The Control of Nature Response Paper
It is an extremely difficult task for engineers to design a “dam” like the Old River Control Structure in southern Louisiana so that they can be sure that it will prevent avulsion of the Mississippi into the Atchafalaya. The flood of 1973 that caused so much damage to the Old River Control Structure was the affect of many things. There were unusually heavy snows in the upper valley. The South of the state received an exceptional amount of rainfall. Eventually, the runoffs came down to the tributaries, built-up, and ultimately signaled computers a warning that the mainline levees were not adequate to contain the amount of water collected. In a state of panic there were sandbags, potato ridges and barriers of uncompacted dirt added to the levees to try to prevent a flood. During the continued spring high water the collected drainage all came together at Old River in units exceeding two million cubic feet per second. Twenty-five per cent of that left the Mississippi channel and went to the Atchafalaya. Professor Racphael G. Kazmann remembers his experience walking over the structure prior to the flood of 1973. Kazmann recalls, “That whole miserable structure was vibrating... This thing weighs two hundred thousand tons. When two hundred thousand tons vibrates like this, this is no place for R. G. Kazmann. I got in my care, turned around, and hot the hell out of there.” The structure and its stilling basin had been built to disperse energy- but not quite that much energy. The Mississippi delta is subsiding and eroding
Deltas are normally slowly increasing in size due to sediment deposited by the river. The slow increase is due to a slight imbalance between sedimentation by the river, and sinking of the delta due to consolidation of deeper sediments. The balance has been upset by the construction of levees and dams along the Mississippi River leading to rapid erosion of the Mississippi River delta in Louisiana. The construction of levees along the lower river that channel water and sediments past New Orleans and out into the Gulf. This has stopped sedimentation throughout the delta, and the delta is now rapidly sinking below sea level. If the levees did not exist the river channel carrying most of the river water would change position, and deposit sediments throughout the delta. The dredging of many canals to provide access to oil and gas wells. The canals help salt water reach further inland, resulting in death of trees and vegetation that stabilizes wetlands. Wind blowing along the canals produces waves that erode the banks. And, storm surges produced by storms travel along canals causing erosion further inland. All areas are not eroded at the same rate during a storm. Some areas have severe erosion during an event. Other areas have much less erosion.