Figure 1. Major geomorphic provinces in Louisiana. 



Notural Factors Leading to Land Loss 



The Mississippi deltaic plain is a large area of dynamic geomorphic change. Over 

 the past several thousand years Mississippi River sedimentation has formed the coastal 

 wetlands of Louisiana, building seven major deltaic lobes since the stabilization of sea 

 level. Within this process of overall growth were large-scale cycles of land growth and 

 decay of land. 



In an active delta, sedimentation exceeds erosion and there is a net land gain. 

 Land building occurs at the mouth of the river's channel, through overbank flooding, and 

 through sedimentation in older deteriorating marshes (Baumann and Adams 1982). But 

 as its channel lengthens, the Mississippi seeks a new, shorter course to the Gulf of 

 Mexico and ultimately abandons the older channel. During this phase, active land 

 building ceases in the old delta and there is a net loss of land from erosion and 

 subsidence. Historically, land loss in old Mississippi River deltas was compensated for by 

 land gain in the active delta. 



There are three major natural mechanisms involved in the process of land loss: (I) 

 Gulf of Mexico beach retreat, (2) lateral erosion of streamside marsh shores, and (3) 

 gradual sinking of inland marshes. Wave action is the primary cause of shoreline retreat 



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