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Part 9. LEVEES AND CREVASSES. Model levee design. The theory of levees proposed to confine the river’s mass in its main flow channel, encouraging scour during high flow. Natural crevasses beneath levees.

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Part 9
Part 9

LEVEES AND CREVASSES


Model levee design
Model levee design

  • The theory of levees proposed to confine the river’s mass in its main flow channel, encouraging scour during high flow.


Natural crevasses beneath levees
Natural crevasses beneath levees

Crevasses are sand filled distributary channels that form at high flow, and lie beneath earthen levees like ticking time bombs, waiting to explode.


Part 9

Seepage crevasse exposed at the east levee of the IHNC breach in New Orleans after Hurricanes Katrina and Rita


Part 9

  • Permeability contrasts caused by clay filled oxbows create treacherous and contrasting foundation conditions beneath levees.


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Part 9


Raising levees
Raising Levees earthen levees, causing these levees to settle and sink.

  • The rising bed of the Mississippi River has necessitated the heightening of levees, beginning in the 1890s, as shown above.

  • Lower image shows dynamite charge being detonated on levee south of New Orleans in Plaquemines Parish during the Great 1927 flood.


Levee failures
Levee Failures earthen levees, causing these levees to settle and sink.

  • Levees tend to fail during sustained high flow events because of underseepage problems, toe scour, and overtopping

  • This shows the 1999 Celotex levee failure in Louisiana, along the Mississippi River


Part 9