Crescent City Connection – connects the east and west banks of New Orleans, Louisiana; the fifth-longest cantilever bridge in the world. Clark Bridge (also known as the “Super Bridge” as the result of an appearance on PBS program Nova) – This cable-stay bridge constructed in 1994 connects Alton, Illinois to Black Jack, Missouri. It is the northernmost river crossing in the St. Louis metropolitan area and is named after explorer William Clark.
The main channel has been locked into one position, preventing it from meandering and creating new aquatic areas. By diverting all current to the main channel, water in the backwaters is slowed down, increasing the rate of sedimentation. The lock and dam system has turned a dynamic river system into something that resembles a long series of lakes, which are filling up with silt.
It was thought that the river’s velocity would scour off bottom sediments, deepening the river and decreasing the possibility of flooding. Many communities threatened by the flood began to construct their own levee breaks to relieve the tension of the rising river. The Great Flood of 1993 was another significant flood, although it primarily affected the Mississippi above its confluence with the Ohio River at Cairo, Illinois. The Army Corps of Engineers now actively creates floodways to divert periodic water surges into backwater channels and lakes.
But the speed changes as water levels rise or fall and where the river widens, narrows, becomes more shallow or some combination of these factors. It takes about three months for water that leaves Lake Itasca, the river’s source, to reach the Gulf of Mexico. Prior to the 1927 flood, the primary strategy to stop flooding was to close off as many side channels as possible to increase the flow in the main river.
The area of the Mississippi River basin was first settled by hunting and gathering Native American peoples and is considered one of the few independent centers of plant domestication in human history. Evidence of early cultivation of sunflower, a goosefoot, a marsh elder and an indigenous squash dates to the 4th millennium BC. The lifestyle gradually became more settled after around 1000 BC during what is now called the Woodland period, with increasing evidence of shelter construction, pottery, weaving and other practices.
Images from NASA’s MODIS (Moderate-resolution Imaging Spectroradiometer) show a large plume of fresh water, which appears as a dark ribbon against the lighter-blue surrounding waters. The Mississippi continues around the tip of Florida before it mixes thoroughly with the salt waters of the ocean. There is an ongoing effort to keep saltwater out of the Mississippi’s fresh water before it enters the ocean. Saltwater reset anki deck wreaks havoc on the delicate habitat of fresh water biospheres inland. A series of 29 locks and dams on the upper Mississippi, most of which were built in the 1930s, is designed primarily to maintain a nine-foot (2.7 meter) deep channel for commercial barge traffic. Prior to the 1927 flood, the Corps’ primary strategy was to close off as many side channels as possible to increase the flow in the main river.
