Lesson plan Grade 7 Engineering & Design

Tamarisk Flats Berm Spillway: Iterative Erosion-Control Testing

A 55-minute grade 7 lesson where teams test a model berm spillway across three redesigns, recording freeboard changes to find the most flood-resistant version.

Grade: Grade 7
Subject: Engineering & Design
Material: Lesson plan
Time: 55 min
Prep: Moderate prep
Materials: Plastic tray or bin (1 per team), Sand or modeling clay (enough to build a 4-inch berm per team), Ruler marked in inches, Measuring cup, Water, Gravel or small pebbles for lining the spillway in Trial 3, Data recording sheet

Standards

MS-ETS1-4 NGSS

Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.

How this material aligns: Students run three testing rounds of a model berm spillway, recording freeboard data after each redesign to converge on the optimal notch width for the design.

All materials for MS-ETS1-4 →

7.NS.A.3 Common Core Math

Solve real-world and mathematical problems involving the four operations with rational numbers.

How this material aligns: Students subtract starting freeboard from ending freeboard across three trials, working with negative results to track how each redesign changes the berm's margin.

All materials for 7.NS.A.3 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-16.

Objectives

Students will build and test a model berm spillway, redesigning it across three trials.
Students will calculate the change in freeboard for each trial and identify the design with the smallest loss.

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: berm, freeboard, iterative testing, overtopping

Teacher overview

A fictional rural crossing at Tamarisk Flats is protected by an earthen berm that keeps a seasonal creek off the road, and this lesson has student teams build and test a small model of that berm to see how a design choice, the width of its spillway notch, affects how close the water comes to overtopping it. Teams run the same simulated storm three times, redesigning the spillway notch between each run, and use the resulting data to identify which version protects the road best. A common misconception is that notch width is the only thing that matters. An unlined sand notch can wear away during the pour, which is why Trial 3 adds a gravel lining.

Procedure

Hook (5 min): Describe or show an image of a berm that overtopped during a storm and ask students what "freeboard" might mean, based on context. Confirm the definition: freeboard is the vertical distance between the water surface and the top of the berm, the margin of safety before overtopping.

Direct instruction (10 min): Explain the model setup: each team builds a 4-inch-tall sand or clay berm across the middle of a tray, with a narrow notch cut in the top to act as a spillway. A measured 2-cup pour of water represents one storm. Demonstrate how to measure freeboard before and after a pour, and how to calculate the change by subtracting the starting freeboard from the ending freeboard (a negative number means freeboard was lost).

Trial 1 test and calculation (10 min): Teams build their berm with a narrow spillway notch, measure the starting freeboard (4 inches for every team, since all berms start 4 inches tall and the tray starts dry), pour the 2-cup storm, measure the ending freeboard, and calculate the change.

Trial 2 redesign and calculation (10 min): Teams widen the spillway notch, empty the tray, rebuild the berm to the same 4-inch height, repeat the same 2-cup pour, and calculate the new change in freeboard, comparing it to Trial 1.

Trial 3 redesign and calculation (10 min): Teams widen and reinforce the spillway channel further (for example, lining it with a layer of gravel or pebbles to resist erosion), repeat the test, and calculate the change, then identify which of their three designs performed best based on the data.

Closure / exit ticket (10 min): Each student answers: "A fourth team's berm starts at 4 inches of freeboard and ends at 3.8 inches after the same pour. What is the change in freeboard, and is this design better or worse than a Trial 3 result of −0.5 inch?" Collect responses and check that students correctly identify the smaller loss as the better design.

Tamarisk Flats Berm Spillway: Iterative Erosion-Control Testing — Grade 7 Engineering & Design

Name: ____________________________ Date: ______________

Student Handout

Tamarisk Flats is a fictional rural crossing protected by an earthen berm. Freeboard is the vertical distance between the water surface and the top of the berm. To find the change in freeboard for a trial, subtract the starting freeboard from the ending freeboard; a negative result means freeboard was lost. Record your own team's measurements on your data sheet, then use the sample measurements below to check your method.

Trial 1, narrow notch: a team's freeboard starts at 4 inches and ends at 1 inch after the 2-cup pour. What is the change in freeboard, in inches?
Trial 2, widened notch: the same team rebuilds to a starting freeboard of 4 inches, and after the same pour the freeboard ends at 2.5 inches. What is the change in freeboard, in inches?
Trial 3, widened and reinforced spillway: the team rebuilds to a starting freeboard of 4 inches, and after the same pour the freeboard ends at 3.5 inches. What is the change in freeboard, in inches?
Using the three changes you found in questions 1 through 3, which trial's design performed best, and how do you know?
A fourth team's berm starts at 4 inches of freeboard and ends at 3.8 inches after the same pour. What is the change in freeboard, in inches, and is this design better or worse than a Trial 3 result of −0.5 inch?

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key

The trial values below are illustrative sample results for modeling the calculations; actual freeboard measurements will vary by team.

Answer: -3 inches.
Trial 1 (narrow notch): freeboard drops from 4 inches to 1 inch, so 1 − 4 = −3 inches.
Answer: -1.5 inches.
Trial 2 (widened notch): freeboard drops from 4 inches to 2.5 inches, so 2.5 − 4 = −1.5 inches.
Answer: -0.5 inch.
Trial 3 (widened and reinforced spillway): freeboard drops from 4 inches to 3.5 inches, so 3.5 − 4 = −0.5 inch.
Answer: Trial 3's widened, reinforced spillway performed best.
Its freeboard change of −0.5 inch is the smallest loss of the three trials, showing that each redesign, from −3 to −1.5 to −0.5 inch, moved the team closer to an optimal design.
Answer: -0.2 inch.
Exit ticket answer: 3.8 − 4 = −0.2 inch, which is a smaller loss than the Trial 3 example's −0.5 inch, so the fourth team's design performed better.

Differentiation

Support

Provide a printed data table with the starting freeboard (4 inches) already filled in for every trial, so students only measure and record the ending freeboard and complete the subtraction. Allow students to use a number line taped to their desk to model the subtraction of freeboard values.

Extension

Ask students to predict, using the pattern in the three changes (−3, −1.5, −0.5 inch), what a fourth redesign's change might be if the improvement pattern continued, and to explain what real-world limit would eventually stop the freeboard loss from reaching zero.

ELL supports

Pre-teach "berm," "spillway," "notch," and "freeboard" using a labeled diagram of the model tray before building begins. Provide a sentence frame for recording results: "In Trial ___, the freeboard changed by ___ inches."