Storm Hydrographs


A storm hydrograph shows the change in the water level from before to after the passage of the storm water through a given location. It is a graph showing the stream discharge through time.

The same rainstorm falls on two watersheds, one urban and one rural, each drained by a separate stream. Geologists measure the change in discharge over time for both streams. This data is contained in the attached table.

8. Plot the discharge data on a sheet of graph paper or import the data using into Microsoft Excel or other spreadsheet. The X axis will be time, the Y axis discharge. If you put them on the same base, you will have two overlapping graphs. One will contain the data for Slapneck Creek; the other for Possum Trot Creek.

9. After plotting the data, indicate the time the rainstorm occurred and the time of peak discharge for each creek.

10. Determine the lag time for each stream?

11. Determine which stream is flashier?

12. Which is the rural stream and which is the urban stream?

13. In conclusion, consider how urbanization affects stream flow in terms of "flashiness," the potential for flooding, and the speed at which floodwater subsides.

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