original high land, most of modern New 

 Orleans is well below sea level by as 

 much as 4.5 m (15 ft). Nearly 1.8 m (6 

 ft) of annual rainfall must be pumped 

 out of the city and up to Lake Pont- 

 chartrain using aging pumps with limited 

 capacity (Lewis 1976). New Orleans is 

 therefore one of the most vulnerable of 

 major U. S. cities to hurricane 

 flooding. 



Natural levee land that formed the 

 original city was quickly settled, and 

 later developments occurred in drained 

 wetland below sea level. When swamps 

 and marshes were drained, the soil oxi- 

 dized, compacted, and sank, resulting in 

 severe problems for residents in parts 

 of New Orleans including both Orleans 

 and Jefferson Parishes (Earle 1975). 

 Much wetland "reclamation" has occurred 

 since World War II, and despite its high 

 cost, development continues. For exam- 

 ple, there are long-standing plans to 

 develop the New Orleans East area, one 

 of the last marsh areas remaining adja- 

 cent to Lake Pontchartrain (see Figure 

 43). Recent population growth has oc- 

 curred along the north shore of Lake 

 Pontchartrain. The Lake Pontchartrain 

 causeway, completed in the late sixties, 

 has greatly accelerated this growth. 

 Additional expansion has occurred west- 

 ward into Jefferson Parish, on the West 

 Bank, and further up the Baton Rouge 

 corridor. A decade ago some planners 

 stated that New Orleans had already 

 exceeded its optimum size (Earle and 

 Gagliano 1972). 



Early New Orleans residents were 

 often plagued by mosquitoes, both salt 

 marsh species and freshwater forms that 

 spread yellow fever and malaria. The 

 mosquito problem is presently held in 

 check with a major control program that 

 relies heavily on aerial spraying of 

 malathion. 



Many modern residents are concerned 

 about the quality of their drinking 

 water, drawn from the Mississippi River 

 downstream from the heavily industrial- 

 ized corridor south of Baton Rouge. A 

 statistically significant correlation 

 between mortality from bladder cancer 

 and consumption of drinking water from 



the lower Mississippi has been docu- 

 mented (Page et al. 1976). Other 

 studies have indicated the presence of 

 mutagens and carcinogens in the treated 

 drinking water (Dowty et al. 1975; Pelon 

 et al. 1979). 



New Orleans dropped from the second 

 largest city in the nation in 1835 to 

 the ninetenth largest in 1970, (Figure 

 43) largely because of the space con- 

 straints and a shift away from water- 

 borne transportation. There are plans 

 to develop additional marsh and swamp- 

 land but these projects are expensive, 

 e.g., draining the land, providing 

 ongoing flood protection, and about a 50 

 percent increase in building costs over 

 high land construction. In addition, 

 the natural value of the marshes is 

 lost. Major management decisions center 

 on the conflicting costs and benefits of 

 urban expansion versus the long term 

 values of wetlands and estuaries. Should 

 the remaining marsh and swamp areas near 

 the city be drained and developed, or 

 should development be shifted to the 

 more distant Pleistocene uplands on the 

 north shore of Lake Pontchartrain? 

 These issues cannot be resolved without 

 an accurate estimate of the value of the 

 natural systems that would be lost by 

 continued development. 



MISSISSIPPI RIVER DELTA HYDROLOGIC UNIT 

 (III) 



The Mississippi River Delta hydro- 

 logic unit is limited to the extreme end 

 of the major distributary of the river, 

 and occupies the area known as the 

 modern bird's foot delta. The sediments 

 composing this unit are the most re- 

 cently deposited of any portion of the 

 MDPR. Accretion of the modern delta has 

 spanned the breadth of the coastal 

 shelf, and because there is no more 

 shelf on which to build, much of the 

 sediment load flows over the edge of the 

 shelf break and is permanently lost to 

 the deltaic system. More land could be 

 built locally among the major passes 

 were it not for artificial levees, 

 sills, groins, and continuous dredging 

 by the USACE to maintain navigation 

 channels . 



103 



