title: Understanding contemporary Māori demographic fertility patterns and trends in Aotearoa New Zealand

authors: Rarere, Moana

abstract: This thesis re-examines demographic studies of contemporary Māori fertility patterns and trends. Analysing fertility is a core undertaking in demography, and in studies that include Māori fertility, most have been undertaken by non-Māori demographers who instinctively draw on Western-based frameworks to analyse and interpret these trends.  Consequently, Māori perspectives are virtually invisible.  Incorporating Māori perspectives are needed because despite a convergence of fertility similar to Pākehā, important fertility patterns persist.  Notably, Māori women bear their babies earlier and over a longer period.  Fertility studies of other Indigenous peoples in settler-colonial states share striking similarities.  While demographic and economic factors are important in fertility outcomes, this thesis primarily explores the potential influence of culture, which has received little attention.  Hence, this doctoral study asks: To what extent does culture influence contemporary Māori fertility patterns?

This thesis draws on Kaupapa Māori and Mana Wahine frameworks, along with the tools of demography, to deploy a mixed methods design of statistical techniques – using secondary data from the 2013 Aotearoa NZ Census and the 1995 New Zealand Women: Family, Employment, and Education Survey – and thematic analysis of interviews with nine Māori women.  While acknowledging the limitations of the analyses, the empirical results suggest that ‘cultural identity’ is an important factor in Māori fertility, and that ‘whakapapa’ and ‘whānau’ are at the heart of fertility decisions.  These findings broadly imply that taken-for-granted demographic theories and analytical practices need to incorporate Indigenous-centred frameworks and perspectives for a better understanding of Indigenous fertility and population change.

text: Understanding contemporary Māori demographic fertility patterns and trends in Aotearoa New Zealand This thesis re-examines demographic studies of contemporary Māori fertility patterns and trends. Analysing fertility is a core undertaking in demography, and in studies that include Māori fertility, most have been undertaken by non-Māori demographers who instinctively draw on Western-based frameworks to analyse and interpret these trends.  Consequently, Māori perspectives are virtually invisible.  Incorporating Māori perspectives are needed because despite a convergence of fertility similar to Pākehā, important fertility patterns persist.  Notably, Māori women bear their babies earlier and over a longer period.  Fertility studies of other Indigenous peoples in settler-colonial states share striking similarities.  While demographic and economic factors are important in fertility outcomes, this thesis primarily explores the potential influence of culture, which has received little attention.  Hence, this doctoral study asks: To what extent does culture influence contemporary Māori fertility patterns?

This thesis draws on Kaupapa Māori and Mana Wahine frameworks, along with the tools of demography, to deploy a mixed methods design of statistical techniques – using secondary data from the 2013 Aotearoa NZ Census and the 1995 New Zealand Women: Family, Employment, and Education Survey – and thematic analysis of interviews with nine Māori women.  While acknowledging the limitations of the analyses, the empirical results suggest that ‘cultural identity’ is an important factor in Māori fertility, and that ‘whakapapa’ and ‘whānau’ are at the heart of fertility decisions.  These findings broadly imply that taken-for-granted demographic theories and analytical practices need to incorporate Indigenous-centred frameworks and perspectives for a better understanding of Indigenous fertility and population change.

year: 2024

title: A New Technique for Measuring Runup Variation Using Sub-Aerial Video Imagery

authors: Salmon, Summer Anne

subjects: Wave Runup

abstract: Video monitoring of beaches is becoming the preferred method for observing changes to nearshore morphology. Consequently this work investigates a new technique for predicting the probability of inundation that is based on measuring runup variation using video. Runup is defined as the water-level elevation maxima on the foreshore relative to the still water level and the waterline is defined as the position where the MWL intersects the beach face. Tairua, and Pauanui Beaches, on the north east coast of the North Island of New Zealand, were used as the field site in this study and represent two very different beaches with the same incoming wave and meteorological conditions. Tairua is most frequently in an intermediate beach state, whereas Pauanui is usually flatter in nature.

