goegraphy homework quiz
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FLOOD ANALYSIS
The following assignment will test your skill at graph construction, and knowledge in flood analysis. Go to “Hand-outs” and download you linear graph and one of the 4-cycle semi- log graphs (your choice of style). Construct graphs and answer the questions. Submit your questions before the due date.
Part (I): Constructing and using a rating curve.
Use the Black River data in Table 1 to construct a rating curve on a linear graph. Then answer the questions below the table.
Table 1. Stage and discharge data for the Black River.
Stage (meters) Discharge (m3/s)
0.524 28.9
0.592 40.7
0.762 76.4
1.058 138.7
1.225 186.8
1.298 217.9
1.548 267.4
1.605 282.0
1.710 302.8
1.823 370.7
2.042 427.3
2.081 455.6
2.377 537.7
2.667 582.0
2.720 651.5
2.807 707.5
3.018 772.6
Answer the following questions in regard to your carefully constructed rating curve. Questions 1 through 3 are worth 2 points each.
1) (2pts) The current stage of the river is 2.50 meters. What is the current discharge?
a) 400 m3/s b) 580 m3/s c) 800 m3/s d) 480 m3/s
2) (2pts) When discharge is 700 m3/s, what is the river’s stage?
a) 2.75 m b) 2 m b) 3.9 m d) 3.5 m
3) (2 pts) When the river’s stage is 3.0 meters (flood stage), what will be the river’s discharge?
a) 600 m3/s b) 580 m3/s c) 780 m3/s d) 480 m3/s
Part (II): Ranking river discharge data.
In Table 2 rank the discharge data and for each rank determine the recurrence interval and the one-year probability for each stage. N = 34.
After completing Table 2, rank the river discharges from #1 to #10 and complete Table 3. Then answer the following questions. Questions 4 through 13 are worth 1 point each, 4) What is the discharge for your #1 rank?
a) 1800 ft3/s b) 1450 ft3/s c) 1170 ft3/s d) 1130 ft3/s
5) What is the probability for your #1 rank?
a) 1% b) 5.71 % c) 2.86% 5.71% 6) What is the discharge for your #5 rank?
a) 908 ft3/s b) 966 ft3/s c) 1170 ft3/s d) 1130 ft3/s 7) What is the probability for your #5 rank?
a) 14.30% b) 17.20 % c) 2.86% d) 8.60%
8) What is the discharge for your #10 rank?
a) 908 ft3/s b) 884 ft3/s c) 728 ft3/s d) 696 ft3/s 9) What is the probability for your #10 rank?
a) 28.60% b) 25.70 % c) 22.9% d) 20.00% 10) What would be the one-year percent probability for a 100-year flood for any river?
a) 1% b) 2.86 % c) 100% d) 0.1% 11) What would be the one-year percent probability for a 500-year flood for any river?
a) 1% b) 0.2 % c) 500% d) 2% 12) What would be the one-year percent probability for a 1000-year flood for any river?
a) 1% b) 0.001 % c) 0.1% d) 1000% 13) When you are told that a river has just experienced a 100-year flood, are you being provided with discharge data or probability data?
a) discharge data b) probability data
Table 2. Mean Annual Discharge for the Crase River: 1937-1970: N = 34
Year
Discharge (ft3/s)
Rank Recurrence
Interval (Years)
Percent Probability
(for one year)
1937 266 1938 419 1939 159 1940 76.7 1941 199 1942 690 1943 282 1944 696 1945 884 1946 228 1947 685 1948 728 1949 1170 1950 375 1951 1450 1952 254 1953 109 1954 71 1955 307 1956 168 1957 979 1958 426 1959 468 1960 908 1961 656 1962 535 1963 184 1964 189 1965 966 1966 97.6 1967 150 1968 337 1969 1130 1970 960
Table 3. Data for the Crase River — ranks from #1 to #10.
Rank
Year
Discharge (ft3 / s)
Recurrence Interval (years)
Percent Probability
(for one year)
1 2 3 4 5 6 7 8 9 10
PART (III): More flood predictions. Complete Table 4 below using the following equation:
€
Px = 1− 1− 1 RI
#
$ %
&
' ( x
= probability in x years
Your possibilities are located in questions 14-19. You may wish to review the PowerPoint lecture on “Floods”. RI = recurrence interval and X = years. (–––––––––– means don’t do this one). Table 4. Flood probabilities.
Recurrence Interval (RI)
Years
Probability Each Year
P in 10 years
P in 50 years
P in in 100 years
2 0.5 = 50% _____________ _____________ _____________
10 0.1 = 10% 65.1% _____________ _____________
25 0.04 = 4% 33.5% 87% 18) =
50 14) = 18.3% 63.6% 86.7%
100 0.01 = 1.0% 16) = 39.5% 19) =
1,000 0.001 = 0.1% 1% 17) = 9.5
10,000 15) = 0.1% 0.5% 1.0
14) (1-pt) Your possible choices are:
a) 0.02% b) 2% c) 0.2% d) 0.05% 15) (1-pt) Your possible choices are:
a) 0.01% b) 0.001% c) 0.05% d) 0.005%
16) (1-pt) Your possible choices are:
a) 17.5% b) 15.3% c) 11.55% d) 9.56% 17) (1-pt) Your possible choices are:
a) 30.88% b) 20.10% c) 11.12% d) 4.88% 18) (1-pt) Your possible choices are:
a) 98% b) 94% c) 90% d) 88% 19) (1-pt) Your possible choices are:
a) 73.25% b) 83.32% c) 63.4% d) 70.2%