CITY OF SAN ANTONIO - Texas Water Development Board

812 Pages·2001·32.71 MB·English

CITY OF SAN ANTONIO
.'d~~ll
' '( ·1_1 •
~J,j ',~ '. •. J ' • ·'
-
Regional Flood Mitigation
Plan
December 2000
PAPE-DAWSON ENGINEERS, INC.
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
TABLE OF CONTENTS
Page
I. INTRODUCTION ........................................................................................................... 1
II. PLAN PREPARATION PROCESS ............................................................................... 6
III. EVALUATION OF EXISTING HAZARDS .................................................................. 8
IV. GOALS OF THE FLOOD MITIGATION PLAN .......................................................... 9
V. EVALUATION OF THE EXISTING FLOOD PLAIN MANAGEMENT
PROGRAM ..................................................................................................................... lO
VI. EVALUATION OF POTENTIAL MITIGATION ALTERNATIVES ........................... 13
VII. ACTION PLAN .............................................................................................................. 14
VIII. FORMAL ADOPTION OF THE FLOOD MITIGATION PLAN .................................. 29
IX. PROCEDURES TO REVIEW AND REVISE THE PLAN ........................................... 34
X. APPENDICES
APPENDIX A - LIST OF FLOOD HAZARD AREAS BY WATERSHED
APPENDIX B - FLOOD HAZARD AREAS MAP
APPENDIX C - LIST OF POTENTIAL MITIGATION PROJECTS BY
WATERSHED
APPENDIX D - POTENTIAL MITIGATION PROJECTS MAP
APPENDIX E- BEXAR COUNTY FLOOD ANALYSIS REPORT (VOLUME I)
APPENDIX F - LEON CREEK WATERSHED MASTER DRAINAGE PLAN
APPENDIX G - SALADO CREEK WATERSHED STUDY AND DRAINAGE
MASTERPLAN
APPENDIX H - UPPER OLMOS CREEK WATERSHED MASTER DRAINAGE
PLAN
APPENDIX I - CITY OF SAN ANTONIO MASTER DRAINAGE PROJECTS
LIST
APPENDIX J- CITY OF SAN ANTONIO ORDINANCE NO. 86711
APPENDIX K - CITY OF SAN ANTONIO BUY BACK PROGRAM, 1998
PAPE·DAWSON ENGINEERS, INC. 4851\DO\WonNiepoi'I1DODZ10•1
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
APPENDIX L- CITY OF SAN ANTONIO LOW WATER CROSSINGS
APPENDIX M- THE EMERGENCY OPERATIONS PLAN FOR THE CITY OF
SAN ANTONIO
APPENDIX N - OCTOBER 1999 CITY OF SAN ANTONIO REGIONAL
DETENTION FACILITIES PROJECT
APPENDIX 0- CITY OF SAN ANTONIO FLOOD ASSESSMENT REPORT
OCTOBER 17-18, 1998
APPENDIX P - 1999 CITY OF SAN ANTONIO BOND ELECTION
APPENDIX Q- 1999 CITY OF SAN ANTONIO CAPITAL IMPROVEMENT
PROGRAM
APPENDIX R- 1999 CITY OF SAN ANTONIO/MPO CAPITAL IMPROVEMENT
PROGRAM
APPENDIX S- 1989 BEXAR COUNTY WATERSHED STUDY BY CH2M-HILL
APPENDIX T- 1990 SARA/BEXAR COUNTY CONTRACT AND IDENTIFIED
PROJECT LIST
APPENDIX U- 1006 BEXAR COUNTY/CITY OF SAN ANTONIO/SARA JOINT
PROJECT
APPENDIX V- 1999 BEXAR COUNTY FLOOD CONTROL PROJECTS
APPENDIX W- 1998 BEXAR COUNTY PROPERTY BUY BACK PROGRAM
APPENDIX X - 1999 TxDOT PROGRAM FYOO
APPENDIX Y- TxDOT ROAD CLOSURE LIST- OCTOBER 17-18, FLOOD
APPENDIX Z - FLOOD DAMAGE PROJECT IDENTIFICATION BY CITY OF
SAN ANTONIO TO CORPS OF ENGINEERS- OCTOBER 17-18,
1998
APPENDIX AA- FEMA FLOOD INSURANCE STUDY (FIS) FEBRUARY 16, 1996
APPENDIX BB - RESPONSE LETTERS TO SARA FROM AREA UTILITIES AND
MUNICIPALITIES REGARDING FLOOD CONTROL NEEDS
APPENDIX CC - MEDIAN RIVER FLOOD CONTROL PLAN AND GREENBELT
CORRIDOR
APPENDIX DD - RESPONSE LETTER FROM THE CITY OF GREY FOREST
PAPE-DAWSON ENGINEERS, INC. 4851\00\Word'tlleportlDD02tDat
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
-
I. INTRODUCTION
San Antonio is located in the south-central portion of Texas, approximately 150 miles from
the Gulf of Mexico and 100 miles from the geographical center of Texas. Situated in
Bexar County on the San Antonio River, the terrain to the northwest slopes upward to the
Edwards Plateau and to the southeast it slopes downward to the Gulf Coastal Plains. These
two distinct geological regions are divided by the Balcones Escarpment, a critical recharge
zone for the Edwards Aquifer. The rolling hills of the area account for the range in
elevation from 500 feet MSL (feet above mean seal level) in southern San Antonio to 1000
feet MSL just below the Balcones Escarpment to over 1600 feet MSL in the upper reaches
of the San Antonio River in Bexar County. A location map of the project area is shown in
Figure 1-1
-
