River response and climate change in the Wet Tropics, northeast Queensland Australia

Abstract

An improved understanding of the relationship between climate change and river response is critical for predicting future trajectories of fluvial landforms. This is particularly important with climate change projections showing an increase in extreme events such as floods and cyclones. In Australia and internationally, a valuable record of river response has been developed from the morphologic and sedimentologic archives of river terraces and floodplains, mainly in temperate regions. These studies reveal the key role of climate over timescales ranging from 100 kyr glacial/interglacial cycles through to decadal cycles driven by the El Niño Southern Oscillation (ENSO). However, the understanding of fluvial records in the humid (wet) tropics is comparatively poor despite these regions being geomorphic hotspots for catastrophic change. The relevance of key geomorphic concepts to wet tropical rivers is largely unknown and therefore the knowledge gained from studying these settings is invaluable. The overarching aim of this thesis is to characterise the nature of regional river response and its relationship to climatic change in the Wet Tropics of tropical northeast Queensland, Australia. Chapters 2 to 6 explore the various aspects of this research question and an overall synthesis of the thesis key findings and future research priorities is presented in Chapter 7.Chapter 2 presents the research on terrace distribution and chronostratigraphic characteristics to provide the overall spatial context of river landforms across five catchments. Two terraces are correlated and mapped across the study area, while the terrace chronology details two periods of aggradation-incision that post-date the Last Glacial Maximum. Explanations for spatial differences in terrace preservation are explored using a range of catchment force-resistance variables with the results underpinning a new conceptual model of terrace types and preservation processes. Author A. Sharma Data collection (sediment dating data in Table 3) (10%).v i i Contributions by others to the thesisChapter 2: Hughes, K., Croke, J., Bartley, R., Thompson, C., Sharma, A.Alluvial terrace preservation in the Wet Tropics, northeast Queensland, Australia. KH was responsible for 70% of conception and design, 90% of data collection, 80% of data analysis and interpretation, and 60% of writing and editing. JC was responsible for 30% of conception and design, 20% of data analysis and interpretation, and 20% of writing and editing. RB was responsible for 10% of writing and editing. CT was responsible for 10% of data analysis and interpretation and 10% of writing and editing. AS was responsible for 10% of data collection.Chapter 3: Hughes, K., Croke, J., Thompson, C., Sharma, A., K. Tilly.KH was responsible for 70% of conception and design, 90% of data collection, 80% of data analysis and interpretation, and 75% of writing and editing. JC was responsible for 30% of conception and design, 10% of data analysis and interpretation, and 20% of writing and editing. CT was respon...

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