Small-scale Strategic Wood Addition: Proposed Wetland Restoration Field Practice

Throughout the Champlain Valley, a large number of wetland plant communities are being overrun by Phalaris arundinacea (reed canary grass). Streams within these wetlands, be it perennial or seasonal, are often single channel and moderately to highly incised.

These conditions in concert pose a threat to wetland functions and values. The Phalaris infestations are driving plant communities towards non-native mono-culture, and the incised stream channels are lowering water tables. Observations suggest that this is a positive feedback cycle; the Phalaris creates a thick, dense sod layer that act to armor the single channels, while the incised single channels promote vertical erosion, lowering water tables and thus creating conditions more favorable to Phalaris (as well as other non-native/invasive plant species) at the expense of native wetland plant populations.

A plan that restores hydrology and resists Phalaris spread would certainly help. We are experimenting with field practices that could break this feedback scenario.

Strategic Wood Addition: This is a philosophy and practice that is gaining widespread acceptance for ecosystem restoration. It is intended to replicate the natural accumulation of wood in stream channels and across floodplains that has been lost to legacy land use practices. It is generally regarded as a low-tech, low-disturbance, and cost-effective practice that can yield a wide range of positive outcomes.

Case Study: A Chittenden County site, characterized by a 4 acre riparian wetland running north-south, bounded by forest cover east and west transitioning to upland. Much of the stream channel is obscured by heavy Phalaris growth. Observable reaches are single channel, bankfull width estimated 24-32”, flowing south. Wetland floodplain is estimated at 100-125’ in width. Stream flows (observed 12/8/20) were contained within the single channel, depth of stream was estimated to be 8”, approximately 6” below floodplain.

We chose two sites 25 ft. apart, and placed a single log (14-16” dia.) across the channel, anchored with locally sourced wooden stakes. Immediately, channel flow was effectively blocked. In real time we observed inundation of adjacent Phalaris and formation of alternate stream flow paths. We believe both of these dynamics will have a locally positive effect on riparian and wetland functions and values.

The overall impact of two wood addition sites within this stream channel are modest at best. What it does illustrate is the ease and cost effectiveness of implementing this field practice. Within this site, the stream channel retains these characteristics for approximately 625 linear feet through this riparian wetland. An installation of 12-20 structures would have a measurable impact upon the stream channel and would provide a strong indication whether such a practice would yield a positive effect upon wetland/riparian hydrology and plant community composition.