Mt. Ruapehu is one of the most lahar prone volcanoes in the world, having both a crater lake and six small glaciers upon its 2797 m summit. The major outlet for the crater lake, the Whangaehu Gorge, has hosted over 46 historic lahars. However, the low preservation of debris flow deposits, as a result of frequent remobilisation on steep slopes, allows for the detailed description of only 9 lahar events over the last 150 years. Field investigation, historic aerial photos, two airborne LiDAR surveys and direct measurements have been utilised to describe the sedimentology, geomorphology and distribution of historic lahar deposits in the first 11 km of the Whangaehu Gorge. Inundation maps have been created for 1945, 1953, 1975, September 1995, October 1995, March 2007 and September 2007. Grain size distribution, componentry and geomorphology of the 1861, 1975, September 1995, October 1995, 1999 and 2007 lahar deposits have been compared. The lahar deposits are massive, very poorly sorted, silty gravels that form a series of unconsolidated terraces. The limited sediment sources in the steep sided Whangaehu Gorge, including minor historic eruption products, results in significant recycling of lahar deposits. However, the deposits can be differentiated by proportions of lithological components and in some cases anthropogenic debris. The abundance of hydrothermally altered material reflects the role of Crater Lake in lahar formation, although, some of these materials (gypsum, sulphur and snow) are only temporary. Non-cohesive debris flows and occasional snow slurry lahars have been formed by a range of triggering mechanisms associated with and independent of eruptions. Lahars have been formed in the Whangaehu Valley as the result of ejected crater lake water and associated snow melt (1975, September 1995 and September 2007), as well as the progressive displacement of lake water as a result of lava dome growth (1945) and uplift of the lake floor (1968). Inter-eruption lahars occur as a result of Crater Lake outburst floods (1861, 1953 and March 2007) and remobilisation by precipitation and the collapse of tephra laden snow (October 1995 and 1999). The comparison of historic lahars also reflects the range of lahar magnitudes experienced historically on Ruapehu. The most recent Crater Lake outburst of March 2007, with a peak discharge of 1700-2500 m3/s is the second largest recorded lahar, behind only the eruption-generated lahar of April 1975 with a peak discharge of 5000-7500 m3/s. Lahar mitigation can subsequently be based on lahar generation and incorporation of the vast amounts of data collected before and after the 2007 outburst flood. Recent remobilisation and phreatic activity suggest the significant under-representation of small volume events like rain-generated and snow slurry lahars in the geologic record.

Thesis (Ph. D.)--Open University.

Thesis (M.Sc. Earth and Ocean Science)--University of Waikato, 2008. / Title from PDF cover (viewed August 26, 2008) Includes bibliographical references (p. 169-177)

White Island and Ruapehu are currently the most active volcanoes in New Zealand. During non-eruptive periods, intense quiescent degassing through fumaroles can occur. The current project studies the quiescent degassing plumes, including aerosol sampling on White Island and dispersion modelling of SO₂ and PM₁₀ from White Island and Ruapehu volcanoes. Aerosol sampling from fumaroles at the crater floor on White Island volcano was carried out on 9 February and 6 April 2005. The exposed filters were analysed for various anions and cations and the particle mass concentration and molar concentration determined. Major elemental constituents were sodium and chlorine (Na⁺: 413 µg m⁻³, Cl⁻: 1520 µg m⁻³), which show best correlation at both sampling sessions. Other ions detected, with little correlation, are Ca²⁺, PO₄³⁻ and to a certain extent Mg²⁺. Other constituents found, which cannot correlate explicitly to other ions, are K⁺, NH₄⁺, NO₃⁻, and SO₄²⁻. SEM study of one exposed filter was performed and mainly NaCl particles could be distinguished due to their well-defined cubic shape. The Air Pollution Model (TAPM) was used for dispersion modelling of SO₂ (models 1-4) and PM₁₀ (models 5 and 6) from White Island and Ruapehu volcanoes. Annual modelling was performed using different parameters of emission rate, exit temperature and exit velocity. The resulting plume dispersions show relatively low concentrations at ground level ≤10 m), particularly for the models of PM₁₀ dispersion. TAPM calculated the highest SO₂ ground level concentrations with model 4, where the NES values of 350 and 570 µg m⁻³ were exceeded several times. The data was then used for detailed hazard assessment of urban population in the North Island. The meteorological data from annual modelling was used for model evaluation and compared with observation data from different weather stations by statistical calculations. Overall, TAPM performed well with most good and very good results. To evaluate SO₂ dispersion modelling, airborne plume measurements were carried out on 22 November 2006 by plume traverses at 3, 10 and 20 km. Although there is some variation, the calculated correlation coefficients indicate good model results for two plume traverses at 3 and 20 km and one plume traverse at 10 km. The meteorological data was also used for model evaluation, and the results indicate good model performance. TAPM is therefore suggested for future studies when more observation data are available to verify the calculated model data.

