Detailed freshwater and geophysical hazards case studies. Each case study is written underneath a syllabus point so all the case studies for each topic are covered.
Freshwater and Geophysical hazards case studies - IB GEOGRAPHY
Freshwater
Two contrasting detailed examples of flood mitigation of drainage basins:
Protecting the Mississippi:
- The Mississippi river is located in the USA and flows through 10 states and
drains 1/3 of the USA
- It contains some of the USAs most important agricultural regions
- A number of methods have been used to control flooding in the river and its
effects including: stone and earthen levees to raise the banks of a river,
holding dams to hold back water in times of flood, lateral dykes to divert water
away from the river and straightening the channel to remove water quickly.
- About $10 billion has been spent on controlling the river. Annual maintenance
costs reach about $200 million.
- This was not enough, however, and in July 1993 following heavy rain, many of
the levees collapsed and allowed the river to flood. Over 25000km squared of
land was flooded.
- According to some geographers, if the river was left to its own devices, a new
channel would have been formed, however river protection schemes
prevented this from happening. Flood relief measures include: Bonnet Carre
Water way from New Orleans to the Gulf of Mexico, Atchafalaya river which
carries up to 25% of the Mississippi flow.
Flood mitigation in Bangladesh:
- Bangladesh is located to the east of India on the Bay of Bengal. The country
suffers from frequent flooding, with rainfall originating in the Himalayas.
- In the short term, embankments prevent overflow but they may lead to
deposition in the channel, which in turn raises the river bed and encourages
flooding
- The Flood Action Plan 1989 – 1995, involved a plan in which there were three
main water resource development options: minimum intervention (which
involved improving existing flood schemes), selective intervention (protecting
densely populated areas and key infrastructure from floods and erosion) and
major intervention (large scale developments such as river engineering work
on all main rivers.)
- There are over 10000km of embankments (levees) and a number of flood and
cyclone shelters
- There are gabions to protect important townships
- In addition to structural measures, there are also several non-structural
measures such as flood forecasting, flood preparedness and flood relief.
- The flood forecasting warning center issues five day forecasts during the
monsoon season.
, Detailed examples to illustrate the role of different stakeholders:
- Agriculture is the largest user, consuming about two thirds of all water from
lakes, rivers and groundwater.
- Population growth, urbanization and industrialization have increased the use
of water in these sectors.
- Growing pressures on rivers have meant that a number of them no longer
reach the sea. They may also be heavily polluted.
- The Rio Nuevo that flows from Baja California into California is now
contaminated with agricultural, industrial and municipal waste. There are now
regular algal blooms and the river has become increasingly saline. There
have been major fish deaths due to the salinity.
- Between 2004 and 2016, the Flint river in Michigan was polluted with
chemicals related to industrial activity. They began using the river water for
their drinking supply and gave all the residents lead poisoning.
- Rapid economic growth in China has resulted in widespread declining of
water quality. Over 70% of the country’s rivers have such high levels of
pollution that the water cannot be safely used as drinking water.
One internationally shared water resource as a source of conflict:
The Grand Ethiopian Renaissance Dam:
- Ethiopia is currently building Africa’s largest dam – The Grand Ethiopian
Renaissance Dam (GERD). When it is finished it will be 170 m tall and 1.8 km
wide. Its reservoir will be able to hold more than the volume of the entire Blue
Nile.
- It is designed to produce 6000 MW of electricity within double Ethiopia’s
current output which leaves three out of four people in the dark.
- This opportunity for Ethiopia could spell disaster for Egypt. The Nile provides
nearly all of Egypt’s water. Egypt claims two thirds of that flow based on a
treaty signed with Sudan in 1959 however this is no longer enough to satisfy
the growing population. Annual water supply per person has fallen buy well
over half since 1970.
- The stakeholders include the governments of Egypt Ethiopia and Sudan as
well as the United Nations and the people who will make use of the water.
- In March 2015, the leaders in Egypt Ethiopia and Sudan signed the
declaration of the approved construction of the dumb as long as there is no
significant harm to downstream countries.
- Ethiopia insists that it will only produce power and that the water pushing his
turbines will ultimately flow downstream. Egyptians fear it will also be used for
irrigation reducing downstream supply.
- A reasonable concern is that the if the dam’s reservoir is filled too quickly, it
would significantly reduce Egypt’s water supply and affect the electricity
generating capacity of its own Aswan Dam.
- Sudan has long sided with Egypt in opposition to the dam, which is only about
20km from its border. But there are also benefits to Sudan. Sudan will receive
some of the power produced by the dam. By stabilizing the Nile’s flow, it will
also allow Sudan to prevent flooding.
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