ORCID Profile
0000-0002-4020-5639
Current Organisation
University of Otago
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Physical Geography | Geomorphology | Physical Geography and Environmental Geoscience
Climate change | Physical and chemical conditions | Oceanic processes (excl. climate related) |
Publisher: Informa UK Limited
Date: 02-11-2013
Publisher: Copernicus GmbH
Date: 20-06-2022
DOI: 10.5194/ICG2022-298
Abstract: & & Oblique terrestrial laser scanning (TLS) enables topographic change detection at scales (10& sup& & #8722 & /sup& & #8211 & sup& & /sup& cm) that are appropriate for coastal cliff erosion monitoring. Despite this, its application has been limited to a select few regions around the world. Here we report new TLS point cloud datasets from 13 years of monitoring (2009-2022) at Rothesay Bay, Hauraki Gulf, New Zealand, which has a relatively low wave energy setting with a meso tidal range. The 120 m-long scan area includes cliffs of 10-30 m in height, formed of horizontally bedded soft sedimentary flysch rock. The cliffs are fronted by an ~140m wide near-horizontal shore platform that terminates in an abrupt seaward edge. Formation of such platform morphology is based on the assumption that: a) the platform has developed during several millennia of stable Holocene Sea level (around 6,000 years) b) the seaward edge of the shore platform does not erode c) and the rate of cliff retreat reduces over time due to increased dissipation of wave energy across a widening shore platform. On this basis it has been previously assumed that the long-term cliff retreat rate at this field site is between 1.4& #177 .1 to 14.3& #177 .1 mm/year. In contrast, volumetric cliff-face erosion detected with intensive monthly TLS scanning (July 2021- April 2022) at this site indicates a cliff recession rate of 140-660 mm/year (during dry and wet seasons), and three scans over a 12-year window (2009, 2014, 2021) indicate an average erosion rate of 47 mm/year. If erosion had been constant at this rate over approximately 6,000 years, a total cliff retreat of 282 m would be expected, which presents a striking contrast to the width of the contemporary shore platform. The anomaly is even more pronounced given: a) the widely held assumption that cliff erosion rates should decline as platform width increases or that the long-term cliff retreat rates are constant, an assumption made previously for this site and b) that Holocene Sea level appears to have been higher than present during the past 6,000 years. This presentation evaluates two possible hypotheses for the confounding width of the modern shore platform in comparison to current cliff erosion rates: 1) that current rates of cliff retreat are faster than past erosion rates (perhaps the TLS captured an unusually fast period of erosion, or perhaps there has been some modern acceleration in cliff erosion rates) 2) that the seaward edge has not remained in its original position or does not reliably indicate the original location of the cliff. These possibilities will be assessed through offshore bathymetric mapping and numerical model experiments. & & &
Publisher: Elsevier BV
Date: 06-2009
Publisher: Elsevier BV
Date: 2010
Publisher: Copernicus GmbH
Date: 21-03-2022
DOI: 10.5194/NHESS-22-931-2022
Abstract: Abstract. The increasing vulnerability of coastal megacities to storm surge inundation means both infrastructure and populations are subject to significant threat. Planning for further urban development should include consideration of the changing circumstances in coastal cities to ensure a sustainable future. A sustainable urban plan relies on sound preparedness and prediction of future climate change and multiple natural hazards. In light of these needs for urban planning, this paper develops a general method to simulate typhoon-generated storm surge at the mesoscale (1–100 km in length). Mesoscale simulation provides a general approach with reasonable accuracy that could be implemented for planning purposes while having a relatively low computation resource requirement. The case study of Shanghai was chosen to implement this method. The mesoscale simulations of two historical typhoons not only provides realistic typhoon storm surge inundation results at the city level but is also suitable for implementing a large amount of simulations for future scenario studies. The method will be generally applicable to all coastal cities around the world to examine the effect of future climate change on typhoon-generated storm surge even when historical observation data are inadequate or not available.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-10394
