OCR Text |
Show Bars 139 General ( -As As ) ( indicated -indicated indicated ) by the ( large-scale largescale ) surveys ( Compl . Exhibit 76 ) ( tlie the ) principal permanent ( fea- fea ) tures of the Green River are its rock walls . ( These Theav ) : walls , however , are rarely closer than 1,500 to 2,000 feet ; therefore , the river although in canyon has considerable freedom of action and meanders in an alluvial channel , cutting the banks where they are exposed to the thrust of the current and building up bars where the velocities diminish . The river is constantly shifting , sorting , and redistributing the enormous volumes of silt and sediment brought into it in suspension and bed load . The bed of Ahe Green River between the San Rafael River and ( its i'C's iCs ) mouth and the Colorado River from the mouth of the Green River to ( Moab -Moab Moab ) ( was -was was ) found to be sand of various degrees of fineness . As is to be expected in a river flowing in a bed composed of fine material , the bed , ( although althoug1i ) most irregular , had characteristics which are common to channels in unstable material . Within the limits of the rock walls the river is flowing in a channel unstable as to bed and banks but at the same time , having certain prominent features , such as side bars and crossing bars , which are common to all ( rivers kivers ) flowing in alluvial material . The ( crossing CfOSSiDg ) bars are probably the most troublesome as far as depth and permanency of channel are concerned . . Since these crossing bars are for the most part submerged , , it is practically impossible to map them . Although all |