Glossary of Terms

Abiotic: Not relating to life or specific life conditions.

Accessible Route: A continuous unobstructed path connecting accessible elements and spaces in a building or within a site that can be negotiated by a person with a severe disability using a wheelchair, and that is also safe for and usable by people with other disabilities. Interior accessible routes may include corridors, floors, ramps, elevators, and lifts. Exterior accessible routes may include parking access aisles, curb ramps, walks, ramps, and lifts.

Affected environment: Existing biological, physical, and social conditions of an area that are subject to change, both directly and indirectly, as a result of a proposed human action.

Alluvial: An adjective referring to alluvium, which are sediments deposited by erosional processes, usually by streams.

Alluvial Fan: Sediments deposited that channel outward in different directions from a centralized point.

Alluvium: A general term for clay, silt, sand, gravel, or similar unconsolidated rock fragments or particles deposited during comparatively recent geologic time by a stream or other body of running water.

Alternatives: Sets of management elements that represent a range of options for how, or whether to proceed, with a proposed project. An environmental assessment analyzes the potential environmental and social impacts of the range of alternatives presented.

Area of Potential Effect: The area a project could potentially by affected by a proposed action.

Bank: The area below the ordinary highwater mark in a river or stream. The ordinary highwater mark is defined by the U.S. Army Corps of Engineers as the line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding area.

Bed: Refers to the relatively flat or level bottom (substrate) of a body of water, as in a lakebed or riverbed.

Best Management Practices: Effective, feasible (considering technological, economic, and institutional constraints) conservation practices and land- and water-management measures that avoid or minimize adverse impacts to natural and cultural resources. Best Management Practices may include schedules for activities, prohibitions, maintenance guidelines, and other management practices.

Biotic: Relating to life or specific life conditions.

Boundaries: The areas that receive protection under the Wild and Scenic Rivers Act. Boundaries include an average of not more than 320 acres of land per mile, measured from the ordinary high-water mark on both sides of the river.

Braided stream channel: A stream channel that is characterized by the division of water flow into more than one channel. A basic characteristic of this pattern is the diversion of a single trunk channel into a network of interconnected branches and the formation of interspersed islands.

Canopy: The uppermost layer of a forest where a layer of tree branches spread.

CEQ Regulations: The Council on Environmental Quality (CEQ) was established by the National Environmental Policy Act (see NEPA) and given the responsibility for developing federal environmental policy and overseeing the implementation of NEPA by federal agencies.

Classifications: The status of rivers or river segments under the Wild and Scenic Rivers Act ("Wild," "Scenic," or "Recreational"). Classification is based on the existing level of access and human alteration of the site.

Comprehensive management plan: A plan to protect and enhance a Wild and Scenic River. The Merced Wild and Scenic River Comprehensive Management Plan is the National Park Service’s comprehensive management plan for segments of the Merced River corridor under its jurisdiction.

Cowardin wetlands: The Cowardin system is used as the basis for wetland classification and protection by the National Park Service. The Cowardin system classifies wetlands based on the type of vegetative cover and lifeform, flooding regime, and substrate material. Cowardin wetlands include jurisdictional wetlands but may also include certain non-vegetated sites and sites lacking soil, if they meet specific criteria.

Jurisdictional wetlands: Jurisdictional wetlands are delineated and classified to meet regulations of Section 404 of the Clean Water Act.

Cultural landscape: A reflection of human adaptation and use of natural resources and is often expressed in the way land is organized and divided, patterns of settlement, land use, systems of circulation, and the types of structures that are built. The character of a cultural landscape is defined both by physical materials, such as roads, buildings, walls, and vegetation, and by use reflecting cultural values and traditions.

Decibel: A decibel (dB) is a unit of sound energy intensity. Sound waves, traveling outward from a source, exert a sound pressure level (commonly called "sound level") measured in dB. An A-weighted decibel (dBA) is a decibel corrected for the variation in frequency response of the typical human ear at commonly encountered noise levels.

