FFOOUUNNTTAAIINN HHIILLLLSS FFLLOOOODD RREESSPPOONNSSEE PPLLAANN Photo source: www.myfountainhills.com TTEECCHHNNIICCAALL MMEEMMOORRAANNDDUUMM Prepared For: Flood Control District of Maricopa County 2801 West Durango Street Phoenix, AZ 85009 (602) 506-1501 JE Fuller/ Hydrology & Geomorphology, Inc. 6101 S. Rural Road, Suite 110 Tempe, AZ 85283 (480) 752-2124 April 2002 NOTE: THE USER SHOULD READ THE ENTIRE FLOOD RESPONSE PLAN CAREFULLY AND SHOULD BE AWARE OF ALL ELEMENTS OF THIS PLAN, INCLUDING STRENGTHS AND LIMITATIONS, AND INDIVIDUAL RESPONSIBILITIES. THE FLOOD WARNING/ RESPONSE PLAN PRESENTED HEREIN, AND IN THE DISPATCHER ATLAS AND THE EMERGENCY ACCESS MAP, IS USEFUL AS ONE STEP IN DEVELOPING A FLOOD WARNING SYSTEM FOR THE RESIDENTS WITHIN THE FOUNTAIN HILLS WARNING AREA. HOWEVER, THE POSSIBILITY OF INADVERTENT ERROR IN DESIGN OR FAILURE OF EQUIPMENT FUNCTION EXISTS AND MAY PREVENT THE SYSTEM FROM OPERATING PERFECTLY AT ALL TIMES. THEREFORE, NOTHING CONTAINED HEREIN MAY BE CONSTRUED AS A GUARANTEE OF THE SYSTEM OR ITS OPERATION, OR CREATE ANY LIABILITY ON THE PART OF ANY PARTY OR ITS DIRECTORS, OFFICERS, EMPLOYEES OR AGENTS FOR ANY DAMAGE THAT MAY BE ALLEGED TO RESULT FROM THE OPERATION, OR FAILURE TO OPERATE, OF THE SYSTEM OR ANY OF ITS COMPONENT PARTS. THIS CONSTITUTES NOTICE TO ANY AND ALL PERSONS OR PARTIES THAT THE NATIONAL WEATHER SERVICE, FLOOD CONTROL DISTRICT OF MARICOPA COUNTY, MARICOPA COUNTY DEPARTMENT OF EMERGENCY MANAGEMENT, MARICOPA COUNTY SHERIFF’S OFFICE, FOUNTAIN HILLS MARSHALS DEPARTMENT, RURAL METRO FIRE DEPARTMENT, FOUNTAIN HILLS PUBLIC WORKS DEPARTMENT, AND JE FULLER/ HYDROLOGY & GEOMORPHOLOGY, INC. OR ANY OFFICER, AGENT OR EMPLOYEE THEREOF, SHALL NOT BE LIABLE FOR ANY DEATHS, INJURIES, OR DAMAGES OF WHAT EVER KIND THAT MAY RESULT FROM RELIANCE ON THE TERMS AND CONDITIONS OF THIS SYSTEM. i FOUNTAIN HILLS FLOOD RESPONSE PLAN TECHNICAL MEMORANDUM TABLE OF CONTENTS PREFACE................................................................................................................................... viii SECTION 1: INTRODUCTION ..................................................................................................1 1.1 Purpose.............................................................................................................................1 1.2 Project Description...........................................................................................................1 1.3 Project Location...............................................................................................................2 1.4 Study Area Description....................................................................................................4 1.4.1 Geology....................................................................................................................4 1.4.2 Hydrology ................................................................................................................7 1.4.3 Flood History ...........................................................................................................8 SECTION 2: FLOOD VULNERABILITY ...............................................................................10 2.1 Flood Alert Levels .........................................................................................................10 2.2 Flood Vulnerability Assessment....................................................................................12 2.2.1 General...................................................................................................................12 2.2.2 Roadway Crossing Evaluation...............................................................................12 2.2.3 Flood Vulnerable Structures ..................................................................................16 2.2.4 Spillway Inundation Evaluation.............................................................................20 2.2.5 Dam Break Evaluation...........................................................................................21 2.3 Lead Time Estimation....................................................................................................24 2.3.1 Hydrologic Lead Time...........................................................................................25 2.3.2 Decision/Action Time............................................................................................28 2.3.3 Effective Lead Time ..............................................................................................29 SECTION 3: FLOOD DETECTION.........................................................................................33 3.1 Flood Prediction Capability ...........................................................................................33 3.1.1 District Meteorological Services Program.............................................................33 3.1.2 National Weather Service Products .......................................................................35 3.2 Flood Detection Network.....................................................................................................36 3.3 Flood Detection Criteria ................................................................................................39 3.3.1 Green Alert.............................................................................................................39 3.3.2 Red Alert................................................................................................................54 3.3.3 Blue Alert...............................................................................................................54 3.3.4 Purple Alert............................................................................................................61 3.4 Flood Detection Network Enhancements ......................................................................63 3.5 Summary........................................................................................................................64 ii SECTION 4: INFORMATION DISSEMINATION.................................................................65 4.1 Dissemination of NWS and FCDMC Messages............................................................65 4.2 Dissemination of TOFH Flood Alert Messages.............................................................67 4.2.1 Agency Dissemination...........................................................................................67 4.2.2 Public Dissemination .............................................................................................72 4.3 Communications Flowchart...........................................................................................73 SECTION 5: FLOOD WARNING MESSAGE SUITE ...........................................................75 SECTION 6: ACTION PLANS ..................................................................................................78 6.1 Agency Action Plans......................................................................................................78 6.2 Evacuation Procedures...................................................................................................81 6.3 Post-Flood Actions.........................................................................................................82 SECTION 7: IMPLEMENTATION..........................................................................................83 7.1 Training..........................................................................................................................83 7.2 Flood Exercises..............................................................................................................84 7.3 FRP Updates ..................................................................................................................85 7.4 FRP Follow-Up..............................................................................................................86 SECTION 8: LIMITATIONS.....................................................................................................89 SECTION 9: CITED REFERENCES......................................................................................900 iii LIST OF TABLES 2-1 Data Sources for Flood Vulnerability Assessment ............................................................13 2-2 Flood Alert Priority Levels ................................................................................................16 2-3 Summary of Structures Impacted by Red Alert.................................................................18 2-4 Data Sources for the Spillway Inundation Evaluation.......................................................20 2-5 Data Sources for the Dam Break Evaluation .....................................................................22 2-6 Data Sources for Hydrologic Lead Time Estimates ..........................................................26 2-7 System Average Effective Lead Time ...............................................................................31 3-1 ALERT Stations in the Fountain Hills Area......................................................................38 3-2 Temporal Distributions and Most Intense Portions ...........................................................43 3-3 Percentage of Total Storm Rainfall During Maximum Rainfall Intensity for Various Durations............................................................................................................................45 3-4 Roadway Crossings and Rainfall Depths That Create