inactive floodplain — 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. 



Manning's equation — In current usage, an empirical formula for the calcula- 

 tion of discharge in a channel. The formula is usually written 



- 1.49 ^ 2/5 ^1/2 . 



= R S A. 



^ n 



mean flow — The average discharge at a given stream location computed for 



the period of record by dividing the total volume of flow by the number 

 of days, months, or years in the specified period. 



mean water velocity — The average velocity of water in a stream channel, 

 which is equal to the discharge in cubic feet per second divided by 

 the cross-sectional area in square feet. For a specific point location, 

 it is the velocity measured at 0.6 of the depth of the average of the 

 velocities as measured at 0.2 and 0.8 of the depth. 



meander wave length — The average downvalley distance of two meanders. 



meandering river — A river winding back and forth within the floodplain. 

 The meandering channel shifts downvalley by a regular pattern of ero- 

 sion and deposition. Few islands are found in this type of river and 

 gravel deosits typically are found on the point bars at the insides of 

 meanders. 



164 



