FLOOD02838

• County: Douglas
• County: Arapahoe
• Community: Greenwood Village, Aurora
• Stream Name: Cherry Creek
• Basin: South Platte
• Title: Probable Maximum Precipitation Study for Cherry Creek Reservoir - Final Report
• Date: 8/1/2003
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Project

.
.
.
.
.
.
.
.
.
.
.
.
'.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

1. Introduction

The Applied Weather Associates (A W A) team has completed a site-specific
Probable Maximum Precipitation (PMP) study for the Cherry Creek drainage basin and a
technical review of the 1995 National Weather Service (NWS) titled "Site-Specific PMP
for the Cherry Creek Drainage in Colorado". The A W A team members were as follows:

Applied Weather Associates

Dr, Ed Tomlinson
Mr. Ross Williams
Mr. John Henz
Mr. Doug Trieste
Mr. Dan Dansereau

HDR Engineering
Flow Technologies
GeoClim Consulting Group

1.1 Background

The NWS completed a site-specific PMP study for the US Army Corps of
Engineers (U8ACE) in July 1995. The results from that study were used by the USACE
to compute the Probable Maximum Flood (PMF). During public hearings related to
modifications ofthe Cherry Creek dam for reservoir and dam safety issues, concern was
expressed over assumptions and procedures used in the NWS study. Subsequently, the
Colorado Water Conservation Board (CWCB) in cooperation with Greenwood Village,
Aurora, Arapahoe County and Douglas County provided funding to conduct an
independent site-specific PMP study for the Cherry Creek drainage basin, A Fact Sheet
for the Cherry Creek Reservoir is provided by the CWCB in Appendix A. The Scope of
Services is provided in Appendix B. The study was reviewed by a Technical Review
Panel (TRP) and a Project Advisory Committee (PAC). Members of the TRP are listed
below and members of the PAC are listed in Appendix C.

Mr. Lou Schreiner
Mr. Nolan Doesken
Mr. Gary Lewis

Bureau of Reclamation, Denver, Colorado
Colorado Climate Center, Fort Collins, Colorado
Parsons Engineering, Denver, Colorado

1.2 Project Overview

The project consisted of 13 tasks, The Scope of Services for these tasks is
provided in Appendix B. Some of the tasks addressed reviewing the 1995 NWS Site-
Specific Study (NWSSSS) for the Cherry Creek drainage and verifYing the NWS
procedures and calculations. Other tasks were related to conducting an independent site-
specific PMP study and comparing the A W A team approach with the NWS approach.
Two interim reports were produced - Interim Report #1 in April, 2002 and Interim Report
#2 in June, 2002, These were reviewed by the TRC and NWS. Periodic review meetings
were held with the TRP and PAC to review progress on the study.

I