1. River Cross Sections and Bed Sediment Size Data

Supplementary Material

1. River cross sections and bed sediment size data

The Ells River originates in the Southeast slopes of the Birch Mountains in Alberta, Canada at an elevation of about 730 m. The river descends to an elevation of 230 m, and meanders through the boggy landscape of the lower reaches before joining the Athabasca River from the west. In this study, a 40 Km reach of the lower main stem of the Ells River is modelled. The modelled reach

(see Figure S1) is between two Regional Aquatics Monitoring Program’s (RAMP) Hydrometric stations: S45 and S14A (see website, http://www.ramp-alberta.org). The RAMP monitoring program was set up to collect baseline data to assess the impact of Oil-sands development in this region. These stations provided the upper and lower boundary conditions for the modelling study. The Ells River has a mean annual flow of 9 m3s-1 (Environment Canada 2011) and drains an area of 2450 km2 (Carson 1990). The River drains into a variety of different soil types ranging from non to exceedingly stony, loams to clay and is predominately formed on calcareous till with the exception of the many bogs surrounding the river (Alberta Environment 1982). The river cuts through the McMurray formation, which constitute the oil sands. This basin is only beginning to be deforested for the purposes of bitumen open pit mining and represents a relatively undisturbed basin at the present time.

The river cross sectional data and the bed sediment size data for the river reach were collected by

Environment Canada at the km markers in Figure S1 using survey methods (Leveling with a

Sokkia SDL50 electronic Level, relative to Temporary Bench Marks (TBM’s) set using a Sokkia

GSR2700ISX GNSS receiver system) and by visual bed observations along with the collection of cross-sectional bed grab samples for sizing. Bulk samples were dried and using a tower of stacked Tyler TM sieves and a shaker, the size distribution determined by gravimetric weighing. Visual observation of the river bed suggests that the bed is covered with cobbles, pebbles and gravel. Two cross-sections (one at 2 KM mark and the other at 40 KM mark) are shown in

Figures S3a and b respectively as examples. These figures depict the flow cross sectional shape, the water levels at the time of measurement and the depth average velocity distributions across the river cross sections. From these figures, we can see that the river is about 30 and 40 m wide at the upstream and downstream sections with average flow depths of 60 and 40 cm respectively.

Using these measurements, the flow cross-sectional areas were computed for these two sections as 12.5 m2 and 22.7 m2 respectively, and the discharges were calculated as 8.82 m3 s-1 and 12.50 m3 s-1. From the surveyed elevations an average bed slope of 0.0012 was calculated for the river reach which in turn gives the bed shear stresses for two sections as 4.76 Pa and 7.72 Pa respectively. From the flow rate and flow cross sectional area, the average flow velocities for the two sections were calculated as 0.71 m s-1 and 0.55 m s-1 respectively. Knowing the average velocity and bed shear stress, bed roughness parameters (Manning’s n) for the two sections were calculated as 0.027 and 0.043 respectively. From the survey data, input data files for MOBED and RIVFLOC models were prepared and the models were run for a range of flow rates in the river. Details of model runs are given in section 3.3 and 3.4.

2. Fine sediment transport characteristics data

The hydrophobic fine sediment transport characteristics data that were needed for the RIVFLOC model were obtained by collecting fine sediment samples and testing them in a rotating circular flume. Details of sample collection, testing of the samples in the rotating circular flume and the analysis of laboratory data are described below. 2a. Collection of fine sediment samples - Sediment-water mixture (800 L) from the river was collected from the Lower Ells River at section S14A (see Figure S1) using a specially designed inverted cone sediment sampler (Krishnappan, 2007). The sampler consists of an inverted cone fitted with a propeller to create sufficiently strong circulation inside the chamber to erode the surface drape of sediment, and a submersible pump that pushes the dislodged sediment and water mixture to a 1000 L polyethylene container. The sampler was deployed at several locations within the river. The sediment-water mixture was transported to the laboratory in a refrigerated transport truck.

