RUSSELL 41 



from old ships, and the like, all of which get incorporated in the beach deposit. One of the in- 

 teresting things is the amount of Indian pottery which also gets incorporated because it is 

 coarse. I think it is not possible to walk very far along the beach, the way Mclntire walked 

 around the beach, before a pottery fragment will be picked up. The beach has been straightened 

 since Indians, who had used the pottery, had been living south of the current beach. 



In general, this land has grown southward when the Mississippi River and Red River have 

 discharged considerable amounts of sediment toward western Louisiana. At other times, as 

 under recent conditions when the river has been much further east, the deposition of the delta 

 has been concentrated away from this area. Those times are, in general, periods when the 

 beach encroaches northward over the marshes. There have been alternations in the past, which 

 are shown by the presence of old beach ridges, old cheniers, that lie back in the marshes. They 

 each represent a time when sediments were deficient in quantity and the beach had a chance to 

 be driven some distance inland. 



There is ample mechanism for making a beach move inland and no mechanism for pulling 

 a beach out. Once the accumulation, the sand, shells, etc., is driven back, there it stays. If 

 sediments come in quantities, the marsh grows off the beach and the coast grows outward. 

 Thus there is the alternation of the shoreline back and forth. 



It is very interesting that the Indian story ties in nicely with this. As Mr. Mclntire has 

 shown, the oldest Indian settlements are predominantly inland, and the most recent ones are 

 close to the coast. 



The dramatic part of the recent history is this: starting a little over five years ago, the 

 pattern changed. This coast, after that retreat of 800 feet in the twenty-year period prior to 

 1952, is starting to grow out again. This is another cycle that has set in. 



There are several elements involved in the reason for this. In the first place, the 

 Atchafalaya River, which comes down through a low basin, in the year 1900 was carrying 13 

 percent of the combined flow of the Lower Atchafalaya and the Mississippi. By 1950 this quan- 

 tity had climbed to 31 percent. Every single decade since 1860, when artificial accumulations 

 were cleared out on a stretch of this river, has seen more water coming down the Atchafalaya 

 River than came in the decade preceding. The amount of alluviation in the Atchafalaya Basin 

 has so overwhelmed the old water bodies that most of the lakes have been obliterated. Most of 

 the lakes on the maps are very shallow. The basins are essentially full. People throughout the 

 Atchafalaya Basin can recall old landmarks and points that in earlier times they used as guides 

 in steering their boats, and now these landmarks are entirely inland. In one place, a prominent 

 citizen of Louisiana had a hunting lodge out in the basin, and he built a levee around his place 

 to protect it. Today the house is in a depression, with an alluvial plain surrounding it. 



Since these lakes have filled up, they are no longer trapping the sediment. About six 

 years ago the first of the sediment reached the Gulf of Mexico. With increasing discharges 

 down the Atchafalaya River, not only is more sediment being brought down, but it is no longer 

 being held in the basin; so the sediment is now coming to the Gulf. 



In the Gulf, the present dominant set of the current is westward. Atchafalaya sediment 

 has now formed an ooze or mud flat across this western coast, which has advanced westward 

 about 125 miles during the last five years. We have probed this. You can drag a skiff over it 

 and probe to determine the depth of this accumulation. You could run right through this ooze 

 with any sort of a landing boat but it is up to six feet deep. We have mapped it in three dimen- 

 sions for a report which we have submitted on this project. In many places the exposed flat is 

 100 yards in width at sea level. Pioneer salt water plants are now starting to get a good hold 

 on it, and this soon will become a brackish salt marsh area. The old beach is now becoming a 

 chenier. 



These older cheniers were formed in the same way. In general, the chenier cross sec- 

 tion, exhibited by Mr. Treadwell, indicates a deposit 8 to 10 feet deep of beach material, over- 

 lying marsh and various other things, and up to a mile or so in width. Of course, any such 

 diagram is greatly exaggerated in its vertical and horizontal scales, but these are the general 

 dimensions. 



