Glossary

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Glossary terms for letter: A

Abiotic

Not biological; not involving or produced by organisms. Non-living, as opposed to living, or "biotic;" examples of biotic factors controlling biological activity include pH, temperature, moisture, and chemicals.

Abrasion

Removal of streambank soil as a result of sediment-laden water, ice, or debris rubbing against the bank.

Accretion

Natural accretion is the buildup of land, solely by the action of the forces of nature, on a beach by deposition of water-borne or airborne material. Artificial accretion is a similar buildup of land by reason of an act of man, such as the accretion formed by a groin, breakwater, or beach fill deposited by mechanical means.

Aerobic

Requiring oxygen or in the presence of oxygen.

Aggradation

The long-term hydraulic process by which streambeds and floodplains are raised in elevation by the deposition of materials. It is the opposite of degradation.

Aggregation (Soil)

Where many soil particles are held in a single mass or cluster such as a clod, crumb, block, or prism.

Algae

Simple, usually microscopic, rootless plants that usually grow in water, that have no true root, stem or leaf.

Algal Blooms

A large population of algae that is obvious to the naked eye; usually caused by an abundance of nutrients in the water.

Alongshore

Parallel to and near the shoreline.

Alluvial

Deposited by running water.

Anadromous

Fish or other organisms that are born in freshwater, and migrate to and live in salt water, and then return to freshwater to reproduce.

Anaerobic

Life or processes that occur in the absence of oxygen; a condition where oxygen is absent.

Aquatic

Growing or living in or upon water.

Armoring

The natural process of forming an erosion resistant layer of relatively large particles on the surface of the streambed.

Artificial Headlands

Man-made offshore structures connected to the shoreline to provide coastal protection or to restrict longshore transport.

Available Water Capacity

The capacity of soil to hold water for use by plants.

A-Zone

Flood zone subject to still-water flooding during storms that have a 100-year recurrence interval.

 

Revised 5/15/07

Institute for Water Resources