Ecosystem: An ecosystem can be defined as a geographically identifiable area that encompasses unique physical and biological characteristics. It is the sum of the plant community, animal community, and environment in a particular region or habitat.

Environmental assessment: A public document required under the National Environmental Policy Act (NEPA) that identifies and analyzes activities that might affect the human and natural environment. An environmental assessment is a concise public document that provides sufficient evidence and analysis for determining whether to prepare an environmental impact statement, aids an agency’s compliance with NEPA when no environmental impact statement is necessary, and facilitates preparation of an environmental impact statement when one is necessary.

Environmental impact statement (EIS): A public document required under the National Environmental Policy Act (NEPA) that identifies and analyzes activities that might affect the human and natural environment.

Ethnographic resource: Gathering area, spiritual place, remains of historic village, or place considered important to maintaining the culture and ongoing traditions of local native people.

Exfoliation: The process in which concentrated shells of weathering form on the outside of a rock and become separated from the rock. These thin shells of weathered rock are separated by stresses that result from changes in volume of the minerals that occur as a result of the formation of new minerals. See "pressure release."

Facilities: Buildings and the associated supporting infrastructure such as roads, trails, and utilities.

Finding of No Significant Impact (FONSI): The public document describing the decision made on selecting the preferred alternative in an environmental assessment. See "environmental assessment."

Fissure: An extensive crack, break, or fracture in the rocks. It may contain mineral-bearing material.

Floodplain: A nearly level alluvial plain that borders a stream and is subject to flooding unless protected artificially.

Frazil ice: Stream ice with the consistency of slush, formed when small ice crystals develop in super-cooled stream water as air temperatures drop below freezing. These ice crystals join and are pressed together by newer crystals as they form.

Glacial till: Unconsolidated mixtures of clay, silt, sand, and gravel deposited directly by and underneath a glacier without being reworked by melt-water.

Glaciation: Effects on landforms produced by the presence and movement of a glacier.

Geomorphology: Geologic study of the configuration and evolution of landforms.

Grader: A piece of heavy equipment used to level or smooth road or other surfaces to the desired gradient.

Granitic rocks: Igneous rocks (intrusive magma) that have cooled slowly below the earth’s surface, typically consisting of quartz, feldspar, and mica. In contrast to granitic rocks, if magma erupts at the earth’s surface, it is referred to as lava. Lava, when cooled, forms volcanic rocks.

Groundwater: All subsurface water (below soil/ground surface), distinct from surface water.

Hazardous material: A substance or combination of substances that, because of quantity, concentration, or physical, chemical, or infectious characteristics, may either: (1) cause or significantly contribute to an increase in mortality or an increase in serious, irreversible, or incapacitating illness; or (2) pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, disposed of, or otherwise managed.

Hazardous waste: Hazardous wastes are hazardous materials that no longer have practical use, such as substances that have been discarded, spilled, or contaminated, or that are being stored temporarily prior to proper disposal.

Jurisdictional wetlands: Jurisdictional wetlands are delineated and classified to meet regulations of Section 404 of the Clean Water Act.

L_eq: The energy-equivalent noise level (or "average" noise level), L_eq, is the equivalent steady-state continuous noise level which, in a stated period of time, contains the same acoustic energy as the time-varying sound level that actually occurs during the same period.

L_dn: The day-night average noise level, L_dn, is a weighted 24-hour noise level. With the L_dn descriptor, noise levels between 10:00 p.m. and 7:00 a.m. are adjusted upward by 10 dBA to take into account the greater annoyance of nighttime noise as compared to daytime noise.

Milling features: Bedrock and/or other type of stone used for the grinding of materials.

Milling slicks: Smooth parts of a stone where grains were milled.

Mitigation: Activities that will avoid, reduce the severity of, or eliminate an adverse environmental impact.

Moraine: Debris such as boulders, stones, or sediment deposited by a glacier.

Mortar cup: A depression in stone made by the pounding or rubbing of material with a pestle.

