The role of fire in coastal dune geomorphology
thesisposted on 2022-03-28, 10:23 authored by Samuel Joel Shumack
After disturbance to protective covering, vegetated sand dunes may become bare and mobile. This thesis addresses the hypothesis that fire is a disturbance which plays a role in de-stabilising coastal dunes. Firstly, we conducted a regional scale remote sensing analysis of Landsat Thematic Mapper, Enhanced Thematic Mapper Plus, and Operational Land Imager data on 31 fire-scars on coastal dunes in Western Australia (WA). We used the Normalised Difference Vegetation Index to assess medium-to-long term vegetation recovery and maximum-likelihood image classification to monitor substantial changes in bare sand area. Secondly, we surveyed recently burnt coastal dunes near Esperance to characterise the disturbance to the dunes' protective covering in terms of remnant vegetation structure, wind flow, surface characteristics, aeolian activity, and regeneration. Results suggested that a) no active dunes were initiated by 30 fires over 28 years; b) native dune vegetation regenerates well after fires, particularly within six months; c) burnt vegetation allows wind to impact the surface with minimal obstruction, but may not allow the same topographic acceleration seen on active dunes; d) remnant ground cover inhibits post-fire sand movement; and e) complex interactions between burn severity, seedbank distribution and post-fire precipitation affect regeneration, and may prolong surface exposure to wind.