Poydras, Louisiana, and openings of 

 the Bonnet Carre Spillway in 1950, 

 1973, 1975, and 1979. The spillway 

 is a feature of the Mississippi 

 River and tributaries project, lo- 

 cated about 33 miles above New 

 Orleans. It is designed to introduce 

 floodwaters from the Mississippi 

 River to Lake Ponchartrain to prevent 

 overtopping of levees at and below 

 New Orleans. Data on these flood 

 control diversions indicate that 

 after a short-term adverse impact, 

 dramatic increases in fish and wild- 

 life populations have been experi- 

 enced for the next several years. 

 Considering the limited information 

 on actual experiences, the technical 

 studies will necessarily be mostly 

 theoretical . 



Of the technical studies that 

 must be conducted, the ecological 

 studies play a crucial role and form 

 a base for the engineering and 

 economic studies. The ecological 

 studies must quantify the physical 

 and chemical changes desired in the 

 environment to produce optimal con- 

 ditions for fish and wildlife re- 

 sources. However, because of the 

 presently imprecise nature of the 

 science, these analyses are diffi- 

 cult to perform. Our current knowl- 

 edge of relationships between 

 changes in the physical and chemical 

 parameters and biological communi- 

 ties are based largely on inductive 

 reasoning and expert judgment. 



Because the optimal conditions 

 to be achieved by the diversions 

 cannot be precisely defined, a logi- 

 cal approach to the study is to 

 stage development of the project. 

 Under this approach, a diversion 

 plan would be developed based on 

 current ecological studies and other 

 technical studies that are dependent 

 on the ecological studies, all of 

 which would be performed at the 



same level of detail. Studies for 

 site evaluation, design, and cost 

 estimates would be performed at a 

 full level of detail. Prior to 

 construction of the entire project, 

 a pilot element would be constructed 

 to provide sufficient data to re- 

 evaluate and modify additional ele- 

 ments of the plan, as necessary. 

 Such an approach would also facili- 

 tate resolution of institutional 

 arrangements for specific sites and 

 permit construction at the earliest 

 practicable time. 



INSTITUTIONAL CONCERNS 



Developing institutional ar- 

 rangements to divert Mississippi Riv- 

 er flow to adjacent estuaries is a 

 difficult task. Both political and 

 social institutions play an essential 

 role in the planning process and can 

 be critical determinants of the im- 

 plementability of a plan. The capa- 

 bility and willingness of existing 

 institutions to meet project require- 

 ments in monetary, and nonmonetary 

 terms is a necessary ingredient for 

 eventual realization of a diversion 

 plan. The institutions considered 

 critical include, among others, 

 State, parish (same as county), and 

 municipal governments and agencies, 

 tax structures, and general local and 

 regional attitudes. Potential diver- 

 sion sites along the Mississippi Riv- 

 er are all located in the State of 

 Louisiana in 10 parishes which have 

 political jurisdiction over the lands 

 adjacent to the river. In addition, 

 numerous cities, towns, and communi- 

 ties, including the city of New Or- 

 leans, are located on the banks of 

 the river in the area. 



A major complication with fresh- 

 water diversion is that a project of 

 the magnitude being considered would 



372 



