CE 374K Hydrology Homework Assignment on

Flood Frequency Analysis

 

The attached spreadsheet guadalupe.xls and comma separated file guadalupe.csv contain the annual maximum discharges of the Guadalupe River at Victoria for the period 1935 2002. These data are also obtainable in the LRC in /class/maidment/ce374k00. Actually these data are for water years, which begin on October 1 of the previous year and continue to September 30 of the current year. These data were obtained from the Peak Flow file at http://waterdata.usgs.gov/tx/nwis/peak for USGS Station 08176500.

The data for 1935 to 1998 are plotted below. In October 1998, an enormous flood occurred on the Guadalupe River (in the 1999 water year) for which the discharge has been estimated by the USGS as being 466,000 cfs. This is not shown on the graph below to avoid making all the other floods seem very small.

 

(1) Plot a graph of all the data, including the flows in 1999 and 2002.

 

(2) Estimate the return period of annual maximum discharges which exceed 30,000, 40,000, 50,000, and 60,000 cfs directly from the data by looking at the recurrence interval between flows exceeding those magnitudes in the data from 1935-2002.

 

(3) Take the logs to base 10 of the data and calculate their mean, standard deviation and coefficient of skewness for the data from 1935 1998, and also including the last four years of data, i.e. 1935-2002.

 

(4) Estimate the 100 year flood on the Guadalupe River using the Log normal (if coefficient of skewness ~ 0) or Log Pearson III method (if coefficient of skewness is significant). By how much does the inclusion of the October 1998 flood increase the 100 year flood estimate?

 

This assignment is due on Tuesday April 27

 

Annual Maximum Discharges of Guadalupe River at Victoria

 

 

 

Date of Occurrence

Year

Peak Discharge (cfs)

6/20/1935

1935

38500

7/3/1936

1936

179000

10/4/1936

1937

17200

4/30/1938

1938

25400

6/6/1939

1939

4940

7/3/1940

1940

55900

5/3/1941

1941

58000

7/9/1942

1942

56000

10/21/1942

1943

7710

6/1/1944

1944

12300

4/6/1945

1945

22000

9/3/1946

1946

17900

10/17/1946

1947

46000

5/28/1948

1948

6970

4/30/1949

1949

20600

10/28/1949

1950

13300

6/8/1951

1951

12300

9/16/1952

1952

28400

5/4/1953

1953

11600

10/26/1953

1954

8560

5/22/1955

1955

4950

5/18/1956

1956

1730

5/2/1957

1957

35300

2/26/1958

1958

58300

4/15/1959

1959

10100

7/1/1960

1960

23700

6/22/1961

1961

55800

11/17/1961

1962

10800

2/21/1963

1963

4100

11/11/1963

1964

5720

2/21/1965

1965

15000

12/8/1965

1966

9790

9/21/1967

1967

70000

1/25/1968

1968

44300

4/13/1969

1969

15200

5/20/1970

1970

9190

9/12/1971

1971

9740

5/16/1972

1972

58500

6/17/1973

1973

33100

10/16/1973

1974

25200

5/29/1975

1975

30200

4/19/1976

1976

14100

4/24/1977

1977

54500

9/14/1978

1978

12700

5/12/1979

1979

19300

5/19/1980

1980

11600

9/2/1981

1981

105000

5/19/1982

1982

18500

11/20/1982

1983

10900

10/21/1983

1984

3280

4/21/1985

1985

10600

11/29/1985

1986

13700

6/7/1987

1987

83400

11/28/1987

1988

3900

5/21/1989

1989

4280

9/12/1990

1990

5230

4/5/1991

1991

17000

12/25/1991

1992

61500

6/30/1993

1993

17700

5/19/1994

1994

13300

10/19/1994

1995

39600

9/22/1996

1996

9760

4/4/1997

1997

32700

10/13/1997

1998

20600

10/20/1998

1999

466000

6/12/2000

2000

6220

9/3/2001

2001

39300

7/10/2002

2002

71700