Geomorphic impacts of wood in streams and the role of forest disturbance

Wood that enters channels plays a number of biophysical roles in rivers and streams, such as forming steps, diverting flow and forming pools, storing sediment and stabilizing banks.

field 121

Wood storing a sediment as up upstream wedge.

In the Okanagan, a number of disturbances can lead to large influxes of wood into channels over short periods of time, including fire and Mountain Pine Beetle (MPB).

My MSc research quantified the changes to wood inputs resulting from these disturbances, and the impacts of these changes on channel morphology.  We found that at reference (undisturbed) sites in the Okanagan, wood was slowly depleting.  Fire increases wood recruitment and leads to net storage in disturbed channels.  MPB impacts were not yet apparent, but are expected to increase in the coming decades.  Or in other words, dead trees fall down! And sometimes they end up in channels.

Methods summary: channel surveys using a total station, many, many pebble counts, and long term wood surveys by tagging and surveying wood annually.

Main highlights: produced wood budgets of wood recruitment, export and storage, related wood function to wood stability, and wood stability to relative wood size.

You can find a copy of the published paper here.

summer09 167-ANIMATION

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