have serious adverse as well as bene- 

 ficial effects. The beneficial 

 effects would be widespread in 

 relation to the adverse effects, 

 which would be concentrated at and 

 near the diversion sites. The ad- 

 verse effects can be separated into 

 two distinct categories: those that 

 would occur in the developed areas 

 adjacent to the river, and those 

 that would occur in the estuarine 

 area at and in the vicinity of the 

 freshwater introduction. The lat- 

 ter type would be an adverse impact 

 on the environment and fish and 

 wildlife resources. 



The general configuration of 

 the lower Mississippi River and the 

 development of the area play a major 

 role in the problem. The natural 

 alluvial levees and ridges located 

 beteeen the Mississippi River and 

 uplands adjacent become highly 

 developed as urban, industrial, and 

 prime agricultural lands. These 

 developed lands have been protected 

 from Mississippi River floods and, 

 in most cases, from tidal flooding 

 from the direction of the estuaries. 

 Any diverted river flow must be 

 routed through these developed lands, 

 which would cause problems in these 

 areas. Each diversion site would 

 require at least structures in the 

 Mississippi River levee to insure 

 continued flood protection, and at 

 many possible sites, additional 

 structures would be required in 

 levees bordering the estuaries. For 

 diversions of the magnitude con- 

 sidered essential to affect major 

 portions of the estuaries, channels 

 are required to convey the flow. 

 These channels would require lands, 

 relocations of residential and com- 

 mercial structures , and modifica- 

 tions to intercepted drainage sys- 

 tems, roads, streets, railroad 

 tracks, pipelines, and utilities. 



The detrimental effects on the 

 estuaries could include localized 

 short-term impacts in the vicinity 

 of the freshwater introduction and 

 long-term impacts that would encom- 

 pass a much larger area. Antici- 

 pated adverse impacts consist of the 

 following: high levels of coliform 

 bacteria, heavy metals, pesticides, 

 phenols, and PCBs ; too fresh an area 

 for oysters and other sessile organ- 

 isms to survive; temperature differ- 

 ences (river water is cooler) ; and 

 increased turbidity. The magnitude 

 and extent of the areas adversely 

 affected would vary depending on 

 the location of diversions. However, 

 the percentage of the area adversely 

 affected would probably be small 

 compared to the area benefited. 

 Downriver sites are the most effec- 

 tive, but the estuarine areas that 

 would be adversely affected are 

 among the most productive and are 

 heavily fished. 



Another factor that will influ- 

 ence local institutions is the con- 

 tribution that fish and wildlife re- 

 sources make to the local economies. 

 Generally, the importance of fish and 

 wildlife to the local economies in- 

 creases progressively from upriver to 

 downriver. Therefore, the situation 

 occurs that where fish and wildlife 

 are not economically important, the 

 adverse impacts and commitments ne- 

 cessary are not offset by the bene- 

 fits to the local area. At downriver 

 sites, fish and wildlife may be im- 

 portant from an economic viewpoint, 

 but because the detrimental effects 

 in both the developed and estuarine 

 areas are not offset by the benefits 

 in the local area, local interests 

 do not usually find such a plan 

 acceptable. This latter situation 

 is one of the reasons why the 

 authorized Mississippi Delta Region 

 has not been implemented. 



373 



