tidal conditions occurring at the 

 time of the satellite pass (Figure 

 10). Since the estuary is shallow 

 and well mixed, patterns which appear 

 at the surface on Landsat were con- 

 sidered to be representative of the 

 water column in the bays. Offshore, 

 the high sediment concentrations and 

 sharp interface between the sediment 

 plume and the more saline gulf water 

 are thought to indicate strong mass 

 density differences and a zone of 

 f locculation. 



The results of the remote sens- 

 ing model study indicate a more pro- 

 nounced impact to the west, due in 

 part to the predominance of south- 

 easterly winds in the spring during 

 the peak discharge period. Compli- 

 menting tidal currents carry large 

 volumes of sediment into the bays 

 west of Atchafalaya Bay, as evidenced 

 by a thick accumulation of sediments 

 recently sampled in Vermilion Bay 

 (Van Beek 1977) . Mud flat accretion 

 has been detected as far west as the 

 Texas coast, carried by the prevail- 

 ing westerly littoral drift. 



An extensive prototype data- 

 collection program, to provide data 

 for a study of system hydrodynamics, 

 sediment transport and delta growth 

 trends, is currently underway in the 

 estuary and near offshore areas. 

 LSU-Sea Grant and Waterways Experi- 

 ment Station are working coopera- 

 tively, as well as independently, on 

 this extensive modeling effort. 



PROSPECTS FOR THE REGION 



Projections of delta growth made 

 by the Corps of Engineers indicate 

 that the bay will be essentially 

 filled by subaerial delta deposits 

 by the year 2000, extending well off- 



shore by the year 2020 (USCOE 1974). 

 LSU studies indicate a slightly more 

 conservative estimate of bay filling 

 in light of recent evidence of bay 

 scour on the delta flanks and the 

 sporadic flood-related nature of 

 delta growth (Roberts et al. 1980). 



Projections of delta growth are 

 made somewhat easier since the Atcha- 

 falaya Delta is evolving in a similar 

 manner as those described for sub- 

 deltas of the modern Mississippi Riv- 

 er and other shallow water deltas 

 (Figure 11). Presently the mass and 

 aerial extent of the Atchafalaya 

 Delta are comparable to that of the 

 Mississippi River's Baptiste Collette 

 sub-delta, which started its building 

 phase in 1874. Deltas of the Colo- 

 rado, Trinity and Guadalupe Rivers in 

 Texas, which are growing into shallow 

 bays behind barrier islands, are also 

 somewhat analogous to the Atchafalaya 

 setting. 



However, several dilemmas are 

 being posed by the growth of the At- 

 chafalaya Delta which may bring about 

 an alteration of natural delta growth 

 patterns. Fisheries in the region 

 have been severely impacted by ex- 

 cess fresh water and sediment loads. 

 There has been a decline in shrimp 

 and fish catches, and a near collapse 

 of the oyster industry in the area 

 (Van Beek 1977). The State of Louis- 

 iana discarded a sediment barrier 

 plan, designed to ease these impacts 

 in the bays to the west of Atcha- 

 falaya Bay, as ineffective. 



There are equally pressing pro- 

 blems faced by flood control and 

 navigation interests. Morgan City, 

 for example, is severely threatened 

 with flood problems created by rising 

 flowlines resulting from delta growth. 

 Navigation interests are plagued with 

 shoaling problems and, at the same 

 time, are requiring deeper draft 



361 



