Project Highlights

ACEC/TN Engineering Excellence Award

S&ME, in a design/build arrangement with Jen-Hill, Inc., was retained by the Nature Conservancy to provide bank stabilization for approximately 5,000 feet of Big Rock Creek, a bedrock dominated stream, which flows through downtown Lewisburg, Tennessee. The stream has lost most of its floodplain and has historically been altered for flood control and has multiple sewer and utility crossings of the creek. Currently the stream has an oversized channel which carries the flood waters as well as the bankfull flow. The banks were assessed for stability and prioritized bank using the Bank Erosion Hazard Index (BEHI). Due to the urban setting and bedrock streambed, the pattern and profile of the stream could not be significantly altered. Data gathered from the longitudinal profile, cross-sections, and BEHI was used to generate a design incorporating bioengineering and natural channel design principles. The design used rock J-hook structures, bankfull benching, vegetated coir rolls, and bio-gabions to reduce near bank stresses and stabilize the banks. Where possible, rock was removed from the bed to build the structures, thereby reducing the overall cost of construction.

A major design factor was the need to comply with “no-rise” provisions of the Federal Emergency Management Agency (FEMA) and City of Lewisburg.  Intensive modeling was undertaken using the U.S. Army Corps of Engineers HEC-2 surface water model as part of satisfying these requirements. This iterative modeling resulted in modifications to the structure locations and designs to meet the government requirements.

The relationship between S&ME and the experienced construction contractor allowed for changes to be made in the field to the design without additional cost to the client or delaying the construction schedule. The project was completed in the spring of 2006.