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: Kōura in the Rotorua Te Arawa Lakes and potential effects of catfish

authors: Kusabs, Ian

abstract: I am going to talk about kōura and the novel sampling method we are using, then talk about the population characteristics of kōura in the Rotorua Te Arawa Lakes, including results from my PhD research, the Lake Taupō experience with catfish, which Michel Dedual has more than adequately described, and also future work.

text: Kōura in the Rotorua Te Arawa Lakes and potential effects of catfish I am going to talk about kōura and the novel sampling method we are using, then talk about the population characteristics of kōura in the Rotorua Te Arawa Lakes, including results from my PhD research, the Lake Taupō experience with catfish, which Michel Dedual has more than adequately described, and also future work.

year: 2017

title: An examination of the managerial decision-making processes of experts from a behavioural perspective

authors: Gilmour, Peter John

abstract: The purpose of this study was to develop an understanding of the interaction between expertise, managerial role, and subjective behavioural characteristics. The research seeks answers to the question: What shapes the managerial decision-making processes of an expert? 

Four case studies examined the decision-making processes of four domain experts who have taken on managerial roles. The studies follow a triangulated approach using interviews, observations and psychological evaluations to discover the dominant decision making processes of the experts in their managerial roles. This study includes interviews with each of the four experts, interviews with people associated with them in their work environment, the researcher’s observations, and three psychological evaluations. 
The research indicates that the subjective characteristics of the experts studied may determine the domain in which they became expert, and consequently the managerial role that they chose and also the managerial decision-making processes that they follow. The experts’ decision-making processes seem to be shaped initially by their subjective characteristics, second by their expertise and last by their managerial role. There was however, an indication that these experts dichotomise their managerial decision-making processes to distinguish between decisions that directly involve people and other decisions. Managerial requirements create situations that require the use of the experts’ subjective characteristics that are not otherwise used. It is therefore concluded that the subjective characteristics of the experts studied have shaped their managerial decision-making processes. 

The outcome from a study of four experts is not expected to be valid for all experts, however it may add weight to an argument that more consideration needs to be made of the two-way interaction between expert and domain.

text: An examination of the managerial decision-making processes of experts from a behavioural perspective The purpose of this study was to develop an understanding of the interaction between expertise, managerial role, and subjective behavioural characteristics. The research seeks answers to the question: What shapes the managerial decision-making processes of an expert? 

Four case studies examined the decision-making processes of four domain experts who have taken on managerial roles. The studies follow a triangulated approach using interviews, observations and psychological evaluations to discover the dominant decision making processes of the experts in their managerial roles. This study includes interviews with each of the four experts, interviews with people associated with them in their work environment, the researcher’s observations, and three psychological evaluations. 
The research indicates that the subjective characteristics of the experts studied may determine the domain in which they became expert, and consequently the managerial role that they chose and also the managerial decision-making processes that they follow. The experts’ decision-making processes seem to be shaped initially by their subjective characteristics, second by their expertise and last by their managerial role. There was however, an indication that these experts dichotomise their managerial decision-making processes to distinguish between decisions that directly involve people and other decisions. Managerial requirements create situations that require the use of the experts’ subjective characteristics that are not otherwise used. It is therefore concluded that the subjective characteristics of the experts studied have shaped their managerial decision-making processes. 

The outcome from a study of four experts is not expected to be valid for all experts, however it may add weight to an argument that more consideration needs to be made of the two-way interaction between expert and domain.

year: 2001