This is one of the few locations along the lower Mississippi River that is not protected by a levee. Therefore the river and land beside it are interacting as they have for ages, unhampered by the hand of man.
The Mississippi River is the chief river of the largest drainage system in North America. Flowing entirely in the United States (though its drainage basin reaches into Canada), it rises in northern Minnesota and meanders slowly southwards for 2,530 miles to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 31 US states and 2 Canadian provinces between the Rocky and Appalachian Mountains. The Mississippi ranks as the fourth longest and tenth largest river in the world. The river either borders or cuts through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.
Native Americans long lived along the Mississippi and its tributaries. Most were hunter-gatherers or herders, but some, such as the Mound builders, formed prolific agricultural societies. The arrival of Europeans in the 1500s changed the native way of life as first explorers, then settlers, ventured into the basin in increasing numbers. The river served first as barrier – forming borders for New Spain, New France, and the early United States – then as vital transportation artery and communications link. In the 19th century, the Mississippi and several western tributaries, most notably the Missouri, formed pathways for the western expansion of the United States.
Formed from thick layers of this river's silt deposits, the Mississippi River Valley is one of the most fertile agricultural regions of the country, which resulted in the river's storied steamboat era. Because of substantial growth of cities and the larger ships and barges that supplanted riverboats, the decades following the 1900s saw the construction of massive engineering works such as levees, locks and dams, often built in combination.
Since modern development of the basin began, the Mississippi has also seen its share of pollution and environmental problems – most notably large volumes of agricultural runoff, which has led to the Gulf of Mexico dead zone off the Delta. In recent years, the river has shown a steady shift towards the Atchafalaya River channel in the Delta; a course change would prove disastrous to seaports such as New Orleans. A system of dikes and gates has, so far, held the Mississippi at bay but, due to fluvial processes, the shift becomes more likely each year.
A flood plain is an area of land adjacent to a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge. It includes the floodway, which consists of the stream channel and adjacent areas that actively carry flood flows downstream, and the flood fringe, which are areas inundated by the flood, but which do not experience a strong current. In other words, a floodplain is an area near a river or a stream which floods when the water level reaches flood stage.
Floodplains can support particularly rich ecosystems, both in quantity and diversity. They are a category of riparian zones or systems. A floodplain can contain 100 or even 1,000 times as many species as a river. Wetting of the floodplain soil releases an immediate surge of nutrients: those left over from the last flood, and those that result from the rapid decomposition of organic matter that has accumulated since then. Microscopic organisms thrive and larger species enter a rapid breeding cycle. Opportunistic feeders (particularly birds) move in to take advantage. The production of nutrients peaks and falls away quickly; however the surge of new growth endures for some time. This makes floodplains particularly valuable for agriculture.
To complete this earthcache, send me the answers to the following questions.
1. Estimate the width of the Mississippi River at this location.
2. Approximately how high is the land at the cache site above the current river level (this may change according to the river level)?
- 10 - 20 feet
- 20 - 40 feet
- 40 - 60 feet
3. The soil at this location is sediment or silt deposited when the river floods. Which of the following best describes it?
4. The silt is slowly raising the ground level as it is deposited. How much has the ground risen above the road level?