Flood Frequency Analysis


Flood Frequency Analysis using Log Pearson III Distribution


The purpose of this model is to calculate the return periods and exceedence probabilities of peak annual flow rates obtained from a time series of historic daily average flows from a streamflow measuring site in Colorado. This model uses historic records obtained from the USGS National Water Information System (see reference below) for the Williams Fork flow gage near Parshall, Colorado. The first step is to calculate the annual peak flow rates and save these for each year of record. Nex, we analyze the data set to calculate Log Pearson III distribution parameters. Using this distribution, we run a Monte Carlo simulation to develop the distribution curve that we can compare historic peak flows to. With this model, you can check the return period and exceedence probability of various peak flow rates. This model can be used for any dataset as long as you adjust the array label sets to match the number of years on record.


Making Better Decisions In An Uncertain World