Lesson plan Grade 5 Engineering & Design

Alder Grove Rain Garden: A Grade 5 Runoff Sizing Lesson

A grade 5 engineering lesson where students use the roof-runoff formula to size a rain garden for Alder Grove Elementary and decide whether it can hold a storm's water.

Grade: Grade 5
Subject: Engineering & Design
Material: Lesson plan
Time: 55 min
Prep: Low prep
Materials: Printed runoff calculation handout, one per student, Chart paper and markers for team garden sketches, Calculator (optional), A shallow tray, sponge, and cup of water for the demonstration

Standards

3-5-ETS1-1 NGSS

Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.

How this material aligns: The framing step has students define the rain-garden design problem, with the success criterion of holding a storm's runoff and constraints on the garden's area and depth, meeting this standard's criteria-and-constraints requirement.

All materials for 3-5-ETS1-1 →

5-ESS3-1 NGSS

Obtain and combine information about ways individual communities use science ideas to protect the Earth's resources and environment.

How this material aligns: The overview and handout question 8 have students explain how a community uses a rain garden to soak up runoff and protect nearby streams from pollution, the human-use-of-science idea this standard describes.

All materials for 5-ESS3-1 →

5.NBT.B.7 Common Core Math

Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

How this material aligns: Handout questions 2, 3, 4, and 6 multiply roof area by rainfall and the decimal 0.623 and then subtract the results, and question 7 multiplies an area by the decimal 0.75, practicing the decimal multiplication and subtraction to hundredths this standard targets.

All materials for 5.NBT.B.7 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will define a rain-garden design problem with a clear success criterion and area constraint.
Students will use the roof-runoff formula to calculate storm runoff in gallons for two roof sizes.
Students will decide whether a rain garden of a given capacity can hold a storm's runoff and justify the choice.

Vocabulary

Rain garden: A rain garden is a shallow planted dip in the ground that catches rain running off a roof or driveway and lets it soak slowly into the soil. Its deep-rooted plants help clean the water.
Storm drain: A storm drain is the grate at the edge of a street that swallows rainwater and sends it through pipes to the nearest creek or river. That water is usually not treated, so only rain belongs down the drain.

Also: runoff, impermeable, area, capacity

Teacher overview

When rain falls on a roof or a paved yard, the water cannot soak in, so it rushes off toward storm drains and streets, carrying dirt and litter into streams. A rain garden is a low, planted dip in the ground that catches that runoff and lets it soak slowly into the soil. In this lesson, students at the fictional Alder Grove Elementary act as engineers who must size a rain garden to hold the water from a storm. They use a standard formula that turns roof area and rainfall into gallons, then decide whether their garden is big enough. A common misconception this lesson corrects is that any rain garden will do; students learn that a garden must be sized to the runoff it will actually receive, or it overflows.

Procedure

Hook (5 min): Pour a cup of water onto a tilted tray with no sponge and watch it run straight off. Then set a damp sponge in the path and pour again, showing how the sponge soaks water in. Tell students the sponge acts like a rain garden.

Frame the design problem (10 min): Explain that Alder Grove Elementary floods near its front steps in heavy rain. As a class, write the success criterion: the rain garden must hold the runoff from a storm without overflowing. Then write the constraints: the garden can only be so wide because of the sidewalk, and its soil layer can only be so deep. Note that this is a made-up scenario, so all the numbers are given on the handout.

Model the runoff formula (10 min): Introduce the roof-runoff formula: gallons of runoff = roof area in square feet x rainfall in inches x 0.623. Explain that this counts all the rain that falls on the roof, and in a real yard somewhat less reaches the garden, so the answer is the most the garden would need to hold. Model handout question 1, finding a 40-by-25-foot roof's area (40 x 25 = 1,000 square feet), then question 2, finding the runoff in a 2-inch storm (1,000 x 2 x 0.623 = 1,246 gallons). Emphasize that students must multiply by both the rainfall and 0.623, not stop at the area.

Independent and team work (20 min): Students complete handout questions 3 through 7 on their own, then meet in teams to sketch a rain-garden design on chart paper that could hold the runoff they calculated. Circulate and ask each team to point to the number on their handout that sets how big their garden must be.

Closure and exit ticket (10 min): Teams share one sketch. As an exit check, each student answers on a slip: "A 500-square-foot roof gets 1 inch of rain. Using area x inches x 0.623, how many gallons run off?" Scan for correct use of the formula. If fewer than three-quarters multiply all three numbers, reteach the formula before the next lesson.

Alder Grove Rain Garden: A Grade 5 Runoff Sizing Lesson — Grade 5 Engineering & Design

Name: ____________________________ Date: ______________

Student Handout

Alder Grove Elementary is a fictional school, and all numbers here are part of that scenario. Use gallons of runoff = roof area (square feet) x rainfall (inches) x 0.623. Show your work.

A section of the school roof is 40 feet long and 25 feet wide. Find its area in square feet.
In a storm, 2 inches of rain fall on that 1,000-square-foot roof. Find the runoff in gallons.
A smaller roof section is 30 feet long and 20 feet wide, so its area is 600 square feet. Find its runoff in the same 2-inch storm.
How many more gallons run off the big roof than the small roof in that 2-inch storm?
A rain garden can soak up 500 gallons before it overflows. In the 2-inch storm, will the small roof's runoff fit? If not, by how many gallons does it overflow?
If only 1 inch of rain falls on the big 1,000-square-foot roof, how many gallons run off?
The rain garden's soil layer is 0.75 feet deep and covers 200 square feet. Find the volume of that soil in cubic feet using area x depth.
Why does building a rain garden help the whole neighborhood during storms? Explain in one or two sentences.

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

Answer Key

Answer: 1,000 square feet. 40 x 25 = 1,000 square feet.
Answer: 1,246 gallons. 1,000 x 2 x 0.623 = 1,246 gallons.
Answer: 747.6 gallons. 600 x 2 x 0.623 = 747.6 gallons.
Answer: 498.4 gallons. 1,246 - 747.6 = 498.4 gallons more from the big roof.
Answer: No, it overflows by 247.6 gallons. The small roof's 747.6 gallons is more than the 500-gallon capacity: 747.6 - 500 = 247.6 gallons over.
Answer: 623 gallons. 1,000 x 1 x 0.623 = 623 gallons. Halving the rainfall halves the runoff.
Answer: 150 cubic feet. 200 square feet x 0.75 feet = 150 cubic feet of soil.
Answer: A rain garden soaks storm runoff into the ground instead of letting it rush to storm drains and streets. That reduces flooding near the school and keeps dirt and litter out of nearby streams.

Differentiation

Support

Provide a filled-in first row of the formula (area already calculated) for questions 2, 3, and 6, so students focus on multiplying by rainfall and 0.623. Allow a calculator and a printed formula strip reading "area x inches x 0.623 = gallons."

Extension

Ask students to find the rainfall amount, to the nearest tenth of an inch, that would make the big roof's runoff exactly fill a 1,000-gallon rain garden, working backward from the formula. Have them explain their steps.

ELL supports

Pre-teach "runoff," "area," "capacity," and "overflow" with a labeled sketch showing rain hitting a roof, running off, and collecting in a garden. Provide sentence frames for question 8: "A rain garden helps because it ___ instead of ___."

Extensions

Have students walk the schoolyard and mark where puddles form after rain, then propose the best spot for a real rain garden and explain their choice using what they learned about area and runoff. Many local stormwater programs offer classroom visits or small grants for school rain gardens, which can turn this lesson into a real project.