GED Seminar Series: Fan-deltas of the Western Coromandel Peninsula: an integrated study of fluvial dynamics, delta building and marine deposition

Thursday 20^th March, 4-5pm

Cotton Seminar Room 304, Kelburn Campus

Victoria University of Wellington

speaker:

     Dr Jon Tunnicliffe

      School of Environment, University of Auckland 

Residential development and recreational use along the western coast of the Coromandel Peninsula is largely concentrated upon six major coarse-grained fan-deltas. These landforms preserve a record of long-term adjustments amongst fluvial sedimentation from floods and debris flows, long-shore and cross-shore coastal processes, and sea-level fluctuations throughout the Holocene. We have employed a combination of geophysical sounding, sediment tracing, and sonic drilling to develop a chronology and stratigraphic record of adjustment and changes in river base-level over the last 10,000 years. The record is consistent with earlier studies of the Firth, most notably the chronology developed on the chenier plain of the western coast. The record clearly reveals the timing of major geomorphic events, including the onset of marine sedimentation following sea incursion of the Firth at roughly 6,500 years BP. The semi-enclosed Firth effectively provides a ‘sink’ term for a Holocene fluvial-coastal sediment budget, and a reasonable proxy for long-term sediment yield from these rivers.

In this talk, we consider the ‘sediment delivery problem’ – how to leverage long-term records of sedimentation such as this one to develop a sediment budget that takes explicit account of sediment storage, abrasion, and changes in system configuration, within the fluvial and coastal systems. Records such as these are important for calibrating our models of sediment delivery, and for providing guidance to managers and engineers who are working to minimize risk in these important and sensitive coastal environments.