Kansas City, Kansas /
Kansas City, Missouri
Client:
HNTB Corporation
As a subcontractor to the lead civil engineering firm with the US Army Corps of Engineers Kansas City District, Terra Technologies performed a study to determine the applicability of bioengineering solutions on a 15,000 linear foot section of Turkey Creek. The frequency of flooding in the Turkey Creek basin is well documented and severe. The development within the stream floodplain is the primary cause of the flooding and has possibly been aggravated by the development within the watershed.
A geomorphic evaluation was performed to document and inventory the existing conditions prior to the construction of any improvements. This survey provides preliminary insight into the environmental condition of the existing stream system as a benchmark for design and construction of proposed channel modifications associated with the widening of Interstate 35.
The Turkey Creek channel has been in the current alignment for a long enough period of time to develop a reasonably healthy riparian corridor. The corridor represents some of the only wildlife habitat present for a significant distance in all directions. Because of this, bioengineering options were preferred over traditional solutions; bioengineering solutions can significantly accelerate the redevelopment of disturbed areas to a healthy and diverse condition without sacrificing the structural integrity or flood control ability of the proposed channel modifications.
The concept of vegetative erosion control is merely the process of mimicking natural processes, in an accelerated fashion. The existing Turkey Creek riparian corridor is largely stable without a significant amount of erosion that would indicate an unstable stream alignment. While most of Turkey Creek is in a re-aligned location, the channel has naturally found a configuration that is maintained by the stream’s own hydrology and hydraulics. This process occurred over a period of decades. The process of bioengineering attempts to achieve the same result within one or two growing seasons.
Terra Technologies provided applicable bioengineering recommendations for the proposed Turkey Creek Improvements from Railroad Bridge 4.4, downstream to the Turkey Creek tunnel. Recommendations were provided for four separate reaches of the section of stream. Recommendations were based on the existing stream system conditions including the hydrology and hydraulics, geomorphology, biology, and horticulture. Recommendations included such alternatives as buried gabions or lunkers at the toe of the stream bank slope for stabilization and aquatic habitat enhancement, installation of turf-reinforced matrix (TRM) or wire-reinforced TRM based on the location and flows. In locations where hydraulic conveyance was not critical, selected vegetation included various trees and woody shrubs to accelerate the development of the area into a mature hardwood riparian corridor. Areas that did not require extensive armoring were recommended to be established with native vegetation using low cost erosion control blankets or bonded fiber matrices. In one reach where the channel was highly constricted by bridge structures, hydraulic conveyance needs as well as geomorphological instability did not allow for consideration of bioengineering improvements. The recommendations provided were submitted in the Spring of 2002. The project is presently in construction, and represents the largest natural stream channel restoration project in the midwestern USA. |
