Variable hillslope‐channel coupling and channel characteristics of forested mountain streams in glaciated landscapes. Issue 3 (13th November 2018)

• Record Type: Journal Article
• Authors: Hassan, Marwan A.; Bird, Stephen; Reid, David; Ferrer‐Boix, Carles; Hogan, Dan; Brardinoni, Francesco; Chartrand, Shawn
• Is Part Of: Earth surface processes and landforms. Volume 44:Issue 3(2019)
• Page Start: 736
• Page End: 751
• Publication Date: 2018-11-13
• Subjects: mountain streams -- hillslope–channel coupling -- hydraulic geometry -- wood -- landslides -- process domains -- channel classification -- divide breaching -- glacial history; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4527
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Channel morphology of forested, mountain streams in glaciated landscapes is regulated by a complex suite of processes, and remains difficult to predict. Here, we analyze models of channel geometry against a comprehensive field dataset collected in two previously glaciated basins in Haida Gwaii, B.C., to explore the influence of variable hillslope–channel coupling imposed by the glacial legacy on channel form. Our objective is to better understand the relation between hillslope–channel coupling and stream character within glaciated basins. We find that the glacial legacy on landscape structure is characterized by relatively large spatial variation in hillslope–channel coupling. Spatial differences in coupling influence the frequency and magnitude of coarse sediment and woody material delivery to the channel network. Analyses using a model for channel gradient and multiple models for width and depth show that hillslope–channel coupling and high wood loading induce deviations from standard downstream predictions for all three variables in the study basins. Examination of model residuals using Boosted Regression Trees and nine additional channel variables indicates that ~10 to ~40% of residual variance can be explained by logjam variables, ~15–40% by the degree of hillslope–channel coupling, and 10–20% by proximity to slope failures. These results indicate that channel classification systems incorporating hillslope–channel coupling, and, indirectly, the catchment glacial legacy, may present a more complete understanding of mountain channels. From these results, we propose a conceptual framework which describes the linkages between landscape history, hillslope–channel coupling, and channel form. © 2018 John Wiley & Sons, Ltd. Abstract : We investigate the influence of glacial history on hillslope‐channel coupling, channel geometry, and morphology in two forested mountain streams in coastal British Columbia. Glaciation of the catchments introduced variable patterns of hillslope–channel coupling, resulting in variability of hillslope sediment and wood input, channel morphology, and channel geometry. We evaluate observed channel geometry against models predicting width, depth, and slope, and results of statistically analyzing model residuals indicate that substantial variability can be explained by slope failure and logjam variables.