Jason Anderson, age 13, of Memphis, Tenn., for his question:
WHEN WAS THE FIRST MISSISSIPPI LEVEE BUILT?
A levee is a wide wall built along the banks of rivers to keep them from flooding over the land. In the United States, the term is used especially to describe walls, or dikes, built along the southern part of the Mississippi River.
The first Mississippi River levee was only three feet high. It was built at New Orelans, La., in 1718 to keep the river from flooding a strip of fertile land. Gradually a few more levees were built.
Many years later, the seven states that lie south of where the Mississippi meets the Ohio River asked the federal government for help to check floods.
In 1882, the year of a great Mississippi River flood, the government set aside $1.3 million for the improvement of the river. Part of the money was to be used for making levees. Since then, the federal and state governments have spent many millions of dollars for the building and repairing of levees.
Most levees are made up of sandbags and banked up earth. The name comes from the French word lever, which means to raise. Irrigation engineers now use the term levee to also describe a small dike or ridge of earth which confines areas of land that are to be flooded for agricultural purposes.
The earth embankments on the Mississippi River are 15 to 30 feet high. They are eight feet wide on top and over 100 feet wide at the base.
More than 2,000 miles of levees have been built along the Mississippi River, but they still do not fully control the overflow. The completed program will have an additional 2,500 miles of levee. About 1,500 miles of the levees have been built since 1905.
Some authorities object to the building of levees that enclose a river so much that the water is high above the surrounding countryside. This system does lead to some danger.
When a levee puts the surface of the river high above the ground, a break could bring a wall of water rushing across the countryside, smashing everthing in its way. This makes floods even more dangerous when they occur. If a levee were to break under these conditions, disaster could be the final result.
Experts who oppose high levees believe regulating floods by headwater control is better than attempting to regulate them with levees. Meanwhile, high levees continue to be built as part of the flood control program.
A jetty is a pier or wall built into a river. It is used as a breakwater, to break the force of rough water or to deepen a channel by increasing the current. Many jetties can be found along the Mississippi.
The Mississippi River carries great quantities of fine sand and silt to the place where it empties into the Gulf of Mexico. It flows through four mouths, called passes. In 1874, these mouths were all so choked that steamers could not get through.
A man named James Bads suggested building two long jetties which would force the water through a narrower channel, making the current carry the sand and silt out to sea. When finished in 1879, the jetties in the South Pass provided a channel 30 feet deep.