title: Wave-induced sediment transport on an estuarine intertidal flat

authors: Dolphin, Tony J.

abstract: Waves and tides are the primary processes responsible for sediment entrainment on estuarine intertidal flats, however a detailed understanding of the temporal and spatial variability of wave processes, and the way in which these control estuarine sediment transport, is lacking. The aim of this thesis is to redress this deficiency. 

Wave, current and suspended-sediment meters were deployed along a 1600-m-long cross-shore transect of the Wiroa Island intertidal flat (Manukau Harbour, New Zealand) for a period of ten weeks. Additional data were obtained by four further experiments: a pilot experiment in the shallow estuarine fringes; field experiments to test an antifouling device and to develop a way of correcting data from biofouled optical backscatter sensors; field trials of pressure and velocity sensors under estuarine and open-coast waves; and experiments to test whether optical and acoustic backscatter sensors could be used to separately measure the concentration of suspended silts and suspended sands. 

Comparison of pressure and velocity data revealed an inconsistency in some wave data from the Wiroa flat and in Green and MacDonald's (2001) data from the Okura estuary: wave amplitudes estimated from pressure were significantly smaller (factor of 2-50) than corresponding amplitudes estimated from velocity data, and there was a phase lag (45-90°) between the pressure and velocity signals. The inconsistency could be interpreted as evidence of standing waves, however, data from some instruments do not support this. Tests of linear theory and sensor performance in estuarine and open-coast settings, the effect of sensor orientation, and comparisons with observed sand entrainment, suggest that the inconsistency is due to imperfect pressure-sensor frequency response. 

Waves vary systematically in response to changes in fetch, which in turn are associated with the submergence and emergence of intertidal banks during the rise and fall of the tide. For a given wind, growth in fetch on a rising tide equates to growth in wave height and period. Variation in the bed-orbital speed, Uw,bed, is due to different combinations of wave height (H), period (T) and depth (h̄).When the depth is large, bed-orbital speeds are small due to poor penetration of wave motions through the water column. On the other hand, when depth is smaller, or when period is longer, penetration is more 111 effective and bed-orbital speeds are larger as a result. Consequently, in some instances, Uw,bed is largest at high tide (when fetch, H and T are large) and smaller near the start and finish of the inundation. At other times, Uw,bed is smallest around high tide (when h̄ is too large for wave orbitals to penetrate effectively to the bed). Depth-limited wave breaking was not observed, but whitecaps were common. 

Sand and silt suspensions were switched on and off by wave activity (when the purewave
skin friction, θ’w , exceeded the sand threshold, θcr.sand, but not by tidal currents. Silt held in the local bed was released when sand was entrained, but there was no obvious relationship between the silt reference concentration and θ’w because a component of the silt was advected from elsewhere in the estuary and silt in the intertidal flat is supply-limited (<2% abundance). Sand reference concentration, Co, plots in three distinct clusters against θ’w which presumably correspond to rippled, transitional and flat beds. The three clusters collapsed onto a single line when flow contraction over ripple crests was accounted for, as observed by Nielsen (1986). The transitional data have not been previously identified and may represent the co-existence of rippled and flat beds. Suspended-silt concentrations were vertically homogeneous, but suspended-sand concentrations follow the simple exponential profile model (Nielsen, 1984), where the mixing length is controlled by ripple height, settling velocity and bed-orbital speed. 

Silt concentrations were highest in the edge of estuarine water body known as the turbid fringe (Green et al., 1997). Enhanced settling and onshore-directed wave-orbital asymmetry are thought to aid silt deposition observed on the upper flats. Patterns in sand transport are complex because the primary drivers - tidal currents and the wave induced concentration field - are independent of each other and both vary with location across the flat and in time through the tidal cycle. This was explored by schematic modelling, which showed that combinations of different tidal regimes and fetch types produce different spatial and temporal patterns in current and concentration fields, and therefore in sediment transport. The field data showed drainage currents can be responsible for offshore transport, while asymmetry in wave-orbital motions was a means for onshore sand transport. 

Spatial patterns in processes align with sedimentary and geomorphic features. Silts were found to be abundant on the channel margins, where θ’w < Ocr.sand. The intermittently inundated region near the top of the flat has the lowest slopes, and is a potential deposition zone for sands transported to the tidal edge and stranded there during the receding ebb tide. Patterns in time-integrated work due to waves, Ww, also correspond to changes in slope: slope was lowest on the upper flat where Ww was greatest, but steepened where Ww declined as a result of high tidal-translation rates across the middle flats. 

