TOLL GATE CREEK FLOOD WARNING PLAN TOLL GATE CREEK FLOOD WARNING PLAN TABLE OF CONTENTS I. INTRODUCTION ........................................................................................................................................... I-1 II. THE DRAINAGE BASIN............................................................................................................................. II-1 DRAINAGE BASIN DESCRIPTION ............................................................................................................................. II-1 EXISTING FLOOD CONTROL FACILITIES ................................................................................................................... II-5 FLOOD HISTORY .................................................................................................................................................... II-6 FLOOD HYDROLOGY .............................................................................................................................................. II-7 FLOODING EXTENT (100-YEAR FLOODPLAIN) ..................................................................................................... II-24 III. DECISION AIDS ..................................................................................................................................... III-1 GENERAL ............................................................................................................................................................. III-1 THE DECISION MAKING PROCESS ........................................................................................................................ III-3 PROBLEM AREAS & RUNOFF RESPONSE TIMING .................................................................................................. III-7 IV. REQUIRED ELEMENTS OF THE WARNING PLAN ...................................................................... IV-1 DETECTION AND EVALUATION OF THE FLOOD THREAT ....................................................................................... IV-1 DISSEMINATION OF WARNINGS, WATCHES AND ADVISORIES TO THE PUBLIC ...................................................... IV-3 RESPONSE OF THE PUBLIC TO THE WARNING ....................................................................................................... IV-5 V. COMMUNICATIONS .................................................................................................................................. V-1 VI. METEOROLOGICAL SUPPORT ........................................................................................................ VI-1 VII. FLOOD THREAT RECOGNITION AND WARNING PROCESS ................................................. VII-1 DETECTION AND EVALUATION OF THE FLOOD THREAT ...................................................................................... VII-1 DISSEMINATION OF THE WARNING ...................................................................................................................... VII-1 STEP-BY-STEP PROCEDURE ................................................................................................................................ VII-2 VIII. PROCEDURES AND GENERAL RESPONSIBILITIES ................................................................ VIII-1 NATIONAL WEATHER SERVICE AND PRIVATE METEOROLOGICAL SERVICE ...................................................... VIII-1 CITY OF AURORA .............................................................................................................................................. VIII-3 MULTI-AGENCY COORDINATING SYSTEM (MACS) .......................................................................................... VIII-9 FLOOD MODES ................................................................................................................................................ VIII-10 IX. PUBLIC DISSEMINATION .................................................................................................................. IX-1 X. MEDIA CONTACTS .................................................................................................................................... X-1 XI. ANNUAL REVISIONS AND PRACTICES .......................................................................................... XI-1 Toll Gate Creek Flood Warning Plan.doc ii (April 2009) TOLL GATE CREEK FLOOD WARNING PLAN LIST OF FIGURES FIGURE II-1 TOLL GATE CREEK WATERSHED ........................................................................................................ II-4 FIGURE II-2 EAST TOLL GATE CREEK PEAK DISCHARGE (EXISTING CONDITIONS) ................................................ II-8 FIGURE II-3 WEST TOLL GATE CREEK PEAK DISCHARGE (EXISTING CONDITIONS) ............................................... II-9 FIGURE II-4 EAST TOLL GATE CREEK PEAK DISCHARGE (FUTURE CONDITIONS)................................................. II-10 FIGURE II-5 WEST TOLL GATE CREEK PEAK DISCHARGE (FUTURE CONDITIONS) ............................................... II-11 FIGURE II-6 TOLL GATE CREEK WATERSHED – MODELED PEAK FLOWS (CFS) .................................................... II-12 FIGURE II-7 LOWER TOLL GATE CREEK HYDROGRAPHS (EXISTING AND FUTURE CONDITIONS) .......................... II-13 FIGURE II-8 LOWER TOLL GATE CREEK HYDROGRAPHS (CONT.) ........................................................................ II-14 FIGURE II-9 WEST TOLL GATE CREEK HYDROGRAPHS (EXISTING AND FUTURE CONDITIONS) ............................ II-15 FIGURE II-10 WEST TOLL GATE CREEK HYDROGRAPHS (CONT.) ...................................................................... II-16 FIGURE II-11 WEST TOLL GATE CREEK HYDROGRAPHS (CONT.) ...................................................................... II-17 FIGURE II-12 WEST TOLL GATE CREEK HYDROGRAPHS (CONT.) ...................................................................... II-18 FIGURE II-13 EAST TOLL GATE CREEK HYDROGRAPHS (EXISTING AND FUTURE CONDITIONS) ........................ II-19 FIGURE II-14 EAST TOLL GATE CREEK HYDROGRAPHS (CONT.) ....................................................................... II-20 FIGURE II-15 EAST TOLL GATE CREEK HYDROGRAPHS (CONT.) ....................................................................... II-21 FIGURE II-16 EAST TOLL GATE CREEK HYDROGRAPHS (CONT.) ....................................................................... II-22 FIGURE II-17 GRANBY DRAINAGEWAY HYDROGRAPHS (EXISTING AND FUTURE CONDITIONS) ........................ II-23 FIGURE II-18 TOLL GATE AT 6TH AVENUE ......................................................................................................... II-25 FIGURE II-19 WEST TOLL GATE AT MEXICO AVENUE ....................................................................................... II-26 FIGURE II-20 WEST TOLL GATE AT CONFLUENCE POND ................................................................................... II-27 FIGURE II-21 NO NAME TRIBUTARY AT QUINCY AVENUE ................................................................................ II-28 FIGURE II-22 SABLE DITCH AT 18TH AVENUE ................................................................................................... II-29 FIGURE II-23 GRANBY DITCH AT 6TH AVENUE ................................................................................................. II-30 FIGURE II-24 EAST TOLL GATE AT BUCKLEY ROAD .......................................................................................... II-31 FIGURE III-1 ALERT FLOOD DETECTION NETWORK ........................................................................................ III-4 FIGURE III-2 HYDROLOGIC FORECAST POINT GUIDANCE ................................................................................. III-6 FIGURE III-3 APPROXIMATE LOCATION OF FLOOD HAZARD AREAS ................................................................. III-8 FIGURE III-4 TYPICAL ALERT STREAM GAGE GRAPHICS .............................................................................. III-17 FIGURE III-5 STORM DRAINAGE OPERATIONS RESPONSE AREAS (AUGUST 1992) .......................................... III-18 FIGURE III-6 STORM DRAINAGE OPERATIONS PLAN (AUGUST 1992) ............................................................. III-19 FIGURE V-1 INTERNAL COMMUNICATIONS FLOW CHART...................................................................................... V-3 FIGURE VIII-1 EXCERPT: AURORA – EOP - FLASH FLOOD ANNEX (AUGUST 1992) ......................................... VIII-4 Toll Gate Creek Flood Warning Plan.doc iii (April 2009) LIST OF TABLES TABLE II-1 DESIGN RAINFALL (TOTAL DEPTHS IN INCHES) .................................................................................... II-3 TABLE II-2 QUINCY RESERVOIR FLOOD DETENTION RATING CURVE ................................................................... II-5 TABLE II-3 HISTORIC FLOODING/HIGH WATER MEASUREMENTS ......................................................................... II-7 TABLE III-1 TOLL GATE CREEK ALERT FLOOD DETECTION NETWORK .............................................................. III-5 TABLE III-2 URBAN FLASH FLOOD GUIDANCE ..................................................................................................... III-5 TABLE III-3 CONVECTIVE STORM CHARACTERISTICS (ALL DEPTHS IN INCHES) ................................................... III-5 TABLE III-4 HYDROLOGIC FORECAST POINT LOCATION DESCRIPTIONS ............................................................... III-7