OCR Text |
Show shape of the channel . As 135 pointed out by Howard ( Abs . R . , , vol . 2 , , p . . 970 ) , there is no uniformity in the rate of movement of the sediment or in its ( distribu- distribu ) tion in the cross section . As a result of these ( condi- condi ) tions there is a ( variation variatiDn ) in the amount carried past any particular point ranging from a few thousand tons per day to as ( much miieh ) as 20,000,000 tons a day . ( Love , Abs . R , vol . 2 , p . 979 . ) This is the natural result of the wide range in channel velocities shown to exist and which result in a continual process of , scour and fill ; a ( building buildinr ) up of bars in one place and tearing down in another ; a sorting and redistributing of the millions of tons of sediment ; a movement at ( times 'times times ) in the form of sand waves of the entire bed of the stream . These conditions account for the ( un- un ) stability of the beds of the Colorado and Green Rivers . Unstable channel Evidence shows that with respect to sand bars and gravel bars the rivers divide into fairly definite sections where one or the other predominates . On the Green River above the mouth of San Rafael , the bars are gravel ( almost aliaost ) without exception . ( Be- Be ) low the mouth of the San Rafael the river bed is in sand and silt without exception . On the Colorado River gravel bars occur in the short stretch between Castle Creek and ( Nigger Niggex ) Bill Creek and frequently at the mouths of creeks , drains , and washes in the Glen Canyon section . Elsewhere , ' excluding the Cataract Canyon section and the section where ( bed- bed ) rock is near the surface , the bed of the river is sand |