DRIFTCRETIONS: A STUDY OF LAND GROWTH FROM DRIFTWOOD, GREAT SLAVE LAKE, CANADA

Islands and shorelines near the Slave River Delta on the Great Slave Lake, Northwest Territories, Canada, are enlarging over time directly due to accretion of large, successive parallel berms or mats of driftwood (driftcretions). This study describes wood accretion processes on the leeward and windward sides of islands and on the shores of protected bays. Large driftcretions are deposited episodically by ice, wind, and seiches (lake tsunamis). Accretion rates (e.g. 0.13 meters/year) were calculated by using tree rings from bands of even-aged stands of spruce parallel to shorelines. The Slave River provides 74% of the inflow to the Great Slave Lake and a large yearly wood flux (>3300 m³/yr). The W.A.C. Bennett dam and nearby Peace Canyon dam are the only in stream obstructions in the Slave River catchment. Approximately 87% of the 6 x 10⁵ km² basin is free flowing. Due to minimal development along river corridors, recruitment of trees within the basin is likely the same or very similar to pre-settlement by Europeans. Thus, the processes described by this study may be a good proxy for shoreline dynamics in marine and freshwater water bodies near river deltas before widespread historical deforestation and wood removal along major rivers