The piece of bleached, smooth wood resting at the tideline began its journey somewhere entirely different — most likely a forested watershed tens or hundreds of kilometres from the coast. Understanding that journey involves looking at river dynamics, saltwater chemistry, and the biological activity that happens to submerged wood over periods of years.
Origin: Forests and River Systems
Most driftwood entering Canadian coastal waters originates as terrestrial timber. Trees fall into rivers through bank erosion, windthrow, or flooding, and the current carries them downstream. In British Columbia, the major river systems — the Fraser, the Skeena, the Nass, and others — move substantial volumes of wood toward saltwater each year. The natural disturbance regimes documented by Natural Resources Canada indicate that windstorm and flooding events contribute the majority of large wood to BC's coastal drift system.
On the Atlantic side, the Saint John River in New Brunswick, the Miramichi, and the various rivers draining into the Gulf of St. Lawrence provide comparable input. The species differ markedly — the Atlantic drift is dominated by balsam fir, black spruce, and white birch, while the Pacific drift carries large volumes of Douglas fir, western red cedar, and Sitka spruce.
The Transition from River to Sea
When timber crosses from freshwater to saltwater, several processes begin. Salt infiltration changes the wood's internal moisture dynamics. Marine borers — primarily molluscs in the genera Teredo and Bankia — begin to colonize submerged surfaces within weeks of ocean entry. These organisms can reduce a dense softwood log to a hollow shell within a few years, though the rate depends heavily on water temperature and salinity levels.
Floating timber is also affected by ultraviolet radiation on its upper surfaces and by wave abrasion as it moves. This combination — bleaching above, boring below, and mechanical rounding at the ends — produces the characteristic appearance of mature driftwood: pale grey or silver surface coloring, smooth rounded edges, and an internal structure that may be partially hollowed or furrowed.
Time at Sea and Arrival Patterns
Research on drift trajectories in the North Pacific, including work associated with the Department of Fisheries and Oceans, indicates that large wood pieces may remain in circulation for two to fifteen years before making landfall in a stable intertidal position. Smaller pieces move faster and tend to strand on beaches more readily; larger logs may travel great distances and arrive carrying evidence of their journey — attached kelp holdfasts, barnacle scars, and the entry holes of marine borers.
Arrival patterns along the BC coast follow prevailing wind and current directions. The north-to-south flow of the California Current brings material from Alaska and the northern BC coast to beaches further south. On the Atlantic coast, the Gulf Stream and Labrador Current systems create different movement patterns, with material from the St. Lawrence watershed distributing along the shores of the Maritime provinces and Newfoundland.
Species Identification in the Drift
Identifying the species of a driftwood piece is possible in many cases, though the weathering process obscures the distinguishing characteristics of some species over time. Cedar remains identifiable by its grain pattern and light weight even after extended marine exposure. Douglas fir retains its density and often shows its characteristic resin ducts. Hardwoods from the Atlantic drift — birch, ash, maple — tend to lose surface bark early but maintain a finer grain texture that distinguishes them from softwoods.
The wood's origin species matters for anyone working with the material, because density, moisture behavior, and splitting tendency all vary considerably between species. A piece of dense Douglas fir that has not been fully colonized by marine borers will behave very differently from a lightweight cedar log that has spent a decade at sea.
Summary of Species by Coast
The following species account for the majority of identified drift material along Canada's two main coastal zones:
- BC Pacific Coast: Douglas fir, western red cedar, Sitka spruce, western hemlock, yellow cedar
- Atlantic and Gulf: Balsam fir, black spruce, white spruce, trembling aspen, white birch, sugar maple (in St. Lawrence watershed)
Intertidal Accumulation and Beach Dynamics
Where driftwood accumulates on a beach depends on beach morphology, prevailing storm directions, and seasonal variation in storm intensity. High-energy winter storms push large material well above the normal tideline; summer conditions allow finer pieces to settle at lower intertidal zones. Some beaches in sheltered bays accumulate deep windrows of driftwood that shift significantly after each major storm. Others in exposed locations have relatively little accumulation because material is re-floated on each high tide.
The pattern of accumulation also affects what a collector finds at any given time. A beach with a stable driftwood windrow above the storm line will have older, more weathered material with more pronounced marine borer activity. A recently cleared beach after a storm may expose freshly deposited pieces that still show bark, branch stubs, and a range of moisture content not yet equilibrated to ambient conditions.
Sources consulted: Natural Resources Canada Forest Disturbance Database; Fisheries and Oceans Canada Pacific Region publications on marine debris and coastal wood dynamics; published research on Teredo distribution in BC coastal waters.