Abstract: & & On tectonically active rock coasts, there is a dearth of erosion data documenting how rocks adjust (either fast or slow) in response to marine and subaerial processes immediately after coseismic uplift. Here we report erosion rates and evidence of reshaping of shore platform morphology on intertidal- and previously subtidal- rocks at Kaik& #333 ura Peninsula, South Island New Zealand. As a result of the November 2016 Kaik& #333 ura 7.8 (Mw) earthquake, platforms around the peninsula were uplifted by ~1.01 m, extended in width, and a 43-year active erosion monitoring c aign was abruptly halted but an opportunity to record how rocks respond to sudden environmental change like tectonics was presented. High-resolution topographic data obtained from quarterly surveys over four years using the micro-erosion meters (MEM) and Structure-from-Motion Multi View Stereo (SfM-MVS) surveys have provided accurate quantitative rates of erosion and visual representation of surface morphologies. MEM erosion data revealed variations in erosion, weathering and deposition rates across lithology, seasons, tidal positions, and platform elevation after the uplift. Four-years post-uplift erosion data shows a resetting of erosion rates and faster rock breakdown on both mudstone and limestone lithologies compared to pre-uplift rates. Over the 4-year period, surface downwearing rates for all platforms was 2.19 mm/yr, a 99.9% increase from a pre-uplift rate of 1.10 mm/yr. Average lowering rates on limestone, hard mudstone and soft mudstone platforms are 1.31 mm/yr, 2.13 mm/yr and 3.60 mm/yr, respectively. Seasonal trends in erosion rates remain unchanged as higher rates are still experienced during summer than winter seasons due to greater periods of higher temperatures and increased wetting and drying cycles. A year after uplift, previously reported across shore variations where erosion rates decreased from inner/landward margins of the platform to the outer/seaward sections disappeared with higher erosion rates fluctuating across all platform sections. Increased lowering rates on limestone rocks at the inner and outer sections were attributed to greater periods of wetting and drying, and loss of biological cover. These initially rapid rates decreased on the seaward sections after 3 years as a result of bioprotection and increased tidal wetting.& On one of the harder mudstone rocks, a dramatic increase from a pre-uplift erosion rate of 0.43 mm/yr to 19.23 mm/yr (1-year after uplift) and subsequent decline to 1.54 mm/yr after four years is suggestive of isolated incidents of block detachment and erosion. For the first time, we complement MEM data with available SfM-MVS derived orthomosaics to provide evidence of changing rock morphology and processes such as intense granular disintegration, flaking, algal growth, and boring. On tectonically active rock coasts, the strong fluctuations in erosion rates and platform morphological expressions indicate the actions of not only waves, tides, and weathering processes but also tectonics in shore platform development.& &
Publisher: Elsevier BV
Date: 09-2010
Publisher: Elsevier BV
Date: 11-2019
Publisher: Wiley
Date: 15-06-2017
DOI: 10.1002/ESP.4176
Publisher: Informa UK Limited
Date: 04-06-2020
Publisher: Springer Science and Business Media LLC
Date: 31-01-2023
DOI: 10.1038/S41467-023-36171-2
Abstract: Global environmental change is identified as a driver of physical transformation of coral reef islands over the past half-century, and next 100 years, posing major adaptation challenges to island nations. Here we resolve whether these recent documented changes in islands are unprecedented compared with the pre-industrial era. We utilise radiometric dating, geological, and remote sensing techniques to document the dynamics of a Mal ian reef island at millennial to decadal timescales. Results show the magnitude of island change over the past half-century (±40 m movement) is not unprecedented compared with paleo-dynamic evidence that reveals large-scale changes in island dimension, shape, beach levels, as well as positional changes of ±200 m since island formation ~1,500 years ago. Results highlight the value of a multi-temporal methodological approach to gain a deeper understanding of the dynamic trajectories of reef islands, to support development of adaptation strategies at timeframes relevant to human security.
