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Hspecially deleterious to primary production are dredging and filling 
projects on submerged banks, tidal areas, and salt marshes, where the 
effects of such operations are painfully obvious. It is testimony to the 
public’s ignorance about the value of the wet lands that such opera- 
tions continue to be so common. 
On the other end of the spectrum are those projects which reduce 
the supply of sediment to the wet lands. While such practices have 
been cited just above as possible remedial measures for overabundance 
of sediment, there are instances in the United States where flood con- 
trol has been championed to the exclusion of all other considerations, 
most notably along the Louisiana coast. Gunter '’ has studied ex- 
tensively the effects of flood control projects on the Mississippi Valley, 
In its natural condition, the Mississippi flooded annually, overflowing 
its natural levees and spreading out over its flood basins for many 
miles on either side. From the first settlement of the area, therefore, 
levees have been built; the present system exceeds 2,500 miles in 
length, and is up to 35 feet high. As the river was cut off from its 
flood basins, flood levels grew even higher, in New Orleans from 14.9 
feet in 1882 to 21 feet in 1912. Gunter estimated that present flood 
heights are 10 times greater than before the levees were constructed, 
because some 35,000 square miles of overflow areas have been walled 
off and receive no flood water. 
It is this overflow area which most concerns us here, much of which 
was formerly floodplain swamps and lower delta marshes. One effect of 
the almost perfect canalization of the Mississippi is the annual loss 
of about 730 million tons of fine soil, which is presently washed into 
the Gulf of Mexico each year. Much of this soil was formerly avail- 
able to aggrade the swamps and marshes of the lower delta, and the 
loss to this area is equivalent to 380,000 acres of soil, 3 feet thick. 
There is clear historical evidence that these areas are indeed no 
longer agerading, but are being destroyed by erosion caused by the 
slowly rising seal level on the Gulf Coast. 
CONCLUSIONS 
The insufficiency of the present data has been a recurrent theme in 
much of this paper. There is no conclusive evidence that sedimentary 
processes are being disturbed to the point of elimination of the wet 
lands entirely, but I think it has been demonstrated that this situation 
is not entirely impossible, either. Problems related to sedimentation 
and primary production will doubtless be low on the list of priorities 
when money is allocated for environmental research, perhaps because 
the problem seems inconsequential to many people. This, in turn, is a 
function of the present commercial appraisal of the value of these 
areas. 
In the event that research were carried out, and even assuming 
that it indicated unambiguoouly that sedimentary processes must be 
considered in managing the wet lands, it would be a task of monu- 
mental proportions to include such considerations in land-use policy. 
The area of the wet lands is minute compared to the area of its water- 
shed, and activities anywhere in that watershed may be concentrated 
at the estuary. Effective management of the wet lands is therefore 
Footnotes at end of article. 
