Paper No. 2
Presentation Time: 8:20 AM
THE USE OF LARGE WOOD IN STREAM RESTORATION AND BANK STABILIZATION PROJECTS IN NEW ENGLAND
Great lengths of New England’s streams and rivers were channelized in the 20th century and earlier for flood control, log drives, transportation, and other reasons. In addition to artificial straightening, the channelization process also included the removal of logs and boulders, leading to the degradation of geomorphic and habitat function. Large wood can be used on these channelized rivers and streams in multiple ways to restore habitat complexity, provide structure in the channel to accelerate the reformation of meanders and other natural features, and stabilize eroding banks. In mountainous areas with little adjacent human infrastructure, whole trees can be directionally felled to fall into the stream channel in a technique referred to as “chop and drop” to encourage the development of channel-spanning log jams that scour deep pools, store large volumes of sand and gravel, and reconnect incised channels to their adjacent floodplains. Such projects have the potential to not only improve habitat within the project reach itself but can also decrease flood peaks and sediment loading downstream. Along valley-bottom systems, marginal log jams can be constructed along straightened channels to encourage the reformation of meanders and divert flow away from eroding banks while single logs can be used to scour pools, trap gravel useful for spawning, and improve flow complexity. In valley-bottom settings where wood movement could potentially threaten infrastructure, wood can be anchored by driving logs into the bed and banks without the use of boulders or steel cables to ensure the constructed log structures appear natural even in sandy environments. While trees falling into stream channels can often exacerbate flooding and erosion problems during storm events, large wood can actually be used in restoration projects to reduce threats to human infrastructure while simultaneously improving geomorphic and habitat function degraded by historic channelization.