Channel geomorphology differences between stream reaches with grass- or tree-dominated riparian vegetation in southern Manitoba

• Main Authors: Sanjayan Satchithanantham, Henry F. Wilson, Patsy Michiels, Melanie Dubois, Sheng Li, Alexander J. Koiter
• Format: Article
• Language: English
• Published: Canadian Science Publishing 2019-07-01
• Series: FACETS
• Subjects: riparian vegetation; stream channel geomorphology; Prairie streams; channel stability
• Online Access: https://www.facetsjournal.com/doi/10.1139/facets-2018-0036

Removal of trees for pasture or crop production is common along the stream reaches in the Canadian Prairies, resulting in a patchwork of forested and nonforest riparian vegetation along most streams. The effect of vegetation type on channel geomorphology and potential to influence sediment dynamics was studied using eight paired reaches (forested and nonforest) within agricultural watersheds in southern Manitoba, Canada. High potential for bank erosion was observed at all sites (bank erosion hazard index scores), but Pfankuch channel stability scores were significantly higher for forested reaches compared with nonforested reaches. Furthermore, forested reaches had higher width to depth ratios, but flood-prone widths did not differ significantly, resulting in lower entrenchment ratios. Reduced channel width and cross-sectional area in nonforested reaches created an overall reduction of in-stream habitat, increased velocity, and increased potential for exceedance of channel capacity and floodplain access during high-flow events. Channel widening in response to riparian afforestation efforts has been observed in a variety of other locations globally and the results of this study suggest that widening with afforestation can still be anticipated in this region where stream gradients are low, hydrology is dominated by snowmelt, and forest cover is minimal.