Explore dam engineering, spillways, water flow, and erosion with this hands-on STEM lesson for age 14 learners. Students build, test, measure, and improve a model spillway using the engineering design cycle.

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Spillway Science: Designing a Safe Path for Water

Materials Needed

Plastic storage bin, baking tray, or shallow dish
Water
Small cup or measuring jug
Sand, soil, or modeling clay
Cardboard, craft sticks, plastic spoons, or foam pieces
Small rocks, gravel, or pebbles
Ruler
Timer or phone stopwatch
Paper and pencil
Optional: food coloring, aluminum foil, blocks, coins, and a digital camera

Lesson Snapshot

Learner: Fisher, age 14

Suggested time: 60–90 minutes

Big question: How can engineers control overflowing water so it moves safely instead of damaging a dam or nearby land?

Learning Objectives

By the end of the lesson, Fisher will be able to:

Explain the purpose of a spillway using accurate scientific vocabulary.
Describe how water level, slope, speed, and erosion affect spillway design.
Design and build a small spillway model that directs water safely.
Test the model, record observations, and make at least one evidence-based improvement.
Use a simple claim-evidence-reasoning explanation to defend the design.

Success Criteria

Fisher’s work is successful when he can:

Identify the reservoir, dam, spillway, channel, and downstream area in a model.
Explain that a spillway gives excess water a controlled route around or over a dam.
Build a model that moves water away from the dam without causing major collapse or uncontrolled flooding.
Record at least three observations and use them to improve the design.
Explain why the final design worked better than the first design.

Safety Notes

Use only small amounts of water and work on a washable surface.
Clean up spills immediately to prevent slipping.
Do not climb on, enter, or approach real dams, reservoirs, or spillways. Observe them only from a safe, approved location.
Wash hands after handling soil, sand, or water from outdoors.

Introduction: Hook and Objectives

Hook: “The Dam Emergency”

Tell Fisher:

Imagine that a week of heavy rain has filled a reservoir almost to the top. Water is beginning to rise toward the dam. If the water goes over an unsafe part of the dam, it could wash away soil, weaken the structure, and cause flooding. You are the engineer. How will you give the extra water a safe path to escape?

Ask Fisher:

Where does extra water go when a reservoir becomes too full?
Why might simply letting water flow over any part of a dam be dangerous?
What features could slow water down or guide it away?

Explain the objectives in student-friendly language:

“Today you will learn how spillways work, build a small water-control system, test it, and improve it like a real engineer.”

Key Vocabulary

Dam: A structure built to hold back or control water.
Reservoir: A lake or storage area where water is collected behind a dam.
Spillway: A channel, opening, or structure that safely carries excess water away from a dam or reservoir.
Discharge: The amount of water flowing past a point during a certain amount of time.
Erosion: The wearing away and movement of soil, sand, or rock by water, wind, or ice.
Downstream: The direction in which water flows.
Energy dissipation: The process of reducing the speed and energy of moving water to limit damage.

Body: Learning and Practice

Part 1: I Do — Teacher or Adult Demonstration

Time: 10–15 minutes

Build a quick model in the tray:

Use sand, soil, or clay to make a small raised dam at one end of the tray.
Leave space behind the dam to represent the reservoir.
Pour water into the reservoir until it begins to approach the top of the dam.
Let a small amount of water flow over an unprotected section.
Observe what happens to the soil or sand.
Next, create a sloped channel lined with craft sticks, foil, clay, or small rocks.
Add a rough area of rocks or gravel at the bottom of the channel to slow the water.
Test the spillway again.

Think aloud while demonstrating:

“The spillway must be lower than the unsafe part of the dam so excess water chooses this route.”
“A steep, smooth channel may make water move quickly.”
“Fast water has more power to erode soil, so engineers may use steps, rocks, curves, or rough surfaces to reduce its energy.”
“The water needs a safe outlet downstream. It is not enough to move the problem to another location.”

Quick Check

Ask Fisher to answer verbally or in writing:

What problem does a spillway solve?
Why could fast-moving water cause erosion?
What could engineers add to a channel to slow water down?

Part 2: We Do — Analyze a Spillway Design

Time: 10–15 minutes

Work together to plan the model. Fisher may sketch the design while discussing these questions:

Where will the reservoir be?
Where will the dam be?
Where should the spillway begin?
How steep should the spillway be?
How will the design slow the water down?
Where will the water end up?
How will you know whether erosion occurred?

Introduce the engineering design cycle:

Ask: What water-control problem must be solved?
Imagine: What possible designs could work?
Plan: Which materials and shape will be used?
Create: Build the spillway.
Test: Add water and observe what happens.
Improve: Change one or more features based on evidence.

Prediction

Before building, have Fisher complete this sentence:

“I predict that my spillway will work well because…”

Part 3: You Do — Spillway Engineering Challenge

Time: 25–35 minutes

Challenge

Design and build a model spillway that safely moves excess water from a reservoir to a downstream area.

