The Dallas Trinity Lakes Project: Challenges and Approaches to Designing a Channel Realignment Scheme to Satisfy Multiple Objectives

The Trinity River in Dallas (drainage area of 6,100 square miles at Dallas) has experienced dramatic change over the past century, with the most rapid and extensive changes occurring during the construction of the original Dallas Floodway project in the late-1920s and the US Army Corps of Engineers (USACE) reconstruction of the floodway in the mid-1950s. The City of Dallas is currently designing the Trinity Lakes Project based on the objectives and conceptual design developed in the Balanced Vision Plan (BVP) for the Trinity River Corridor (City of Dallas 2003). The project includes significant physical changes to the channel and floodway including restoration of channel meanders, creation of a mid-channel island or oxbow lake, alterations to channel geometry, and construction of two lakes in the floodway adjacent to the channel. One of the key success criteria for this project is the creation of a realigned channel with enhanced aesthetic, recreational, and habitat features that are sustainable through time and in relation to other features of the project in the floodway. Given the dynamic nature typical of alluvial river channels such as the Trinity, achieving this criterion poses significant challenges during the design process. The purpose of this paper is to summarize hydrologic and geomorphic assessments conducted to document and quantify historical and ongoing channel and floodway change. In addition, we present a design process that combines these historical analyses with approaches from landscape architecture and state-of-the art hydraulic and sediment transport modeling to translate the Balanced Vision for the Trinity Lakes project into the most sustainable detailed design possible for the site.