AY Honor Dams and Levees Answer Key
Skill Level
Year
Unknown
Version
30.04.2024
Approval authority
1
Both are barriers that hold back or control the movement of water from one side to the other. A dam is situated across the moving water and a levee is situated parallel to the moving water.
2
A beaver is an excellent dam builder. The reason a beaver builds a dam is so that their home, or lodge, is a safe place. They usually build a dam so that a pond is created. Then they build a lodge in the middle of the pond so that it is safe from predators.
The beaver builds their dam by weaving branches together and then putting mud to seal the dam further so water does not flow through the dam. The beaver gets these branches by cutting down trees with their large sharp teeth. Then they take the small and large branches to the place where they want to build the dam. Beavers are hardworking and won’t stop until they build a dam that will create a pond good enough for their lodge.
Natural dams can also be created by debris getting caught in an obstruction that goes across a river. These tend to be temporary dams, since they will easily fail once the debris is dislodged. Other methods of natural dam formation include glacial deposits from a retreating glacier.
3
Benefits:
- Flood control
- Electric Power production
- Irrigation
- Navigation of boats upriver through locks
- Recreation
Potential Negatives:
- Not allowing sediment to flow down the river.
- Hinders or eliminates the passage of migrating fish.
- Possible catastrophic flooding if a dam fails.
- May affect cultural or historical aspects of the people where a dam is built.
4
Earth, concrete, stone, masonry and wood.
5
5a
An arch dam is a concrete that is curved upstream. The pressure of the water against these arch compresses and strengthens the structure.
5b
A buttress dam is a dam with a water tight upstream face that is supported by a series of supports at intervals on the downstream side.
5c
A gravity dam is a dam that is constructed to hold back water by primarily the weight of the dam material alone.
5d
A diversion dam is a dam that diverts all or a portion of the flow of a river from where it would normally flow.
5e
This is a dam that has a generator and turbine installed to produce electricity.
5f
5g
5h
A low-head dam is a relatively short dam (1-15 feet tall) typically concrete and built within a river or stream spanning from bank to bank for the purpose of raising the level of the upstream water, such as for a drinking water intake. The crest of the dam functions as a weir as the water is designed to flow over the dam.
5i
5j
6
6a
6b
6c
6d
6e
7
Low-head dams have the nickname “killing machines” because many drowning deaths have occurred just downstream of these dams. Under the right conditions, water flows over the dam and may appear tranquil on the surface, but beneath the surface strong water currents stay in a circular pattern making it hard to escape as the current can keep pulling a person under water. To make matters worse, the agitated water is often high in oxygen making the water a much lighter density that is very difficult or even impossible for a person to float or swim. A person should not play around a low head dam when water is flowing over the dam.
8
8a
8b
8c
8d
8e
8f
8g
8h
8i
8j
8k
9
An interview with a Civil or Geotechnical engineer is preferable. If one is not available, the state department of natural resources (or equivalent agencies) have personnel dedicated to this issue. At a minimum, most such agencies have literature for owners of dams on responsibilities and inspection concerns.
Suggested agenda for interview: discuss and understand terms for high-hazard dam, low-hazard dam, design storm, flow net diagrams, emergency overflow, outlet structure, free-board and piping concerns. From this research or interview, understand inspection techniques and how to identify a failing dam.
10
10a
- It is important to discuss and practice safety skills with the pathfinder while around the dam with slopes, wet surfaces, and water. Especially be careful of areas just downstream of the dam as these can be deadly.
- Pathfinders will need to take measurements or best guess estimates in locations that they cannot safely measure. Use scaled aerials to assist in horizontal measurements and head-on photography is helpful to compare a known feature that is X-feet tall and other dimensions may be scaled accordingly.
- Research types of fish that are available in local waters and their swimming patterns and capabilities.
- Research types of fish passage and ladders on the internet. Note horizontal and vertical limitations and which features will fit on the subject dam.
- Plan and profile views may be drawn to show location and how the passage may be constructed.
10b
Note that it says “moving parts,” not “functional system.”
Pathfinders may use LEGO, cardboard/tape or glued plastic. Give them bonus points if they can do this in a wet environment that functions.
10c
10ci
10cii
10ciii
10civ
10cv
11
12
Perhaps a theme of how God acts as a dam and catches all that life throws at us and lets them pass slowly so that we can manage it.
No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it.
