Decadal-scale morphological adjustment of a lowland tropical river

Dingle, E. H., Paringit, E. C., Tolentino, P. L.M., Williams, R. D. , Hoey, T. B. , Barrett, B. , Long, H., Smiley, C. and Stott, E. (2019) Decadal-scale morphological adjustment of a lowland tropical river. Geomorphology, 333, pp. 30-42. (doi: 10.1016/j.geomorph.2019.01.022)

Abstract

Compared with temperate regions, much less is known about the dynamics of tropical river systems. Tropical rivers are typically characterised by pronounced seasonal changes in precipitation, large sediment loads and high rates of lateral channel migration across often very low-gradient and densely populated floodplains. Understanding the controls on channel migration or change is integral to our ability to fully predict and build resilience against flood risk and wider river-related hazards. Here, we analyse channel and confluence migration over the last ~40 years along a ~85 km reach of the Cagayan River and one of its tributaries, the Pinacanauan de Ilagan (Luzon, Philippines) using optical satellite imagery captured during this period. Combining this with spatial variations in channel pattern, valley width and new bed material grain size data, we demonstrate that sediment transport and deposition are key drivers of the observed tropical channel morphodynamics in this region. The high sediment supply generated in the catchment headwaters (by mass-wasting of hillslopes triggered especially in typhoons) results in high aggradation rates and channel widening on the lower gradient alluvial plain. We suggest that this aggradation enhances local confluence and lateral channel migration rates, which can reach >300 m per decade, and that lateral migration rates of tropical rivers are typically greater than those of temperate rivers. Channel morphodynamics have implications for how to best manage these types of tropical river systems, where hard bank protection structures may result in a complex geomorphic response and flood risk mapping may need to include assessment of sensitivity to varying channel position and topography.

• Item Type: Articles
• Additional Information: This research was funded by the Scottish Funding Council through the University of Glasgow's Small Grants Fund [SFC-AN-12-2017].
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Long, Dr Hazel and Barrett, Dr Brian and Stott, Eilidh and Dingle, Miss Elizabeth and Hoey, Professor Trevor and Smiley, Miss Crystal and Williams, Professor Richard
• Authors: Dingle, E. H., Paringit, E. C., Tolentino, P. L.M., Williams, R. D., Hoey, T. B., Barrett, B., Long, H., Smiley, C., and Stott, E.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Geomorphology
• Publisher: Elsevier
• ISSN: 0169-555X
• ISSN (Online): 1872-695X
• Published Online: 20 February 2019
• Copyright Holders: Copyright © 2019 Elsevier
• First Published: First published in Geomorphology 333:30-42
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher