Mississippi rivers case study. Flashcards
How long is the Mississippi river?
The Mississippi is the 4th longest river in the world and its drainage basin covers ⅓ of the USA.
It flows the entire length of the USA, from the boundary waters in Minnesota all the way to the Gulf of Mexico in Louisiana.
Despite many attempts of humans to tame this great river, the Mississippi is subject to periodic flooding.
The largest disaster in history was the 1927 river flood, which was the most destructive flood event in US history.
What are the benefits of living close to the Mississippi River?
Settlements - in the lower course of the river the land is flat and easy to build on.
Tourism – Recreational hobbies like canoeing, swimming, boating, fishing etc are popular.
Industry – Water from the river is used for cooling in factories and power stations.
Transportation - Waterways are useful and important for transportation. Often this is for cargo boats. The total cargo of 2004 was around 31.5 million short tons consisting of 72% imported cargo and 28% exported cargo.
Commercial fishing (and shrimping in the delta) are important to the people of the Mississippi drainage basin economically and for a food supply. They rely on a healthy river and delta.
Farming - The floodplain in particular is rich in nutrients and the soils are used for agriculture.
What are the causes of river flooding in Mississippi?
Urbanisation: Because rivers provide many opportunities for people, many settlements have been built along the banks of the Mississippi e.g. cities such as St Louis and New Orleans. Urbanisation reduces permeability in the river basin and increases the flood risk. Prior to urbanisation there would have been more floodplain available for water to occupy during times of flood.
Risks from tropical storm systems can also lead to flooding in the lower Mississippi valley, for example Hurricane Camille in 1969 and Hurricane Katrina in 2005 both led to significant flood events.
What are the more specific causes of the 1993 flood?
A volcanic winter is thought to have started with the 1991 eruption of Mount Pinatubo. It has been suggested that excess cloud condensation nuclei from the eruption were responsible for the Great Flood of 1993 in the Midwestern United States.
Like many floods this flood was caused by large amounts of precipitation over a long period of time, in June and July of 1993 much of the area experienced over 150% of normal rainfall and some areas e.g., parts of North Dakota, Kansas and Iowa experienced more than double their normal rainfall.
On top of this, the ground was already saturated, not only by the previous rainfalls, but during the previous year the weather conditions were considerably cooler which meant less evaporation.
Human causes included the development on the floodplain, including the draining of wetlands which could have absorbed water. Continued urbanisation of the river valley has reduced permeable surfaces, leaving fewer areas for water to go. In addition, the levees were poorly built and not federally made.
What were the effects of the 1993 flooding?
43 deaths
50,000 people evacuated
26,000km of land flooded
$2.46 billion crop losses
River traffic stopped for several months
$15 billion in damages
Contents of and the buildings themselves destroyed
Threat of disease from sewage
Insurance claims high
Stagnant water attracted mosquitoes and rats
Flood management of Mississippi (hard and soft engineering)
Typical flood management techniques:
Hard engineering involves building artificial structures which try to control rivers. They tend to be more expensive.
Soft engineering does not involve building artificial structures but takes a more sustainable and natural approach to managing the potential for river flooding.
Hard engineering on the Mississippi:
6 huge dams and 105 reservoir
Strengthening the levees with concrete mattresses
Making the course shorter and straighter by cutting through the necks of meanders to get the water past towns and more quickly to the sea
Diversionary spillways – overflow channels
Soft engineering on the Mississippi:
Afforestation to delay runoff
Less construction on the floodplain e.g. St Louis.
Detailed notes on the impacts of the 1993 floods.
The 1993 Mississippi River floods were one of the most significant and devastating flood events in the history of the United States. Some of the key impacts include:
Economic Damage: The floods caused widespread economic damage, with estimates of losses ranging from $15 billion to $20 billion. This included damage to agricultural land, infrastructure, homes, businesses, and transportation networks.
Agricultural Losses: The floods submerged millions of acres of farmland, particularly in the Midwest, destroying crops and causing significant losses for farmers. The inundation of farmland led to crop failures and livestock losses, impacting the agricultural economy of the region.
Displacement of Residents: Thousands of people were forced to evacuate their homes as floodwaters inundated residential areas along the Mississippi River and its tributaries. Many communities were submerged under several feet of water, leading to widespread displacement and disruption of normal life.
Environmental Impact: The floods had significant environmental consequences, including contamination of water sources, damage to wildlife habitats, and disruption of ecosystems. Chemical spills and contamination from flooded industrial sites also posed environmental hazards.
Infrastructure Damage: Floodwaters damaged roads, bridges, levees, and other critical infrastructure, hindering transportation and emergency response efforts. The destruction of infrastructure further exacerbated the challenges of recovery and rebuilding in affected areas.
