53:078 Principles of Hydrology (Spring 2004)
Problem #26
Flood Frequency Analysis for Ralston Creek at Iowa City (July 1972)
Evaluate the return period of the 17-18 July 1972 flood for
Ralston Creek at Iowa City (USGS Station Number 05455000) assuming an
extreme value type I (EV1) distribution for the annual maximum flood
series.
- Estimate exceedance probabilities using the plotting position formula
(non-parametric method).
- Estimate parameters for the extreme value type I (EV1) distribution.
- Estimate quantiles (in cfs) for return periods of 2-, 5-, 10-, 25-, 50-,
100-, 200-, and 500-years.
- Estimate the return period (years) of the July 1972 flood based on the
plotting position (non-parametric) and the fitted EV1 distribution
(parametric) approaches.
- One a single graph:
- Plot the sample data versus the EV1 reduced variate (as points)
- Plot the quantile estimates from part (c) versus the EV1 reduced variate
(as a line).
To obtain the annual annual maximum peak flow, go to the
USGS Surface-Water Data
Retrieval site. Select Peaks from the list. Next, select Site
Number under the Site Identifier list and press Submit. To locate the
Ralston Creek information, enter the USGS station number, choose the Table
of data option under the Retrieve Published peak
streamflow data for Selected Sites, then click on Submit. Either
cut-and-paste the data or use the Output format options to save the
data. Be careful not to confuse the Peak Streamflow Qualification Codes
for flow values (e.g., the 1987 flood is 151, not 1516).
Last changed on
04/07/04
by aab.