Avoca valley, South Island, New Zealand.

Alluvial fan evolution over contemporary and Holocene timescales

Andrew has collaborated with Tim Quine to investigate controls on alluvial fan evolution using field, numerical modelling and laboratory experimentation.

Field studies have been carried out in the Avoca valley, South Island, New Zealand as part of a recent NERC funded project, that focused on the relationships between fan evolution and post-glacial environmental change.

Fan responses to environmental change have been quantified using a range of numerical models, including both two-dimensional cellular approaches (below left) and quasi-two-dimensional approaches that simulate fan terrace sequences at a series of cross-sections down the fan profile (below right).

These simulations have provided new insight into the role of autogenic feedbacks as a control on fan evolution, and have demonstrated that fan entrenchment can be promoted by flow channelisation due to a decline in fan aggradation rate as the fan becomes coupled to the larger river channel in the main valley floor.

To help evaluate these models and to investigate fan construction and entrenchment under controlled laboratory conditions we have conducted experimental work in a custom built sedimentation basin within the Exeter Sediment Research Facility. This experimental work was undertaken by PhD student Lucy Clarke.

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