412 A NATIONAL PLAN FOR. AMERICAN FORESTRY 



the drainages appears desirable. This will include about 2.2 million 

 acres of abandoned agricultural lands and 17 million acres of forest 

 land. The very large national interest created by conditions in these 

 drainages suggest that this public ownership be Federal rather than 

 State or other local. 



LOWER MISSISSIPPI RIVER BASIN 



Floods in the Mississippi Valley are most common and of greatest 

 concern in the " Delta" or bottomland region of the lower Mississippi 

 Basin. Here all the major tributaries of the big river pour in their 

 flood contributions, the control of which constitutes the outstanding 

 flood problem in the United States. Responsibility for the havoc 

 wrought by floods in the bottomlands of the lower Mississippi Basin 

 must be attributed largely to flood waters from other sections. How- 

 ever, were the latter all under control, there would still be a local 

 flood problem of considerable magnitude in the lower Mississippi 

 Basin as a result of the condition of its watershed and the relatively 

 large area of alluvial bottomlands on which its own flood waters are 

 poured. 



LOCATION AND DESCRIPTION OF DRAINAGE BASIN 



For purposes of this discussion, the lower Mississippi Basin (shown 

 in fig. 6) includes not only the alluvial lands extending from Cairo, 

 111., to the Gulf of Mexico but also the upland watersheds of the streams 

 draining directly into the lower river. These are small and relatively 

 unimportant streams with the exception of the Yazoo River which 

 heads in the uplands of north-central Mississippi and flows over a 

 wide alluvial flood plain to join the Mississippi River at Vicksburg. 



The lower Mississippi Basin is from 500 to 600 miles long and up 

 to 150 miles wide. It has a total area of 33,886,000 acres. Nearly 

 one half the total area is in overflow bottomlands. Here forest occu- 

 pies lands not protected by levees and lands behind the levees which 

 have not been cleared for agriculture. These overflow areas are often 

 covered with water during the winter season and thus perform an 

 important service in flood control since they serve as natural storage 

 reservoirs for the detention of flood waters. 



The remainder of the drainage basin^ consists of rolling to hilly 

 uplands. The principal area the Mississippi bluffs and silt loam 

 uplands borders the Mississippi Delta on the east and extends in a 

 strip 35 to 100 miles wide throughout the length of the drainage basin. 

 A much smaller but similar upland area known as Crowley's Ridge is 

 located west of the Mississippi River. The latter area occupies a 

 narrow belt up to 10 miles wide and about 200 miles long and rises 

 about 150 feet above the level of the surrounding bottomlands. Also 

 included in the drainage is a relatively small area of hilly country in 

 southeastern Missouri. 



These uplands because of their location with reference to low-lying 

 bottomlands and because of their present condition play an important 

 part in the destructive floods and soil erosion that are the major 

 watershed problems of the drainage. 



