Mangroves and seagrass: Indicators of estuarine health?

Mangrove and seagrass occupy different environments within an estuary, and both potentially respond to environmental stressors such as, nutrient loading, sedimentation, turbidity and climate change. Therefore, they could be useful indicators of the health of the estuary. However, there are common misunderstandings about the function of flowering plants such as mangrove and seagrass in the marine environment that can lead to contradictory and possibly inappropriate actions by the public. For example, pressure to protect mangroves and remove seagrass. This talk will discuss the interactions between physical processes within estuaries and mangrove and seagrass, consider the changes that have occurred in the distribution of these plants over the recent past, and suggest possible causes for these changes

Sea-level change and storm surges in the context of climate change

This paper reviews the latest research in New Zealand surrounding the issues of sea-level rise and extreme sea levels in the context of global warming and variability in the Pacific-wide El Nino– Southern Oscillation (ENSO). Past records of climate, sea level (excluding tides) and sea and air temperatures have shown that they are continuously fluctuating over various long-term timescales of years, decades and centuries. This has made it very difficult to determine whether the anthropogenic effects such as increased levels of “greenhouse” gases are having an accelerating effect on global sea levels or an increased incidence of extreme storms. Over the past century, global sea level has risen by 10–25 cm, and is in line with the rise in relative sea level at New Zealand’s main ports of +1.7 mm yr –1. What has become very clear is the need to better understand interannual (year-to-year) and decadal variability in sea-level, as these larger signals of the order of 5–15 cm in annual-mean sea level have a significant “flow-on” effect on the long-term trend in sea level. The paper describes sea level variability in northern New Zealand—both long- and short-term—involved in assessing the regional trends in sea level. The paper also discusses the relative contributions of tides, barometric pressure and wind set-up in causing extreme sea levels during storm surges. Some recent research also looked at a related question—Is there any sign of increased storminess, and hence storm surge, in northern New Zealand due to climate change? The paper concludes that, while no one can be completely sure how sea-level and the degree of storminess will respond in the near future, what is clear is that interannual and decadal variability in sea level is inextricably linked with Pacific-wide ENSO response and longer inter-decadal shifts in the Pacific climate regime, such as the latest shift in 1976

Leveling the playing field: Exploiting technology to enhance tertiary learning

This paper reports on an on-going case study project to explore ICT/ eLearning across several disciplines and with students from diverse backgrounds at tertiary level in New Zealand. The project has been designed to address issues of tertiary-level pedagogy, epedagogy, and research with the goal of building eLearning capacity, leveraging pedagogical change, and closing participatory gaps for students and lecturers. Initial design decisions, the pedagogy that has informed the case studies, and the challenges and benefits of working across subjects and levels in a multi-disciplinary team are described. We also discuss research knowledge mobilization within our own instructional context and more broadly elsewhere

Volcanic Generation of Tsunamis: Two New Zealand Palaeo-Events

Rapid emplacement of a mass via pyroclastic flows, or edifice failure, generates volcanic tsunamis. Physical modelling demonstrates that the efficiency of tsuna-mi generation is influenced by the angle the mass enters the ocean. Efficiency de-creases with increasing slope angle from 20° to 60°, before increasing to a maxi-mum at 90°, which corresponds to a mass falling directly into the ocean without interacting with the slope (impact tsunami). Further, in the case of surging pyro-clastic flows or regressive failures, successive closely spaced events may generate larger tsunami waves than a single event of comparable volume. It is difficult to assess if physical model results are meaningful for real world tsu-nami events due to limited observational data. This paper compares numerical models developed from physical simulations with palaeotsunami deposits from two New Zealand palaeo-events – pyroclastic flows from Mt Tarawera and edi-fice failure at Whakaari (White Island) – which constrains numerical simulations of the source mechanisms. The Mt Tarawera event involved multiple pyroclastic flows entering a lake during the AD 1314±12 Kaharoa Eruption. The interaction of multiple closely spaced pyroclastic flows is necessary to generate the 6-7 m maximum wave height inferred from near source tsunami deposits. Tsunami de-posits in the Bay of Plenty, dated to 2962±52 BP, are consistent with edifice fail-ure at Whakaari. In this case a single event with a volume of 0.23 km3 is suffi-cient to account for the tsunami deposits. Hence, if the failure was regressive, the successive stages were sufficiently close together to be indistinguishable from a large single event

