Another example of subsidence or gradual sinking of the delta is seen in the Jean Lafitte National Historical Park and Preserve located in southern Louisiana. Bayou des Familles runs parallel to a natural levee and a lower swamp. This is a transitional area in which one can see evidence of subsidence. Once long ago, the land was higher and oak trees where found in this area. Today, this area is full of dead or dying oak trees. The land has subsided and the water table has risen which is killing the once large oak trees in this area. Now the area is considered a swamp. The area offers an opportunity to observe the transition from river channel to swamp and marsh. For more information on this preserve contact the Visitor Center at (504) 589-2330.
The
uneven distribution of rainfall through the year causes many rivers to
rise seasonally. A flood occurs when a river's discharge exceeds the capacity
of the channel and water overflows the stream banks. As discharge increases
during a flood, so does the velocity. This enables a stream to carry a
greater load as well as larger particles. Floods are also capable of moving
very large objects as well as great volumes of sediment which can cause
major problems.
Some areas have developed ways to control flooding.
An example of this is the Bonnet Carre' Spillway. The spillway is a mile
and a half long dam which is used in case of emergency flooding. If a flood
occurs planks are lifted from the spillway and water is diverted into Lake
Pontchartrain. This helps to prevent the Mississippi River from getting
out of control and possibly taking down a levee.
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