building strong ® trinity common vision steering committee september 10, 2015
TRANSCRIPT
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Trinity COMMON VISION Steering Committee
September 10, 2015
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Trinity River COMMON VISION What is the program about, and why is it important?
► The program was developed in the late 1980’s and is a cooperative management effort among local governments, NCTCOG, and the USACE, along the Trinity Corridor, that results in a comprehensive and regional approach in addressing flood damage reduction, recreation, and environmental quality.
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NINE CITIES:Arlington Carrollton CoppellDallas Farmers Branch Fort WorthGrand Prairie Irving Lewisville
THREE COUNTIES:Dallas Denton Tarrant
TWO SPECIAL DISTRICTS:Tarrant Regional Water District
Trinity River Authority
NCTCOG TRINITY RIVER CORRIDOR INTERLOCAL
AGREEMENTest. 1989
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Timeline and Background Discussion Pre 1970’s - Dallas and Fort Worth Floodways constructed by USACE 1972 – Clean Water Act involving USACE permits 1980’s – Cumulative impact of floodplain reclamation projects identified as
a concern 1988 – National Environmental Policy Act (NEPA) drives USACE
Environmental Impact Statement (EIS) & Record of Decision (ROD) 1988 - Member cities come forward to form the NCTCOG Trinity River
COMMON VISION Steering Committee 1990 – Upper Trinity River Basin Reconnaissance Report – common permit
strategy based on interest of the locals 1990 –Interlocal Agreements signed by member cities & Congress
authorizes the Upper Trinity River Feasibility Study (UTRFS) Flood Management Task Force formed and CDC criteria developed based
on ROD May 1991 - 1st Edition of the Corridor Development Certificate (CDC)
Manual Today - Approximately 100 projects permitted and four CDC manual
updates since 1991
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Historical Background – EIS & ROD
Regional Environmental Impact Statement Trinity River and Tributaries (1988)► Cumulative impact of development is “Measurable and
Significant”► Record of Decision (ROD) (1988)
• Applied through 404 permit process• No rise in 100-yr water surface elevation• No rise in SPF water surface elevation• No loss of valley storage for 100 yr• Up to5% loss of valley storage allowed for SPF
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CDC Program Goals
Limits (but does not eliminate) the impact of floodplain encroachments for regulated streams on downstream areas
Establishes a consistent regional criteria and review process
Provides a funding stream for updates and state-of-the-art models and modeling tools
Provides oversight for projects constructed in the 100 yr floodplain
Allows development in the floodplain Allows all FMTF members to review projects for the
entire regulatory footprint
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• Flood control system• Over $70 billion in
damages prevented (60 years)
• $2-3 billion per year
Trinity Corridor Development Certificate (CDC)
Where is the 7th flood control reservoir?
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Corridor Development CertificateFloodplain as a Reservoir
RIVER CHANNEL
WATER SURFACE
Full floodplain conveyance and storage
19901949 1989
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Corridor Development CertificateFloodplain as a Reservoir
Downstream flood risk increases
► Higher flows► Higher water surface
elevations
RIVER CHANNEL
WATER SURFACE
Full floodplain conveyance and storage
Reduced floodplain conveyance and storage
RIVER CHANNEL
BUILDABLE AREA BUILDABLE AREACDC Cor-
ridor
Ray Roberts
Lewisville
Grapevine
Lavon
Joe Pool
Benbrook
Active Flood Storage
Bad things happen when you do this!
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Benefits of the CDC Process
• Establishment of the CDC Process provides a number of benefits and innovations, including the stabilization of flood risk. • Common regional criteria • State-of-the-art floodplain mapping• Hydrologic modeling based on year 2055 Upper Trinity River watershed development• A current hydraulic model incorporating CDC permitted floodplain development• U.S. Army Corps of Engineers technical review• Regional review and comment
TREIS 1987 ROD 1988 CDC 1991
Chronology of the Regulatory Program
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Corridor Development CertificateFloodplain as a Reservoir
RIVER CHANNEL
WATER SURFACE
Full floodplain conveyance and storage
RIVER CHANNEL
BUILD AREA
BUILD AREA
STORAGE AREA STORAGE AREA
Recovered conveyance and compensatory storage
Reduces, but does not eliminate, impacts on downstream flood potential (compromise)
Approx. 100 projects permitted Leveraging to expand SW management practices
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Questions or Comments?
