title: Rip current dynamics on an embayed beach

authors: Gallop, Shari L.

subjects: rip currents

abstract: Rip currents are fast, narrow currents which traverse the surf-zone in the seaward direction. The most important effect of rip currents is that they can pose a deadly hazard to beach-users. Rip currents and their interaction with waves and underwater morphology are still poorly understood. This is often attributed to a lack of high quality long-term datasets. This shortcoming is due to the difficulty of sampling in the turbulent surf-zone. Past attempts to compare rip current behaviour (e.g. alongshore spacing) to waves have failed to show that they interact. 

In this thesis, an improved technique of locating rip channels in video imagery is presented. Previous studies to create computer algorithms to locate rips in video imagery have only looked at one alongshore transect which is averaged in the cross-shore direction, and there have been issues making the algorithms work in complicated cases. The method created in this thesis uses computer algorithms to locate light intensity minima across the entire expanse of the surf-zone in video imagery. This was applied to a dataset from Tairua Beach. The light intensity minima are sorted into distinct rip channels to create a dataset spanning 3.3 years from 1999 until April 2002. Using the high quality rip data output from the algorithms, rip channel morphological reconfiguration events were defined using a measure of change. Wave climate was compared to the timing of these reconfiguration events. It was found that mean wave energy averaged over ten days and wave event duration showed a better relationship to the reconfiguration events than immediate, instantaneous measures of significant wave height. 

Rip channel spatial scale (i.e. cross-shore extent) was found to be critical in determining how rip channels behave during high wave events. At Tairua Beach, it was not uncommon for the surf-zone to be wide on one half of the beach and narrow on the other. This 'dual' surf-zone can be attributed to wave shadowing by offshore islands under certain wave directions. Smaller rip channels on the narrow half of the beach changed rapidly whereas larger rips were stable during the same period. This situation shows the importance of both hydrodynamic-control and topographic-control of rips, where rips may respond directly to changes in the wave conditions or be stabilised by the pre-existing morphology respectively. There was also a tendency for rips to form and persist at the headlands of the beach. 

A conceptual model was created to demonstrate how rip channels of different spatial scales respond to changes in the wave conditions. Small rips relative to the wave energy are more likely than larger rips to evolve, and vice versa.

text: Rip current dynamics on an embayed beach Rip currents are fast, narrow currents which traverse the surf-zone in the seaward direction. The most important effect of rip currents is that they can pose a deadly hazard to beach-users. Rip currents and their interaction with waves and underwater morphology are still poorly understood. This is often attributed to a lack of high quality long-term datasets. This shortcoming is due to the difficulty of sampling in the turbulent surf-zone. Past attempts to compare rip current behaviour (e.g. alongshore spacing) to waves have failed to show that they interact. 

In this thesis, an improved technique of locating rip channels in video imagery is presented. Previous studies to create computer algorithms to locate rips in video imagery have only looked at one alongshore transect which is averaged in the cross-shore direction, and there have been issues making the algorithms work in complicated cases. The method created in this thesis uses computer algorithms to locate light intensity minima across the entire expanse of the surf-zone in video imagery. This was applied to a dataset from Tairua Beach. The light intensity minima are sorted into distinct rip channels to create a dataset spanning 3.3 years from 1999 until April 2002. Using the high quality rip data output from the algorithms, rip channel morphological reconfiguration events were defined using a measure of change. Wave climate was compared to the timing of these reconfiguration events. It was found that mean wave energy averaged over ten days and wave event duration showed a better relationship to the reconfiguration events than immediate, instantaneous measures of significant wave height. 

Rip channel spatial scale (i.e. cross-shore extent) was found to be critical in determining how rip channels behave during high wave events. At Tairua Beach, it was not uncommon for the surf-zone to be wide on one half of the beach and narrow on the other. This 'dual' surf-zone can be attributed to wave shadowing by offshore islands under certain wave directions. Smaller rip channels on the narrow half of the beach changed rapidly whereas larger rips were stable during the same period. This situation shows the importance of both hydrodynamic-control and topographic-control of rips, where rips may respond directly to changes in the wave conditions or be stabilised by the pre-existing morphology respectively. There was also a tendency for rips to form and persist at the headlands of the beach. 

A conceptual model was created to demonstrate how rip channels of different spatial scales respond to changes in the wave conditions. Small rips relative to the wave energy are more likely than larger rips to evolve, and vice versa.

