1、 GLOSSARY OF HIGHWAY-RELATED DRAINAGE TERMS 2007 by the American Association of State Highway and Transportation Officials.GLOSSARY OF HIGHWAY-RELATED DRAINAGE TERMS TABLE OF CONTENTS G.1 OVERVIEW G-1 G.2 GLOSSARY G-3 G.3 REFERENCES G-151 G.3.1 Cited References . G-151 G.3.2 Uncited G-156 2007 by th
2、e American Association of State Highway and Transportation Officials.Glossary of Highway-Related Drainage Terms G.1 OVERVIEW This glossary is divided into three parts: Overview, Glossary, and References. It is not intended that all the terms in this glossary be rigorously accurate or complete. Reali
3、stically, this is impossible. Depending on the circumstance, a particular term may have several meanings; this can never change. The primary purpose of this glossary is to define the terms found in the Highway Drainage Guidelines and Model Drainage Manual in a manner that makes them easier to interp
4、ret and understand. A lesser purpose is to provide a compendium of terms that will be useful for both the novice and the more experienced hydraulics engineer. This glossary may also help those who are unfamiliar with highway drainage design to become more understanding and appreciative of this compl
5、ex science and facilitate communication between the highway hydraulics engineer and others. Where readily available, the source of a definition has been referenced. For clarity or format purposes, cited definitions may have some additional verbiage contained in double brackets . Conversely, three “d
6、ots” (. . .) are used to indicate where some parts of a cited definition were eliminated. Also, as might be expected, different sources were found to use different hyphenation and terminology practices for the same words. Insignificant changes in this regard were made to some cited references and el
7、sewhere to gain uniformity for the terms contained in this glossary, e.g., “groundwater” vs. “ground-water” or “ground water,” and “cross section area” vs. “cross-sectional area.” Cited definitions were taken primarily from two sourcesW.B. Langbein and K.T. Iseris “General Introduction and Hydrologi
8、c Definitions” (36) and a draft of a glossary being developed by the Interagency Hydrology Committee. A few cited definitions were considered to be partially outdated; corrections were suggested where this occurred. Future plans of the AASHTO Task Force on Hydrology and Hydraulics are to integrate t
9、he current American Society of Civil Engineers Glossary of hydrologic terms with this glossary. 2007 by the American Association of State Highway and Transportation Officials.Highway Drainage Guidelines G-2 Many terms are explained and defined in several wayssometimes with considerable detail. This
10、was done intentionally in order to: facilitate understanding for those who respond better to a particular written format or detail of explanation, highlight actual or apparent contradictions in current terminology, avoid or minimize litigation problems from overly restrictive definitions, and select
11、ively augment certain subject matter in the AASHTO Highway Drainage Guidelines and Model Drainage Manual. Some terms included in this glossary will have limited application to highway drainage design. They have been included in order to: facilitate communication with other, related sciences; and pre
12、clude confusion with similar but different hydraulics-related terms. As often happens in any science, some practitioners have different names for the same thing. Every attempt has been made to sort out these colloquialisms and synonyms and assign all the definitions to one term. Cross referencing of
13、 these terms was attempted but is unlikely to ever be complete or to satisfy all practitioners. It is anticipated that errors and oversights will be resolved with revisions of this glossary. The reader is encouraged to submit their experience with this glossary to the AASHTO Task Force on Hydrology
14、and Hydraulics. In particular, the following information is solicited: proposed terms and definitions, proposed revisions of present terms to include reasons where appropriate, and problems (particularly legal) with the present definitions. In cross referencing, two terms are used“See” and “Compare
15、with.” The term “see” usually means one of two things: (1) The definition is provided under a different term, or (2) the cross-referenced term provides additional information. The term “compare with” infers that the cross-referenced term may be at variance with or an antonym of the defined term; jud
16、gmental decisions may be needed in such cases. This glossary also attempts to “package” similar terms having two or more words. This provides the added advantage of facilitating a comparison of terms without flipping back and forth between pages. As an example, see the section of this glossary that
17、addresses “streams,” “gages,” “probability distribution,” or “weir.” In some instances, this might prove inconvenient and add some length to the glossary, but it was felt the advantages outweighed the disadvantages. An exception was made where a particular term might best be left with another, small
