The nature of channel planform change: Brazos River, Texas
- Texas A and M Univ., College Station, TX (United States). Geography Dept.
This study describes the nature of planform change that has occurred in three contiguous alluvial reaches of the Brazos River, Texas, from the 1930s to 1988. The reaches encompassed 260 km and more than 125 bends. A migratory activity index (MAI) was developed which provides an objective means of assessing changes in channel stability. The MAI indicated that the river's rate of migration has decreased substantially since 1939. This change in behavior results from diminished discharges and sediment loads brought about by flow regulation and is consistent with previous findings on the effects of flow regulation on channel activity. However, the other results were contrary to those found in studies of freely migrating rivers. Bend planform size was controlled not by discharge, but by the presence or absence of resistant rock and sediment layers interspersed among the alluvial sediments in a small number of bends. 37% of the bends on the river experienced negative migration, i.e., migration toward the baseline connecting the inflection points which 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 precludes the development of predictive models of migration and planform evolution. This is because its occurrence makes it impossible to predict the direction of channel migration. Also of significance is the fact that its occurrence contradicts standard theoretical models of fluid flow and erosion in channel bends which have been developed to describe conditions in freely migrating rivers. Given that most rivers are not freely migrating, the above results pose limitations to the applicability of models based on studies of freely migrating rivers.
- OSTI ID:
- 5587004
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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