GO150 Pre-Weather Unit LAB

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Streams and Flooding

Name:  ______________________________________________ 20 points

The most common natural disaster in the U.S. is flooding.  Everywhere is a flood zone because where there is water, there can be flooding.  1st:  Click on each of the following links.  2nd:  Read and study the content.  3rd:  Answer the questions below.  4th:  Save and upload your document into the “Floods and Flooding Drop Box”.

QUESTIONS:

Part I:  Stream Discharge,

  1. A stream has a width of 20 feet and a depth of 5 feet. Its cross-sectional area is:   
  2. A stream has a width of 25 feet and a depth of 10feet. Its cross-sectional area is: 
  3. A stream has a width of 30 feet and a depth of 5 feet. Its cross-sectional area is:
  4. The velocity of the stream in question #3 is 10 feet per second. The discharge of the stream is:
  5. Engineers fix the stream (#3) so that its width and depth cannot increase. Perhaps they force the stream to flow through a concrete liner. A flood occurs and the discharge increases to 1,000 cubic feet per second. What is the velocity of the stream?
  6. What usually happens to the velocity of a stream downstream?
  7. The gradient (slope) of the stream typically ____ _____ but gravity, elimination of bed roughness and an increase in the amount of water from the entry of tributaries tends to _____ _______ the velocity.
  8. Similarly, the increase in the amount of water and the typical increase in ____ ____and ____ ______ of the stream allow the discharge to increase downstream.

Part II:  Flooding History,

  1. Predictions of frequency of flooding are based on stream gauging records.   These predictions use which values measured at that station that year.  Give the name of this value along with what the value actually represents. 

Part III:  Flood Prediction

  1. What is the Recurrence Interval for the largest event out of 99 events?
  2. What is the Recurrence Interval for the smallest event out of 99 events?
  3. What is the probability of occurrence of an event with a discharge of 5,200 cfs?
  4. True or False:  An event has a Recurrence Interval of 3. This means that there is an average interval of 3 years between events of this (or greater) magnitude.
  5. True or False:  A 100-Year flood occurs in 2022. You can be confident that there will be no flood of equal or greater magnitude until 2122.

Part IV:  Flood Prediction Case History : Simonton, Texas Has A Problem

  1.  What two natural phenomena was predicted to continue to plague the residents of Valley Lodge? 

          Part V:  How can we have two “100-Year Floods” in less than two years?

This question points out the importance of proper terminology. The term “100-year flood” is used in an attempt to simplify the definition of a flood that statistically has a ____________________chance of occurring in any given year. Therefore, each year begins with the same __________________chance that a 100-year event will occur.