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A spatio-temporal analysis of sediment sources in the Caraulun catchment, East Timor

Rouwenhorst, Juno (2013). A spatio-temporal analysis of sediment sources in the Caraulun catchment, East Timor. PhD Thesis, Charles Darwin University.

Document type: Thesis
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Author Rouwenhorst, Juno
Title A spatio-temporal analysis of sediment sources in the Caraulun catchment, East Timor
Institution Charles Darwin University
Publication Date 2013
Thesis Type PhD
Supervisor Boggs, Guy
Wasson, Bob
Pearson, Diane
Abstract Throughout East Timor’s mountainous regions, high sediment loads are causing rivers to aggrade, which is leading to increases in the severity of flooding. Annually, human lives, livestock, infrastructure, and fertile farm land are lost during flood events. The first step towards management of this situation is to determine the sources of sediment which is causing the aggradation of the river channels. Consequently, three types of erosion thought to be main sources of sediment in the Caraulun River are evaluated. Sheet erosion, landsliding, and river bank erosion are analysed with regard to their spatial distribution and temporal changes in estimated sediment volumes.

Methods are based on a combination of remote sensing, field work, and geographic information systems (GIS) analysis techniques. Vegetation cover mapped from Landsat 5 TM imagery from 1986, 1996, and 2006 forms the foundation for further analyses, and is linked with fieldwork, RUSLE modelling, slope threshold models, and change analysis techniques to determine the spatial distribution and net sediment loss associated with sheet erosion, landslides and bank erosion.

A sediment budget focussing on sediment sources estimates a total denudation rate (DR) of 2.9±0.5 mm/yr for the Caraulun catchment between 1986 and 2006, with landsliding being the major source of sediment. The estimated mean DR from landsliding for the period is 1.4±0.3 mm/yr (assuming a sediment delivery rate, SDR, to channels of 90%) of which 0.4±0.05 mm/yr is thought to be due to earthquakes. The mean DR from bank erosion is estimated to be 1.0±0.03 mm/yr, and mean DRs from sheet erosion range from 0.2±0.02 mm/yr in the lower catchment to 1.7±0.07 mm/yr in the upper catchment, with an average for the whole catchment of 0.5±0.2 mm/yr (60% SDR) for 1986-2006. Future work should include research into sediment sinks, such as the floodplains, and transport processes to complete the sediment budget and to improve catchment management.

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