Channel Sequences and Braided-Stream Development in South Canadian River, Hutchinson, Roberts, and Hemphill Counties, Texas: ABSTRACT

Abstract

End_Page 1785------------------------------The South Canadian River in the eastern Texas Panhandle and western Oklahoma has produced a complex anastomosing channel system. At least 8 aggradational channel sequences (including the present channel system) are present in this part of the Canadian River valley, and are distinguished on aerial photographs and in the field by vegetational changes and overlapping stratigraphic relations. Earlier channel sequences are represented by remnants of earlier active braided-channel systems. Analysis of daily discharge data from 1938 to 1966 reveals, that though average flow in the Canadian River is quite low, a few large floods with a flow in excess of 20,000 cu ft/second have altered severely floodplain and channel morphology. These flash events eradicate parts of earlier channel sequences and set the stage for channel braiding under lower discharge rates. Longitudinal and transverse bars are observed in the active and younger inactive channel sequences of the river. Average orientation of these bars is nearly parallel with the orientation of the active channel in a given reach. Despite the similar average direction, there is wide variation of bar orientation in all reaches studied. Unvegetated areas of the Canadian River floodplain show widespread eolian-dune alteration. These dunes parallel the orientation of the river valley. Channel-wall instability and variable discharge rate are the principal factors causing braiding in the Canadian River. Serious doubts are raised about the importance of stream gradient as cause of braiding in the Canadian River system. End_of_Article - Last_Page 1786------------