CWR 4101 Lab 3

Development of an IDF Curve

PURPOSE:
  • To use the principles of probability and statistics and computer software to produce an IDF curve.  Points = 3

 

 

EQUIPMENT:

 

 

PROCEDURE:

The supplied data are compiled rainfall data (in inches) for a rainfall station. The data was compiled by determining the maximum amount of rainfall which occurred for a time period (1 hr, 2 hrs, etc...) during the year in question. We wish to use this data to develop an IDF (Intensity-Duration-Frequency) curve for the location. The IDF Curve should be for the 5, 10, 25, 50, and 100 year return periods.

  • Copy the compiled rainfall data into a spreadsheet and label it accordingly.
  • Each rainfall data value (given in inches) must be converted to an intensity (inches/hour).  These are average intensities because for a given duration, the total volume is used for that duration.
  • For each duration, fit the intensities to a distribution. To do this enter each of the annual maximum intensities for the duration in question into the DISTRIB program. After determining the best distribution, tabulate the intensities for the 5, 10, 25, 50, and 100 year return periods. The step is repeated for each duration using the annual maximum intensities.
  • Each set of intensities for a given return period must then be fit to a curve such that intensity is expressed as a function of duration. The curve fit form usually used is:

 

 

i = a/(b + D)

where:
i = rainfall intensity = inches/hour
a, b = coefficients
D = rainfall duration

However, you will need to determine if it is the best fit in this case. There will be a curve fit for each return period in question.

  • Plot Intensity vs. Duration for each of the 5, 10, 25, 50, and 100 year return periods (frequencies) on one log-log plot. The log-log plot is the IDF (Intensity-Duration-Frequency) curve.

 

 

OUTPUT:

Your report should include the following:

  • A tabulation of the raw data (Rainfall Intensity data table) (Appendix)
  • A justification of the selected distribution with at least two plots showing the distribution fit (Appendix)
  • A tabulation of the data predicted from the distribution fit (Appendix)
  • A tabulation of the data predicted from the regression analysis (Appendix)
  • A tabulation of the coefficients and the r^2 values from the regression analysis (Appendix)
  • A final plotted IDF curve using log-log scales (this should be a publishable-quality, fully-labeled plot; use the plotting software of your choice) (Results)
  • Text Problems 3.11 (10,11)

 

 

 

 

 

 

 

 

 

Maximum Rainfall in each year and for given duration storms (in)

YEAR

DURATION (hr)

1

2

4

6

10

12

24

1951

1.8

2.0

2.5

2.9

3.3

3.5

4.2

1952

1.5

2.1

2.3

2.3

2.5

2.5

3.3

1953

1.5

3.0

3.0

3.0

3.5

3.5

3.9

1954

1.6

1.8

2.3

2.5

3.1

3.1

3.1

1955

2.0

3.1

3.7

3.7

3.8

3.8

4.4

1956

0.9

1.1

1.4

1.5

1.5

1.5

1.5

1957

2.3

2.3

2.7

3.1

3.1

3.1

3.6

1958

1.1

1.3

1.7

2.2

2.9

3.1

3.4

1959

2.3

2.7

2.8

3.4

4.3

4.7

4.9

1960

1.7

1.8

2.3

3.4

4.6

4.9

6.4

1961

1.5

2.3

2.3

2.3

2.3

2.3

2.3

1962

1.3

2.2

2.3

2.6

3.1

3.7

5.2

1963

1.2

2.1

2.6

3.1

3.5

3.5

3.7

1964

1.4

1.5

1.9

2.2

3.0

3.0

3.4

1965

1.1

1.5

2.0

2.3

2.5

2.6

2.7

1966

1.2

1.3

1.3

1.9

2.1

2.3

2.3

1967

1.5

1.5

2.0

2.3

2.4

2.4

3.6

1968

1.6

2.2

3.4

4.2

4.2

4.3

4.4

1969

1.5

2.7

3.1

3.2

3.2

3.2

3.2

1970

1.1

1.4

1.5

1.5

1.5

1.5

2.3

1971

1.5

1.8

2.7

2.8

3.1

3.5

4.0

1972

1.4

1.7

1.9

2.2

2.3

2.3

2.3

1973

1.6

2.3

2.3

2.4

2.4

2.4

2.4

1974

2.6

2.8

3.0

3.0

3.0

3.0

3.1

1975

1.3

1.4

1.8

2.4

3.0

3.0

3.5

1976

2.4

2.8

3.3

3.4

3.6

3.7

4.0

1977

1.2

2.1

2.3

2.3

2.3

2.3

2.4

1978

1.4

1.8

1.9

1.9

1.9

1.9

2.3

1979

1.9

1.9

3.7

4.3

6.2

6.3

6.3

1980

2.1

2.5

2.7

2.7

3.5

3.8

3.9

1981

1.8

2.5

2.6

2.6

2.6

2.6

4.1

1982

1.4

1.9

2.3

2.7

3.1

3.4

4.1

1983

1.1

1.5

1.8

2.1

2.1

2.1

2.2

1984

1.3

3.5

3.5

3.5

3.5

3.5

3.5

1985

1.5

2.3

2.3

2.3

2.3

2.4

2.9

1986

3.1

5.5

7.9

8.4

8.4

8.7

9.5

1987

2.3

3.9

3.9

3.9

5.1

5.1

5.5

1988

1.7

5.6

5.6

5.6

5.6

5.6

8.2

1989

1.6

2.4

2.5

2.5

2.5

2.5

2.7

1990

1.6

2.2

2.2

2.5

3.1

3.1

3.9

1991

1.5

3.0

3.0

3.0

3.5

3.5

3.9

1992

1.1

1.3

1.7

2.2

2.9

3.1

3.4

1993

1.3

2.2

2.3

2.6

3.1

3.7

5.2

1994

1.3

1.4

1.8

2.4

3.0

3.0

3.5

1995

1.3

3.5

3.5

3.5

3.5

3.5

3.5

1996

2.6

2.8

3.0

3.0

3.0

3.0

3.1

1997

1.2

2.1

2.6

3.1

3.5

3.5

3.7

1998

2.0

3.1

3.7

3.7

3.8

3.8

4.4

1999

4.9

5.7

6.0

6.5

6.5

7.1

8.2

2000

1.2

2.1

2.3

2.3

2.3

2.3

2.4

2001

1.1

1.3

1.7

2.2

2.9

3.1

3.4

2002

1.1

1.2

1.4

1.5

1.8

1.8

2.1

2003

1.7

2.2

2.5

2.8

3.3

4.6

6.8