Publisher: Copernicus GmbH
Date: 15-03-2017
Abstract: Abstract. The increasing vulnerability of coastal mega-cities to storm surge inundation means both infrastructure and populations are subject to significant threat. Planning for further urban development should include consideration of the changing circumstances in coastal cities to ensure a sustainable future. A sustainable urban plan relies on well preparedness and prediction of future climate change and multiple natural hazards. In light of these needs for urban planning, this paper develops a general method to simulate typhoon generated storm surge at the meso-scale (1–100 km in length). Meso-scale simulation provides a general approach that could be implemented to fulfil the purpose of planning, and has relatively low requirements for computation time and data, while still providing reasonable accuracy. The case study of Shanghai was chosen to implement this method. The meso-scale simulated results of two historical typhoons not only provides a realistic result at the city level, but is also suitable for implementing a large amount of simulations for future scenario studies. The method is generally applicable to all coastal cities around the world to examine the effect of future climate change on typhoon generated storm surge, even where historical observed data are inadequate or not available.
Publisher: Geological Society of London
Date: 25-07-2014
DOI: 10.1144/M40.13
Abstract: Arthur Bloom once wrote, in a statement of posthumous appreciation of Sir Charles Cotton, that no New Zealand geomorphologist could ever really be away from the coast ( Bloom 1974 ). It is true to that sentiment that, despite being few in number, geomorphologists working in New Zealand have made a significant and enduring contribution to our understanding of rocky coasts. In large part that contribution can be traced to the countries’ spectacular geographical setting and associated variety of rock coast landforms. In this chapter we summarize the geographical setting in which New Zealand's rocky landscape is situated and describe the various lithological and process controls on landscape evolution. The remainder of the chapter provides a perspective on the contribution made by geomorphologists studying New Zealand's rocky coast. That review is centred on three methodological epochs: (a) explanatory description (b) emerging emphasis on measurement and (c) process-based studies.
Publisher: Geological Society of London
Date: 25-07-2014
DOI: 10.1144/M40.1
Publisher: Elsevier BV
Date: 2023
Publisher: Elsevier BV
Date: 2010
Publisher: Geological Society of London
Date: 25-07-2014
DOI: 10.1144/M40.17
Publisher: Elsevier BV
Date: 05-2011
Publisher: Elsevier BV
Date: 11-2006
Publisher: Wiley
Date: 14-02-2019
DOI: 10.1002/ESP.4581
Publisher: Elsevier BV
Date: 2005
Publisher: Springer Science and Business Media LLC
Date: 04-01-2020
Publisher: Coastal Education and Research Foundation
Date: 2006
DOI: 10.2112/05A-0017.1
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-11019
Abstract: & & Sequences of Holocene marine terraces are widely used in paleoseismic research to understand the timing and magnitude of earthquakes along tectonically active coastal margins worldwide. But the potential for marine terraces to be destroyed through erosion after uplift can result in incomplete records of paleoseismicity as derived from terrace chronologies, leading to misinterpretations of the paleoseismic history of a region. Here, we present measurements across a unique set of exposed bedrock marine terraces in the north-eastern South Island, NZ, to quantify the ages and erosion rates of the surfaces and produce a new chronology for paleoseismic interpretation. Surface exposure dating and multi-nuclide approaches offer the potential to quantify marine terrace preservation and destruction, potentially elucidating where terraces may be missing or removed from a sequence. Needles Point, Marlborough, NZ exhibits three well defined bare rock marine terraces and a gravel covered shore platform which was recently uplifted ~2.5m in the M& em& & sub& W & /sub& & /em& .8 2016 Kaik& #333 ura earthquake. & sup& & /sup& Be-derived ages for the platform surface and terrace 1 (T1) align with known ground surface rupturing earthquakes on the Kekerengu fault. T2 and T3 preserve older events not previously identified, potentially extending the earthquake record in this region. However, other known ground surface rupturing earthquakes on the Kekerengu fault are not preserved as terraces at Needles indicating that the preserved terraces at Needles Point do not therefore represent a full record of local paleoseismicity. As such, estimates of fault throw derived from these terraces would over-estimate earthquake magnitude.& &
Publisher: Wiley
Date: 08-07-2022
DOI: 10.1002/ESP.5438
Abstract: Co‐seismic uplift of Kaikōura Peninsula in 2016 has substantially reduced the number of wetting and drying cycles that occur on the shore platforms and the newly uplifted incipient marine terraces. A simple empirical model incorporating field and laboratory measurements was used to determine the number and frequency of wetting and drying cycles. The mudstone supratidal terraces are vulnerable to material disintegration and slaking through sustained drying, and occasional sweeping by storm waves. Overall, wetting and drying cycles have decreased on six of eight field transects, between −8% and −148%, resulting in prolonged drying of the supratidal terraces following uplift (upwards of a 29% increase in annual drying hours). We conclude that accelerated rates of denudation due to enhanced drying post‐uplift are likely to return sections of the incipient mudstone terraces to their former intertidal pre‐uplift state, potentially removing evidence of the co‐seismic uplift event. Terrace preservation, however, will likely be highly variable between locations depending on its inherited morphology, lithological vulnerability, and the timing of any future tectonism.