2b. Testing of fine sediment in a rotating circular flume - Fine sediment samples were tested in a rotating circular flume housed at Environment Canada in Burlington, Ontario, Canada. Figure

S4 shows a sectional view of the flume schematically. The flume is 5.0 m in mean diameter,

0.30 m wide and 0.30 m deep and it rests on a rotating platform, which is 7.0 m in diameter. A counter rotating top cover (ring) fits just inside the flume (~ 1.5 mm gap on either side) and makes contact with the water surface within the flume. The maximum rotational speed of the flume and the ring is 3 rpm. The flows generated in the flume are close to two dimensional with a bed shear stress distribution across the width of the flume that is relatively uniform

(Krishnappan and Engel, 2004). The flume calibration results of Krishnappan and Engel (2004) were used to predict the relationship between the bed shear stress and the rotational speeds of the flume. A three dimensional hydrodynamic model (PHOENICS supplied by CHAM Ltd.,

London, UK) was used to compute the flow characteristics in the flume for different operational speeds of the flume and the ring assembly. River water was placed in the flume with a known amount of cohesive sediment sieved at 75 µm

(approximately 300 mg l-1). The sediment-water suspension was then thoroughly mixed in the flume first by mechanical mixing and then by rotating the flume and the lid at relatively high speeds (2.5 rpm for the lid and 2.0 rpm for the flume, which yielded a bed shear stress of 0.6 Pa) for 30 minutes. Following this mixing period, the flume speed was turned down to a lower shear stress and maintained at this shear stress for the duration of the experimental run. Shear stress values used in the flume were as follows: 0.005Pa, 0.028Pa, 0.072Pa and 0.134 Pa. During each deposition experiment with a particular shear stress level, sediment-water samples were withdrawn from the flume at five-minute intervals during the first hour of the test and every ten minutes thereafter until the completion of the test. Each time a sample was withdrawn, the volume removed was replaced by adding an equivalent amount of sediment-water mixture back into the flume in order to keep the water surface in contact with the lid all the time. A test was considered complete after the suspended sediment concentration remained nearly constant for about one hour (generally requiring eight hours for most runs). In order to investigate the effects of initial concentration on sediment deposition, a flume run at a shear stress of 0.028 Pa was also performed with an initial concentration of 600 mg l-1.

Sediment-water samples were analysed for concentrations of solids as well as for size distribution of the suspended flocs. The concentration was measured using a gravimetric method that consisted of filtering the sample (0.45 µm pre-weighed Millipore filter), and drying and weighing the residue. The size distribution of the suspended flocs was measured using a Laser particle Size Analyzer (CILASTM). Once a run was completed, the whole procedure was repeated for other bed shear stress levels. 3. Supplementary material references

Alberta Environment (1982) Soil inventory of the Alberta Oil Sands Environmental Research

Program Study Area (Report No. 122). Retrieved from:

http://sis.agr.gc.ca/cansis/publications/surveys/ab/ab42/ab42_report.pdf

Carson MA (1990) Evaluation of sediment data for the lower Athabasca River basin Alberta.

Calgary, Alberta: Water Resources Branch Inland Water Directorate, Environment Canada,

56 pp.

Environment Canada (EC) (2011) Lower Athabasca water quality monitoring plan: Phase 1.

(Catalogue No. En14-42/2011E-PDF). ISBN 978-1-100-18471-5 Retrieved from

http://www.ec.gc.ca/Content/8/A/1/8A1AB11A-1AA6-4E12-9373-

60CF8CF98C76/WQMP_ENG.pdf

Krishnappan BG (2007) Recent advances in basic and applied research on cohesive sediment

transport in aquatic systems. Can J Civil Eng 34:731-743

Krishnappan BG, Engel P (2004) Distribution of bed shear stress in rotating circular flume. J

Hydraul Eng, ASCE 130(4):324-331