Water Pollution Culvert Observation

Learn how much sediment enters waterways by observing a nearby culvert or stream. Sediment loading decreases a stream’s ability to support the fish and plants essential to a healthy aquaculture. Heavy sediment loads increase the erosive power of a watercourse, causing even more erosion.

Observe a Culvert or Stream

Locate an unlined culvert or small stream in your neighborhood. Unlined culverts and small streams will erode where water flows quickly, or fill in where it slows. Take photos from several angles to document the culvert’s original state.

Drive stakes along the length of your culvert from one opening to the next. Measure the culvert’s depth and width in at least three places between the two openings. Take new measurements after every rainstorm and once a week between storms. Graph any changes. Estimate the amount of soil, in cubic inches, that is removed after every rainstorm, using the data from your graphs.

Examine the area downstream from your section of culvert for evidence that the soil carried from your section is settling elsewhere. Note whether or not the settled sediment is causing any downstream flooding. Photograph areas where downstream flooding occurs. Measure the maximum depth of any standing water, and calculate the total area. Use your calculations to determine the volume of the standing water, in liters or gallons. Document how much sediment is left behind after all the standing water has been carried away, absorbed into the ground or evaporated.

Choose a second, lined culvert and make the same observations. Graph any difference between the amount of soil removed after each rainstorm. Note whether there is more or less sediment downstream of the lined culvert than the unlined one. Make charts of your observations and create a photo story to document your findings.

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