Spatial patterns and drivers of floodplain change in the Squamish River, a dynamic gravel bed river

The geomorphic interplay between river channels and their floodplains is important for human society and natural ecosystems. Alluvial floodplains have long been ideal locations for human settlement. Thus, for as long as humans have lived along rivers, flooding and channel erosion have posed a hazard to their settlements. As a result, humans have often sought to restrict the natural river-floodplain interactions, including inundation and erosional-depositional processes, and engineer rivers to allow development of floodplains. These actions have been detrimental to floodplain ecology. Unaltered river floodplains are biologically diverse and highly productive ecosystems. They contain a diverse array of habitats that are important for the survival of aquatic, amphibious, and terrestrial organisms. In order to restore floodplain functions, we need to know more about spatial patterns and drivers of floodplain change. This thesis examines the spatial patterns and drivers of floodplain dynamics in the Squamish River, in southern British Columbia, Canada, between 2009 and 2019. Patterns and magnitudes of floodplain construction and erosion were identified and measured from annual remotely-sensed data from Planet.com. The area of interest was classified into water, sediment, and vegetation using a simple but effective classification based on the Normalized Difference Vegetation Index (NDVI). Change was quantified by comparing each year with the next using the Change Detection Wizard in ArcGIS Pro. The effect of three drivers of floodplain change – channel slope, valley confinement, and sediment supply – were examined with regard to rates of floodplain construction and erosion. The calculated rates of change in the Squamish River were in the range of 0.9 m – 13.4 m per year for construction and 1.7 – 15 m per year for erosion. However, no clear driver emerged as the specific cause of the floodplain change; instead, channel and floodplain dynamics seem to be driven by the complicated interplay of multiple limiting factors including channel slope, valley width, and sediment supply, as well as by human interventions and floodplain vegetation.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Geography and GIS

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Allen, Emily Elizabeth

Contributors dc:contributor

• Cienciała, Piotr P

• Floodplain
• Channel Change
• Gravel Bed River
• Geomorphology
• British Columbia
• Erosion
• Deposition

Statement dc:rights

• Copyright 2023 Emily E. Allen

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/122052

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F122052