Is there a way to find out the classification (20 years,100years,100year....?)of the storm event produced by Subtropical Storm Tammy when it flooded the Housatonic river in the Berkshire of Massachusetts.
Find a USGS stream gage located on the Houstatonic and run a frequency analysis. Compare the result to the peak discharge that occurred October 2005. I like to use USACE HEC-SSP for such things. It's fast and simple to run.