National Environmental Policy Act (NEPA): The federal act that requires the development of an environmental assessment or environmental impact statement for federal actions that have the potential for environmental, social, or other impacts.

No Action Alternative: The alternative in a plan that proposes to continue current management direction. "No action" means the proposed activity would not take place, and the resulting environmental effects from taking no action would be compared with the effects of permitting the proposed activity or an alternative activity to go forward.

Non-native species: Species of plants or wildlife that are not native to a particular area and often interfere with natural biological systems. Sometimes referred to as "exotics."

Non-point source pollution: Pollution that occurs when water runs over land or through the ground, picks up pollutants, and deposits them in surface water and introduces then into groundwater. Examples of nonpoint sources are roadways, parking lots, and landscaped areas. Pollutants from these locations can include petrochemicals, heavy metals, and fertilizers.

Ordinary high water: The line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding area.

Outdoor Recreation Access Route: The outdoor recreation access route is a continuous unobstructed path designated for pedestrian use that connects accessible elements within a picnic area, camping area, or designated trailhead. Examples include the paths connecting parking spaces to a picnic or camp unit, or a picnic unit to a toilet building, or those connecting accessible picnic tables to other accessible camping elements. Outdoor recreation access routes do not include pathways such as sidewalks, pathways in amusement parks, visitor center, commercial theme parks, or carnivals and between buildings on college campuses.

Outstandingly Remarkable Values: Those resources in the corridor of a Wild and Scenic River that are of special value and warrant protection. Outstandingly Remarkable Values are the "scenic, recreational, geologic, fish and wildlife, historic, cultural or other similar values…that shall be protected for the benefit and enjoyment of present and future generations" (16 USC 1272).

Palustrine: The palustrine system was developed to group the vegetated wetlands traditionally called by such names as marsh, swamp, bog, fen, and prairie, which are found throughout the United States. It also includes the small, shallow, permanent, or intermittent water bodies often called ponds. Palustrine wetlands may be situated shoreward of lakes, river channels, or estuaries; on river floodplains; in isolated catchments; or on slopes. They may also occur as islands in lakes or rivers. The palustrine system includes all nontidal wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to ocean-derived salts is below 0.5%. It also includes wetlands lacking such vegetation, but with all of the following four characteristics: (1) area less than 8 hectares (20 acres); (2) active wave-formed or bedrock shoreline features lacking; (3) water depth in the deepest part of basin less than 2 meters at low water; and (4) salinity due to ocean-derived salts less than 0.5%.

Physical weathering: Represents the disintegration of rocks and minerals into smaller pieces. Physical weathering can be further subdivided into pressure release and ice wedging.

Potential effect: Change or impact to an environment that may be caused by implementing a proposed action.

Pressure release: Rocks below the earth surface support the weight of the overlying column of rock. Erosion strips away this overlying rock and decreases pressure on buried rocks. All rocks are slightly elastic, so the buried rocks respond to the reduction of pressure by expanding upwards. This result in the formation of pressure release fractures (cracks) that form parallel to the surface. With continued erosion, these rocks are exposed on the surface and slabs of rock break off along the pressure release fractures. This weathering creates bare rock surfaces that may be more resistant than surrounding rocks. These features are termed exfoliation domes; the slabs of rock that break off are termed exfoliation sheets.

Regulatory threshold: The concentration threshold set by a regulatory agency or agencies.

Rehabilitation: To restore or renew to a former capacity or function. Regarding structures it would include rebuilding while maintaining similar character of appearance and using existing materials when feasible.

Restoration (cultural): The act or process of accurately depicting the form, features, and character of an existing historic structure, landscape, or object as it appeared at a particular period of time, by removing modern additions and replacing lost portions of historic fabric, paint, or other elements. For the purpose of this environmental assessment, restoration does not necessarily match the definition given in The Secretary of the Interior’s Standards and Guidelines for Archeology, and Historic Preservation (USDOI 1983)

Restoration (natural): Work conducted to remove impacts to natural resources and restore natural processes, and to return a site to natural conditions. For the purpose of this environmental assessment, restoration does not necessarily match the definition given in The Secretary of the Interior’s Standards and Guidelines for Archeology, and Historic Preservation (USDOI 1983)

Riparian areas: The land area and associated vegetation bordering a stream or river.

