Nearly 6 miles of Grace Creek flows through downtown Longview, Texas, before emptying into the Sabine River. Much of the land along the river is flat and prone to flooding. Heavy overgrowth of brush inhibits the flow of floodwaters and raised upstream water levels. The Grace Creek Floodplain Management Project sought to reduce the creek's 100-year flood levels by as much as 2.2 feet; planners arrived at a novel approach that saved the city millions while preserving the area's natural beauty.
The first option considered would have required constructing a channel up to 75 feet wide to rapidly remove floodwaters. This option, while effective, would have dramatically and adversely impacted the creek's natural setting. That, coupled with a price tag of more than $20 million, prompted the city to seek alternatives. A second option called for converting existing underbrush into a mature, forested floodplain with complete tree canopy coverage. This option would mitigate floodwaters without compromising the environment.
Work proceeded in two phases, starting along Lower Grace Creek, followed by Upper Grace Creek. The project identified areas within both portions to be managed and arrived upon three techniques:
Wetlands remained undisturbed throughout the project.
The project tapped Terry Anderson and Mike Bird of Advanced Ecology Inc., an environmental and natural resources consulting firm in Center, Texas, as the local contractors. Bird said the project “had a tremendous amount of brush and hardwood. We were able to remove the vegetation without being intrusive and without a lot of soil disturbance.” While similar in the scope of work, there were no areas to be cleared and reforested during the second phase.
Two different pieces of equipment were used on the project, which spanned nearly three years. The first was a Tigercat 760M, a 425-hp, four-wheel-drive carrier with a Bull Hog mulching attachment. The machine worked through the dense underbrush, leaving a carpet of mulch in its wake. The Tigercat and Bull Hog combination was ideal for clearing large areas, such as the 16-foot rows and the clearing prior to re-forestation in other areas.
The selective thinning was trickier and called for a more compact machine. The contractors opted for a Franklin 3650, a 200-hp machine with a slightly smaller Bull Hog mulcher. Its enhanced maneuverability was ideal for getting around the reserved trees while removing the waste trees and underbrush.
Bird gave the Bull Hog high marks, saying that previous swinging-flail-type machines delivered maintenance problems and ate into productivity, while the Tigercat endured harsh working conditions and boosted production considerably. He credits the machine's low maintenance and fixed-tooth cutter head design.
The project cost approximately $2.5 million and saved the taxpayers an estimated $ 18.2 million over structural flood management. In addition to the practical gains, the project created enhanced aesthetics, preserved vegetation, and created opportunities for recreation and natural resource education (such as a bicycle trail). By offering this unique opportunity for nature study opportunities, the city hopes for increased tourism and a boost in the local economy.
The project boasted a high level of community cooperation. The replanting of pine and hardwood trees was handled largely by the Hardwood Association, a local group that volunteered its time and service. Also, the bicycle trail may not have been possible without support from individuals and organizations that wrote letters to the Texas DOT.
— Jim Wahl is a Cincinnati business writer; Shawn Ham is with the city of Longview, Texas.