In order to rectify runup observations, an estimate of the runup elevation was needed (Z). This was estimated by measuring the variation of the waterline over a tidal cycle from time-averaged video images during a storm event and provided beach morphology statistics (i.e. beach slope (α) and beach intercept (b)) used in the rectification process where Z=aX+b. The maximum swash excursions were digitized from time-stacks, and rectified to provide run-up timeseries with duration 20 minutes. Field calibrations revealed a videoed waterline that was seaward of the surveyed waterline. Quantification of this error gave a vertical offset of 0.33m at Tairua and 0.25m at Pauanui. 

At Tairua, incident wave energy was dominant in the swash zone, and the runup distributions followed a Rayleigh distribution. At Pauanui, the flatter beach, the runup distributions were approximately bimodal due to the dominance of infragravity energy in the swash signal. The slope of the beach was a major control on the runup elevation; runup at Pauanui was directly affected by the deepwater wave height and the tide, while at Tairua there was no correlation. Overall, the results of the study indicate realistic runup measurements, over a wide range of time scales and, importantly, during storm events. However, comparisons of videoed runup and empirical runup formulae revealed larger deviations as the beach steepness increased. Furthur tests need to be carried out to see if this is a limitation of this technique, used to measure runup. The runup statistics are consistently higher at Tairua and suggests that swash runs up higher on steeper beaches. However, because of the characteristics of flatter beaches (such as high water tables and low drainage efficiencies) the impact of extreme runup elevations on such beaches are more critical in regards to erosion and/ or inundation.

The coastal environment is of great importance to Māori. Damage to the coast and coastal waahi tapu (places of spiritual importance) caused by erosion and inundation, adversely affects the spiritual and cultural well-being of Māori. For this reason, a chapter was dedicated to investigating the practices used by Māori to protect and preserve the coasts in accordance with tikanga Māori (Māori protocols). Mimicking nature was and still is a practice used by Māori to restore the beaches after erosive events, and includes replanting native dune plants and using natural materials on the beaches to stabilize the dunes. Tapu and rahui (the power and influence of the gods) were imposed on communities to prohibit and prevent people from free access to either food resources or to a particular place, in order to protect people and/ or resources. Interpretations of Māori oral histories provide insights into past local hazards and inform about the safety and viability of certain activities within an area. Environmental indicators were used to identify and forecast extreme weather conditions locally.  Māori knowledge of past hazards, and the coastal environment as a whole, is a valuable resource and provides a unique source of expertise that can contribute to current coastal hazards management plans in New Zealand and provide insights about the areas that may again be impacted by natural hazards.

text: A New Technique for Measuring Runup Variation Using Sub-Aerial Video Imagery Video monitoring of beaches is becoming the preferred method for observing changes to nearshore morphology. Consequently this work investigates a new technique for predicting the probability of inundation that is based on measuring runup variation using video. Runup is defined as the water-level elevation maxima on the foreshore relative to the still water level and the waterline is defined as the position where the MWL intersects the beach face. Tairua, and Pauanui Beaches, on the north east coast of the North Island of New Zealand, were used as the field site in this study and represent two very different beaches with the same incoming wave and meteorological conditions. Tairua is most frequently in an intermediate beach state, whereas Pauanui is usually flatter in nature.

In order to rectify runup observations, an estimate of the runup elevation was needed (Z). This was estimated by measuring the variation of the waterline over a tidal cycle from time-averaged video images during a storm event and provided beach morphology statistics (i.e. beach slope (α) and beach intercept (b)) used in the rectification process where Z=aX+b. The maximum swash excursions were digitized from time-stacks, and rectified to provide run-up timeseries with duration 20 minutes. Field calibrations revealed a videoed waterline that was seaward of the surveyed waterline. Quantification of this error gave a vertical offset of 0.33m at Tairua and 0.25m at Pauanui. 

At Tairua, incident wave energy was dominant in the swash zone, and the runup distributions followed a Rayleigh distribution. At Pauanui, the flatter beach, the runup distributions were approximately bimodal due to the dominance of infragravity energy in the swash signal. The slope of the beach was a major control on the runup elevation; runup at Pauanui was directly affected by the deepwater wave height and the tide, while at Tairua there was no correlation. Overall, the results of the study indicate realistic runup measurements, over a wide range of time scales and, importantly, during storm events. However, comparisons of videoed runup and empirical runup formulae revealed larger deviations as the beach steepness increased. Furthur tests need to be carried out to see if this is a limitation of this technique, used to measure runup. The runup statistics are consistently higher at Tairua and suggests that swash runs up higher on steeper beaches. However, because of the characteristics of flatter beaches (such as high water tables and low drainage efficiencies) the impact of extreme runup elevations on such beaches are more critical in regards to erosion and/ or inundation.

