engineering

Levee breach

Levee breach is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Levee breach rather than just read about it. In short: A levee breach or levee failure (also known as dyke breach or dyke failure) is a situation where a levee (or dyke) fails or is intentionally breached, causing the previously contained water to flood the land behind the levee. Causes Man-made levees can fail in a number of ways.

Key takeaways

Levee breach belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Levee breach to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Levee breach from memory before moving on to harder problems.

Reference excerpt

A levee breach or levee failure (also known as dyke breach or dyke failure) is a situation where a levee (or dyke) fails or is intentionally breached, causing the previously contained water to flood the land behind the levee.

Causes Man-made levees can fail in a number of ways. The most frequent (and dangerous) form of levee failure is a breach. A levee breach is when part of the levee actually breaks away, leaving a large opening for water to flood the land protected by the levee.

Foundation failure A breach can be a sudden or gradual failure that is caused either by surface erosion or by a subsurface failure of the levee. Levee breaches are often accompanied by levee boils, or sand boils. The underseepage resurfaces on the landside, in the form of a volcano-like cone of sand. Boils signal a condition of incipient instability which may lead to erosion of the levee toe or foundation or result in sinking of the levee into the liquefied foundation below. Some engineers think that boils lead to a form of internal erosion called piping which undermines the levee, but others consider them a symptom of generalized instability of the foundation.

Erosion and damage Surface erosion of the surface of a levee is usually caused by the action of wind and water (waves but also normal flow). Erosion can be worsened by pre-existing or new damage to a levee. Areas with no surface protection are more prone to erosion. A levee grazed by certain types of animals, like sheep, can show trails used by the animals where grass does not grow. Trees in levees are a special risk. A tree can become unstable after the soil of the levee has become saturated with water. When the tree falls the root system will likely take a chunk of the saturated soil out of the levee. This shallow hole can quickly erode and result in a breach. If the tree falls in the water and floats away it can damage the levee further downstream. Floating trees near levees should be quickly removed by the agency responsible for the maintenance of the levee. Other forms of damage can be caused by ships or other (large) floating objects or from objects in the levee, like traffic signs or fences that are damaged or completely removed by wind or water. Barbed wire fences can collect large amounts of floating plant material, resulting in a large amount of drag from the water. Whole fences can be dragged away by the water.

Overtopping Sometimes levees are said to fail when water overtops the crest of the levee. Levee overtopping can be caused when flood waters simply exceed the lowest crest of the levee system or if high winds begin to generate significant swells (a storm surge) in the ocean or river water to bring waves crashing over the levee. Overtopping can lead to significant landside erosion of the levee or even be the mechanism for complete breach. Often levees are armored or reinforced with rocks or concrete to prevent erosion and failure.

Kolk lakes After a levee breach a kolk lake can often be seen. This is a crater-like depression just behind the breach where soil and other material has been violently scoured out by the rushing water. After a breach, a kolk lake can sometimes remain after the water level recedes.

Intentional breaches In some cases levees are breached intentionally. This can be done to protect other areas, to drain flooded areas, or to give back land to nature. In most cases an intentional breach is not without discussion since valuable land is given up. During the Great Mississippi Flood of 1927 a levee was blown up with dynamite to prevent the flooding of New Orleans. Again during record-breaking flooding in 2011, the US Army Corps of Engineers blew up a section of a Mississippi River levee with dynamite to open the New Madrid Floodway. The floodway was used for farming and had about 200 residents at the time. The levee at Bird's Point was designed to be removed if necessary so that Mississippi water levels would be lowered, taking pressure off levees for miles upstream in more populated areas such as Cairo, Illinois, and New Madrid, Missouri. Taking land from the cycle of flooding by putting a dike around it prevents it from being raised by silt left behind after a flood. At the same time the drained soil consolidates and peat decomposes leading to land subsidence. In this way the difference between the water level on one side and land level on the other side of the dike grows. In some areas reclaimed land is given back to nature by breaching and removing dikes to allow flooding to occur (again). This restores the natural environment in the area. This happened in the Glory River in Iraq.

Examples

New Orleans

The words levee and levee breach were brought heavily into the public consciousness after the levee failures in metro New Orleans on August 29, 2005, when Hurricane Katrina passed east of the city. Levees breached in over 50 different places submerging 80 percent of the city. Most levees failed due to water overtopping them but some failed when water passed underneath the levee foundations causing the levee wall to shift and resulting in catastrophic sudden breaching. The sudden breaching released water at a high velocity that moved houses off their foundations and tossed cars into trees. This happened in the Lower Ninth Ward when the Industrial Canal breached and also in the Lakeview neighborhood when the 17th Street Canal breached. At least 1,464 people perished. In New Orleans, the United States Army Corps of Engineers is the Federal agency responsible for levee design and construction as defined in the Flood Control Act of 1965 and subject to local participation requirements, some of which were later waived. Fault has been aimed at the Corps of Engineers, their local contractors, and local levee boards.

North Sea

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Levee breach

Start with the simplest possible case. Write down what Levee breach claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Levee breach before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Levee breach ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Levee breach

In research: Levee breach appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Levee breach in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Levee breach is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dikes, Engineering failures, so understanding it makes those chapters shorter.
In everyday life: Look for Levee breach outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Levee breach in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Levee breach means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Levee breach out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Levee breach in simple terms?

Why does Levee breach matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Levee breach?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Levee breach.