Build a Buffer!
Contact: Melissa Brandt
York County Soil & Water Conservation District
melissabrandt@yorkswcd.org
developed by Sarah Plummer, CCSWCD
Objective: Students will learn how vegetation can prevent or lessen runoff and pollution.
Grade level: Upper elementary, middle school
Time: 1 hour
Materials (for a class divided into 5 groups):
5 dish mats (used underneath dish drainers)
5 soap dishes
Pieces of green netted shelf liners – not enough to cover entire dish mat
Pieces of black/gray foam “paper” (available in arts & craft stores)
5 pairs of scissors
13 sponges, cut lengthwise in half (each group receives 5 halves)
1 spray bottle filled with water
1 “trough”/long container for collecting water from models
Pollutants – food coloring, jimmies, soil, torn paper
Polluters – toys: cars, tractors, dogs, people, cows, construction equipment, etc.
Paper towels & rags
Bins & bags to collect used, wet, dirty materials
Marble (option, if time)
Felt or shelf liner (optional, if time)
Sphagnum moss (optional, if time)
Vocabulary:
Shrub, buffer, vegetation, runoff, impervious surface, pervious surface.
Activity:
Divide students equally into 5 groups. Ask them if they know what a landscape is. Tell them
they are going to work cooperatively in groups to design a landscape that is next to a
river/lake/ocean (use your local waterbody name if desired).
Take out each of the following materials one at a time and explain they will be part of the
landscape and will represent real features. Ask students if they can guess what each material
represents.
Dish mat – (students will probably not guess this one!) bottom of landscape. Anything they do
not cover is bare, exposed soil. Make sure to mention that the lower end of the mat (where
water drains) is the shorefront.
Shelf liner – grass.
Soap dish – house, garage, pool, hot tub, boat house; use your imagination!
Sponges – vegetation – large shrubs (a.k.a bushes) and trees.
Foam “paper” – pavement, asphalt.
Explain that each group will get the same amount of all materials and cannot have any more,
with the exception of the foam (this will ensure equality in landscape designs, meaning students
can design a landscape that prevents pollution with the same amounts of materials as one that
allows more pollution to occur). They can use as much foam as they would like.
Materials may be cut (sponges, shelf liner, foam), but students should be mindful of 2 things: 1)
Try to cut in sizes and shapes that other students can use later, since we would like to reuse
these materials, and 2) do not cut pieces too small as the landscapes will be held up at an angle
later and if materials are cut too small, they’ll fall off (ex – do not cut sponges any smaller than
~ 1 inch).
After these directions, hand out a pair of scissors and all above articles except for foam,
explaining they can come and get as much foam as they would like.
Encourage students to collaborate with each other as they start construction! Note: Ask
students not to put sponges on top of shelf liner, especially at waters’ edge. Water will not
absorb as well into the sponges if they are on top of the shelf liner. Sometimes this cannot be
prevented, however.
Once the designs are complete, tell the students that a pollution demonstration will be enacted
on each landscape. Chose a model and have one person from the group tell the class about their
design. Spray water on the landscape, while walking it around to the groups. Ask students to
observe how water is behaving on the different surfaces. Is it doing the same thing on each
surface? Water on the pavement (foam) and houses (soap dishes) will bead and run off, while
water on the grass and vegetation will soak in. Explain the concept of runoff and of impervious
versus pervious surfaces. Ask students which areas have more impervious surfaces – cities or
rural areas? Use local town/city names or areas within their towns if possible.
Bring the next four models to the front of the class and have one person from the group explain
their design to the rest of the class. Next, create a pollution scenario using the pollutants (food
coloring, etc.) and the polluters (toys). For example, a car might drive to the house and leak
some oil (food coloring). Then it “rains” – tilt the model over the trough and “rain” while
students watch the pollution and runoff move. It will race down impervious surfaces, infiltrate
grass (shelf liner) slowly, then move quickly, and get absorbed by the larger vegetation
(sponges). Other scenarios: dog pooping, tractor/lawn mower leaking oil, person spreading
fertilizers/pesticides, cow pooping, person littering, soil being disturbed by construction
equipment, etc. (Note: You can use the jimmies, paper, and other soil pollution, but they don’t
move as well as the food coloring and soil when it “rains.”).
On the last model, you can rearrange the materials so vegetation, pavement, and grass all abut
the shoreline. Add your pollutant and spray, comparing how differently the surfaces absorb
the pollution. Picking up the sponges is very striking – you can see how vegetation absorbs or
stops pollution! This might be a good opportunity to discuss natural resource/shoreland
zoning laws which limit shoreline development and ensure proper erosion and sediment
control barriers.
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Demonstrate how larger vegetation absorbs and slows runoff and pollutants effectively. Tell
students you are a piece of trash (ex – cigarette butt) on an impervious surface, being pushed by
runoff. One side of the room is the top of the slope, the other is a waterbody. Run from one
side of the room to the next, explaining there’s nothing to stop you as runoff pushes you down
into the water. Next, you are the same piece of trash going over grass. It is a little bumpy, but
you still make it to the other side/water. Place a bag/box in your pathway, explaining that is a
shrub or tree. Bump along as if on grass, then crash into the bag/box. Explain that larger
vegetation both stops some types of pollution on its journey, and then it also has the capacity to
absorb it through larger roots than grass. Talk about short grass versus long grass versus larger
shrubs and trees.
Ask students to compare the models. Which ones allowed less runoff/pollution into the
waterbody? Discuss the ability of water to pick debris up when it’s traveling downhill. Where
does the water go once it’s stopped by the vegetation? What happens to the things it may have
picked up? Discuss groundwater and its cleansing effect. Discuss different best management
practices (ex – winding pathways, waterbars, etc.) used to prevent or lessen the impacts of
runoff.
If time, as an assessment activity - allow students to reconstruct their models. Have students
discuss their changes and why they made them. (If there’s more time, add pollutants again to
see if the new design helps prevent or lessen pollution.) If there is not time to do this, ask
students how they would rearrange them to make them better at keeping pollution out of the
water. Or, have students draw before and after landscape scenarios or a water-friendly
landscape design and explain their placement of the elements.
Clean up the models. Be careful of food coloring (it stains clothing).
If time – do this demonstration: use a marble to demonstrate how water moves. Roll it on a
table (pavement/impervious surface), on green drawer mat or felt (grass), and on sphagnum
moss (larger vegetation, woods, wetlands, etc.). Discuss the different types of vegetation and
how each slows water/diffuses pollutants at different rates.
Assessment (see above as part of activity):
Have students:
1. Explain the value of vegetation and buffers in terms of keeping water clean and in terms of
reducing runoff.
2. Construct different landscape designs in class, or draw their landscapes before and after to
demonstrate proper waterfront design.
3. Explain what happens to runoff and sediment once stopped or slowed by vegetation.
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