Why streams rise faster in a paved town
1 min 34 s. The words are spoken and shown in the picture; the player can also show them as subtitles.
For the Earth and Space Sciences Regents. Topic: Human activity and Earth systems, with the past questions on it.
What Dr. Mars says (the words of the video)
Why do streams rise faster in a paved town?
Rain can soak into the ground, or flow over its surface.
Dr. Mars pours one cup of water on each kind of ground.
On grass, the water soaks into the soil.
Soil has open spaces between its particles.
Water soaking into the ground is called infiltration.
On the parking lot, the water cannot soak in.
It flows over the pavement to the storm drain.
Water flowing over the surface is called runoff.
A pipe carries the runoff straight to the stream.
In a storm, much of the rain on grass soaks in.
Most of the rain on pavement runs off.
Runoff reaches the stream quickly, through the pipe.
So paving the ground makes streams rise higher and faster.
Check yourself! The grass is paved too. In the same storm, how high will the stream rise? A, below the dashed line. B, up to the dashed line. C, above the dashed line.
Remember where the water went on the pavement.
Answer: C! Less rain soaks in, so more runs off.
Dr. Mars's cup of water ran straight to the drain on the pavement.
Dr. Mars. Free practice for the New York Earth and Space Sciences Regents.