Publisher: Elsevier BV
Date: 11-2001
Publisher: Elsevier BV
Date: 12-2023
Publisher: SAGE Publications
Date: 2006
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-16696
Abstract: Recent erosion rates from tectonically active coasts provide evidence of rapid rock breakdown following coseismic uplift. These rates are needed to solve puzzles about 'missing' marine terraces that prevent accurate reconstruction of past sea levels, earthquakes and rock coast evolution. Yet little scientific effort has been put into investigating the impact of tectonism on shore platform development. It is also presently unclear if erosion records from one coast can be extrapolated to other regions with similar tectonic, geologic, or geomorphic characteristics. We present shore platform downwearing rates and processes measured using the traversing micro-erosion meter (TMEM) and Structure-from-Motion photogrammetry from an inter-tidal shore platform uplifted by 3.1 m between 100 to 300 years ago. The site is a mudstone platform at Kahutara Point, M& #257 hia Peninsula, North Island, New Zealand. Over 1.43 years, the mean annual downwearing rate was 1.94 mm/yr, while the total erosion at in idual TMEM stations ranged from 0.29 to 8.31 mm (equivalent to mean erosion rates of 0.07 to 5.82 mm/yr). We found a lack of any spatial pattern in erosion rates cross-shore, suggesting the equal efficiency of waves and weathering processes. Orthophotographs of the eroded rock surfaces support the combined role of marine processes (waves and tides), sub-aerial weathering processes, salt weathering and biological activity in the erosion of the mudstone platforms at Kahutara Point. The mean erosion rate of 1.94 mm/yr from the M& #257 hia Peninsula is similar to the mean post-uplift rate of 2.25 mm/yr reported for the Kaik& #333 ura Peninsula, New Zealand, where platforms were uplifted by ~1 m in 2016. This result suggests a comparable pattern of erosion response at both sites following co-seismic uplift and provides the first field evidence to support the comparison of the Kaik& #333 ura and M& #257 hia shore platforms, thus helping to inform marine terrace development and destruction.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 07-2016
Publisher: Elsevier BV
Date: 2004
Publisher: American Geophysical Union (AGU)
Date: 09-2021
DOI: 10.1029/2020JC016910
Abstract: Spurs and Grooves (SAG) are coral forereef structures with their main axis normal to the reef crest. The dimensions of SAG vary considerably on a global scale. Despite being common, there are relatively few studies that relate SAG morphology with wave transformation processes. Measurements of wave transformation are presented from Xahuayxol, Quintana Roo, Mexico, across a SAG zone with larger spurs than in previous studies. An array of pressure sensors and current meters s ling at high frequencies were deployed over 8 days. Our results show that SAG structures are more important for wave transformation than previously reported since a high rate of wave energy flux dissipation (up to 0.077 kW/m 2 ) was found and the corresponding wave dissipation friction factor, f w (1.01), was four times higher as compared to other reefs. We also found that the wave dissipation rate over the spurs can be up to three times higher than the adjacent grooves (0.098 vs. 0.028 kW/m 2 ). This study demonstrates that SAG plays a very important role in wave dissipation over coral reefs.
