The incised fluvial valleys of the northern Gulf Coast are subdivided into two general categories, high and low sediment supply systems. Low sediment supply valleys are those fluvial valleys where sediment supply is relatively low and the valley is filled partially with estuarine and marine deposits. High sediment supply valleys are those where sediment supply is high enough to fill the valley with fluvial deposits. Modern low sediment supply valleys are occupied by bays, such as Mobile and Galveston bays. Modern high sediment supply rivers flow directly to the coast, such as the Brazos River. High sediment supply rivers are prone to avulsion and therefore occupy numbers valleys over repeated glacial eustatic cycles whereas low sediment supply rivers tend to re-occupy the same valley during several glacial eustatic cycles. Therefore, low sediment supply rivers act more a point sources of sediment to the shelf and slope whereas high sediment supply rivers act more as line sources over several glacial eustatic cycles.

Western Louisiana Shelf

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