DEVOLPMENT OF THE MODERN BRAZOS RIVER DELTA: A DELTAIC RESPONSE TO NATURAL AND ANTHROPOGENIC CHANGES IN THE COASTAL ZONE AND THE WATERSHED

The modern Brazos delta in the northwestern Gulf of Mexico began forming in 1929 after a diversion of the mouth. This study utilized high-resolution geophysics, historical aerial photography, historical bathymetric data, water column data, and sediment cores to better understand the current structure and how changes to this system in the past have influenced evolution of the modern delta. Results indicate that over time the delta has responded to changes in the relative dominance of sediment supplied to the shelf by the river and the ability of marine processes to rework sediments. After diverting the river mouth, a new delta immediately began rapidly prograding, while the old delta rapidly retreated. Progradation of the new delta continued until a sever drought in the 1950s lead to significant retreat. Following the drought, sediment load remained low due to changes within the watershed. In 1961 Hurricane Carla significantly shifted sediment and deflected the delta westward. Currently export of sediment from the river occurs only part of the time, and flood deposits on the shelf can be completely remobilized within a couple of years.