366 Department of Conservation of Louisiana 



builders. The Mississippi itself flows near the eastern 

 edge of this area, while the Atchafalaya flows near the 

 western edge. The other distributaries, both taose aban- 

 doned by the river naturally and those closed artificially, 

 originate at the Mississippi or Atchafalaya, and, by 

 branching, spread fan-shaped over the area. That por- 

 tion of the flood plain which lies west of Morgan City 

 was built originally by the Red river alone and later in 

 combination with the Mississippi, whereas the remainder 

 was built by the Mississippi alone or later in combination 

 with the Red. 



Geological Age 



Geologically speaking, the Louisiana portion of the 

 Mississippi flood plain belongs to the immediate present. 

 Its topography has resulted from a differential building 

 up by sedimentation, and not from upheaval or erosion. 

 Along the main river or its distributaries, present or past, 

 are the natural levees, popularly called "front lands," 

 formed by the deposition of the coarser sediments, where- 

 as the "back lands" differ not only in their lower level 

 but in finer texture, due to an excess of clays. The slope 

 and transition from one to the other, however, is gradual. 



Where the level of the back lands dips below the 

 mean ground water level, swamps are formed. These 

 vary from shallow swamps characterized by a variety 

 of hardwoods to the deeper swamps in which only tupelo 

 and cypress grow. Many of these swamps, especially 

 those in the lower region, differ from those associated 

 with the chain lakes already described in that they are 

 not flooded by back waters but are merely catch basins 

 for the high waters which normally overflow the natural 

 levees in times of flood, although today this occurs only 

 when the artificial levees give way. They also catch the 

 rainfall in the alluvial plain, since the drainage is away 

 from the master streams. Some swamps partake of the 

 nature of both types. 



