Project Grade 4 Engineering & Design
A Spillway for Pebblecreek Pond: A Grade 4 Flood Design Project
A four-session grade 4 project where teams build a model earth dam, watch it wash out in a storm pour, then design and fair-test a spillway on a token budget.
Objectives
- Students will write a problem statement naming the flood targets and the build limits.
- Students will build a model dam and record where it fails during a storm pour.
- Students will fair-test a spillway design by changing one part at a time.
- Students will compare two flood fixes and recommend one with reasons.
Vocabulary
- Spillway
- A dam's overflow channel, giving extra water a safe path around or over the dam when the reservoir gets too full. It protects the dam from being damaged in floods.
Also: dam crest, overtop, fair test, failure point
Teacher overview
Teams build a small earth dam across a sand tray, watch it wash out under a measured storm pour, and then design a spillway that carries the extra water away without letting any of it cross the dam crest. The driving question is how a village can keep a storm from turning its pond into a flood, and the answer students arrive at is the one real dam owners use, which is that the safe path for extra water has to be built in on purpose rather than left to chance. The final deliverable is a three-minute recommendation to a fictional village board, backed by a test sheet and a budget sheet. Session 2's failure is the heart of the project, so teams should not skip straight to the fix.
Project Brief
Driving question: How can Pebblecreek keep a big storm from washing out the pond dam and flooding the ball field?
The scene. Pebblecreek is a village invented for this project. A pond sits on the hill above the ball field. A low earth dam holds the pond in place. In a big storm the pond rises fast. Water runs over the top of the dam. That flowing water cuts a deep groove in the dam. Then a surge of water and mud runs down onto the ball field.
What a spillway is. A spillway is a low, lined channel built to one side of a dam. It sits lower than the top of the dam. Extra water leaves through the channel. The water never has to cross the top of the dam at all.
Your targets. Your model must meet all three.
- Hold the normal pond, which is 2 cups of water, for 1 full minute with no leak through the dam.
- During the storm pour, no water may cross the top of the dam.
- After the storm pour, the paper marker on the ball field square must still be dry.
Your limits.
- Everything must fit in the team tray.
- The dam must be at least 3 inches tall.
- You may spend 15 supply tokens or fewer. Sand costs 1 token per cup. Stones cost 2 tokens per cup. A sheet of foil costs 3 tokens. A craft stick costs 1 token. A plastic spoon costs 2 tokens.
The storm pour. The teacher pours 4 cups of water into the pond in 20 seconds. Every team gets the same pour every time. That is what makes the tests fair.
What you turn in. A working tray model. A test sheet with a row for every run. A budget sheet that adds up your tokens. A three-minute talk to the village board. In the talk, name your fix, show one number from your test sheet, and say what you would change next.
Milestones
Session 1: define the problem and sketch. Read the brief as a team. Write a problem statement in your own words. It must name all three targets and all three limits. Then sketch two different spillway ideas. Label the width, the depth, and the lining on each one. Pick one to build. Output: a written problem statement and two labeled sketches.
Session 2: build the dam and watch it fail. Build the dam across the tray with no spillway yet. Hold the 2-cup pond for 1 minute and check for leaks. Then take the storm pour. Watch closely. Mark on your sketch the exact spot where water first crossed the top. Measure how wide the groove is. Output: a baseline test row with the failure point marked.
Session 3: build the spillway and fair-test it. Add your spillway. Take the same storm pour and record the result. Then change one part of the spillway, and only one. You may make it wider, or deeper, or line it with foil or stones. Take the same pour again. Output: two test rows and one sentence naming the single part you changed.
Session 4: compare, then present. Build the rival fix, which is raising the top of the dam by 1 inch with extra sand. Take the same storm pour. Compare the two fixes on your test sheet. Then give your three-minute talk to the village board. Say which fix you recommend and why the other one lost. Output: a comparison row, a finished budget sheet, and the talk.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Problem statement | Names fewer than three of the six targets and limits | Names most targets and limits but leaves the token limit or tray size out | Names all three targets and all three limits in the team's own words | Names all six and adds a target the brief left out, such as how long the fix must last |
| Model performance | Dam leaks at the 2-cup hold, or the fix is never tested | Dam holds the pond, but water still crosses the top during the storm pour | Dam holds the pond, no water crosses the top, and the ball field marker stays dry | Meets all three targets and the team can point to the design choice that made the difference |
| Fair testing | More than one part changes between runs, so runs cannot be compared | One part changes, but the pour or the pond level is not kept the same | Exactly one part changes between runs while the pour and pond level stay the same | Exactly one part changes, and the team names the failure point that change was meant to fix |
| Budget and recommendation | Token total is missing or above 15 with no correction | Token total is at or under 15 but is not itemized | Token total is at or under 15, itemized, and the talk names one test number | Token total is itemized, and the talk explains a trade the team made between cost and performance |
Differentiation
Support
Pre-build the dam for these teams before session 2 so the session can start at the storm pour, which is the part that carries the idea. Give them a test sheet with the columns already labeled and the baseline row partly filled. Offer a menu of three ready spillway shapes to choose among rather than an open sketch, and let the team explain the choice instead of inventing the shape.
Extension
Ask these teams to find the cheapest design that still meets all three targets, then prove the limit by building one version that costs two tokens less and showing exactly where it fails. They can also add a second storm pour of 6 cups in 20 seconds and report at what pour size their spillway stops working, which is how dam owners talk about design storms.
ELL supports
Provide a labeled cross-section drawing of a pond, a dam, a spillway, and a ball field, and keep it on the table through all four sessions. Pre-teach crest, groove, channel, lining, and surge with gestures and a finger traced along the drawing. Let the session 4 talk be given from a labeled poster with short phrases, and allow a team member to narrate while another points.
Extensions
Show students an aerial photograph of a real earth dam and ask them to find the spillway before anyone names it, then discuss why the spillway is usually at one end rather than in the middle. Invite a public works employee or a county engineer to describe what a dam inspection looks for after a heavy storm, and have students compare that list with the failure points their own trays produced.