Riprap: Any hardening of a shoreline (with rocks or cement) to stabilize river banks for the protection of facilities on or near the bank.

River corridor: The area within the boundaries of a Wild and Scenic River (e.g., the Merced River corridor).

Rockfall: Associated forms of mass movement such as rock avalanches, rockslides, debris slides, and debris flows.

Rockfall shadow zone: A distance calculated to determine outlying boulder locations beyond the extent of talus. The rockfall shadow zone is determined by a procedure based on the apex of the talus and a minimum shadow angle of 22 degrees.

Root-rot disease: Disease caused by fungal pathogens that typically leads to live tree failure or predisposing the tree to bark beetle attack, colonization, and subsequent death.

Scenic Category: A classification of scenic values based on their viewing significance, scenic quality, and inclusion of meadows and the Merced River. Categories of scenic views range from A to C (A being of most significance and C being of least significance).

Sediment: A particle of soil or rock that was dislodged, entrained, and deposited by surface runoff or a stream. The particle can range in size from microscopic to cobblestones.

Snag: A standing dead tree.

Soil horizon: A layer of soil, approximately parallel to the soil surface, with characteristics produced by soil-forming processes (time, biota, parent material, topograhy, and climate). Soil horizons are usually described by their color, texture, and depth. Other characteristics that can be described are there consistence, structure, cutans, nodules and concretions, voids, pH, boundary characteristics, and horizon continuity.

Spall: To break up into flakes, chips, or fragments.

Talus: Rock fragments of any size or shape derived from and lying at the base of a cliff or very steep rocky slope. Also refers to outward sloping and accumulated heap of loose, broken rock considered as a unit and formed primarily by falling, rolling, or sliding.

Talus slope zone: Area where the majority of rock materials are deposited during a mass movement (rockfall) event.

Threatened and endangered species: Species of plants that receive special protection under state and/or federal laws. Also referred to as "listed species" or "special-status species."

Till: Glacially transported and unconsolidated material deposited directly by ice, without having been reworked by melt-water. Material size varies widely and can range from clay to boulders.

Trail: A route that is designed, designated, or constructed for recreational pedestrian use or provided as a pedestrian alternative to vehicular routes within a transportation system.

Weathering: The decomposition and disintegration of rocks and minerals at the earth’s surface. Weathering results in the formation of sediment that is carried away by erosion to form sedimentary rocks, and regolith that remains in place to form soils. Weathering can be subdivided into two types: physical (mechanical) and chemical.

Wetland: Wetlands are defined by the U.S. Army Corps of Engineers (CFR, Section 328.3[b], 1986) as those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.

Wild and Scenic Rivers: Those rivers receiving special protection under the Wild and Scenic Rivers Act.

Wilderness: Those areas protected by the provisions of the 1964 Wilderness Act. These areas are characterized by a lack of human interference in natural processes.

Acronyms

BOCA Building Officials and Code Administration

CEQ Council on Environmental Quality

CFR Code of Federal Regulations

CO carbon monoxide

dBA A-weighted decibels

EA Environmental assessment

EIS Environmental impact statement

EPA Environmental Protection Agency

FEIS Final Environmental Impact Statement

L_eq energy-equivalent noise level

NAGPRA Native American Graves Protection and Repatriation Act

NEPA National Environmental Policy Act

NO_x nitrogen oxides

O₃ ozone

ORV Outstandingly Remarkable Value

NPS National Park Service

Pb lead

PM₁₀ particulate matter less than 10 microns in diameter

SEIS Supplemental Environmental Impact Statement

SO₂ sulfur dioxide

VERP Visitor Experience and Resource Protection

USC United States Code

USDOI U.S. Department of the Interior

USFS U.S. Forest Service

VIA VIA Adventures, Inc.; Grayline of Yosemite