Modes of response of a gravel bed river to meander straightening: The case of the Sainte‐Marguerite River, Saguenay Region, Quebec, Canada

Abstract

[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.

Shrinkage of shrub forest and recovery of mire ecosystem by river restoration in northern Japan

“…The estimated annual flux of SS in Kucyoro River inflowing to the mire is about 3000 m 3 /year (Table 4), which is in the range of the previous studies 2440 m 3 / year (Ministry of Environment, 2004) to 7400 m 3 /year (Nakamura, 2003). The simulation results without changing the land cover in the catchment also indicate that annual-averaged sediment load into the mire may decrease about 10% at the downstream of restoration area in the future (Table 4), which may slow down slightly the elevation change in the mire by the sediment aggradation (Brookes, 1985;Talbot and Lapointe, 2002). This may also promote the increase of the groundwater level relative to ground surface and attribute to the relaxation of drying in the mire.…”

“…5B), where there is a complicated mechanism of linkage between surface, unsaturated, and saturated waters. This suggests that the river restoration will also cause the decreased sedimentation and less flooding downstream (Talbot and Lapointe, 2002). This restoration also affects the increases of groundwater level around the mire (Fig.…”

Forecasting Environmental Responses to Restoration of Rivers Used as Log Floatways: An Interdisciplinary Challenge

“…Such changes cause the channel to adjust to a new equilibrium, or sometimes a state of disequilibrium (Brookes 1988;Knighton 1998;Surian and Rinaldi 2003). Straightened reaches usually experience an increase in shear stress and the capacity to transport bed material, leading to erosion and degradation of the channel bed, destruction of pool-riffle variability, and increased sedimentation and flooding downstream (Yearke 1971;Brookes 1985;Wyzga 2001;but see Petts 1984;Dietrich and others 1989;Talbot and Lapointe 2002). Although much of the channel work was conducted in rapids, most pristine rapids in the Swedish rivers were relatively gently-sloping with plenty of fine material available in sections with less turbulent flow, such as in backwaters and downstream of boulders.…”

“…As rapids and fast-flowing river reaches became channelized and dredged, river forms that had evolved over thousands of years changed abruptly. Geomorphic effects of river channelization include a reduced channel roughness, shortened flow path distances and steepened slopes (Talbot and Lapointe 2002). Such changes cause the channel to adjust to a new equilibrium, or sometimes a state of disequilibrium (Brookes 1988;Knighton 1998;Surian and Rinaldi 2003).…”

Simulation of hydrologic and geomorphic changes affecting a shrinking mire

“…Previous studies investigating the responses to river channel straightening and rectification report increased sedimentation and flooding downstream (Brookes, 1985;Schilling and Wolter, 2000;Talbot and Lapointe, 2002). In the Kushiro Mire, this has led to a drying of the mire (Nakamura et al, 1997;Nakayama and Watanabe, 2004).…”