Design Requirements

The model must include a reservoir, dam, spillway, and downstream area.
The spillway must direct water away from the dam.
The dam should remain mostly intact during testing.
The design should reduce uncontrolled erosion.
Fisher must test the model at least twice and make one improvement.

Optional Design Constraints

For an extra challenge, choose two or more constraints:

Use no more than five different materials.
Complete the first design in 10 minutes.
Use only one cup of water per test.
Include at least one bend, step, or rough section.
Make the spillway fit within a specific width, such as 10 centimeters.

Testing Procedure

Place the model on a level, washable surface.
Measure and record the starting height of the dam.
Pour the same amount of water into the reservoir for each test.
Start the timer as the water enters the spillway.
Observe the water’s speed, direction, splashing, and erosion.
Record the time it takes for the water to reach the downstream area.
Measure or estimate how much the dam or channel changed.
Modify one feature, such as the slope, lining, width, or rock placement.
Repeat the test and compare the results.

Observation Table

Test	Design Change	Water Speed	Erosion Observed	Time to Downstream Area	What Happened?
1	First design
2
3, optional

Discussion During Testing

Pause after each test and ask:

What part of the design worked best?
Where was the water moving fastest?
Where did erosion occur?
Did the spillway control the water, or did the water find another route?
What evidence supports your answer?

Real-World Connection

Explain that real spillways can be made from concrete, rock, soil, steel, or other materials. Some are wide and gently sloped. Others use steps, drops, basins, or rough surfaces to reduce the energy of water before it reaches rivers and communities.

Ask Fisher to choose one real-world setting and explain how the design might need to change:

A mountain reservoir receiving snowmelt
A city stormwater basin during a hurricane
A farm pond after several days of rain
A hydroelectric dam that must release water at a controlled rate

Assessment

Formative Assessment

Vocabulary quick check during the introduction
Prediction before construction
Observation notes during each water test
Questions about water speed, slope, and erosion
Adult feedback focused on evidence rather than appearance

Summative Assessment: Engineer’s Brief

Fisher should give a short presentation or write a one-page engineer’s brief using this structure:

Claim: My final spillway design was effective because…
Evidence: During testing, I observed…
Reasoning: This happened because…
Improvement: I changed… and the result was…
Real-world use: This feature could be useful in…

Simple Rubric

Category	Excellent	Developing	Needs More Practice
Science Understanding	Clearly explains spillways, water flow, and erosion.	Explains most ideas with minor errors.	Needs support explaining the main ideas.
Design	Directs water safely and includes a method for reducing erosion.	Directs water but has some control or erosion problems.	Water is mostly uncontrolled or damages the model.
Testing and Data	Completes repeated tests and records useful observations.	Completes tests but records limited details.	Needs reminders to test or record results.
Improvement	Uses evidence to make and explain a meaningful improvement.	Makes an improvement with some explanation.	Makes little connection between evidence and changes.

Differentiation and Choice

Scaffolds for Learners Who Need Support

Provide a labeled sketch showing the reservoir, dam, spillway, and downstream area.
Offer sentence starters such as “The water moved faster when…” and “Erosion happened because…”
Use a smaller amount of water and test one variable at a time.
Allow Fisher to explain observations verbally instead of writing every detail.
Pre-sort materials by possible use: lining, support, slowing water, or shaping the channel.

Extensions for Advanced Learners

Calculate approximate discharge using: discharge = volume ÷ time.
Compare a wide, shallow spillway with a narrow, steep spillway.
Investigate why engineers use stilling basins or stepped spillways.
Design a spillway that works with two different water volumes.
Create a scale drawing with measurements and explain how the design would change at full size.
Research a famous spillway or dam failure and identify the engineering lessons.

Learning-Format Options

Hands-on: Build and test the physical model.
Digital: Use a drawing or simulation tool to model water flow.
Outdoor: Study how rainwater moves along a driveway, garden, or slope without approaching dangerous water structures.
Discussion-based: Debate whether a spillway should prioritize speed, capacity, erosion control, or cost.

Conclusion: Closure and Recap

Three-Minute Recap

Ask Fisher to complete these statements:

A spillway is important because…
Water causes more erosion when…
One feature that helped control water was…
The strongest evidence from my tests was…

Reinforce the main ideas:

Spillways provide a controlled route for excess water.
Water’s speed and direction affect erosion and damage.
Good engineering designs are tested, measured, and improved.
A successful spillway protects the dam and safely moves water downstream.

Exit Ticket

Answer in three to five sentences:

“If I were designing a spillway for a community reservoir, I would include ________. I would include it because ________. My model showed this when ________.”

Optional Follow-Up Project

Fisher can create a “Spillway Engineer’s Field Guide” with a labeled diagram, vocabulary, test results, photographs or sketches, and recommendations for building a safer full-sized spillway.

Spillway Science STEM Lesson: Design a Safe Water-Flow Model