Permeability Part 4 - Build a Permeability Model of a Watershed
New York’s Urban Ecosystem Lessons
This is the fourth in a series of four lessons on the permeability of surfaces in a watershed. These lessons can be done together or individually. If you plan on doing all the lessons in the permeability series, then you should consider doing them in the order suggested: Part 1, 2, 3, and then 4. This series works particularly well after the Watersheds series of lessons. In this lesson, students will create a model of the permeable and impermeable surfaces in a location that you have chosen and visited in previous lessons. They will use this model to make judgments about what they think the surfaces should be in that location. Optionally, they can also build a model of their proposed surfaces.
Materials and Resources
Suppliesaluminum trays Thick cardboard for the bases of the models Extra paper to ball or fold up and create elevation water aluminum foil (or something else non-absorbent like plastic, fleece or wool) different types of sponges -- details in Tips for Teachers Knives and scissors to cut up the materials -- or you can pre-cut the sponges into thin enough pieces for the students to cut them further just using scissors water bottle Ways to attach these materials to the base -- glue, glue gun, staple gun, two-sided tape, string and a way of punching holes in the cardboard, etc. None of these joining methods works all that cleanly, so you’ll want to either: Leave a lot of time for construction, but have another quiet activity for some students to do while others are still constructing, Interrupt construction to have the closing discussion, and then come back to it when you find some extra time, perhaps with students volunteering to complete construction outside of class time, or potentially with you completing the execution of the students’ design. A way for everyone to look at the same online Google Map at any time. Projecting works best. This is also possible if everyone has their own screen and you provide very detailed instructions about what to look at when. A good color printer/copier might also be able to produce the satellite images you need, for distribution. Items to jog students’ memories of their work so far toward this goal, such as: The satellite image of the location you have chosen The Surface Types chart Their initial predictions about which surface types could be found where on the satellite image The sponges they tested Their data from testing the sponges Photographs of their field visit Photographs they took in the field, to document the surfaces they tested Their data from testing surfaces in the field Markers in at least two colors, if you decide to build the Ideal Model
Before you get started
Tips for Teachers
At this point, you will have selected the area you want students to model, and they will have studied satellite imagery and surface types, tested different types of sponges to see how they will function in the model, and tested the permeability of real surfaces, directly, in the field. Building models is time-consuming! If at all possible, arrange an opportunity for students to present their models to decision-making adults. That can make it very much worth the time! You need at least two adults to assist with construction of each model. If you decide to build two models at once, you’ll need four adults in the room for that. Sponge Suggestions use a car-washing sponge to represent loose, very permeable soil use a dishwashing sponge to represent compacted, less-permeable soil use a green scouring sponge to represent compacted, barely-permeable soil use something that does not absorb like aluminum foil, plastic, or even certain types of fleece or wool where the water beads up and runs off, to represent an impermeable surface use a hard sponge that has totally dried up for the “bone-dry sponge”, to represent dry soil
Remind your students of all the work they have done so far toward this goal! Show them things like:
The satellite image of the location you have chosen
The Surface Types chart
Their initial predictions about which surface types could be found where on the satellite image
The sponges they tested
Their data from testing the sponges
Photographs of their field visit
Photographs they took in the field, to document the surfaces they tested
Their data from testing surfaces in the field
Ask your students what they noticed about people during their field visit.
Were there people at the site? Near the site?
What did you notice about them?
Was there other evidence that people use the site?
What do they use it for?
Could people be using the site when we’re not there and leaving no trace?
- What might they be using it for?
Lead a discussion or prepare a handout in which you ask your students:
In the the location, why might we want some surfaces to absorb rainwater? Why might we want other surfaces to cause rainwater to runoff? Where do we want each type of surface, and why?
Which types of surfaces do we see the most of in our location?
How do you think the different surfaces will impact the local:
People? -- which people, using the place for what purposes?
Ecosystem? -- does this also affect the people, in your opinion?
(It’s important to allow students to take the position that no, the ecosystem is not important to the people. Like always, those students should be asked -- ideally by other students who disagree, but also by you -- to provide the evidence and reasoning that leads them to take that position. Their opinions may change over time, and it’s important neither to force it nor to silence the dissent.)
- What are some of the pros and cons of impermeable surfaces? (e.g. Impermeable surfaces are better to play basketball on because you can’t dribble on gravel, but impermeable surfaces create a lot of runoff.)
There are two parts to the model-building activity. You can do one or the other, or you can do them in sequence, or you can divide up your class and assign one part to one group and the other part to the other group.
Model-building -- This is where you need at least two adults for each large group of students working on a single model: one adult to assign and monitor construction tasks, and the other adult to help with technical issues.
Part I: Real Model
Give students a map of the watershed you are studying, and skem to use all the information they’ve learned about this place so far to color in different permeability zones, according to the collection of materials you are providing. So for example, they could use:
Gray to color in the most impermeable (least permeable) areas, where they think the class should use tin foil in its model
Pink to color in the most permeable areas, where they think the class should use a car-washing sponge
Green to color in slightly permeable areas, where they think the class should use a scouring sponge
Help the group reach a consensus map, and post this prominently.
Guide the students in building a model to represent the consensus map.
This is where you’ll need at least two adults to support the group process.
Part II: Ideal Model
Give students a map of the watershed you are studying, and ask them to sketch in they think is an ideal distribution of permeable surfaces in one color, and impermeable surfaces in another color.
Then lead a discussion about what students consider to be ideal, and why.
If there is consensus, at this point you could:
Sketch this yourself, to represent the group’s ideal
Assign the sketch to one or two students
Ask the group to make a 3D model of the group’s ideal
If you have a group building models, you will need at least two adults, one to assign tasks and one to trouble-shoot
If there is thoughtful disagreement, at this point you could:
Sketch the competing visions yourself
Assign the sketches to students who hold those views
Split up the group further to make 3D models of their competing visions
If you now have large groups building models, you will need at least two more adults: one to assign and monitor tasks, and one to trouble-shoot technical issues
Ideally, follow up by making an opportunity for students to present their models to decision-making adults!
This is a particularly good follow-up activity to do if you find that your students have noticed and raised questions about the difference between new, used and damp, and used and bone-dry sponges -- either after the initial sponge-testing, or after the field visit.
Procedure - Dry vs Damp Sponges
Use another Observation/Inference Chart.
Hand out one sponge that is “bone dry” and one that is damp (wet all the way through and wrung out).
Observe the two sponges and describe what they look like in the “Observation” section of the Observation/Inference Chart.
Predict which sponge will hold more water and how much water each will hold.
Record predictions in the “Inferences/Predictions” section of the Observation/Inference Chart
Test the absorbency of your sponges in different conditions. Again, this is a wonderful opportunity to let students design their own tests, and compare their methodologies! If you don’t want to do that, you could provide instructions, such as:
Place sponge in tray and gently hold down for 10 seconds. Do not touch the sponge in any other way.
Take sponge out and squeeze it into the measuring cup and record results in the “Notes/Results” section of the Observation/Inference Chart.
Do this with each sponge.
Compare your predictions with your results.
Which sponge held the most water? Why do you think this was the case?
Which sponge held the least? Why do you think this was the case?
Why do you think one type of sponge holds more water than the other?
How do you think the wetness of the soil relates to the soil’s ability to hold water? In what ways do you think sponges and soil are similar? In what ways do you think sponges and soil are different?
How do the dry and damp sponges compare to the environment? Which surface types do you think are like the dry sponge? Which surface types do you think are like the damp sponge?