Lawn Flooding: Fresh vs. Salt Water Damage
People often pay a high price to purchase land and build a house along the coast, or along a scenic river or stream. The view is always magnificent; the fresh air and walking along the shore are especially healthy. However, not only is the initial cost of real estate expensive, but so is property upkeep. For coastal homes, the salt air and strong winds act as sand blasters to pit the metal on door knobs, window casings, and house paint. Coastal storms are an ever-present threat, too. Another risk for home owners living along rivers or oceans is flooding. Even a small flood can damage the beautiful and expensive lawns around a home.
Is more damage done to a lawn by fresh water river flooding or coastal salt water flooding?
Hypothesize that more damage to lawns is caused by coastal salt water flooding than by the flooding of a fresh water stream or river.
- Two large dishpans
- Several pieces of 1×2 lumber
- Small nails
- Use of a hammer and hand saw
- Several feet of cheesecloth
- Instant synthetic sea salt mix (available inexpensively from school science supply catalogs)
- Grass seed
- Potting soil
- Staple gun
- Kitchen measuring cup
- Four empty plastic gallon milk or water jugs
- A warm, lighted area indoors, but not in direct sunlight
- Several weeks of time, because we are dealing with germination and growth
Grass seed will germinate and grow in two wooden frames of potting soil. Both "miniature lawns" will be kept next to each other to maintain the same environment, each receiving an equal amount of light and being kept at the same temperature.
The variable in this project is the exposure of one lawn to severe salt water flooding, and the other to fresh water flooding.
Locate two large rectangular dishpans, used for washing dishes.
With several pieces of 1×2 wood and small nails (or screws), construct two rectangular frames that fit inside the dishpans. Cut a rectangular piece of cheesecloth to cover a frame. Staple the cheesecloth to the wooden frame, keeping it pulled tight. Repeat for the other frame. Now, turn the frames upside down and fill them with potting soil. The cheesecloth holds the potting soil in the frames, but it allows excess water to pass through.
Place the two dishpans in a warm, well-lit area, but not in direct sunlight. Across the top of each dishpan, lay two pieces of wood, and set a wooden frame over each one. The pieces of wood will support the frames over the dishpans. Pour some grass seed in a kitchen measuring cup, and then spread the seeds out on the soil of one of the frames. Pour an equal amount of seed into the cup, and spread over the soil in the second frame. Lightly cover the seeds with soil and moisten the soil in the frames.
Make observations daily and keep the soil moist (but not soaked), watching for germination. Equal amounts of water should be given to each lawn frame. Allow the grass to grow until the blades are around one to two inches tall. When that happens, continue to the next step.
Fill four 1-gallon plastic milk or water jugs with tap water. To two of the jugs, add a synthetic sea salt mix, as per the instructions on the package. These mixes are available at science shops and through science catalogs from your school science teacher. They are inexpensive. The mix contains all the essential major and minor elements to create a solution that closely matches ocean water.
Remove the two wooden supports on one flat and lower it into the dishpan. Slowly, so you don't cause erosion of the soil, pour the two gallons of salt water solution into the dishpan. Leave the water in the pan for one hour, and then pour it off. You can save the solution by using a funnel and pouring it back into the bottles. Lift the frame out of the dishpan and place the wood supports back under it, so the soil can drain.
Similarly, lower the other lawn frame into its dishpan and flood it with two gallons of fresh water. Let it sit for one hour, and then pour off the water and place the supports back under the frame.
Allow the lawn frames to dry for two days. Make observations, looking for any changes in grass (color, turgor, and so forth) Record your observations. If no differences are observed, repeat the flooding procedure on the third day. Then, again allow to dry for three days. Continue to repeat the flooding and drying process until you see an observable difference.
Write down the results of your experiment. Document all observations and data collected.
Come to a conclusion as to whether or not your hypothesis was correct.
- If a lawn is killed by salt water flooding, can the home owner simply replant grass seed on the lawn once the flooding has passed, or is the soil made unfit for growing new plants? If the soil is unfit, how can it be cleared of salt and made ready to support life again? Should a home owner turn on his lawn sprinklers after a flood to dilute and wash the salts and other materials left by the sea water?
- Is one type of seed more tolerant of salt water flooding? This would be important to know for landscapers and home owners in seashore communities.
- Does pouring salt in the cracks in a sidewalk or driveway kill any grass or weeds that grow there? If so, this would be a safe way to kill unwanted weeds, because salt is not a hazard to people or pets.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.