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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