Incorporating Site-specific Variables in the Design of Vegetated Channels

Vegetated channels are commonly used along roadsides, in residential neighborhoods, and in commercial developments for both conveying water and achieving water quality benefits. In some cases, the integrity of the channels depends solely on the success of vegetative establishment by itself, while in other cases, the vegetation is established with the aid of turf reinforcing mats (TRMs). However, the experience with vegetative channels varies with climate and soil type, to name two major site-specific variables. In addition, there is an impressive array of TRMs available with little objective guidance on how to incorporate TRMs in the design of vegetated channels. The authors have completed preparation of the 3 rd Edition of the Federal Highway Administration’s Hydraulic Engineering Circular (HEC) number 15 “Design of Roadside Channels with Flexible Linings.” This paper describes new guidance for incorporating site-specific soil and vegetation characteristics into the design of a stable channel. It also summarizes a model for the interaction between vegetation and TRMs as well as the data required from the manufacturer for design following specific testing protocols. With this new national guidance, successful designs may be implemented considering local conditions and material availability.