Influence of Meander Confinement on Hydro-Morphodynamics of a Cohesive Meandering Channel

Abstract

Despite several decades of intensive study of the morphological changes in meandering rivers, less attention has been paid to confined meanders. This paper studies the hydromorphodynamics of two adjacent sub-reaches of a meandering creek, located in the City of Ottawa, Canada. Both of these sub-reaches are meandering channels with cohesive bed and banks, but one is confined by a railway embankment. Field reconnaissance revealed distinct differences in the morphological characteristics of the sub-reaches. To further study this, channel migration and morphological changes of the channel banks along each of these sub-reaches were analyzed by comparing the historical aerial photography (2004, 2014), light detection and ranging (LIDAR) data (2006), bathymetric data obtained from a total station survey (2014), and field examination. Moreover, two different spatially intensive acoustic Doppler current profiler (ADCP) surveys were conducted in the study area to find the linkage between the hydrodynamics and morphological changes in the two different sub-reaches. The unconfined sub-reach is shown to have a typical channel migration pattern with deposition on the inner bank and erosion on the outer bank of the meander bend. The confined sub-reach, on the other hand, experienced greater bank instabilities than the unconfined sub-reach. The average rate of bank retreat was 0.2 m/year in the confined sub-reach whereas it was lower (0.08 m/year) in the unconfined sampling reach. In the confined sub-reach, an irregular meandering pattern occurred by the evolution of a concave-bank bench, which was caused by reverse flow eddies. The sinuosity of the confined sub-reach decreased from 1.55 to 1.49 in the 10-year study period. The results of the present study demonstrate the physical mechanisms by which meander confinement can change the meandering pattern and morphological characteristics of a cohesive clay bed creek.

Fluvial geomorphic factors affecting liquefaction-induced lateral spreading

“…This percentage includes the bends that have tributary connections at the cut bank as this geomorphic complexity is not expected to have effect on the point bar deposits. Given the location of the Heathcote River, in close vicinity of the Port Hills (Figure 3), bend confinement could have altered typical downstream fining expected for simple meanders (Parsapour-Moghaddam and Rennie, 2018). Analogous to Hypothesis 1, addition of the Heathcote River data increases the variability of the results (Figure 7b).…”

“…H1, H2, H3, and H4), and it is the confinement of the Heathcote River by the Port Hills, which can affect river migration and subsequently the grain size trends (e.g. Grace, 2015; Parsapour-Moghaddam and Rennie, 2018). Additional observed geomorphic complexities include the considerable overlap between cut bank deposits and point bar deposits of adjacent river bends (i.e.…”

Analysis of Effects of Rough Strip Energy Dissipator on Hydraulic Property of Bend Flow

“…The water flow through a bend (i.e., the bend flow) is different from the straight flow. Due to the combined effect of inertial centrifugal forces and bend slope, uneven distribution of water depth at both banks, uneven crosssectional velocity distribution, and secondary flows may occur in curved spillways [4,7,8]. These complex flow patterns lead to sediment movement, riverbed evolution, and channel deformation [9].…”

On the Relationship between Experimental and Numerical Modelling of Gravel-Bed Channel Aggradation

“…River morphologic processes are among the most important agents that shape the Earth's surface. These phenomena have been extensively studied for decades due to a major relevance for a number of applications, such as watercourse management, design of hydraulic structures, land use planning, flood risk evaluation, water quality, and habitat creation (e.g., [1][2][3][4][5][6][7][8][9][10]). Stemming from ongoing research projects by the authors, this communication considers specifically the aggradation processes resulting from sediment overloading of an open channel, with a focus on situations relevant for mountainous environments.…”