The City of San Antonio has a population of over 1.1 million people. Its city limits
encompass approximately 417 square miles with an Extra Territorial Jurisdiction (ETJ) of
approximately 789 square miles covering approximately 80% of Bexar County. Within the
city's ETJ are several smaller municipalities including Alamo Heights, Terrell Hills, Olmos
Park, Castle Hills, Converse, Helotes, Hollywood Park, Leon Valley, and Shavano Park
just to name a few. Also within the city's ETJ are several military bases including Brooks
AFB, Camp Bullis, Fort Sam Houston, Kelly AFB, Lackland AFB, and Randolph AFB.
At least five major watersheds; Cibolo Creek, Leon Creek, Olmos Creek, Salado Creek,
and Medina River watersheds, and several smaller watersheds drain Bexar County from
north to south converging in the San Antonio River in southern Bexar County and northern
Wilson County. Development in these watersheds began over 200 years ago, but has been
extensive in the past 50 years or so, especially in the northern half of Bexar County. The
vast majority of the commercial and residential development outside of Loop 410 has
occurred since the late 1950's. Aerial mapping flown in the early 1960's by the Natural
Resource Conservation Service (NRCS) (formerly known as the Soil Conservation Service
PAPE-DAWSON ENGINEERS, INC. 1
CITY OF SAN ANTONIO
- REGIONAL FLOOD MITIGATION PLAN
[SCS]) Soil Survey for Bexar County, shows very little development outside of Loop 410
as compared to the present.
In 1926, the first of several flood detention dams in Bexar County, the Olmos Dam, was
completed. The Olmos Dam is located just upstream of downtown San Antonio, with
Olmos Creek upstream and the San Antonio River downstream of the dam. Since then, the
NRCS in cooperation with the San Antonio River Authority has built 13 flood detention
dams in the Salado Creek watershed. Six flood retention dams were built in the Martinez
Creek watershed and seven flood retention structures were built in the Calaveras Creek
watershed.
Since the early 1930's, several studies have been conducted on the San Antonio River,
particularly in downtown San Antonio. Many projects ensued including straightening,
widening, and deepening 31 miles of the San Antonio River and many of its tributaries.
Most recently, two massive flood control tunnels, the San Pedro Creek Tunnel (SPCT) and
the San Antonio River Tunnel (SART) were built to divert flood waters beneath downtown
San Antonio.
-
PAPE-DAWSON ENGINEERS, INC. 4851\DD\Wol'd'tlleport'tiJOD21D•1
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
NOT-TO-SCALE
-
Figure I-1
WATERSHED LOCATION MAP
\
PAPE-DAWSON ENGINEERS, INC. 3
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
In 1996, the City of San Antonio contracted with three different engineering firms to
develop complete Master Drainage Plans for three of the major watersheds in Bexar
County; Leon Creek, Salado Creek , and Olmos Creek. Each study revised and updated
the hydrological and hydraulic models for that particular watershed and sub-watersheds.
Flooding problems were identified in several areas and over $100 million in potential flood
mitigation projects were identified in these watersheds and are discussed in Sections III
and IV of this Plan.
The City of San Antonio has participated in the Federal Emergency Management Agency's
(FEMA) National Flood Insurance Program (NFIP) since 1983. The latest Flood Insurance
Study (FIS) by FEMA is dated February 16, 1996. This study incorporated all studies and
mapping revisions up to that date. FEMA is planning to update their maps to include all of
the recent watershed studies and mapping revisions approved since 1996.
Even though the City of San Antonio, Bexar County and other agencies have recently
studied some of the major watersheds, identified needed projects throughout the county,
and implemented some of the more critical flood control projects, an overall flood
mitigation plan for the study area has not been developed. The City of San Antonio is
presenting this plan to the Texas Water Development Board (TWDB) as a tool to identify
and codify all existing flood hazards and technically feasible flood mitigation activities
within its jurisdiction and to provide a comprehensive strategy for implementing these
acti viti es.