Allen's ( 1971) model describes spatial trends in waves and tides across intertidal flats; wave activity at the bed increases at higher elevations while tidal currents decrease. The Wiroa data reveal a more complex situation: Uw,bed and Ww are controlled by variations in wind speed and direction, fetch length, wave height, wave period, penetration, and the tidal translation rate. Thus, while Allen established a paradigm that implies zonation in transport processes, spatial and temporal interactions between waves and tidal currents can create both more subtle and more profoundly different patterns.

text: Wave-induced sediment transport on an estuarine intertidal flat Waves and tides are the primary processes responsible for sediment entrainment on estuarine intertidal flats, however a detailed understanding of the temporal and spatial variability of wave processes, and the way in which these control estuarine sediment transport, is lacking. The aim of this thesis is to redress this deficiency. 

Wave, current and suspended-sediment meters were deployed along a 1600-m-long cross-shore transect of the Wiroa Island intertidal flat (Manukau Harbour, New Zealand) for a period of ten weeks. Additional data were obtained by four further experiments: a pilot experiment in the shallow estuarine fringes; field experiments to test an antifouling device and to develop a way of correcting data from biofouled optical backscatter sensors; field trials of pressure and velocity sensors under estuarine and open-coast waves; and experiments to test whether optical and acoustic backscatter sensors could be used to separately measure the concentration of suspended silts and suspended sands. 

Comparison of pressure and velocity data revealed an inconsistency in some wave data from the Wiroa flat and in Green and MacDonald's (2001) data from the Okura estuary: wave amplitudes estimated from pressure were significantly smaller (factor of 2-50) than corresponding amplitudes estimated from velocity data, and there was a phase lag (45-90°) between the pressure and velocity signals. The inconsistency could be interpreted as evidence of standing waves, however, data from some instruments do not support this. Tests of linear theory and sensor performance in estuarine and open-coast settings, the effect of sensor orientation, and comparisons with observed sand entrainment, suggest that the inconsistency is due to imperfect pressure-sensor frequency response. 

Waves vary systematically in response to changes in fetch, which in turn are associated with the submergence and emergence of intertidal banks during the rise and fall of the tide. For a given wind, growth in fetch on a rising tide equates to growth in wave height and period. Variation in the bed-orbital speed, Uw,bed, is due to different combinations of wave height (H), period (T) and depth (h̄).When the depth is large, bed-orbital speeds are small due to poor penetration of wave motions through the water column. On the other hand, when depth is smaller, or when period is longer, penetration is more 111 effective and bed-orbital speeds are larger as a result. Consequently, in some instances, Uw,bed is largest at high tide (when fetch, H and T are large) and smaller near the start and finish of the inundation. At other times, Uw,bed is smallest around high tide (when h̄ is too large for wave orbitals to penetrate effectively to the bed). Depth-limited wave breaking was not observed, but whitecaps were common. 

Sand and silt suspensions were switched on and off by wave activity (when the purewave
skin friction, θ’w , exceeded the sand threshold, θcr.sand, but not by tidal currents. Silt held in the local bed was released when sand was entrained, but there was no obvious relationship between the silt reference concentration and θ’w because a component of the silt was advected from elsewhere in the estuary and silt in the intertidal flat is supply-limited (<2% abundance). Sand reference concentration, Co, plots in three distinct clusters against θ’w which presumably correspond to rippled, transitional and flat beds. The three clusters collapsed onto a single line when flow contraction over ripple crests was accounted for, as observed by Nielsen (1986). The transitional data have not been previously identified and may represent the co-existence of rippled and flat beds. Suspended-silt concentrations were vertically homogeneous, but suspended-sand concentrations follow the simple exponential profile model (Nielsen, 1984), where the mixing length is controlled by ripple height, settling velocity and bed-orbital speed. 

Silt concentrations were highest in the edge of estuarine water body known as the turbid fringe (Green et al., 1997). Enhanced settling and onshore-directed wave-orbital asymmetry are thought to aid silt deposition observed on the upper flats. Patterns in sand transport are complex because the primary drivers - tidal currents and the wave induced concentration field - are independent of each other and both vary with location across the flat and in time through the tidal cycle. This was explored by schematic modelling, which showed that combinations of different tidal regimes and fetch types produce different spatial and temporal patterns in current and concentration fields, and therefore in sediment transport. The field data showed drainage currents can be responsible for offshore transport, while asymmetry in wave-orbital motions was a means for onshore sand transport. 

Spatial patterns in processes align with sedimentary and geomorphic features. Silts were found to be abundant on the channel margins, where θ’w < Ocr.sand. The intermittently inundated region near the top of the flat has the lowest slopes, and is a potential deposition zone for sands transported to the tidal edge and stranded there during the receding ebb tide. Patterns in time-integrated work due to waves, Ww, also correspond to changes in slope: slope was lowest on the upper flat where Ww was greatest, but steepened where Ww declined as a result of high tidal-translation rates across the middle flats. 

