Flow and sediment dynamics in river channels

点击翻译按钮获取中文摘要

This research proposal deals with various aspects of flow and sediment dynamics in alluvial and bedrock channels. Emphasis will be placed on (i) river morphology at the scale of riffles and pools in coarse-grained channels, (ii) field based measurements of flow characteristics across the ripple-dune transition at a field site in a sand-bed river, and (iii) erosion of rockbed streams in southern Ontario.  Systematic field studies of riffle-pool units need to be undertaken with a goal to achieve a more complete characterization of turbulent flow fields above such units. Computer simulations of both bed morphology and flow characteristics along riffle-pool units will also be undertaken. One-dimensional series of bed elevations will be simulated from autoregressive models and flow characteristics along such sequences from simulation programs such HEC-RAS (US Army Corps of Engineers). Moreover, further questions on bedform transitions in sand-bed rivers will be addressed in a field-based setting. In particular, emphasis will be placed on changes in flow resistance and bedload transport rates as the transition from ripples to dunes takes place. This will be achieved along a field site located on a tributary of the Ganaraska river (southern Ontario). Finally, some river reaches in southern Ontario are bedrock channels (sedimentary rocks). These bedrock channels are dominated by relatively flat sedimentary rock fragments. The evolution of rockbed streams is controlled in part by the characteristics of the exposed bedrock surfaces and how easily rock fragments can be eroded. Little is know, however, on the erodibility of these fragments. Both field and laboratory experiments will be conducted to further enhance our knowledge of flow and sediment transport processes along bedrock-controlled river reaches in southern Ontario. This program of research will contribute significantly to our knowledge of flow and sediment dynamics in both alluvial and bedrock channels. Locally, the proposed program of research will enhance our understanding of erosional problems and channel evolution along bedrock-controlled urban streams