53:171 Water Resources Engineering
Problem #8
Flood Frequency Estimates over Time

The 100-year flood is an estimate based on the available data sample.  Let's look at how this sample estimates changes over time for the Cedar River at Cedar Rapids (USGS 05464500 ) over its period of record.

The peak flow data to estimate the 100-year peak discharge in each year from 1910 to 2008.  The annual peak flow series can downloaded directly from the USGS web site. Go to USGS Surface-Water Data for the Nation page and select the Peak-Flow Data.  Download the data to a file, then read it into Excel.

1. For each year from 1910 to 2008, compute the sample mean and standard deviation.  (Note:  For 1910, that includes data only from 1903-1910.  For 2008, that includes all the data from 1903-2008.)
2. Estimate the parameters of an EV1 distribution for each year from 1910 to 2008.
3. Compute the estimated 2-year and 100-year peak discharge for each year from 1910 to 2008 based on the EV1 distribution.
4. Plot the 2-year and 100-year estimates from 1910 to 2008.  On the same graph, plot the annual maximum peak discharges from the data sample.