Thursday 20th
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.