18、er grouping of similar terms. The scientific and, in particular, the regulatory world is inundated with acronyms and abbreviations. This glossary attempts to define some of the more familiar acronyms and abbreviations likely to be encountered by the highway hydraulics engineer. In a few instances, t
19、hey have different meanings (see “TW,” for instance). A few hydraulic variables and equations are also included. 2007 by the American Association of State Highway and Transportation Officials.Glossary G-3And, finally, because this is a glossary of transportation-related hydraulic terms, an attempt h
20、as been made to provide this unique focus without distorting a terms meaning. G.2 GLOSSARY The following terms are provided to facilitate the application of the AASHTO Highway Drainage Guidelines and Model Drainage Manual. AASHTO. Acronym for American Association of State Highway and Transportation
21、Officials. ablation. The process by which ice and snow waste away from melting and evaporation or by which land wears away by the action of surface water. abrasion. Removal of stream bank material due to entrained sediment, ice, or debris rubbing against the bank. Compare with erosion, scour, and ma
22、ss wasting. absorption. The assimilation or taking up of water or other solutions by soil or other material, i.e., the entrance of water into the soil or rocks by all natural processes. It includes the infiltration of precipitation or snowmelt; gravity flow of streams into the valley alluvium (see s
23、torage, bank), sinks, or other large openings; and the movement of atmospheric moisture. The process by which substances in gaseous, liquid, or solid form dissolve or mix with other substances. Compare with adsorption. abstraction. That portion of rainfall that does not become runoff. It includes in
24、terception, infiltration, and storage in depressions. It is affected by land use, land treatment and condition, and antecedent soil moisture. abutment. The superstructure support at either end of a bridge or similar type structure, usually classified as spillthrough or vertical. Considered part of t
25、he bridge substructure. See spillthrough abutment and vertical abutment. acre-foot. The quantity of water required to cover 1 acre to a depth of 1 foot and equal to 43,560 cubic feet or approximately 326,000 gallons or 1233 m3. Abbreviated as af. See hectare-meter. accretion. Build-up of beach due t
26、o wave and wind action. act (acts). Written law, such as an Act of Congress. Act of God. In law, a direct, sudden, or irresistible action of natural forces that could not reasonably have been foreseen and prevented. action (highway). A highway action as it pertains to drainage design is any construc
27、tion, reconstruction, rehabilitation, repair, or improvement in a watershed or on the transportation system that measurably changes such things as floodplain limits, established flood patterns, and runoff characteristics or that requires a design or review storm system to accommodate storm runoff. 2
28、007 by the American Association of State Highway and Transportation Officials.Highway Drainage Guidelines G-4 adsorption. The adhesion in an extremely thin layer of molecules (such as gases, solutions, or liquids) to the surface of solid bodies or liquids with which they are in contact. Compare with
29、 absorption. adverse slope. See slope, adverse. aeration zone. See zone of aeration. aerobic. A condition in which molecular oxygen is a part of the environment. af. Acronym for acre-foot. Common abbreviation is ac-ft. afflux. Backwater or height by which water levels are raised at a stated point, o
30、wing to presence of a constriction or obstruction, such as a bridge. aggradation. General and progressive upbuilding of the longitudinal profile of a channel or within a drainage facility by the deposition of sediment. Compare with sedimentation. Permanent or continuous aggradation is an indicator t
31、hat a change in the streams discharge and sediment load characteristics is taking place. AHW. Acronym for allowable headwater. Compare with HW. ALERT. Acronym for Automated Local Evaluation in Real Time. An automated, local flood warning system consisting of automatic self-reporting river and rainfa
32、ll gages, a communications system based on line-of-sight radio transmission of data, and a base station. The base station consists of radio receiving electronic equipment and a microprocessor. Data analysis software is available to collect, quality control, and display data. A hydrologic model to pr
33、ovide simulation of streamflow is also available. alfalfa. A deep-rooting plant, Medicago Sativa, native to Eurasia, having compound leaves with three leaflets and a cluster of small purple flowers. It is widely cultivated for forage and is used as a commercial source of chlorophyll. Its deep-rootin