The hydrodynamics of the southern basin of Tauranga Harbour

The circulation of the southern basin of Tauranga Harbour was simulated using a 3-D hydrodynamic model ELCOM. A 9-day field campaign in 1999 provided data on current velocity, temperature and salinity profiles at three stations within the main basin. The tidal wave changed most in amplitude and speed in the constricted entrances to channels, for example the M2 tide attenuated by 10% over 500 m at the main entrance, and only an additional 17% over the 15 km to the top of the southern basin. The modelled temperature was sensitive to wind mixing, particularly in tidal flat regions. Residence times ranged from 3 to 8 days, with higher residence times occurring in sub-estuaries with constricted mouths. The typical annual storm events were predicted to reduce the residence times by 24%–39% depending on season. Model scenarios of storm discharge events in the Wairoa River varying from 41.69 m3/s to 175.9 m3/s show that these events can cause salinity gradients across the harbour of up to 4 PSU

Comments on GWRC Draft Climate Change Strategy

Considering the sea level projections adopted by the DCCS, the key points are: a) Due to vertical land movements, the magnitude of relative sea level changes around the coast of the Wellington region varies significantly, and at centennial scales the effects of a major earthquake and the cumulative effect of slow-slip events are likely to dominate over the effects of global absolute sea level changes. b) It is evident that historic absolute sea level changes observed at Wellington do not agree with estimated historic global absolute sea level changes, or with CMIP5 projections for the available period of overlap this Century. Therefore, it is unlikely that projections of future global absolute sea levels provide a useful estimate of future sea levels in Wellington. c) Relative sea level changes at Wellington are not tracking either the CMIP5 projections for absolute sea level rise, or the MfE guidelines for planning purposes. 1. This is predominantly due to the lack of any statistically significant acceleration, which is an underlying assumption in both the projections and the guidelines. 2. Further, the CMIP5 models do not account for regional-scale variability in the processes driving sea level changes. It is clear that major ocean sub-basins experience different sea level changes at different times, which do not accord with the global average modelled by the sea level projections. Within the sub-basins there are also significant variations. This variability indicates that an anthropic sea level signal is unlike to be detectable at Wellington this Century. 3. Finally, it is clear that the relative contributions of the different components of sea level rise have been changing over the last few decades, which means the processes driving sea level changes are different to those assumed by the projections. d) As identified by the NIWA report on sea level trends and variability for the Wellington, it is unlikely that sea level rise will abruptly accelerate to the rates required to achieve the MfE guidelines. Therefore, the MfE guidelines are an over-estimate of potential sea level rise over the next century, and the values specified should be considered very unlikely. Considering the climate extreme projections adopted by the DCCS, the key points are: a) The projected changes in the frequency and magnitude of extreme wind and precipitation events are smaller than the natural variability of these events at any specific location or between locations within the Wellington region. This is due to the effects of local topography and the scale of the systems associated with extreme events. The projected changes are very unlikely to be detectable during this Century. b) The climate for the Wellington Region is strongly influenced by sea surface temperatures, the local topography, and a range of climate oscillations including ENSO, SAM and PDO. None of these is adequately incorporated into CMIP5 projections (and even less so in earlier projections). It is very unlikely that projections of global mean surface air temperature will provide any useful estimates of future climate for specific locations in the Wellington Region. c) The MfE guidelines utilise downscaled climate projections produced for the IPCC TAR. Apart from being more than a decade out of date, the methodology used was identified by the IPCC TAR as being flawed. The downscaled projections are also provided as a regional “average”, which is very unlikely to provide any useful estimate of future climate for any specific location. d) There appears to be fundamental disagreement over the relative influence of key climate oscillations on the climate of the Wellington Region, particularly the relative affects of ENSO, SAM and PDO on extreme events. Without a better understanding of the influence of these on the present climate of the Wellington Region, it is difficult to accept any projections based on assumed changes to their behaviour in the future. e) There is strong evidence that the CMIP5 models have over-projected future temperature changes, although there is on-going disagreement as to why this has occurred. The same problems are also evident to the earlier models used to produce the MfE guidelines. Until the discrepancies between the out-of-sample observations and model projections are resolved it would be imprudent to rely on model projections for planning purposes

