruction constructed of logs or rocks placed across a stream to create a pool or trap gravel and improve fish habitat.

Wetted width
Width of the water surface within a channel. Contrast bankfull width.
Trees uprooted and felled, or branches broken and felled by strong gusts of wind.  Also called blowdown.