COMMON VISION ActivitiesGIS Mapping Application
Link: http://www.nctcog.org/envir/SEEsafe/fpm/cdc/index.asp
COMMON VISION Activities Ongoing Support Activities
Ongoing Trinity River COMMON VISION Information and Task Force Committee Support
Ongoing Corridor Development Certificate (CDC) Process and mapping support
Continued sponsorship of FEMA’s NFIP training courses
Continued effort toward a Consolidated CDC Model
Ongoing effort to explore partnership and outreach opportunities
Continued exploration of regional cooperative detention/retention strategies
Floodplain Management Seminars for Policy Makers
Trinity River COMMON VISION Work Program FY16 Special Projects
Highlights: Continued effort toward a
Consolidated CDC Model Collection of data from May 2015
weather events Design and distribution of promotional
materials
Related Activities Update
Cooperating Technical Partnership
Community Rating System Users Group
Atlas 14
Cooperating Technical Partnership
In 2002, NCTCOG was named CTP and provided technical information and outreach to assist FEMA in their map modernization efforts.
In 2009, NCTCOG crafted an Upper Trinity River Basin Mapping Needs Assessment Tool for the Texas Water Development Board and FEMA.
In 2013, NCTCOG served to perform Discovery for two basins- the Lower West and Elm Forks of the Trinity. (We also supported Dallas’ efforts in the Upper Trinity.)
For 2015, FEMA is funding NCTCOG for technical production of updated floodplain engineering for portions of the Bear Creek Watershed in Tarrant County, within the Lower West Fork Trinity watershed.
Cooperating Technical Partnership
Bear Creek Watershed Flood Risk
Identification Project
• The key communities are already working together.
• Residents of the Bear Creek watershed and their property are continually threatened by severe
storm events.
• Colleyville & Southlake have 350+ flood insurance policies and over $500,000 paid out in
flood losses over the past several decades.
• Floodplain analyses for Bear Creek are outdated and do not represent the flood risk in the
watershed.
• Stakeholders will be able to accomplish the flood risk reduction goals that could not have been
achieved by any one entity alone.
FEMA’s Community Rating System (CRS)
Voluntary incentive program that recognizes and encourages community floodplain management activities that exceed the minimum NFIP requirements. Partnership between Floodplain Managers and Elected
Officials is essential
Flood insurance premium rates are discounted to reflect the reduced flood risk resulting from the community actions meeting the three goals of the CRS: Reduce flood damage to insurable property;
Strengthen and support the insurance aspects of the NFIP, and
Encourage a comprehensive approach to floodplain management.
North Central Texas CRS Users Group
Date Title
10/22/2014Developing Outreach Projects
(Activity 330)
11/19/2014Flood Warning & Response (Activity
610)
12/17/2014Developing a PPI, CIP, and Using
FloodSmart
01/20/2015 Preparing for a Verification Visit
02/17/2015 Introduction to CRS
03/18/2015 Developing a PPI and CIP
04/22/2015Drainage System Maintenance
(Activity 540)
05/20/2015 CRS and Higher Regulatory Standards
06/17/2015 CRS and Natural Floodplain Functions
07/22/2015 Preparing an Impact Adjustment Map
08/19/2015 Preparing an Annual Recertification
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NOAA Atlas 14Precipitation Frequency Estimates
Used to design:► Storm water run-off facilities
► Size of detention basins and outlet structures
► More accurately designed drainage for Texas roads and Highways
► Bridges and Culverts
Modeling:► Flood Risk Management studies
► Flood plain mapping
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NWS Technical Paper No. 40 (1961)
NWS Technical Paper No. 49 (1964)
NWS Hydro-35 (1977)
Available Precipitation Frequency Products
NOAA/NWS USGSAtlas of Depth-Duration Frequency of
Precipitation Annual Maxima for Texas (2004)
Note: based on data from 1998 study (data from 1994)
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NOAA Atlas 14 Volume for Texas
More accurate, reliable and robust► More observing locations, longer period
of record► Better statistical methods► Objective, high resolution spatial
interpolation► Peer review
De-facto national standards► Local, state and federal agencies
Consistency between states and agencies (equity)
Web based electronic delivery► Precipitation Frequency Data Server► Extensive documentation► Linkage to modern software (HEC)
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Record Lengths & Additional Stations
Development is based on historical observations
► 50+ years to original NOAA studies
► 20+ years to USGS► Many new rainfall stations
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.
DurationAverage recurrence interval (ARI)
1 2 5 10 25 50 100 200 500 1,0005-min 10-min 15-min 30-min 60-min 2-hour 3-hour 6-hour 12-hour 24-hour 2-day 3-day 4-day 7-day 10-day 20-day 30-day 45-day 60-day
PFDS operates from a set of ASCII grids (30-arc sec resolution)
Duration and ARI coverages
USGS project coverag
e
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Current Financial Outlook
Current Partners
• TxDOT
• City of Fort Worth
• U.S. Army Corps of Engineers
• NCTCOG
• Harris County Flood Control District