GLG 110 Natural Disasters Name: __________________________ Investigation 18 Flooding
Instructions: Use the links and figures provided to answer the questions. Part 1: Streamflow 1.
Recall that the discharge (Q) of a stream is calculated by the cross-section area of the stream multiplied by the velocity of the water: ࠵? = ࠵? × ࠵?
Note that since the units of area (in feet) are ft
2
and the units of velocity are ft/s, the units of discharge are ft
3
/s (cubic feet per second). Stream channels usually aren’t neat boxes, so we calculate cross-section area by adding up many small rectangles instead of one big one. Calculate the discharge of the stream in the figure below. 23.3 X 2= 46.6 46.6 X .5 = 23.3 ft
3
/s 2.
The average
depth of the stream in the figure above is 2.59 ft, and the total width is 18 ft. After a rainstorm, assume that the discharge of this stream increases to 35 ft
3
/s at a velocity of 0.7 ft/s. a.
Calculate the new average depth of the stream after the rainstorm. Average of 2.78 ft b.
The stream will flood over its banks if the average depth is greater than 3 ft. Does the stream flood after this rainstorm? No because 2.78 is less than 3
