gage — A device for indicating or registering magnitude or position in spe- 

 cific units, e.g., the elevation of a water surface or the velocity 

 of flowing water. A staff graduated to indicate the elevation of a 

 water surface. 



geomorphology — The study of the- form and development of landscape fea- 

 tures. 



habitat — The place where a population of animals lives and its sur- 

 roundings, both living and nonliving; includes the provision of life 

 requirements such as food and shelter. 



high-water channel — A channel that is dry most of the ice-free season, 

 but contains flowing water during floods. 



hydraulics — The science dealing with the mechanical properties of fluids 

 and their application to engineering; river hydraulics deals with 

 mechanics of the conveyance of water in a natural watercourse. 



hydraulic depth — The average depth of water in a stream channel. It is 

 equal to the cross-sectional area divided by the surface width. 



hydraulic geometry — Those measures of channel configuration, including 

 depth, width, velocity, discharge, slope, and others. 



hydraulic radius — The cross-sectional area of a stream of water divided 



by the length of that part of its periphery in contact with its contain- 

 ing channel; the ratio of area to wetted perimeter. 



hydrograph — A graph showing, for a given point on a stream, the discharge, 

 stage, velocity, or another property of water with respect to time. 



hydrology — The study of the origin, distribution, and properties of water 

 on or near the surface of the earth. 



ice-rich material — Permafrost material with a high water content in the 



form of ice, often taking the shape of a vertical wedge or a horizontal 

 lens. 



impervious — A term applied to a material through which water cannot pass 

 or through which water passes with great difficulty. 



inactive f I oodp I a i n — The portion of a floodplain that is flooded infre- 

 quently; it may contain high-water and abandoned channels and is 

 usually lightly to heavily vegetated. 



island — A heavily vegetated sediment deposit located between two channels. 



2 



large river — A river with a drainage area greater than 1,000 km and a 



mean annual flow channel top width greater than 100 m. 



lateral bar — An unvegetated or lightly vegetated sediment deposit located 

 adjacent to a channel that is not associated with a meander. 



399 



