TWO DIMENSIONAL MORPHOLOGICAL DYNAMIC MODELING OF A COMPLEX FLUVIAL SYSTEM: THE SPATIAL DISTRIBUTION OF THE BED SEDIMENT OF THE BRAZOS RIVER, TX

Dynamic interactions of hydrological and geomorphological processes in the Brazos River result in accumulated deposit on the bed because the capacity to carry sediment has been exceeded. The bed load of the Brazos River is primarily generated by mechanical weathering resulting in boulders, pebbles, and sand, which roll or bounce along the river bed forming temporary deposits as bars on the insides of meander bends, as a result of a loss of transport energy in the system. This dynamic controls the style and range of deposits in the Brazos River. This study focuses on the spatial distribution of bed-load transport of the Brazos River. Understanding the spatial distribution of deposits facilitates the reconstruction of the changes in controlling factors during accumulation of deposits. Sieve analysis illuminates the distribution of sediment changes associate with channel morphology under different flow regimes. The results demonstrate that channel deposits in the Brazos River are formed from four different type of materials: a) pebble (very coarse to coarse) deposited along upstream left bank; b) sand (medium fine to very fine) located on the upstream, downstream, and along meander belts; c and d) silt and clay located along the cut bank of meander bends. Because of different depositional pattern, the distribution of D50 along the river can be used as a surrogate to identify bank stability, as well as to predict critical geometry for meander bend initiation.