Hydrologic control of waveforms on small meandering rivers

Abstract

Small river channels within the Humber Basin of Southern Ontario exhibit irregular meandering patterns; however, contemporary river hydrology appears capable of controlling the scale of regular waveform development. Recent changes in river planform are assessed through a bi-temporal comparison of channel planform using orthorectified aerial photography and statistical analysis of curvature series based on autocorrelation and spectral analysis. Calculated meander wavelengths are acceptable given traditional relationships between wavelength and mean annual flood discharge. It is also evident that changes in stream power are highly correlated with changes in the dominant wavelengths between channel reaches in this study. Gradual development of small scale waveforms following a rare hydrological and geomorphological event in 1954 further confirms that these forms can be attributed to the typical discharge regime. This paper argues that the scaling of wavelengths with discharge can be considered a strong factor controlling planform evolution on some small meandering river systems, despite manifest irregular planforms.

Hydrogeomorphic Scaling and Ecohydraulics for Designing Rescaled Channel and Floodplain Geometry in Regulated Gravel–Cobble Bed Rivers for Pacific Salmon Habitat

“…Vegetation, both woody and herbaceous, exerts a strong control on channel geometry through the alteration of bank strength from roots [101,102]. Generally the presence of vegetation tends to yield channels that are narrower and deeper than channels without vegetation [85].…”

“…Natural meanders and nested gravel bars are very complex [122], but the geometry of a single meander with two alternate gravel bars can most simply be described by wavelength and radius of curvature (Figure 5A). Most relationships express meander wavelength as a function of bankfull channel width [67,80], although bankfull cross-sectional area and depth [67], stream power [102], bed material composition and discharge [66,123] have also been used. A general equation for meander wavelength (λ m ) as a function of mean bankfull width (W b f ) is:…”

Fluvial geomorphology

“…Overall, changes tend to be localized and fit the bend theory of meanders, but with low-sensitivity reaches pinning the planform for longer periods in certain locations. Phillips and Robert (2007) assessed recent changes in river planform in the Humber Basin of Southern Ontario through a bitemporal comparison of channel planform using orthorectified aerial photography and statistical analysis of curvature series based on autocorrelation and spectral analysis. Their paper argues that the scaling of wavelengths with discharge can be considered a strong factor controlling planform evolution on some small meandering river systems, despite manifest irregular planforms.…”

A Simple Model for Estimating Future Channel Migration from Historical Aerial Photographs

“…Phillips and Robert (2007), Stephen et al (2002), Nanson and Hickin (1996), Hooke (1995) have used simple time step comparison and statistical analysis to estimate and describe meander migration and patterns from historical records. Manual overlay of historical maps or aerial photos for assessment of planform adjustment and for estimating meander migration have been developed by Briuad et al (2001) and Lagasse et al (2004).…”