Publisher: Elsevier BV
Date: 02-2000
Publisher: Elsevier
Date: 2013
Publisher: Elsevier BV
Date: 10-2011
Publisher: Springer Science and Business Media LLC
Date: 02-04-2011
Publisher: Wiley
Date: 11-2012
Publisher: SAGE Publications
Date: 12-2003
Publisher: SAGE Publications
Date: 12-2004
Publisher: Springer Science and Business Media LLC
Date: 20-01-2013
Publisher: Elsevier BV
Date: 12-2022
Publisher: Wiley
Date: 24-07-2022
DOI: 10.1002/ESP.5440
Abstract: Flights of Holocene marine terraces are useful for reconstructing past earthquakes, but coastal erosion can remove terraces from the landscape, potentially leading to incorrect estimates of earthquake magnitude and frequency. Relatively little effort has been afforded to studying terrace erosion processes, and this paper presents the first field evidence that we are aware of documenting terrace erosion rates. Two case studies from New Zealand provide a unique opportunity to observe the beginning and end phases of terrace development. We present downwear and backwear erosion measurements, showing that both sets of processes are important. Micro‐erosion meter measurements from Kaikōura Peninsula, South Island, confirm that downwear processes are modifying new marine terraces that were created when the peninsula was uplifted about 1 m during the 2016 earthquake. Erosion rates were high immediately following uplift as the relatively barren intertidal rock shore platform rapidly transformed into an incipient marine terrace with cover deposits. However, the Kaikōura earthquake uplifted shore platforms only a small distance above the upper tidal limit and ongoing downwear and backwear erosion may begin to remove parts of this terrace in future decades. We explored this prospect with a case study at Māhia Peninsula, North Island, where 100–300 years have elapsed since the last terrace‐forming earthquake. Historical photographs were used to document about 80 years of backwear erosion. Terrace erosion rates have been nearly constant through this period, and extrapolation implies that the terrace will be removed in places by 2030. The erosion data in this paper provide new insights into how terraces can be removed from the landscape, but there are many complicating factors. To help understand these factors we present a new conceptual model of marine terrace creation and destruction for soft‐rock coasts.
Publisher: Elsevier BV
Date: 05-2011
Publisher: Informa UK Limited
Date: 03-2005
Publisher: Wiley
Date: 2004
DOI: 10.1002/ESP.1120
Publisher: Wiley
Date: 16-08-2018
DOI: 10.1002/ESP.4476
Publisher: Elsevier BV
Date: 11-2015
Publisher: Wiley
Date: 18-01-2020
DOI: 10.1002/ESP.4797
Publisher: Elsevier BV
Date: 2010
Publisher: Coastal Education and Research Foundation
Date: 12-2011
DOI: 10.2112/SI61-001.59
Publisher: Wiley
Date: 02-2002
DOI: 10.1002/ESP.315
Publisher: Wiley
Date: 08-2013
Publisher: Wiley
Date: 26-11-2011
Publisher: Elsevier BV
Date: 2010
Publisher: Authorea, Inc.
Date: 05-10-2023
Publisher: Elsevier BV
Date: 02-2000
Publisher: Wiley
Date: 12-1998
DOI: 10.1002/(SICI)1096-9837(199812)23:12<1071::AID-ESP922>3.0.CO;2-U
Publisher: Wiley
Date: 2006
DOI: 10.1002/ESP.1373
Publisher: Elsevier BV
Date: 03-2012
Publisher: Wiley
Date: 06-10-2017
DOI: 10.1002/ESP.4245
Publisher: Elsevier BV
Date: 05-2011
Start Date: 2019
End Date: 2022
Funder: Marsden Fund
View Funded ActivityStart Date: 2005
End Date: 2007
Funder: Australian Research Council
View Funded ActivityStart Date: 2005
End Date: 12-2008
Amount: $140,000.00
Funder: Australian Research Council
View Funded Activity