The influence of the macroalgal mats of Enteromorpha intestinalis on near-bed current velocities and sediment dynamics was quantified by placing relatively undisturbed cored sediments in annular flumes. Density-dependent relationships were established for E. intestinalis densities; these ranged from 10 to 60% cover when air-exposed (biomass of 4 to 40 g ash-free dry wt m-2) and in comparison with bare sediment (0% cover). There was a significant increase in friction drag with increasing E. intestinalis biomass and percent cover, ranging from a mean 18% reduction in current velocities at 10% cover to 56% reduction at 60% cover. The net result of a reduction in currents (depth-averaged between 1 to 12 cm above the bed) and the physical protection of the bed by Enteromorpha was a marked reduction in sediment erosion of 60% at 10% cover to 90% at 60% cover. The presence of E. intestinalis also significantly enhanced sediment deposition measured as a flux from the water column to the bed. At 60% cover the deposition rate was 48% higher than on bare sediment during the first 30 min of slack water (< 0.05 m s-1). The results show that E. intestinalis has a marked influence on water flow over the bed and the flux of particulate material across the sediment-water interface.

No abstract

The characteristics of floodplains of major rivers are of interest to many shoreline communities due to issues related to flooding, water demand, and land use. Studies of the hydrogeological conditions within these environments can improve our understanding of these settings. The case study of the JV Industries and Fairway Landfill, located within the floodplain of the Fraser River, highlights the complex groundwater flow dynamics in such an environment. In particular, the study examined the potential for substantial changes to both groundwater flow and groundwater quality during or immediately following the spring freshet due to the presence of permeable, extensive, and hydraulically well-connected floodplain deposits. During spring and early summer, groundwater flow across the landfill is controlled primarily by the Fraser River freshet and the direction of flow varies spatially across the site. During the winter, groundwater flow is controlled primarily by regional topography and is directed to the southwest towards the nearest topographic depression, the remnant Coco-oppelo Slough. In the intervening months, the flow directions are transitional between the winter and spring – early summer flow patterns. The changes in the groundwater flow patterns were inferred to temporally affect the groundwater quality downgradient of the landfill.

Numerical simulations of the Fault Lake Tailings were conducted to assess the long-term impact of AMD-generation on downgradient receptors. The effects of impoundment geometry, contrasting permeability, water content, and mineralogy of tailings and native sediments were considered. Simulation results suggest that over a time period of 1,000 years only the top three meters of tailings become oxidized and that AMD is preferentially released at the periphery of the impoundment. Although the permeability of the tailings is lower than that of the aquifer and groundwater flow is deflected around the deep saturated tailings mass, AMD is not inhibited from percolating into the aquifer, because the bulk of the tailings are located within the vadose zone. The carbonate content of the underlying material likely provides sufficient buffering capacity to attenuate most metals and neutralize pH over the long-term.