Glossary

Description
Habitat Fragmentation
Is a potential effect to wildlife species beyond direct project impacts that may fragment needed habitat for a species survival. Many animals require a range of resources that are naturally patchy and therefore need to move around between resource sites. Linear projects, such as new rail lines and highway projects, can cause extensive fragmentation of wildlife habitat and result in isolated and degraded wildlife populations or increase mortality rates through direct conflicts. Wildlife passages constructed for highway projects are one potential method of minimizing some of the more direct impacts from fragmentation.
Hazardous Spill Catch/Retention Basin (HSCB)
A unique retention facility that is provided at strategic locations along arterial system highways to aid in containment and clean up of accidental spills from tanker trucks. The determination of these strategic locations is based on high truck usage and highway segments over Outstanding Resource Waters or within the critical area of water supply watersheds.
Headwaters
The source and extreme upper reaches of a stream or river [including the land draining to the stream or river. (University of Washington, School of Aquatic & Fishery Sciences; www.cbr.washington.edu/crisp/models/crisp1manual/theory16/TCVchp72.html). USACE defines headwaters as being above the point on a non-tidal stream at which the average annual flow is five cubic feet per second (33 CFR 330, Part C, Condition 26(a).).
Herbaceous
1. Nonwoody vegetation. (Lewis, R. R. Wetlands Restoration/Creation/Enhancement Terminology: Suggestions for Standardization, 1989;). 2. Having little or no woody tissue and persisting usually for a single growing season. (Webster)
High Quality Waters (HQW)
Waters which are rated as excellent based on biological and physical/chemical characteristics through DWQ monitoring or special studies, native and special native trout waters (and their tributaries) designated by WRC, primary areas designated by the Marine Fisheries Commission and other functional nursery areas, all water supply watershed which are either classified as WS-I or WS-II by DWQ and all SA waters.
Highway Needs Inventory (HNI)
A long term planning document, which identifies highway improvements to serve existing and projected population and economic activity in the state.
Highway Trust Fund Act of 1989
See Glossary of Environmental Laws
Horizontal and Vertical Alignment
Horizontal alignment is a measure of the curvature of the roadway, while vertical alignment is a measure of the grade (slope) of the roadway.
Human Environment Unit (HEU, formerly OHE)
Part of NCDOT's PDEA branch, the HEU is responsible for public involvement, community studies, noise, air, archaeology, and historic architecture.
Hydric Soil
A soil that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. (USDA; Revised Definition and Criteria for Hydric Soils, 19Aug94;)
Hydrologic Unit Code (HUC)
A phrase to express the hierarchical system for identifying and sub-dividing river basin units of the U.S. by codes. The system includes the hydrologic data based upon region, sub-region, accounting unit and sub-basin. Sub-basins are identified using an eight-digit code number (e.g., Northeast Cape Fear River near Chinquipin, NC: HUC #03030007).
Hydrophytic Vegetation
Hydrophytic vegetation is defined in the U.S. Army Corps of Engineers Wetland Delineation Manual as the sum total of macrophytic plant life that occurs in areas where the frequency and duration of inundation or soil saturation produce permanently or periodically saturated soils of sufficient duration to exert a controlling influence on the plant species present. The vegetation occurring in a wetland may consist of more than one plant community (species association). The plant community concept is followed throughout the manual. Emphasis is placed on the assemblage of plant species that exert a controlling influence on the character of the plant community, rather than on indicator species. Thus, the presence of scattered individuals of an upland plant species in a community dominated by hydrophytic species is not a sufficient basis for concluding that the area is an upland community. Likewise, the presence of a few individuals of a hydrophytic species in a community dominated by upland species is not a sufficient basis for concluding that the area has hydrophytic vegetation.
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