- 0.2d and 0.8d is next most preferred 



- 0.6d is recommended only if the depth (d) is less than 0.75 m 



If the discharge is changing rapidly and the measurements must be taken at 



that time, the 0.6d method should be used to complete the measurements faster. 



Additional details on discharge measurements can be found in Bovee and Milhous 

 (1978) or Buchanan and Somers (1969). 



Bed Material Size Distribution: The size distribution of the surface 

 layer of bed material is required for evaluating the hydraulic roughness of 

 the channel and floodplain. These data are obtained by an analysis of photo- 

 graphs using a grid-by-number technique as described by Kellerhals and Bray 

 (1971) or Adams (1979). The photographs should be tal<en, vertically downward, 

 of at least a I m square area of undisturbed surface layer gravels. A scale 

 should be included in the photograph. 



Thalweg Profile: A thalweg profile should be surveyed of the channel bed 

 at those sites where the material site is being proposed on a gravel bar 

 adjacent to the channel or in the channel itself (Figure B- I ) . These data are 

 needed in the determination of the maximum depth to which gravel can be ex- 

 tracted. The profile should extend at least five channel widths beyond the 

 ends of the mined site. 



Photographs . Photographs should be taken to show the main habitat fea- 

 tures of the river reach being studied (e.g., riffles, runs, pools, islands, 

 gravel bars, riparian shrub thickets, mud flats, backwater areas, incised and 

 undercut banks). If possible, photographs should be taken from an elevated 

 vantage point, such as a high bank. A sequence covering the entire reach of 

 stream is desirable. A record should be made of each photograph, including 

 date, time, location, direction of photograph, sequence, and main features 

 being photographed. If the visit is a follow-up to a previous field visit, 

 photographs identical to those obtained previously should be taken, as well as 

 those showing new features. If a winter visit occurs, photograph aufeis and 

 river ice characteristics. 



