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    Holocene sea-level change and estuary infill in North West Nelson, central New Zealand
    Kennedy, DM ; Risdon, B ; Woods, JLD (SAGE PUBLICATIONS LTD, 2021-11-21)
    The sedimentary sequences found within estuaries in the north west Nelson region of central New Zealand are investigated in order to quantify the timing of the end of the Post Glacial Marine Transgression. This region has been identified as being relatively stable in terms of vertical tectonic movement during the Holocene, but is yet to yield any reconstructions of eustatic sea level. In this study, we investigate the Holocene infill of a barrier estuary (Parapara Inlet) through sedimentological analysis and radiocarbon dating of 18 vibracores up to 4.2 m in length. It is found that the estuary infilled through a combination of lateral flood tide and fluvial delta progradation as well as vertical central basin infill. The central basin infilled at a consistent rate of 0.4 mm/year in both the mid (7.0–6.0 ka) and late-Holocene (2.5–1.5 ka). By the time of early human (Maori) settlement (c. 1 ka), the estuary surface was at low intertidal elevations with sediment being transported from the fluvial to tidal delta. A discernible change in sedimentation rates could not be associated with Maori settlement; however, infill rates increased to at least 12.5 mm/year in the past 150 years due hydraulic sluicing associated with mining. The sedimentary history of Parapara Inlet is compared to nearby Whanganui Inlet, d’Urville Island and Nelson to establish the character of regional Holocene sea level movement. It is found that relative sea level reached modern elevations between 8 and 7 ka in the region. The similarity between sea level curves for the end of the post glacial marine transgression (PMT) to other tectonically stable sites in northern New Zealand suggests that this curve can now be considered a true eustatic signal for the New Zealand archipelago.
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    sandpyper: A Python package for UAV-SfM beach volumetric and behavioural analysis
    Pucino, N ; Kennedy, D ; Ierodiaconou, D (The Open Journal, 2021-10-13)
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    The temporal and spatial scales of rocky coast geomorphology: a commentary
    Kennedy, DM ; Coombes, MA ; Mottershead, DN (WILEY, 2017-08-01)
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    Citizen science for monitoring seasonal-scale beach erosion and behaviour with aerial drones
    Pucino, N ; Kennedy, DM ; Carvalho, RC ; Allan, B ; Ierodiaconou, D (NATURE PORTFOLIO, 2021-02-16)
    Sandy beaches are highly dynamic systems which provide natural protection from the impact of waves to coastal communities. With coastal erosion hazards predicted to increase globally, data to inform decision making on erosion mitigation and adaptation strategies is becoming critical. However, multi-temporal topographic data over wide geographical areas is expensive and time consuming and often requires highly trained professionals. In this study we demonstrate a novel approach combining citizen science with low-cost unmanned aerial vehicles that reliably produces survey-grade morphological data able to model sediment dynamics from event to annual scales. The high-energy wave-dominated coast of south-eastern Australia, in Victoria, is used as a field laboratory to test the reliability of our protocol and develop a set of indices to study multi-scale erosional dynamics. We found that citizen scientists provide unbiased data as accurate as professional researchers. We then observed that open-ocean beaches mobilise three times as much sediment as embayed beaches and distinguished between slowed and accelerated erosional modes. The data was also able to assess the efficiency of sand nourishment for shore protection. Our citizen science protocol provides high quality monitoring capabilities, which although subject to important legislative preconditions, it is applicable in other parts of the world and transferable to other landscape systems where the understanding of sediment dynamics is critical for management of natural or anthropogenic processes.
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    Hourly to daily-scale microtopographic fluctuations of supratidal sandstone
    Yuan, R ; Kennedy, DM ; Stephenson, WJ (WILEY, 2018-12-01)
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    Wave hazards on microtidal shore platforms: testing the relationship between morphology and exposure
    Kennedy, DM ; Ierodiaconou, D ; Weir, A ; Brighton, B (SPRINGER, 2017-03-01)
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    Postglacial Fringing-Reef to Barrier-Reef conversion on Tahiti links Darwin's reef types
    Blanchon, P ; Granados-Corea, M ; Abbey, E ; Braga, JC ; Braithwaite, C ; Kennedy, DM ; Spencer, T ; Webster, JM ; Woodroffe, CD (NATURE PUBLISHING GROUP, 2014-05-21)
    In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs then atolls. Yet historically no transition between reef types has been discovered and they are widely considered to develop independently from antecedent foundations during glacio-eustatic sea-level rise. Here we reconstruct reef development from cores recovered by IODP Expedition 310 to Tahiti, and show that a fringing reef retreated upslope during postglacial sea-level rise and transformed into a barrier reef when it encountered a Pleistocene reef-flat platform. The reef became stranded on the platform edge, creating a lagoon that isolated it from coastal sediment and facilitated a switch to a faster-growing coral assemblage dominated by acroporids. The switch increased the reef's accretion rate, allowing it to keep pace with rising sea level, and transform into a barrier reef. This retreat mechanism not only links Darwin's reef types, but explains the re-occupation of reefs during Pleistocene glacio-eustacy.
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    The New Zealand Geographer reaches 75
    Bedford, R ; Kearns, R ; Kennedy, D ; Le Heron, R ; Longhurst, R ; Mansvelt, J ; Pawson, E ; Peace, R ; Roche, M (WILEY, 2020-07-03)
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    A first evaluation of the contribution of aeolian sand transport to lagoon island accretion in the Maldives
    Hilton, MJ ; Borrie, DR ; Konlechner, TM ; Wakes, SJ ; Lane, TP ; Kench, PS ; Kennedy, DM ; Aslam, M (Elsevier, 2019-08-01)
    Aeolian sedimentation and dune development have not been reported from coral atolls at equatorial latitudes. This study presents high-frequency measurements of incident and near surface wind flow and aeolian sand transport on a lagoon sand cay (Maaodegalaa) in the Maldives. Sonic anemometers and Wenglor™ particle counters were operated at 1 Hz for 8 days during the Iruvai monsoon in February 2018. Sand traps were deployed to estimate sand flux and island topography and vegetation cover were surveyed using UAV (un-manned aerial vehicle) photogrammetry and a laser level (in 2017 and 2018). Flow over beach scarps is 10 modelled using computational fluid dynamics. Maaodegalaa sand cay reaches just 0.9m above the highest spring high tides. Nebkha, between 0.10 and 0.40 m high, are widespread and are associated with Scaevola taccada and Cyperus conglomeratus. Between 2017 and 2018 the eastern section of the sand cay accreted 0.3 m following Cyperus colonisation. Reptation and aeolian ripple development occurred during fieldwork when near-surface flows exceeded 6 ms-1. Saltation occurred at higher wind speeds (8 ms-1). The highest rates of sand transport occurred during north-east incident winds of 12 ms-1 (at 6 m), that were probably generated by surface-based density currents under cumulonimbus clouds. Spatially, higher rates of sand transport were recorded downwind of a beach scarp, probably forced by flow acceleration. We propose a conceptual model of lagoon island formation, with both over-wash and aeolian sedimentation contributing to island accretion. A period of aeolian sedimentation may be critical to the emergence of sand cays.