Last Modified: Last Modified: 2026-06-02 09:10:34.409

Initial Workshop Files

Overview

The astute HEC-SSP user may wonder "How do the results of a peaks over threshold analysis differ from Bulletin 17C/annual maximum series procedures?" The answer varies by site. However, this tutorial will illustrate the difference between a peaks over threshold analysis and a Bulletin 17C analysis for one site.

This workshop has four tasks:

Site Information

Arroyo Seco is a famous stream.  In its headwaters it is very steep and erosion-prone, and can produce extremely hazardous flash floods.  The drainage area at the Pasadena gage is about 16 mi².  Annual maximum discharges range from 12 cfs to the 1938 flood of record at 8,620 cfs.  In some years there are no remarkable flows, and in some years there are multiple hazardous floods.  Below are two maps of the watershed.  Note how hilly the terrain is.