Channel Patterns of the Grand River in Southern Ontario, Canada—an Example in a Post-glaciated Landscape

Abstract

River channel patterns are recognised as important features associated with the dynamic system of stream flow. This study, examines different channel patterns and the associated geometric variables of a section of the Grand Channel. It also suggests different inter-relationships of the geometric variables for different channel patterns. Comparisons are made between the channel characteristics and other experimental, theoretical and field examples discussed in this literature review.

The study was carried out in a section of the Grand River between Kitchener and Paris. This section was further divided into an upper reach, between Kitchener and Cambridge, and a lower reach, between Cambridge and Paris.

Descriptive statistics, map and aerial photograph interpretation, and statistical correlation method are employed in teh analysis. In particular, varied bed topography, variation of the width-depth ratio and floodplain confinement serve to indicate the differences between this section of the stream and the results found in alluvial streams with low gradients.

This study has found it useful to differentiate channel patterns as straight, meandering or braiding in a general way. The upper reach is pseudomeandering and has high topographic sinuosity index. The thalweg slope is flatter than in meandering patterns. The floodplain is wide and vegetated, thus reducing the erosional capability of the reach. However, some portions of the reach are incising and irregular bends are common.

The lower reach is straight, and braided in some portions, and has rapids. The thalweg slope is steeper than the upper reach showing nickpoints in some sections. The high rate of increase in depth compared to wide increases the erodability of the stream. Most of the reach is incising.

Interrelationships between the geometric parameters between the study reaches are indicators of differences in channel patterns. The lower reach has higher correlation coefficients than the upper reach, although the adjustment of width is more significant in the upper reach than the lower reach. On the other hand, depth is more significant in the lower reach than the upper reach.

Thalweg slope is applied as an independent variable. The use of channel symmetry as a technique in channel pattern investigation compares well with the application of the sinuosity ratio. Topographic sinuosity index and valley symmetry have served to explain some of the impact of the inherited slope on channel pattern development.