The coastal environment is of great importance to Māori. Damage to the coast and coastal waahi tapu (places of spiritual importance) caused by erosion and inundation, adversely affects the spiritual and cultural well-being of Māori. For this reason, a chapter was dedicated to investigating the practices used by Māori to protect and preserve the coasts in accordance with tikanga Māori (Māori protocols). Mimicking nature was and still is a practice used by Māori to restore the beaches after erosive events, and includes replanting native dune plants and using natural materials on the beaches to stabilize the dunes. Tapu and rahui (the power and influence of the gods) were imposed on communities to prohibit and prevent people from free access to either food resources or to a particular place, in order to protect people and/ or resources. Interpretations of Māori oral histories provide insights into past local hazards and inform about the safety and viability of certain activities within an area. Environmental indicators were used to identify and forecast extreme weather conditions locally.  Māori knowledge of past hazards, and the coastal environment as a whole, is a valuable resource and provides a unique source of expertise that can contribute to current coastal hazards management plans in New Zealand and provide insights about the areas that may again be impacted by natural hazards.

year: 2008

title: Steady and unsteady visco-resistive reconnection in the presence of the Hall effect

authors: McMahon, Liam

subjects: Magnetic Reconnection

abstract: In this thesis we investigate the effects of viscosity and the Hall effect on magnetic reconnection. Magnetic reconnection is a process of releasing large amounts of magnetic energy as observed in solar flares. In the first two chapters, we describe the basic mathematics and early models of reconnection.

In Chapter 3, we search for a visco-resistive length scale in reconnection solutions. This is demonstrated in reconnective annihilation and a quasi-one-dimensional series expansion. We find that the visco-resistive length scale appears organically unless a specific geometry is chosen. Upon adding small scale perturbations, the visco-resistive length scale always appears.

 In Chapter 4, we build on Litvinenko’s (2007) self-similar solution that showed singularities appear with a Hall MHD X-point geometry for a certain set of initial conditions. These singularities signal current sheet formation. We consider a general set of initial conditions and find that the singularities will form in this self-similar solution unless the axial field is many orders of magnitude larger than the planar field. 

In Chapter 5, we review the Craig and McClymont (1991) linear, oscillatory  model of reconnection. In Chapter 6, we attempt to quantify a general model that includes viscosity, pressure and axial effects, the Hall effect and electron inertia. We perform a dimensional analysis to find order-of magnitude estimates for how the aforementioned effects perturb the Craig and McClymont (1991) solution. We verify these estimates with numerical simulations. 

In Chapter 7, we give an overview of the thesis and make suggestions for future work.

text: Steady and unsteady visco-resistive reconnection in the presence of the Hall effect In this thesis we investigate the effects of viscosity and the Hall effect on magnetic reconnection. Magnetic reconnection is a process of releasing large amounts of magnetic energy as observed in solar flares. In the first two chapters, we describe the basic mathematics and early models of reconnection.

In Chapter 3, we search for a visco-resistive length scale in reconnection solutions. This is demonstrated in reconnective annihilation and a quasi-one-dimensional series expansion. We find that the visco-resistive length scale appears organically unless a specific geometry is chosen. Upon adding small scale perturbations, the visco-resistive length scale always appears.

 In Chapter 4, we build on Litvinenko’s (2007) self-similar solution that showed singularities appear with a Hall MHD X-point geometry for a certain set of initial conditions. These singularities signal current sheet formation. We consider a general set of initial conditions and find that the singularities will form in this self-similar solution unless the axial field is many orders of magnitude larger than the planar field. 

In Chapter 5, we review the Craig and McClymont (1991) linear, oscillatory  model of reconnection. In Chapter 6, we attempt to quantify a general model that includes viscosity, pressure and axial effects, the Hall effect and electron inertia. We perform a dimensional analysis to find order-of magnitude estimates for how the aforementioned effects perturb the Craig and McClymont (1991) solution. We verify these estimates with numerical simulations. 

In Chapter 7, we give an overview of the thesis and make suggestions for future work.

year: 2021