Glossary - Southern Sonoma County Resource Conservation District, California

100-Year Flood. That flood event that has a one-percent chance of occurrence in any one year.

Acceptable Outlet. That point where storm water runn-off can be released into a watercourse or drainage way of adequate capacity without causing scour or erosion.

Alluvial Fan. A sloping, fan shaped mass of sediment deposited by a stream where it emerges from a nupland onto a plain.

Alluvium. A general term for all detrital material deposited on or in transit by streams, including gravel, silt, clay, and all variations and mixtures of these. Unless otherwise noted, alluvium is unconsolidated.

Angle of Repose. The angle beyween the horizontal and the maximum slope that a soil assumes through natural processes.

Apron. A floor or lining to protect a surface from erosion. For example, the pavement below chutes, spillways, or the toes of dams.

Aquifer. A natural underground formation that is saturated with water, and from which water can be withdrawn.

Attainment Area. An area determined to have met federal or State air quality standards, as defined in the federal Clean Air Act or the California Clean Air Act. An area may be an attainment area for one pollutant and a non-attainment area for others.

Easement. A right given by the owner of land to another party for specific limited use of that land. An easement may be acquired by a government through dedication when the purchase of an entire interest in the property may be too expensive or unnecessary.

Environmental Impact Report (EIR). A document used to evaluate the potential environmental impacts of a project, evaluate reasonable alternatives to the project, and identify mitigation measures necessary to minimize the impacts. The California Environmental Quality Act (CEQA) requires that the agency with primary responsibility over the approval of a project (the lead agency) evaluate the project's potential impacts in an Environmental Impact Report (EIR).

Endangered Species, California. A native species or sub-species of a bird, mammal, fish, amphibian, reptile, or plant, which is in serious danger of becoming extinct throughout all or a significant portion of its range, due to one or more factors, including loss in habitat, change in habitat, over-exploitation, predation, competition, or disease. The status is determined by the State Department of Fish and Game together with the State Fish and Game Commission.

Endangered Species, Federal. A species which is in danger of extinction throughout all or a significant portion of its range, other than the species of the Class Insect determined to constitute a pest whose protection under the provisions of the 1973 Endangered Species Act, as amended, would present an overwhelming and overriding risk to humans. The status is determined by the US Fish and Wildlife Service and the Department of the Interior.

Environmental Setting. The physical conditions in an area, including land, air, water, minerals, flora, fauna, ambient noise, and objects of historical or aesthetic significance, which will be affected by a proposed project. The area involved shall be the area in which significant effects would occur either directly or indirectly as a result of the project. The "environment" includes both natural and man-made conditions.

Erosion. The process by which material is removed from the earth's surface (including weathering, dissolution, abrasion, and transportation), most commonly by wind or water.