Review of sand extraction impacts for Miller’s Bank, Kaipara Harbour

A review of the monitoring reports for resource consent MCO623701 (CON20030623701) involving sand extraction near Millers Bank, and additional reports relating to sediment transport within the Kaipara Harbour was undertaken. The available data indicates that the Waikeri Bank and surrounding channels are mobile, and while occupying approximately the same position since the first full survey in 1852, they are not fixed features. The adjacent shoreline between Ru Point and Tauhara Creek, have undergone phases of erosion and accretion since 1852, with variable behaviour along the coast. Overall this section of coast is tending to erode. Monitoring since sand extraction began indicates that natural phenomena, particularly episodic storm conditions from the northeast quadrant, are the dominant cause of shoreline erosion. No quantitative data are available prior to sand extraction, so it is difficult to determine if there has been any change in the rate of erosion since extraction began. Limited current data, and numerical modelling, suggest that Five Fathom Channel is ebb dominated, and the channel between Waikeri Bank and the shore may be flood dominated. This would cause a recirculation of sediment around Waikeri Bank, and the morphology suggests that sediment tends to accumulate at the northern and southern junctions of the two channels. Bathymetric surveys indicate that the supply of sediment to this region is sufficient to replenish sand extracted. However, the surveys completed to date do not have sufficient resolution and datum controls to quantify volumetric changes. The variations recorded by monitoring are minor compared to historic changes, so it is unlikely that the sand extraction is having any measurable effect on flow through either channel or sedimentation in the vicinity

Hauraki Gulf sedimentation: Unintended consequences of flood protection

The Universities of Waikato and Bremen have examined sedimentation in the Hauraki Gulf, focussing on the sediment discharges from the Coromandel Peninsula and the Waihou/Ohinemuri river systems, to assess whether anthropic land-use changes over the last millennium have resulted in increased sedimentation rates. Previous studies identified increased sedimentation due to burning of vegetation following Polynesian settlement, and Kauri logging, mining and forest clearance following European settlement. Most studies attribute the highest sedimentation rates to European settlement. This paper considers the results of investigations of depocenters in the central Hauraki Gulf, Southern Firth of Thames, and Coromandel Harbour, as well as the sediment pathway along the Ohinemuri and Waihou Rivers from mining areas of the southern Coromandel Peninsula to the Hauraki Gulf. Contrary to expectations, the central Hauraki Gulf was found to consist of palimpsest fluvial and biogenic marine deposits, with minor Holocene sedimentation lacking a clear anthropic signal. The shallower depocenters contain thicker sequences of Holocene sediments, with high spatial variability. Areas with clear anthropic signals were those proximal to potential sources. Commonly there was a significant time gap between the palynological indications of European settlement and changes in metal concentrations or inferred sedimentation rates, which was inconsistent with historical records suggesting land disturbance was contemporary with settlement. Gold mining in the southern Coromandel Peninsula generated tailings that were deposited into the Ohinemuri River. Initially the Ohinemuri River aggraded and annual floods deposited tailings on the floodplains, predominantly between the Waihou and Ohinemuri Rivers south of Paeroa. Since 1910, the floodplains have progressively been drained and protected by stopbanks constructed from sediment dredged from the beds of rivers and canals, and intertidal flats; with the final major scheme being completed in 1972. Metal concentrations in surficial sediments indicate most tailings have been deposited on floodplains upstream of Paeroa, with little evidence of transport downstream of the Waihou/Ohinemuri confluence. Since the completion of the stopbanks major floods have predominantly discharged sediment into the Firth of Thames, instead of onto the floodplains. The progressive removal of the floodplains as potential depositional sites coincides with the documented expansion of mudflats and mangrove in the southern Firth of Thames. This may also account for the delayed onset of a significant anthropic signal in the Firth of Thames depocenter

Location of Te Wahitapu Stream and other possible streams in 1877

Review of evidence to establish, with as much confidence as possible, the path of the Te Wahitapu Stream at Matapouri in 1877. The review also examines if other streams may have been present on or in the vicinity of Te Wahitapu Stream in 1877, and if the 1877 or later tsunami may have latered the course of the boundary stream

Adoption of innovative e-learning support for teaching: A multiple case study at the University of Waikato

In response to recent social, economic, and pedagogical challenges to tertiary-level teaching and learning, universities are increasingly investigating and adopting elearning as a way to engage and motivate students. This paper reports on the first year of a two-year (2009-2010) qualitative multiple case study research project in New Zealand. Using perspectives from activity theory and the scholarship of teaching, the research has the overall goal of documenting, developing, and disseminating effective and innovative practice in which e-learning plays an important role in tertiary teaching. A “snapshot” of each of the four 2009 cases and focused findings within and across cases are provided. This is followed by an overall discussion of the context, “within” and “across” case themes, and implications of the research