HabitatThe natural environment where people, animals and plants live. In an aquatic environment, it includes the water, topography, structure and cover present…
Habitat alterationA change in the particular environment or place where an organism or species lives.
Habitat degradationDecline in habitat quality that accompanies non-natural forms of disturbance.
Hazardous materialAny material that poses a threat to human health and/or the environment. Hazardous materials are typically toxic, corrosive, ignitable, explosive, or…
Hazardous wasteBy-products of society that can pose a substantial or potential hazard to human health or the environment when improperly managed.
Headwater(1) The source and upper reaches of a stream; also the upper reaches of a reservoir; (2) the water upstream from a structure or point on a stream; (3) the…
Heat ExchangerA device used to transfer heat from a fluid (liquid or gas) to another fluid where the two fluids are physically separated.
Heat transfer fluid (HTF)Fluids that transfer heat generated at the solar collectors to a heat exchanger where steam is produced to run a steam generator.
Heavy metalsMetallic elements with high atomic weights (e.g., mercury, chromium, cadmium, arsenic, and lead); can damage living things at low concentrations and tend…
Hedonic – (modeling approach)The hedonic method is a regression technique used to estimate the prices of qualities or models that are not available on the market in particular…
Hedonic statistical frameworkA method of assessing the impact of various structural (number of bedrooms, bathrooms, square footage, age, etc.
HeliostatA device that tracks the movement of the sun; used to orient solar concentrating systems.
HerbaceousThe plant strata that contain soft, not woody, stemmed plants that die to the ground in winter.
Herd Area (HA)Following passage of the Wild Free-Roaming Horses and Burros Act (WFRHBA) in 1971, the Bureau of Land Management was directed to identify areas where wild…
HerpetofaunaAmphibian and reptile species including frogs, toads, salamanders, turtles, lizards, and snakes.
Hertz (Hz)The unit of measurement of frequency, equivalent to one cycle per second.
High liquefaction potentialRefers to the susceptibility of soils to liquefy when subjected to sudden loading, such as intense ground shaking from an earthquake.
Highly discordant land useRefers to development that is at variance with the existing condition of the land. It might also be described as incongruous.
HistoricThe time period after the appearance of written records. In the New World, this generally refers to the time period after the beginning of European…
Historic propertiesAny prehistoric or historic districts, sites, buildings, structures, or objects included in, or eligible for inclusion in, the National Register of…
Historic resourcesMaterial remains and the landscape alterations that have occurred since the arrival of Euro-Americans.
HogbacksAn eroded steep ridge of resistant rocks produced by erosion of the broken edges of highly tilted strata.
HoloceneThe past 10,000 years of geologic time. The most recent epoch of the Quaternary period.
Horizon lineThe apparent line in the landscape formed by the meeting of the visible land surface and the sky.
Horizontal angle of viewThe angle of landscape viewed in sharp focus, measured along the horizon, without turning the head. See also Vertical angle of view; Angle of view
HorstAn elongated crustal block that is relatively raised between two parallel normal faults or grabens. See also Half-graben
Hunter gatherersA term applied to people whose diet is based on hunting, fishing, and gathering, as opposed to domesticating animals or plants.
HuntingIncludes big- and small-game hunting, waterfowl hunting, and trapping.
Hybrid (wet-dry cooling) systemsA variation on a dry cooling system. In this hybrid system, small amounts of water are sprayed as a fine mist into the flow of ambient air being directed…
Hydraulic gradientIn an aquifer, the rate of change of total head per unit of distance of flow at a given point and in a given direction.
Hydrofluorocarbon (HFC)Man-made chemicals, many of which have been developed as alternatives to ozone-depleting substances (ODSs) for industrial, commercial, and consumer…
HydrologyThe science dealing with the distribution, properties and circulation of water on land, in the soil, and in the atmosphere.
HydrostratigraphicGrouping of rock and sedimentary units based on the capacity of the rock, sediment, or soil to transmit water.