year: 2009

title: Assessing Survivor Syndrome During Economic Recession In New Zealand

authors: Singh, Sirjana

subjects: survivor syndrome

abstract: The present study aimed to gain an understanding of and assess survivor syndrome during the time of economic crises among public service employees in New Zealand. This study also explored the relationship between fulfilment of psychological contract and trust and faith in management and the relationship these phenomenon have with survivor syndrome. An online questionnaire was completed by 231 members of the Public Service Association (PSA) of New Zealand. The participants were divided in two groups, those who knew someone who had been made redundant in the previous 12 months (affected by organisational restructuring) and those who did not know anyone in the organisation who had been made redundant (employees not affected by organisational restructuring). Findings suggest that, as in previous studies done in New Zealand, employees do not suffer strongly from survivor syndrome. However there were significant differences in the scores of those affected and those not affected by organisational restructuring in survivor syndrome, morale, job security, job satisfaction, fulfilment of psychological contract and trust and faith in management for both groups. Fulfilment of psychological contract and trust and faith in management shared a positive relationship with survivor syndrome. Research by Wisener, Vermeulen and Littler (1999) and Littler, Wisener and Dunford (2003) has had an influence on the present study by offering a definition of survivor syndrome and the model of assessing it. However in this study survivor syndrome is assessed on an individual level (employees) where it is experienced. Managers in organisations could benefit from extending their awareness of survivor syndrome and managing the most important resource post restructuring – the surviving employees.

text: Assessing Survivor Syndrome During Economic Recession In New Zealand The present study aimed to gain an understanding of and assess survivor syndrome during the time of economic crises among public service employees in New Zealand. This study also explored the relationship between fulfilment of psychological contract and trust and faith in management and the relationship these phenomenon have with survivor syndrome. An online questionnaire was completed by 231 members of the Public Service Association (PSA) of New Zealand. The participants were divided in two groups, those who knew someone who had been made redundant in the previous 12 months (affected by organisational restructuring) and those who did not know anyone in the organisation who had been made redundant (employees not affected by organisational restructuring). Findings suggest that, as in previous studies done in New Zealand, employees do not suffer strongly from survivor syndrome. However there were significant differences in the scores of those affected and those not affected by organisational restructuring in survivor syndrome, morale, job security, job satisfaction, fulfilment of psychological contract and trust and faith in management for both groups. Fulfilment of psychological contract and trust and faith in management shared a positive relationship with survivor syndrome. Research by Wisener, Vermeulen and Littler (1999) and Littler, Wisener and Dunford (2003) has had an influence on the present study by offering a definition of survivor syndrome and the model of assessing it. However in this study survivor syndrome is assessed on an individual level (employees) where it is experienced. Managers in organisations could benefit from extending their awareness of survivor syndrome and managing the most important resource post restructuring – the surviving employees.

year: 2010

title: Unpacking media narratives: Racism and problematic reasonings

authors: Tan, Kyle K. H.

abstract: In this research brief, we present summaries of four case studies of racism in mainstream and social media in Aotearoa. Through a series of carefully selected datasets sourced from TV episodes (Police TEN 7), print media such as news articles (including Northland checkpoints), and tweets (Three Waters reform), we outline how Māori are represented across these mediums. With an expert in language modelling on our team, we analysed large datasets that give us sufficient statistical power to infer specific Māori discourses on respective platforms. Further, we examined key themes that characterise how Māori are represented in the media and signal the scale of anti-Māori attacks. For instance, we found that the predominant discussion on Three Waters reform on Twitter focused on ‘conflict’ (distrust towards government; 33%) and ‘capability’ (questioning the credibility of the reform; 23%) rather than its core intention of promoting water ‘safety’ (7%). The modelling analysis was supplemented by in-depth qualitative analysis that integrates anti-Māori themes (Moewaka-Barnes et al., 2012) and problematic reasoning tactics (Sturgill, 2021) to elucidate how false, deficit-based rhetoric about Māori is deployed to fuel racism and disinformation. In summary, our findings reinforce Kupu Taea’s call for new media sectors to integrate Te Tiriti o Waitangi into their practices to safeguard Māori and other minoritised groups who are likely to be at the fore of racist attacks.

text: Unpacking media narratives: Racism and problematic reasonings In this research brief, we present summaries of four case studies of racism in mainstream and social media in Aotearoa. Through a series of carefully selected datasets sourced from TV episodes (Police TEN 7), print media such as news articles (including Northland checkpoints), and tweets (Three Waters reform), we outline how Māori are represented across these mediums. With an expert in language modelling on our team, we analysed large datasets that give us sufficient statistical power to infer specific Māori discourses on respective platforms. Further, we examined key themes that characterise how Māori are represented in the media and signal the scale of anti-Māori attacks. For instance, we found that the predominant discussion on Three Waters reform on Twitter focused on ‘conflict’ (distrust towards government; 33%) and ‘capability’ (questioning the credibility of the reform; 23%) rather than its core intention of promoting water ‘safety’ (7%). The modelling analysis was supplemented by in-depth qualitative analysis that integrates anti-Māori themes (Moewaka-Barnes et al., 2012) and problematic reasoning tactics (Sturgill, 2021) to elucidate how false, deficit-based rhetoric about Māori is deployed to fuel racism and disinformation. In summary, our findings reinforce Kupu Taea’s call for new media sectors to integrate Te Tiriti o Waitangi into their practices to safeguard Māori and other minoritised groups who are likely to be at the fore of racist attacks.

year: 2025