SEGMENTATION OF RIVERS IN KANSAS BASED ON ACTIVITY LEVELS OF CONTRASTING REACHES

Plains rivers, in general, appear placid and seemingly uninteresting. Detailed research, however, reveals a different situation. The Kansas River, flowing on an average gradient of 1.9 feet/mile for 170 miles eastward from Junction City to its confluence with Missouri River at Kansas City, was examined for the Corps of Engineers. The study is being continued for the Kansas Geological Survey. Bank erosion and consequent migration of the channel is not now proceeding at the same rate along the entire river, nor has it in the past 150 years, the limit of accurate mapping of channel location and configuration. Some reaches have been in motion throughout the period , others for only the earlier or, conversely, later portion; yet other sections have not moved at all. On the basis of this record it is possible to subdivide the river into 11 activity-level segments. Because the valley floor is underlain by 50-100 feet of alluvial fill, it appears that channel activity is not controlled by subjacent bedrock. Data about subtle variations in channel gradient are not available. The Lower Neosho River, which follows a 177-mile course southward to Oklahoma on a gradient of 1.4 feet/mile, also displays reaches having contrasting intensities of channel activity; 15 can be delineated. In this instance, the stream bed lies on or only a few feet above bedrock, but the floodplain scrolls indicative of recent channel migration are insulated form the bedrock by 25-35 feet of alluvial fill.