Glossary of Important Terms

Anadromous Fish  fish, such as salmon and steelhead that spawn in fresh water, migrate to the ocean to grow, and then return to fresh water to spawn.

Fluvial Geomorphic Processes – the processes by which water affects the land surface, eroding mountains to form valleys, transporting rock and sediment to deposit downstream.

Fossilization – the process of stabilization and “hardening” of gravel bars by rooted riparian vegetation, which also contributes to increased deposition of alluvial silts on the bars, promoting establishment of yet more vegetation and so on.

Geomorphology – the science of landforms, with an emphasis on their origin, evolution, form, and distribution across the physical landscape.

Hydraulic – hydraulic action is the movement or wearing down of material by flowing water. In geographic processes, hydraulic action is also known as erosion.

Hydrograph – a chart that displays the change of a hydrologic variable over time. A discharge hydrograph, for example, shows the rate of flow (discharge) past a specific point in a river on the x axis and the time on the y axis.

Hyporheic zone – a region beneath and alongside a streambed where shallow groundwater and surface water mix.

LiDAR—light detection and ranging – an optical remote-sensing technique that uses laser light to densely sample the surface of the earth, producing highly accurate depth, width, and height (x,y,z) measurements

Morphodynamic – the study of landscape changes due to erosion and sedimentation.

Point bars – features of alluvial river channels formed by the deposition of sediment on the convex bank of a curve in the channel as erosion of the opposite concave bank occurs.

Point cloud – a set of three-dimensional point locations that provide a digital representation of an object or surface. Point clouds for natural resource sciences are typically derived from laser scanning methods, including aerial LiDAR and ground-based scanners, sonar methods for bathymetry (underwater topography), and recent methods for processing photographs with computer vision techniques. Point clouds often include thousands to millions of points.

Programmatic environmental document – a programmatic environmental impact statement evaluates the effects of broad proposals or planning-level decisions that may include any or all of the following: a wide range of individual projects; implementation over a long timeframe; and implementation across a large geographic area.

Record of Decision (ROD) – a legally binding document that identifies a Federal agency’s decision on how it will proceed with the proposed action identified in an environmental document prepared to comply with the National Environmental Policy Act.

Restoration flow – all ROD-mandated flows, including summer and winter base flows and peak flows in the spring.

Riparian – an area located on the bank of a river or other water body or the area of direct two-way interactions between aquatic and terrestrial systems.