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Create Your Own Green Infrastructure!

Ever wondered what happens to rainwater after it flows into those holes in the side of the street, called storm drains? In Los Angeles, stormwater that enters storm drains flows through the storm drain system into the Los Angeles River, which eventually outlets into the ocean. In urban and suburban neighborhoods, stormwater that eventually goes into the ocean picks up lots of pollutants like trash, pet waste, and oil and grease as it travels through our neighborhoods over hard surfaces like streets and sidewalks. This is a big problem for fish, birds, and other animals and plants that live in our rivers, streams, and oceans. Stormwater can also cause flooding problems, and it’s no fun to wade through dirty water on your way to school or work!

Swale built as part of the Elmer Avenue Neighborhood Retrofit Demonstration Project.

Enter green infrastructure. Green infrastructure is a nature-based approach to stormwater management that uses landscape design to mimic the slow, spread, and sink functions of a natural watershed. Green infrastructure improves water quality and reduces flooding by capturing and filtering stormwater runoff, rather than allowing it to flow off hard surfaces and eventually into other water bodies. Many kinds of green infrastructure, such as the swale pictured above, use layers of different materials such as rocks, soil, and filter fabric to create a natural water filter that removes pollutants from dirty stormwater as it percolates into the ground. For this week’s #SummerScienceFriday, we show you how to create a natural filter like the ones used in green infrastructure at home!

Visit to learn more about green infrastructure and how it helps keep our neighborhoods, rivers and oceans clean, reduces flooding, and increases green space and local groundwater supply! #RedesignLA


Create Your Own Green Infrastructure activity (adapted from PBS Kids)

Materials needed:

  • Funnel or a 2-liter soda bottle cut in half (by an adult)

  • Napkins or paper towels

  • Gravel, sand, and cotton balls for your filter

  • Pitcher filled with 1 quart of tap water

  • Cooking oil, food coloring, coarse coffee grounds, garlic powder, and tiny pieces of Styrofoam or a cut up plastic straw to add to water

  • Clear plastic or glass cups


  1. Create your dirty stormwater by mixing the cooking oil, food coloring, coarse coffee grounds, garlic powder, and pieces of Styrofoam or a cut up plastic straw to the tap water in your pitcher.

  2. Put the funnel, if using, over a cup or the top half of the soda bottle upside-down (like a funnel) inside the bottom half. The top half will be where you build your filter; the bottom half will hold the filtered water.

  3. Layer the filter materials inside the funnel. Think about what each material might remove from the dirty water and in what order you should layer the materials. For an added challenge, use only two of the materials to build your filter.

  4. Pour the dirty water through the filter. Pour the unfiltered water into another cup and compare it to the filtered water. What “pollutants” were filtered out, and what “pollutants” are still in the filtered water?

  5. Take the filter apart and look at the different layers. Can you tell what each material removed from the water?

  6. Wipe the funnel clean and try again. Try putting materials in different layers or using different amounts of materials to see which combination is the most effective.

The idea for this blog post comes from CWH Staffer Christina Vallejo.

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