Wind‐forced seiche events on Great Slave Lake: hydrologic implications for the Slave River Delta, NWT, Canada

Abstract

Abstract:A limited amount of research has focused on northern lacustrine deltas and the impacts of basin processes prevalent at these deltas. Wind-forced seiche events have received little focus in deltaic studies. The Slave River Delta, located on the south shore of Great Slave Lake (GSL), NWT, is an ideal environment to study the prevalence of wind-forced seiche events and the impact of seiche events on the hydrodynamics of the delta. This paper presents an historical analysis of seiche activity on GSL and the effect of seiches on water levels of the Slave River Delta. The seasonality, frequency, and magnitude of seiche events on the lake are quantified. A description of the wind characteristics that force these events is included. The radial distributary pattern of the delta suggests that water level response to seiche events within the delta may be particularly complex. Hydrologic data from delta distributaries illustrate the temporal and spatial dynamics of seiche response. During the open-water season, seiche response in the delta is affected by the seasonal hydrograph of the Slave River and wind conditions. Spatially, the slope of delta distributaries governs seiche response. Responses are most similar among zones in the delta rather than among different distributaries.

Climate Change, Flow Regulation and Land-Use Effects on the Hydrology of the Peace-Athabasca-Slave System; Findings from the Northern Rivers Ecosystem Initiative

“…Seiches (on a north-south axis) on GSL typically begin in mid-July and continue until freeze-up. Seiches greater than 0.05 m occur approximately 10-15 times per year with most events producing water level increases near the SRD perimeter of 0.05-0.09 m. However, larger seiches do occur each year, with magnitudes as great as 0.4 m. Seiche set-up events at the delta are typically caused by northwesterly winds (85% of all studied events), whereas southeastern winds force seiche setdown events (68% of all studied events; Gardner, 2002;Gardner et al, 2006). Wind direction driving the seiche events can produce a variable response in the water slopes of distributary channels.…”

“…These included assessing the potential for lake-river interactions, changes in morphology of the delta over time, and possible extremes in water levels as produced by lake seiche events (defined as a wind-forced surface water set-up and set-down). Details are provided in Gardner (2002) and Gardner et al (2006). 3.9.1.…”

“…Small seiche events affect distributary water levels in the outer delta and mid-delta, large seiche events affect the entire modern delta. From Gardner et al (2006).…”

Driftcretions: The legacy impacts of driftwood on shoreline morphology

“…Driftwood becomes a driftcretion after it is disconnected from active lakeshore processes and hydraulic forces and subsequently vegetated. Disconnection occurs mechanically when lake level fluctuations from ice, storm waves, or large seiches (lake tsunamis [see Gardner et al, 2006]), push or strand large piles of driftwood farther inland than can be reworked by lake processes before vegetation establishment. Disconnection can also occur when driftwood and shoreline grasses facilitate increased local sedimentation, eventually decreasing local lake depth enough that pioneer woody species like willow, alder, and poplar can grow.…”

“…Thus, volume and mass estimates reflect only a half century of accumulation. [Gardner et al, 2006], lake surface currents [León et al, 2007], and Slave River delta progradation positions [Vanderburgh and Smith, 1988] were adapted from previous literature.…”