Health and Safety Concerns: The floods created health and safety hazards, including risks of waterborne illnesses, contamination of drinking water supplies, and the spread of infectious diseases. Emergency response teams had to address these concerns while providing assistance to affected communities.
Long-Term Recovery: The aftermath of the 1993 floods necessitated extensive long-term recovery efforts, including rebuilding infrastructure, restoring agricultural land, and providing assistance to affected residents and businesses. The floods highlighted the need for improved flood management strategies and infrastructure to mitigate the impact of future flood events.
Some of the named places significantly affected by the 1993 Mississippi River floods include:
St. Louis, Missouri: Experienced major flooding along the Mississippi River, leading to evacuations and damage to infrastructure.
Davenport, Iowa: Saw significant flooding along the Mississippi River, with floodwaters inundating downtown areas and causing widespread damage.
Quincy, Illinois: Experienced severe flooding along the Mississippi River, leading to evacuations and damage to homes and businesses.
Des Moines, Iowa: Experienced flooding along the Des Moines River and other tributaries, resulting in evacuations and damage to homes and businesses.
More detailed notes on the management of flooding on the Mississippi:
The management of the Mississippi River involves a combination of hard and soft engineering approaches aimed at controlling flooding, maintaining navigation, protecting infrastructure, and preserving ecosystems. Here’s an overview of some of the key methods employed:
Hard Engineering Approaches:
Levees: Levees are embankments built along the riverbanks to prevent flooding by confining the river within its channel. Levees have been constructed extensively along the Mississippi River and its tributaries to protect communities and agricultural land from flooding. However, reliance on levees can sometimes increase the risk of catastrophic flooding if they fail or are overtopped.
Channelization: Channelization involves modifying the natural course of the river by straightening and deepening its channel to improve navigation, reduce sediment deposition, and control flooding. While channelization can enhance navigation and flood control, it can also disrupt natural habitats and increase erosion downstream.
Dams and Reservoirs: Dams and reservoirs are built on tributaries of the Mississippi River to regulate flow, store water, and generate hydroelectric power. They can help mitigate flood peaks by storing excess water during periods of heavy rainfall and releasing it gradually downstream. However, dams can also alter river ecosystems and impede the natural flow of sediment, nutrients, and fish migration.
Flood relief channels: channels are built into which water can be diverted during times of high flow. An example is the Morganza spillway, a flood channel on the Mississippi.
Soft Engineering Approaches:
Floodplain Management: Floodplain management involves zoning regulations and land-use planning to restrict development in flood-prone areas and minimise exposure to flood hazards.
Wetland Restoration: Wetlands play a crucial role in flood mitigation by absorbing and storing floodwaters, reducing peak flows, and providing natural flood protection. Wetland restoration projects aim to restore degraded wetlands, enhance their flood storage capacity, and improve ecosystem health along the Mississippi River corridor.
Afforestation: Planting trees reduces the risk of flooding by increasing interception which slows surface run-off.
Explain the conditions in this area which have created the formation of the delta:
- The Mississippi is a major river that is capable of transporting a lot of sediment
- Its flow slows as it enters the Gulf of Mexico
- Sediment is deposited faster than the tides can remove it
- River flow is blocked by so much deposition that the river splits up into distributaries
- Distributaries deposit sediment over a wide area, extending new land into the sea
- The Mississippi River delta has widely spaced distributaries, making it look like a bird’s foot.
- In summary the the Mississippi River forms a bird-foot delta as it empties into the Gulf of Mexico.
What are the advantages for people living in delta area?
The fertile soils deposited by the Mississippi River make the delta an ideal area for agriculture. The region is known for its production of crops such as cotton, soybeans, rice, and corn.
Biodiversity: The delta supports diverse ecosystems, including wetlands, marshes, and swamps, which provide habitats for a wide variety of plant and animal species.
Economic opportunities: The Mississippi Delta is home to cities and towns that support various industries, including agriculture, fishing, shipping, and tourism.
What are the problems caused?
- Flooding: The delta is prone to flooding, especially during hurricanes and heavy rainfall events. This damages to infrastructure, homes, and crops, leading to economic losses.
- Land subsidence: The extraction of groundwater and oil and gas from beneath the delta has contributed to land subsidence, or sinking. This increases the risk of flooding and can cause damage to infrastructure and property.
- Coastal erosion: The Mississippi Delta is experiencing significant coastal erosion, partly due to natural processes and partly due to human activities such as the construction of levees and canals. Coastal erosion threatens communities, infrastructure, and ecosystems along the coast, leading to loss of land and habitat.
- Environmental degradation: Human activities such as pollution, habitat destruction, and drainage of wetlands have contributed to environmental degradation in the delta, including loss of biodiversity and degradation of water quality.
