Stream Restoration Design Components of the Bois d’Arc Lake Watershed-Scale Ecological Restoration and Mitigation Project
Lee Forbes, PE, DWRE
SWCA Environmental Consultants
Houston, TX
Joseph Zang, EIT
SWCA Environmental Consultants
Fort Collins, CO
The North Texas Municipal Water District (NTMWD) is constructing the 16,641 acre-feet Lower Bois d’Arc Creek Reservoir, which will supply water to approximately 80 North Texas communities. Resource Environmental Solutions (RES) was awarded a contract to design and construct ecological restoration to offset the unavoidable impacts from the project to the aquatic resources of the Waters of the U.S. on approximately 15,000 acres of nearby farm and ranch lands adjacent to the Red River. This project created a unique opportunity to bring back the natural landscape of prairie grasslands, wetlands, and streams to lands that had been managed for agricultural purposes. RES retained SWCA to lead the comprehensive stream and wetland hydrologic restoration design efforts restoring, enhancing and preserving nearly 70 miles of ephemeral, intermittent and perennial streams and over 14,000 acres of wetland and upland habitats and within the same watershed. Preliminary designs for the entire site consisting of approximately 900 pages of plan view and details were completed in less than two months, with 90% designs completed within six months. The project is being constructed over 2-years and will be monitored and maintained over a 25-year period. This presentation focuses on the design, construction, and monitoring of the more than 24 miles of Priority 1 and 2 stream restoration components of the project. Existing stream channels were incised with minimal riparian buffers, numerous active head cuts, and vertical instability. Priority I stream restoration designs have been utilized wherever possible to reconnect the streams to the abandoned floodplain and raise the near-surface groundwater table to re-establish and optimize the geomorphic and hydrologic processes that support aquatic ecological function and optimization of surface and groundwater hydrology of the adjacent, broad wetlands. Bankfull width of the design streams range from 5 feet to 32 feet and design slopes range from 0.01% to 2.5%. Final designs include onsite channel and floodplain optimization of the 90% designs and the production of three-dimensional surface machine files for construction of the streams and adjacent riparian corridors/floodplains using GPS-guided equipment. Post-construction surveys and monitoring and adaptive management designs are being used to rapidly tweak the efficacy of the final project channels and riparian floodplains. The presentation will focus on the unique and scalable design process used to complete the massive amount of stream designs and the unique and innovative in-stream structures developed and used to maximize the use of onsite materials and optimize post-construction resiliency and ecological lift.
About Lee Forbes, PE, DWRE
Mr. Forbes serves as a National Director for SWCA’s Ecological Restoration Engineering Group, where he is focused on the development of emerging markets and technologies. His experience as a consulting civil/environmental engineer spans more than 33 years. In the last 19 years, Mr. Forbes has applied his unique and diverse background toward the emerging field of sustainable watershed resources management, with an emphasis on the engineering aspects of ecosystem restoration, and has been certified as a Diplomate, Water Resources Engineer by the Council of Engineering & Scientific Specialty Boards. Of note, he has served as a program manager/project manager/lead design engineer for numerous stream restoration, wetland restoration, and ecologically-enhanced channel stabilization/restoration design projects across the country in numerous physiographic and ecological settings, including mountain, piedmont, great lakes, prairie, coastal plains, estuarine, and arid southwest provinces.
About Joseph Zhang, EIT:
Joseph Zhang works as an Associate Project Restoration Engineer in SWCA’s Ecological Restoration Engineering Group. Using AutoCAD, RiverMorph, HEC-RAS and other programs, he develops and improves engineering design of stream and wetland projects, assesses stream functions, and brings sustainable ecosystems on project sites. Through five years of experience in civil and environmental engineering projects in various states, Joseph has developed skills in multi-criteria decision analysis, stream restoration design, wetland water budget analysis, and hydrology/hydraulic modeling. He has been the design engineer and deputy project manager for projects ranging from small stream restoration to large mitigation banking development. Additionally, he leads groups to achieve goals at work and coaches new professionals in skills to succeed in their fields.