THE NATURE OF CHANNEL PLANFORM CHANGE: BRAZOS RIVER, TEXAS

摘要

This study describes the nature of channel planform change that occurred in three contiguous alluvial reaches of the Brazos River, Texas, from the 1930s to 1988. The reaches encompass 260 km and more than 125 bends. A migratory activity index (MAI) developed for the study indicates that the river's rate of migration has decreased substantially since 1939. This change in behavior results from diminished discharges and suspended sediment loads caused by flow regulation and is consistent with previous findings on the effects of flow regulation on channel activity. However, other results are contrary to those found in studies of freely migrating rivers. Although planform controls on migration rates were found, the interaction of variables resulted in poor correlations with migration. Of greatest significance was that 26% of the bends on the river experienced "negative migration," i.e., migration toward the baseline connecting the inflection points that define a bend. This phenomenon, which is not a form of meander cutoff, has not been described before and its significance lies in the fact that it would seem to preclude the development of predictive models of migration and planform evolution.