Johannes van Beek: In 1973, there was significant accretion along southern Lake 

 Pontchartrain and reductions of salinity lasting at least a year. In view of the 

 warning that the Tangipahoa swamps are giving us, I think it is necessary to consider 

 a major diversion into the Lake Pontchartrain system. Ideally, there would be many 

 smaller diversions across the Mississippi River levee through the swamps into Lake 

 Maurepas, but there are the major obstacles of Airline Highway and the ground level 

 segments of Interstate 10. Those larger diversions to the southern lake are the only 

 ones feasible, although Bonnet Carre may not be the only place. 



John Uhl: What do you mean by small or large diversions? What types of structures are 

 involved? 



Johannes van Beek: Small structures can convey 250 to 2,000 cfs, similar to the Bayou 

 Lamoque structure, and include siphons and box culverts. Large structures can 

 convey about 15,000 cfs and include gates and large box culvert structures. 



Raphael Kazmann: We are dealing with some substantial problems in regulating the 

 Mississippi River flow. For one thing, the sediment available in the Mississippi River 

 has declined by a factor of two since the I950's. Even if we could keep the available 

 load from being transported off the continental shelf, there would be a deficiency in 

 restoring any equilibrum that might have existed. This deficiency may also cause 

 some poorly understood changes in sediment transport. With less sediment 

 transported, there is what could be called "hungry water" with more transport 

 energy available than there is sediment to transport. This results in bank erosion. 

 The nutrient flow to the Gulf of Mexico may have also decreasd as a result of 

 unnecessary secondary treatment of wastes. 



There is much discussion of the management of the Atchafalaya River. The 

 Atchafalaya provides a shorter path to the gulf. This means that in the upstream 

 reaches of the Atchafalaya, the water level is going to degrade, that is, the high 

 water is going to be lower with time, thus providing land owners with the possibility 

 of draining the swamp. At Simmesport, for a flow of about 200,000 cfs the water 

 level has dropped 7 feet since the I940's. At the lower end of the Atchafalaya there 

 is sedimentation which is building natural levees and the water is also transporting 

 more sediment into the Atchafalaya Bay. This deposition will require great expense 

 to maintain navigation channels. 



If the Old River control structure fails, most of the sediment and freshwater 

 will travel down the Atchafalaya. New Orleans will be on a navigable estuary (the 

 present Mississippi course) and all of the lower river diversion structures will simply 

 transmit salt water. We should adapt and accept what is happening, backoff, and 

 enjoy the present conditions while they exist. In this new land and new swamp that 

 the Atchafalaya is building, protect the new habitat. Don't consider the present 

 Atchafalaya Basin as a wildlife refuge; it is a wildlife death trap. Following a large 

 flood of 1.5 million cfs or more, there will be no deer, squirrels, etc. remaining. 



There is much discussion of who is going to manage the present Atchafalaya 

 Basin, but you can't "manage" the area of the greatest geomorphological change in 

 the country. All you can do is adapt. Government policy should not encourage 

 people to move into the area: one such policy that is dangerous is government- 

 subsidized flood insurance. Further, don't build new levees at public expense or raise 

 existing ones. If people want to live there, let them build their own levees at their 



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