[1] In the 1960s, extensive meander straightening (rectification) was conducted along 8 km of the Sainte-Marguerite River to facilitate highway construction along the valley bottom.Comparison of long profiles and data on bed pavement caliber from the current river channel and the man-made oxbows sheds light on the multifaceted responses to this anthropogenic perturbation of the river over the last 4 decades: (1) reprofiling consisting of 1 m of bed incision in the upper 4 km coupled with 2 m of bed aggradation in the lower 2 km of the straightened reach; (2) a doubling of the caliber of bed pavement in the zone of maximum degradation; (3) regrowth of three meanders within the reach, increasing its length by 7% (400 m); and (4) net input of 4 Â 10 4 m 3 of valley-side sediment from channel erosion into three terraces. Hydraulic and sediment transport reconstructions indicate that reprofiling and pavement coarsening over nearly 4 decades equally contributed to transport reequilibration along the reach, while meander regrowth and lateral sediment inputs from terraces played minor roles.

[1] Artificial meander straightening (rectification) was conducted in the early 1960s along the Sainte-Marguerite River, Canada, in order to facilitate highway construction along the valley. Previous studies [Talbot and Lapointe, 2002] confirm that vertical reprofiling, coupled with pavement coarsening in the degrading reach, were the main responses counteracting the disequilibrium in gravel transport rates triggered at rectification of this system. Numerical simulations, using SEDROUT2.0, a one-dimensional hydraulic and sediment transport model, and validated against the observed channel response, show the important role played by an advancing wave of pavement coarsening down the rectified reach in modulating the bed degradation response. Simulations extending into the future reveal an asymptotically slowing approach to equilibrium in the middle of the 21st century, with a response half-time of the order of 10 years. In near-threshold gravel bed systems like the Sainte-Marguerite River, pavement coarsening after rectification buffers the system against extreme degradation. Most significantly for watershed management, this also appears to severely limit the extent of propagation of degradation upstream of the rectification.

This paper presents an evaluation of the feasibility and the reliability of a visual characterization technique for gravelcobble river bed surface substrate. Based on principal axis regressions, using phi scale (f), comparisons of visual estimation and grid sampling techniques show that useful predictive relations (R 2 = 0Á78-0Á88) exist between visual estimates of the surface d 16 This visual characterization allows effective detailed mapping of spatial patterns in substrate size distribution along extensive reaches of gravel-bed rivers. The technique can be very useful in creating terrain models for various geomorphological, hydrological and biological applications such as the determination of entrainment thresholds, hydraulic roughness and substrate suitability for benthic insects or salmonid habitat.

A scientific scenario paper was prepared ahead of the Gulf of Maine (GOM) 2050 International Symposium to review and summarize possible weather-related and sea-level changes within the GOM as a result of climate change. It is projected that the GOM will experience warming temperatures, continued sea-level rise, and changes to storm characteristics and related elements such as precipitation and waves in the intermediate term, by approximately 2050. Coastal communities within the GOM region are particularly vulnerable to the anticipated impacts of climate change. This article aims to provide context on some of the consequential impacts that may occur from the changes projected within the area.

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