White Island and Ruapehu are currently the most active volcanoes in New Zealand. During non-eruptive periods, intense quiescent degassing through fumaroles can occur. The current project studies the quiescent degassing plumes, including aerosol sampling on White Island and dispersion modelling of SO₂ and PM₁₀ from White Island and Ruapehu volcanoes. Aerosol sampling from fumaroles at the crater floor on White Island volcano was carried out on 9 February and 6 April 2005. The exposed filters were analysed for various anions and cations and the particle mass concentration and molar concentration determined. Major elemental constituents were sodium and chlorine (Na⁺: 413 µg m⁻³, Cl⁻: 1520 µg m⁻³), which show best correlation at both sampling sessions. Other ions detected, with little correlation, are Ca²⁺, PO₄³⁻ and to a certain extent Mg²⁺. Other constituents found, which cannot correlate explicitly to other ions, are K⁺, NH₄⁺, NO₃⁻, and SO₄²⁻. SEM study of one exposed filter was performed and mainly NaCl particles could be distinguished due to their well-defined cubic shape. The Air Pollution Model (TAPM) was used for dispersion modelling of SO₂ (models 1-4) and PM₁₀ (models 5 and 6) from White Island and Ruapehu volcanoes. Annual modelling was performed using different parameters of emission rate, exit temperature and exit velocity. The resulting plume dispersions show relatively low concentrations at ground level ≤10 m), particularly for the models of PM₁₀ dispersion. TAPM calculated the highest SO₂ ground level concentrations with model 4, where the NES values of 350 and 570 µg m⁻³ were exceeded several times. The data was then used for detailed hazard assessment of urban population in the North Island. The meteorological data from annual modelling was used for model evaluation and compared with observation data from different weather stations by statistical calculations. Overall, TAPM performed well with most good and very good results. To evaluate SO₂ dispersion modelling, airborne plume measurements were carried out on 22 November 2006 by plume traverses at 3, 10 and 20 km. Although there is some variation, the calculated correlation coefficients indicate good model results for two plume traverses at 3 and 20 km and one plume traverse at 10 km. The meteorological data was also used for model evaluation, and the results indicate good model performance. TAPM is therefore suggested for future studies when more observation data are available to verify the calculated model data.

Ruapehu is an active volcano located on the North Island of New Zealand, with the most recent major eruptions occurring in 1945, 1969, 1975, and 1995/96. Ruapehu is also home to the three major North Island ski areas, Whakapapa, Turoa, and Tukino. Because of the high frequency of eruptions, there is a significant volcanic hazard at the ski areas particularly from lahars which can form even after minor eruptions. Most recently, lahars have affected Whakapapa ski area in 1969, 1975, and 1995/96. The most significant risk at Turoa is from ballistic bombs due to the proximity of the top two T-Bars to the crater. Ash fall has also caused disruption at the ski areas, covering the snow and causing damage to structures. There is yet to be a death at the ski areas from a volcanic event; however the risk at the ski areas is too high to be completely ignored. The ski areas at Whakapapa and Turoa are currently operated by Ruapehu Alpine Lifts (RAL), who have been significantly improving their commitment to providing volcanic hazard training for their staff and preparing for handling a volcanic eruption. RAL is joined by the Institute of Geological Sciences (GNS) and the Department of Conservation (DoC) in trying to mitigate this risk through a range of initiatives, including an automated Eruption Detection System (EDS), linked to sirens and loudspeakers on Whakapapa ski areas, as well as by providing staff training and public education. The aim of this study was to provide RAL with recommendations to improve their staff training and warning system response. Staff induction week at both Turoa and Whakapapa ski areas was observed. Surveys were distributed and collected from staff at both ski areas, and interviews were conducted with staff at Whakapapa ski area. Data obtained from staff interviews and surveys provided the author with insight into staff's mental models regarding a volcanic event response. A simulation of the warning system was observed, as well as a blind test, to collect data on the effectiveness of training on staff response. Results indicated permanent and seasonal staff were knowledgeable of the volcanic hazards that may affect the ski areas, but had differing perspectives on the risk associated with those hazards. They were found to be confident in the initial response to a volcanic event (i.e. move to higher ground), but were unsure of what would happen after this initial response. RAL was also found to have greatly improved their volcanic hazard training in the past year, however further recommendations were suggested to increase training effectiveness. A training needs analysis was done for different departments at the ski areas by taking a new approach of anticipating demands staff may encounter during a volcanic event and complementing these demands with existing staff competencies. Additional recommendations were made to assist RAL in developing an effective plan to use when responding to volcanic events, as well as other changes that could be made to improve the likelihood of customer safety at the ski areas during an eruption.

