6 BULLETIN 71, U. S. DEPAETMEXT OF AGRICULTURE. 



withstanding the proximity of the swamps and standing water, malaria, though 

 occasionally occurring, is not dreaded. Until within the last few years epi- 

 demics of yellow fever caused frequent alarm, but this disease has now been 

 thoroughly eradicated, and with the methods of treating the disease and prevent- 

 ing its spread it is not to be dreaded as formerly, even if it should again appear. 



Since it has been demonstrated that malaria, like yellow fever, can be trans- 

 mitted to man only through the bite of a certain species of mosquito, it may 

 be expected that drainage, which destroys the breeding places of these pests, will 

 result in a decrease in whatever malaria may now exist. As a matter of fact 

 malarial fever is very rare on the immediate coast line, and the health of people 

 from the North seems to be fully as good as that enjoyed by the natives. 



SOILS. 



The area under discussion contains soils that are peculiar to the section and 

 these are now for the first time being drained and cultivated. In the following 

 section are set forth the results of first-hand investigations along with the 

 classification and general descriptive matter taken from publications of the 

 United States Bureau of Soils. 



Abea East of the Atchatalaya Eiveb. 



oeigin axd formation of soils. 



The soil of the area east of the Atchafalaya River and in parts of St. Mary, 

 Iberia, and St. Martin Parishes is of alluvial origin and is largely the result 

 of deposits made by the Mississippi River and its branches. It has been built 

 up from a depth of sevetal thousand feet to the present elevation above the 

 Gulf. In the very newest portions of the Delta at Port Eads, at the mouth of 

 the river, a considerable subsidence of the land is yet going on, the measured 

 rate being about 0.11 foot per year. That this subsidence is due to a compact- 

 ing of the newer deposits is shown by the fact that permanent bench marks 

 along the ^Mississippi River record a decreasing settlement as the distance 

 from the mouth of the river increases. Except in this relatively small area, 

 near the mouth of the river, the remainder of this section of the State shows 

 no change in elevation. As is typical of delta regions, ridges of sandy soil are 

 found along the main river channel and along its branching outlets. The 

 manner in which these ridges were formed is well brought out in the following, 

 from A Preliminary Report upon the Bluff and Mississippi Alluvial Lands of 

 Louisiana, by W. "W. Clendenin.^ 



With every flood the river now overflows its flood plain and deposits much 

 of the sediment from its headwaters. As with a slight increase in velocity the 

 transporting power is vastly increased, so with a slight checking of velocity, 

 as occurs over the flood plain outside of channel, deposit takes place. As 

 the greatest decrease in velocity takes place near the channel, there the heaviest 

 and coarsest sediment is deposited, and in greatest quantity. The river banks 

 are thus built higher by each flood and a system of natural levees is produced. 

 There is thus a marked difference in the "front lands" and the "back lands" 

 along the river. The former are higher and coarser textured than the latter, 

 and therefore much more easily cultivated and drained. 



Drainage from the very channel margin is away from the river, and unless 

 forced by the topography of the land, will not reach the river proper, but unite 

 with some outlet of the river produced during some extraordinary flood period 

 and kept open by the escape of water during ordinary periodic flood stages. 

 As the feeders of the river are called tributaries, these outlets have not inaptly 

 been styled distributaries. 



1 Louisiana Stas. Rpt. Geology and Agriculture, Pt. IV, p. 263. 