The preparation process for this flood mitigation plan is discussed in Section II of this
report. This section describes the City's efforts to attain input from the public and other
organizations and municipalities affected by the plan and the incorporation of previous
studies into this plan.
PAPE-DAWSON ENGINEERS, INC. 4 411511DtltWordtllepOI'fl.tHJ0210a1
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
An Evaluation of Existing Hazards is presented in Section III. Descriptions of existing
flood hazards as identified from several sources are given. Flood hazard areas are grouped
by watershed and listed in Appendix A. Their locations are shown on the map in
Appendix B.
The goals of this Flood Mitigation Plan are discussed in Section IV. Evaluations of the
City's existing Flood Plain Management Program and potential mitigation alternatives are
found in Sections V and VI, respectively. Potential mitigation projects are grouped by
watershed and listed in Appendix C. Their locations are shown on the map in Appendix D.
An Action Plan to implement the recommended flood mitigation activities is included in
Section VII of this report. Potential projects were assessed to determine their feasibility
and funding options.
Section VIII discusses the action taken by the City of San Antonio to present this plan to
interested residents, businesses, organizations, and communities affected by it. Feedback
from these groups was then incorporated into the plan. The final plan was then reviewed
and adopted by the City Council of San Antonio.
Finally, a formal process by which the progress of the Mitigation Plan is measured and
how changes to the Plan can be made is outlined in Section IX.
-
PAPE·DAWSON ENGINEERS, INC. 5 4851\1101Won/1Reporl\ODD:l1Da1
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
PUBLIC WORKS- STORM WATER UTILITY
Program Information
The Storm Water Utility of Public Works, which is funded by the Storm Water Fee,
consists of the following Divisions:
Storm Water Operations Division
+ Vegetation Control - Mowing I Herbicide Applications I Tree Maintenance
• River Maintenance - Channel De-silting I Lake Dredging
+ Street Cleaning -Street Sweeping I Graffiti Removal! Event Cleanups
+ Tunnel Maintenance -Operating and Maintenance of Tunnels and Dams
+ Storm Water Administration - Direction and Planning
Storm Water Engineering Division
+ Design Engineering Master Planning; Development Review; and
CIP/MPO/special projects reviews.
+ Engineering management of Regional Flood Control Facilities
+ Floodplain management
The Storm Water Utility performs various tasks associated with the City's National
Pollution Discharge Elimination System (NPDES) permit. Other divisions of Public Works
and SAWS also help with NPDES permit compliance. Storm Water Engineering, in
addition to design and review of public and private drainage facility plans leads master
planning for drainage issues. This includes implementing regional flood control facilities,
storm water detention systems and floodplain administration. Construction and
maintenance of regional flood control facilities are activities associated with the Regional
Storm Water Management Program.
Goals & Objectives
To perform the functions of planning & coordination, implementation, development, and
management of the City's infrastructure system of lakes, streams, basins, dams and storm
PAPE-DAWSON ENGINEERS, INC. 48511001Word1Reportl000210a1
CITY OF SAN ANTONIO
REGIONAL FLOOD MITIGATION PLAN
water systems in a responsive manner with a focus on quality, customer needs and the
effective protection of public investment in the City's infrastructure.
Storm Water Utility:
• Consider finance strategies and affordability of options as addressed and
recommended in the City of San Antonio Watershed Studies for improved
performance of San Antonio's storm water infrastructure.
• Review the organization of the Storm Water Utility to maximize efficiency and
customer service.
• Continue to execute tasks associated with compliance of the City's NPDES
permit and the accounting methods for those activities.
• Educate the public on storm water issues as they relate to the total drainage
system and individual watersheds.
Storm Water Operations:
• Continue the dredging program, which alleviates problems m the City of San
Antonio's lakes and ponds by removing silt and debris.
• Provide for the protection of our environment by incorporating tree
preservation/mitigation, reduced herbicide use, seeding of low maintenance ground
cover and wildflowers.
• Take corrective course of action to ensure the reliability and functionality of the
existing High Water Detection System and the Early Flood Warning System
through system upgrades.
• Maintain City storm water facilities to ensure optimum capacity.
• Remove pollutants from City streets with an aggressive street cleaning program.
Storm Water Engineering:
• Review and evaluate the Regional Storm Water Management Program and
associated fee structure.
• Implement the Storm Water Compliance for Construction Activity Ordinance.
• Continue implementation and enforcement of all drainage ordinances for the
protection of the floodplain and the orderly development of the vegetation and
natural facilities within it.
PAPE-DAWSON ENGINEERS, INC. 4BS11001Word1Reportl000210a1