Ruapehu is an active volcano located on the North Island of New Zealand, with the most recent major eruptions occurring in 1945, 1969, 1975, and 1995/96. Ruapehu is also home to the three major North Island ski areas, Whakapapa, Turoa, and Tukino. Because of the high frequency of eruptions, there is a significant volcanic hazard at the ski areas particularly from lahars which can form even after minor eruptions. Most recently, lahars have affected Whakapapa ski area in 1969, 1975, and 1995/96. The most significant risk at Turoa is from ballistic bombs due to the proximity of the top two T-Bars to the crater. Ash fall has also caused disruption at the ski areas, covering the snow and causing damage to structures. There is yet to be a death at the ski areas from a volcanic event; however the risk at the ski areas is too high to be completely ignored. The ski areas at Whakapapa and Turoa are currently operated by Ruapehu Alpine Lifts (RAL), who have been significantly improving their commitment to providing volcanic hazard training for their staff and preparing for handling a volcanic eruption. RAL is joined by the Institute of Geological Sciences (GNS) and the Department of Conservation (DoC) in trying to mitigate this risk through a range of initiatives, including an automated Eruption Detection System (EDS), linked to sirens and loudspeakers on Whakapapa ski areas, as well as by providing staff training and public education. The aim of this study was to provide RAL with recommendations to improve their staff training and warning system response. Staff induction week at both Turoa and Whakapapa ski areas was observed. Surveys were distributed and collected from staff at both ski areas, and interviews were conducted with staff at Whakapapa ski area. Data obtained from staff interviews and surveys provided the author with insight into staff's mental models regarding a volcanic event response. A simulation of the warning system was observed, as well as a blind test, to collect data on the effectiveness of training on staff response. Results indicated permanent and seasonal staff were knowledgeable of the volcanic hazards that may affect the ski areas, but had differing perspectives on the risk associated with those hazards. They were found to be confident in the initial response to a volcanic event (i.e. move to higher ground), but were unsure of what would happen after this initial response. RAL was also found to have greatly improved their volcanic hazard training in the past year, however further recommendations were suggested to increase training effectiveness. A training needs analysis was done for different departments at the ski areas by taking a new approach of anticipating demands staff may encounter during a volcanic event and complementing these demands with existing staff competencies. Additional recommendations were made to assist RAL in developing an effective plan to use when responding to volcanic events, as well as other changes that could be made to improve the likelihood of customer safety at the ski areas during an eruption.

Issues management has been practised over the past 30 years. However, the literature has focused on how corporations manage issues, while public service organisations have been ignored. This study looked at the issues management of a tephra dam-break lahar from 1996-2007 on Mount Ruapehu, New Zealand by a group of public service organisations. 19 interviews were conducted with people involved with the management of the ‘lahar issue’ to find out how the issue was managed. Further a content analysis of 309 articles from five newspapers, spanning the full eleven year period, was conducted to examine the salience (attention) given to the issue, the frames commonly used to present the issue and the sources who ‘drove’ the issue. The data from the content analysis was interpreted to create a five-stage lifecycle of the ‘lahar issue’. Further, data from the interviews was compared with a summary process of the issue management process. This comparison showed that five issues management process stages were employed to manage the ‘lahar issue’ although they were not referred to as such. Initially, the Department of Conservation consulted stakeholders during the development of options to deal with the lahar (1996-1999). Later in the lahar’s management, lahar stakeholders fell into two categories: internal - those involved with the mitigation and response - and external - the public. Internal stakeholders were communicated with through meetings and email. External stakeholders were communicated with through local media, presentations and meetings. Overall, it was concluded that media gave substantial attention to the lahar issue over the eleven year period. Some of those involved with managing the ‘lahar issue’ were able to identify the phases of media coverage. Further, this study identified ten frames that media employed when reporting the lahar. The most-frequently used frames were those focusing on the response (lahar response), describing the lahar (diagnosing causes of problem(s)) and discussing the potential impacts from a lahar (definition of problem(s)). Department of Conservation Scientist, Dr Harry Keys, was shown to be a primary definer – an influential source. The results suggest he defined coverage because of his status as both an official source, due to the organisation he was associated with, and also as an authoritative source due to his role as a scientist. Further, he was regularly drawn upon as a source over the entire period of the ‘lahar issue’ coverage.