No abstract

Modern sedimentary processes were studied in Kluane Lake, Yukon Territory, to determine the spatial and temporal patterns of sediment distribution in a large, dynamic, glacier-fed lake. Data from a river monitoring station, moored instruments, sediment traps, and water-column profiles in the lake were used to document lacustrine sedimentary processes in 2006 and 2007. During the peak melt season, the suspended sediment concentration of Slims River is weakly dependent on river discharge and can reach up to 5 g L–1, although a diurnal range between 1 and 2 g L–1 is more commonly observed. The high suspended sediment load in the river generates continuous, diurnally fluctuating turbidity currents in Kluane Lake with maximum velocities up to 0.6 m s–1. During times of peak flow, variations in velocity can be traced to beyond 4 km from the river mouth. The vertical concentration profiles, mass accumulation rates, and suspended sediment loads show distinctive longitudinal variations; the highest rate of accumulation occurs ∼1 km from the point of inflow, which is concurrent with a distinct change in flow structure. Diurnal laminations are apparent in sediment traps close to the point of inflow and can be directly linked to variations in current velocity; however, these laminations do not occur consistently over space or time. These results suggest that long-term measurement records of lacustrine turbidity currents provide valuable insights regarding the multiple scales of environmental variability and have important implications for paleoenvironmental reconstruction using lacustrine sediments.

A 4AE7 km 2 field of sediment waves occurs in front of the Slims River delta in Kluane Lake, the largest lake in the Yukon Territory. Slims River heads in the Kaskawulsh Glacier, part of the St Elias Ice Field and discharges up to 400 m 3 s )1 of water with suspended sediment concentrations of up to 7 g l )1 . The 19 km long sandur of Slims River was created in the past 400 years since Kaskawulsh Glacier advanced and dammed the lake and the sandur has advanced into Kluane Lake at an average rate of 48 m a )1 . However, this rate is decreasing as flow is diverted from Slims River because of the retreat of the Kaskawulsh Glacier. The sandur and a road constructed on the delta remove coarse-grained sediment, so the river delivers dominantly mud to the lake. Inflow during summer generates quasi-continuous turbidity currents with velocities up to 0AE6 m s )1 . The front of the delta consists of a plane surface sloping lakeward at 0AE0188 (1AE08°). A field of sediment waves averaging 130 m in length and 2AE3 m in amplitude has developed on this surface. Slopes on the waves vary from )0AE067 ()3AE83°, i.e. sloping in the opposite direction to the regional slope) to 0AE135 (7AE69°). The internal structure of the sediment waves, as documented by seismic profiling, shows that sedimentation on the stoss portion of the wave averages 2AE7 times that on the lee portion. Rates of sediment accumulation in the wave field are about 0AE3 m a )1 , so these lacustrine waves have formed in a much shorter period of time (less than 200 years) and are advancing upslope towards the delta much more quickly (1 to 2 m a )1 ) than typical marine sediment waves. These waves formed on the flat surface of the lake floor, apparently in the absence of pre-existing forms, and they are altered and destroyed as the wave field advances and the characteristics of the turbidity currents change.

This article provides key questions to consider when planning and operating a small stream hydrometric station. Office planning components include defining hydrometric monitoring objectives; the availability of hydrometric expertise; resource availability; safety plans and standard operating procedures; equipment availability (hydrometric station installation and streamflow measurement); sampling frequency and data availability; permissions and permitting requirements; data processing, access, and archiving; and metadata requirements. Key parts of field-based hydrometric planning include site safety; site accessibility; flow variability; channel control features; flow containment, diversions and additions; low flow considerations; high flow considerations; flow measurement challenges in small streams; benchmarks and survey criteria; and public safety and vandalism. Theoverall  goal of the article is to help non-professionals collect better hydrometric data and to highlight the varied planning aspects of typical hydrometric installations and operations.