Hands-on Activity: Dam Forces
Educational Standards :
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
Each group needs:
Embankment dam materials for each group:
Gravity dam materials for each group:
Arch dam materials for each group:
Buttress dam materials for each group:
Introduction/Motivation (Return to Contents)
How do engineers decide how large or strong to build a dam? Is the weight of the water pushing against the side of the dam important? Did you know that one cubic foot (0.29 cubic meters) of water weighs 64 pounds (29 kg)? The weight of the water actually determines how strong the dam must be. Water pushes against the side of a dam with a certain amount of force or pressure. The dam wall must push the water back with an equal amount of force, and the dam must redirect the force of the water into the ground and canyon walls without collapsing or moving downstream from the force of the water. How does a dam exert force on water? The dam must be strong and sturdy and have strong connections to the ground, in the form of foundations, to help it stand.
By researching the size and direction of all the forces acting on a dam, engineers design a structure that is able to resist all these forces. The principle force acting on a dam is the weight of the water behind the dam. Other forces include the weight of the dam itself and in some cases wave pressure and earthquake forces.
When we make engineering drawings of a dam, we indicate the direction of a force by drawing an arrow (draw an example on the board). Today, you will fill out a worksheet to show forces on the different types of dams — just like engineers do.
Let's talk about four of the most common dam types:
If we want to test various types of dams to see how they work when water is present, how would we do that? What engineers do is create and test models. What would a model of a dam look like? (Take suggestions from students.) A model of a dam would be a small scale version of it. By making and testing many small-size versions of dams, you learn from them without the time and expense of making full-size dams. That's what we're going to do today — just like engineers do. Let's get started!
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Before the Activity
With the Students
Attachments (Return to Contents)
Safety Issues (Return to Contents)
Troubleshooting Tips (Return to Contents)
Before testing with water, have students make sure the plastic walls of the small containers have tight seals into the clay.
Assessment (Return to Contents)
Discussion/Brainstorming: As a class, have students engage in open discussion. Remind them that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have students raise their hands to respond. Record their ideas on the board. Ask the students:
Activity Embedded Assessment
Worksheet: Have students complete the Four Types of Dams Worksheet; review their answers to gauge their mastery of the subject.
Voting: Make sure each student has individually chosen which type of dam they want to use for Thirsty County on their worksheets. Take a class vote by having students raise their hands to vote for their type of dam. Declare the majority vote as the winner — the dam type that Splash Engineering will design for Thirsty County. Review with the students the features and advantages of that type of dam. (Note: In a real engineering analysis, environmental conditions and community requirements/limitations would also be considered in the decision on what type of dam to design and construct. Example considerations include the river's geology and terrain, availability/type of dam building materials, and budget.)
Activity Extensions (Return to Contents)
Have students research a local dam and determine its type. Have them report the physical attributes (height, capacity, type of dam, type of spillway, year constructed, etc.) of the dam, as well as a photograph and/or drawing.
Activity Scaling (Return to Contents)
Additional Multimedia Support (Return to Contents)
To find more examples of certain dam types, look at the "type" column in Wikipedia's list of Reservoirs and Dams in California at: http://en.wikipedia.org/wiki/List_of_reservoirs_and_dams_in_California
See an extensive description of types of dams and spillways at the Wikipedia "Dam," website at: http://en.wikipedia.org/wiki/Dam
A spillway allows water to bypass a dam when it reaches capacity by draining water from the reservoir. See photos and description of the "glory hole" spillway at Monticello Dam in California at the Fish Chris website; it is the largest funnel-type dam outlet in the world: trophybassonly
References (Return to Contents)
Building Big: Dam Basics. WGBH Educational Foundation. Accessed December 4, 2007. (Good description and photos of four dam types) http://www.pbs.org/wgbh/buildingbig/dam/basics.html
ContributorsMegan Podlogar, Sara Born, Kristin Field, Denali Lander, Lauren Cooper, Timothy M. Dittrich, Denise W. Carlson
Copyright© 2008 by Regents of the University of Colorado.
Supporting Program (Return to Contents)Integrated Teaching and Learning Program and Laboratory, University of Colorado Boulder
Acknowledgements (Return to Contents)
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.