34、g characteristics, commercial value, and environmental (forage and bee habitat) qualities often make it desirable as a ground cover to control erosion. algae. Any of various primitive, chiefly aquatic, one-celled or multi-cellular plants that lack true stems, roots, and leaves but usually contain ch
35、lorophyll. allowable headwater. See allowable headwater depth. allowable headwater depth. The depth or elevation of the flow impoundment for a drainage facility above which damage, some other unfavorable result, or a significant flood hazard could occur. Compare with headwater depth. alluvial. Refer
36、ring to deposits of silts, sands, gravels, or similar detrital material that has been transported by running water. 2007 by the American Association of State Highway and Transportation Officials.Glossary G-5alluvial channel. Channel formed wholly in alluvium with no bedrock exposed in the channel at
37、 low flow or likely to be exposed by erosion. A channel whose processes are controlled by the flow and boundary interactions. alluvial fan. A landform shaped like a fan in plan view and deposited where a stream issues from a narrow valley of high slope onto a plain or broad valley of low slope. Comp
38、are with debris cone. alluvium. Unconsolidated material such as clay, silt, sand, or gravel deposited by water in a channel or on a floodplain, alluvial, fan, or delta. alpha (). The kinetic-energy, velocity head coefficient. See velocity head coefficient. alternate bar. See bar, alternate. alternat
39、e depth. See depth, alternate. AMC. Acronym for antecedent moisture condition. amphibian. Any of the various cold-blooded, smooth-skinned vertebrate (with backbone) organisms such as toads, frogs, and salamanders, characteristically hatching as an aquatic larvae that breathe by means of gills and me
40、tamorphosing to an adult form having air-breathing lungs. anabranch. Individual channel of an anabranched stream. A diverging branch of a river that reenters the main stream. anabranched stream. See stream, anabranched. anaerobic. A condition in which molecular oxygen is absent from the environment.
41、 analysis, hydraulic. An evaluation of a drainage-related circumstance or condition based on measured or computed findings coupled with prudent judgment. Compare with assessment, hydraulic. analysis, economic. See economic analysis. Compare with economic assessment. anastomosing stream. See stream,
42、anastomosing. anchor ice. Ice in the bed of a stream or upon a submerged body or structure (55). angle of flare. Angle between direction of wingwall and the centerline of a culvert barrel. angle of repose. The maximum angle, as measured from the horizontal, at which granular particles can stand. ang
43、ularity. The acute angle between the plane of the highway centerline along the bridge, and a line normal to the thread of the stream, i.e., the acute angle between the thread of the stream and a line normal to the centerline along bridge. Angle of skew if abutments are parallel to the flow line. ann
44、ual flood. See flood, annual. 2007 by the American Association of State Highway and Transportation Officials.Highway Drainage Guidelines G-6 annual (flood) series. A list of annual events such as annual maximum floods and minimum flows. See flood, annual. A general term for a set of any kind of data
45、 in which each item is the maximum, minimum, average, or some other consistent value in a year (33). A frequency series in which only the largest value for a particular series of data in each year is used, such as the annual floods (67). annual runoff. See runoff, annual. annual yield. See runoff, a
46、nnual. antecedent moisture. See antecedent moisture condition. antecedent moisture condition (AMC). The degree of wetness of a watersheds surface soils at the beginning of a storm. antecedent precipitation. Rainfall that occurred prior to the particular rainstorm under consideration. antecedent prec
47、ipitation index. An index of moisture stored within a drainage basin before a storm (36), (43). antidune. A particular type of bed form caused by water flowing over a mobile material such as sand. A sand wave indicated on the water surface by a regular undulating wave. The ridges may move upstream a
48、nd the surface waves become gradually steeper on the upstream sides until they break like surf and disappear. These surface waves are usually in series and often reform after disappearing. See bed form. Compare with dune. apex. The highest point, the vertex. approach channel. The reach of channel up
49、stream from a dam, bridge constriction, culvert, or other drainage structure. See approach section. approach section. A cross section of the stream channel, normal to thread of current and for the discharge of interest, located in the approach channel. See approach channel. apron. Protective material laid on a streambed to prevent scour commonly caused by some drainage facility. More specifically, a floor lining of such things as concrete, timber, and riprap, to protect a surface from erosion, such as the pavement below chute
