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Trinity River COMMON VISION Program

Flooded Trinity River Upper Trinity River Feasibility Study

BACKGROUND
The series of events that led to the Feasibility Study began when long-standing federal plans to construct a barge canal along the Trinity were abandoned in the early 1980’s. A new vision began to emerge of significant development of the floodplains of the Trinity in the Dallas/Ft. Worth area. The Fort Worth District of the U.S. Army Corps of Engineers, responsible for Section 404 permitting of development in the Trinity River floodplain, began to be flooded with numerous unrelated requests for federal permits to reclaim portions of the flood plain for commercial and residential development.

Because, individually or cumulatively, the floodplain development projects had the potential to compromise existing flood protection and because of competing public demands for other uses of the river channel and floodplain, it was necessary to develop a regional perspective in order to properly evaluate the impacts on individual permit decisions in accordance with the spirit and intent of the National Environmental Policy Act (NEPA) and other applicable laws. Thus, in response to the numerous floodplain development requests, the US Army Corps of Engineers (USACE) in cooperation with the North Central Texas Council of Governments (NCTCOG) completed a three-year Regional Environmental Impact Study (EIS) of the cumulative effects of permitting floodplain development.

Regional Environmental Impact Statement
The final study document, or Final Regional Environmental Impact Statement, reached two primary conclusions. The first reemphasized that a widespread lack of Standard Project Flood (SPF) protection currently existed throughout the river corridor. Damages to property if a Standard Project Flood were to occur could approach several billion dollars. Even moderate development scenarios would result not only in the Dallas Floodway levees being overtopped with catastrophic results but also in properties in upstream cities sustaining considerable flood damages. Thus, no city could ensure adequate flood protection for itself by itself – only a common approach could be successful.

The second major conclusion of the EIS was that "different permitting strategies have a measurable and significant impact on the extent of increase of this lack of SPF protection." In other words, local policies for floodplain reclamation could increase or reduce the risk of flooding. Under the most extensive development scenario, flood damages could triple the estimates for the baseline condition, not including the catastrophic effects if the Dallas Floodway levees were breached. At the time that the regional EIS was issued, each city in the river corridor was using its own set of criteria for permitting floodplain development.

As a draft Environmental Impact Statement was being developed in the mid-1980s, local governments along the Trinity joined together through NCTCOG to create the Trinity River COMMON VISION Program to ensure a SAFE, CLEAN, NATURAL, ENJOYABLE, and DIVERSE Trinity River. The North Central Texas Council of Governments began to serve as convenor and facilitator of the nine cities, three counties, and two other governmental entities local governments pursuing the COMMON VISION. A Steering Committee of elected officials was established to guide the inter-jurisdictional program, along with a Flood Management Task Force to provide technical expertise.

Reconnaissance Study
In response to the findings of the Environmental Impact Statement, local governments along the Trinity River made a request to Congress that the U.S. Army Corps of Engineers be authorized to undertake a Reconnaissance Study to determine if feasible flood protection plans could be identified which would substantially alleviate the flooding problems. During the Reconnaissance Study, the Corps studied thirteen flood control options and found eleven projects with a cost-benefit ratio that merited further attention in a Feasibility Study.

FEASIBILITY STUDY – PHASE I

Phase I of the Upper Trinity River Feasibility Study was initiated in 1990 to fully evaluate the impacts and optimize the eleven structural measures found viable during the Reconnaissance Study, along with flood warning and other new alternatives identified by the Steering Committee. The scope of study was broadened by Congress to include not only assessment of flood protection but also water quality, environmental enhancement, recreation, and other allied purposes. An improved hydraulic model was developed to compute flood elevations during this phase of study.

The Phase I Information Paper released in early 1995 identified potential projects with a preliminary positive benefit-cost ratio. The Information Paper concluded that seven of the fourteen structural flood control measures were economically viable, and a total of eleven water quality improvement and 20 environmental enhancement measures warranted further study. In addition, 38 recreational development measures were also found to be feasible, as well as cooperative approaches to watershed management.

Several regional projects identified in the Phase I Information Paper have been implemented during Phase II by participating cities. These projects include Federal Emergency Management Agency (FEMA) Mapping, the Corridor Development Certificate Process, and the Trinity Trails System.

FEASIBILITY STUDY – PHASE II

The next step was for the local entities to review the identified measures within their respective jurisdictions. Each local entity had to determine their interest and willingness to individually cost-share 50/50 in more detailed Phase II formulation studies to identify potential construction projects having a federal interest. Phase II will result in a detailed design work plan for each selected alternative. Thus far, Phase II Project Study Plans have been developed for projects in Dallas, Ft. Worth, and Arlington. Several other projects, which will provide flood reduction and other benefits, currently have the potential to be added as Phase II projects.

 

 
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