national guard engineering education. general levee information levees are the most widely used...

National Guard

Engineering Education

General Levee Information

• Levees are the most widely used method of flood control

• The most extensive levee systems in the US are along the Mississippi and Sacramento rivers and their tributaries.

• The first levees were about 3 ft high but now they average 24 feet with some areas as high as 50 feet

Types of Primary Levees

• Earthen Levee:– Built out of soil or other natural material– Least expensive to build– Base must be large to provide the support

required to withstand a heavy water surge– Not ideal in the absence of large amounts of land

I Wall Levee

• A vertical wall partially embedded in the levee crown, or the tapered top

• Not recommended when the soil is soft because the stability is reliant on the resistance from the soil

• For stability reasons, I walls rarely exceed 7 feet above the ground’s surface

T wall levee• Has a horizontal base that reinforces the

soil underneath the levee, making it one of the stronger types of levees

• Requires piles be driven deeply into the ground

• This makes T walls expensive to build• Typically used when walls higher than 7

feet are required

Double Wall Levee

• Relatively new• Consists of 2 metal sheet pilings and filler

made with sand and concrete• Most effective if there is a direct hit by a large

item such as a barge because the filler will absorb some of the hit, preventing the levee from breaking

Secondary Levees: Sandbags

• Made of burlap or other material that are filled with sand, soil or clay]

• Inexpensive, can be transported empty and filled with local sand

• In large flooding, water will seep through the bags and finer materials, such as clay, can leak out

• Only dry sandbags can be stored for future use – wet sandbags become contaminated

• Requires a lot of labor

Secondary Levees: Aqua Fences

• Plywood panels are unfolded and secured with aluminum poles and connected to one another with PVC

• Can be quickly and easily installed and dismantled and stored for future use

• Large initial purchase is required; cannot be used in an unexpected emergency situation unless already acquired

• Best for long-term emergency for areas of repeated floodingwww.youtube.com/watch?v=lExOgQ73Fd4http://www.youtube.com/watch?v=lExOgQ73Fd4

Secondary Levees: HESCO barriers

• Collapsible wire mesh linked open top containers with a heavy-duty fabric liner, filled with sand, dirt or gravel

• Can be quickly and easily set up, harder for water to seep through because of thickness

• Must have room for the equipment required to fill the barriers; once in place, it cannot moved or stored for future use

• Fabric has a lifespan of 3-4 yearswww.youtube.com/watch?v=mADScNThzso

Secondary Levees: DefenCell

• Similar to HESCO barrier, but does not require the wire mesh

• Can be quickly and easily set up, easily transportable, can be carried by a person or pushed off vehicle with no risk of damage

• Harder for water to seep through because of thickness

• Once in place, it cannot be moved

DefenCell

How many sandbags and tons of sand?

Height Required Number of Sandbags

1 foot 82 Feet 203 feet 34

On average, 250-500 sandbags are required to protect a single home that is being

threatened by rising waters. To answer the following questions, use 425 as the number

of sandbags required to protect a single home from rising waters.

There are 65 homes in a threatened area. How many sandbags are required

to protect these homes from rising waters?

65 homes x 425 bags per home = 27,625 bags

• There are a group of buildings alongside a levee that is 15,840 ft. In order to protect these buildings from rising waters, determine the number of sandbags required to build a 2 ft. high secondary levee.

156,840 x 20 = 316,800

• If 1 ton of sand can fill 50 sandbags, how many tons of sand are required to protect the single family homes and groups of buildings above from rising waters?

27,625(homes) + 316,800(buildings) = 344,425 bags

344,425/50 = 6888.5 tons of sand

Fargo flooding 2009