Neighborhood Channel is Redefined with Boulder Armoring

A channel through a neighborhood in Jefferson County, Kentucky was eroding and accumulating complaints of property damage and flooding. The channel, carrying an intermittent stream, had been filled by the developer of this neighborhood to be a grass channel flowing through the backyards. Development upstream increased the flows through this area and caused erosion of the grass channel. Efforts to armor the channel with gabion baskets and rip rap, and in some cases landscape timbers did not stem the tide of damage. The length of channel being evaluated was approximately 1,800 feet. A solution for the entire length under review was desired. Armoring the banks with boulders was the preferred method to stabilize the stream banks. The SCS TR-55 program was utilized to calculate flows to size the proposed channel. The channel width was chosen to allow the channel to achieve bank full depth. The bank full depth was determined by field observation of sections of the entire length of the existing stream. The proposed channel alignment was arranged to closely resemble the existing and to minimize disruption to existing utilities as well as uses by the adjacent property owners. Methodology of the hydraulic analysis and design of the stream bank armoring is discussed herein as a low tech solution for urban and suburban stream projects. Armoring the stream banks provided the protection needed while defining the stream and allowing movement of runoff through the project area without using a concrete channel. The use of boulders along the banks created a more "natural" channel appearance and satisfied the client (MSD) as well as the adjacent property owners.