Allen's ( 1971) model describes spatial trends in waves and tides across intertidal flats; wave activity at the bed increases at higher elevations while tidal currents decrease. The Wiroa data reveal a more complex situation: Uw,bed and Ww are controlled by variations in wind speed and direction, fetch length, wave height, wave period, penetration, and the tidal translation rate. Thus, while Allen established a paradigm that implies zonation in transport processes, spatial and temporal interactions between waves and tidal currents can create both more subtle and more profoundly different patterns.

year: 2004

title: Visualize online collocation dictionary with force-directed graph

authors: Pham, Bob

subjects: Visualization

abstract: For second-language learners, collocational knowledge is very important. Knowing collocational phrases allows learners to speak and write in their targeted language naturally and reduce dramatically side effect of their first language. In order for learners to learn collocations easily, a lot of learning methods have been introduced. Particularly, learning from online-collocational corpus has become popular due to its accessibility and massive database. Although, its current presentation of information is still simple, it can be improved by using optimized representations in order to help users learning.

In this thesis, we represent a suitable way to visualize online collocational dictionary by using graph representation in order to facilitate users’ learning and provide flexible exploration. Animation is also used to increase level of engagement for users. We use force-directed model for the layout, but we develop our own graph component and combine some current algorithms in order to create a proper algorithm for our purposes. The implementation is tested by a small group of participants and the results are promising.

text: Visualize online collocation dictionary with force-directed graph For second-language learners, collocational knowledge is very important. Knowing collocational phrases allows learners to speak and write in their targeted language naturally and reduce dramatically side effect of their first language. In order for learners to learn collocations easily, a lot of learning methods have been introduced. Particularly, learning from online-collocational corpus has become popular due to its accessibility and massive database. Although, its current presentation of information is still simple, it can be improved by using optimized representations in order to help users learning.

In this thesis, we represent a suitable way to visualize online collocational dictionary by using graph representation in order to facilitate users’ learning and provide flexible exploration. Animation is also used to increase level of engagement for users. We use force-directed model for the layout, but we develop our own graph component and combine some current algorithms in order to create a proper algorithm for our purposes. The implementation is tested by a small group of participants and the results are promising.

year: 2012

title: A case study of using the He Pikinga Waiora Implementation Framework: Challenges and successes in implementing a twelve-week lifestyle intervention to reduce weight in Māori men at risk of diabetes, cardiovascular disease and obesity

authors: Oetzel, John G.

subjects: Science & Technology

abstract: BACKGROUND: Māori men have stark health inequities around non-communicable diseases. This study describes the case of a partnership attempting to develop and implement a culturally centred intervention through a collaborative partnership to potentially address the inequities. In particular, the partnership followed a participatory, co-design approach using the He Pikinga Waiora (HPW) Implementation Framework; the study presents lessons learnt in addressing health inequities following this framework. METHODS: The partnership involved a university research team and a Māori community health provider. They engaged with other stakeholders and several cohorts of Māori men through a co-design process to adapt a 12-week lifestyle intervention. The co-design process was documented through meeting notes and interviews with partners. Two cohorts participated in separate single group pre-intervention/post-intervention designs with multi-method data collection. Key outcome measures included weight loss, self-reported health, physical activity, and nutrition. Post-intervention data collection included qualitative data. RESULTS: The co-design process resulted in a strong and engaged partnership between the university team and the provider. There were significant challenges in implementing the intervention including having two additional partner organisations dropping out of the partnership just after the initial implementation phase. However, a flexible and adaptable partnership resulted in developing two distinct lifestyle interventions run with 32 Māori men (in two different cohorts of 8 and 24). All but one in the first cohort completed the programme. The first cohort had a modest although statistically insignificant improvement in weight loss (d = 1.04) and body mass index (BMI; d = 1.08). The second cohort had a significant reduction in weight loss (d = 1.16) and BMI (d = 1.15). They also had a significant increase in health-related quality of life (d = 1.7) and self-rated health (d = 2.0). CONCLUSION: The HPW Framework appears to be well suited to advance implementation science for Indigenous communities in general and Māori in particular. The framework has promise as a policy and planning tool to evaluate and design interventions for chronic disease prevention in Indigenous communities. Despite this promise, there are structural challenges in developing and implementing interventions to address health inequities. TRIAL REGISTRATION: Retrospectively registered, Australia New Zealand Clinical Trials Registry, ACTRN12619001783112.

text: A case study of using the He Pikinga Waiora Implementation Framework: Challenges and successes in implementing a twelve-week lifestyle intervention to reduce weight in Māori men at risk of diabetes, cardiovascular disease and obesity BACKGROUND: Māori men have stark health inequities around non-communicable diseases. This study describes the case of a partnership attempting to develop and implement a culturally centred intervention through a collaborative partnership to potentially address the inequities. In particular, the partnership followed a participatory, co-design approach using the He Pikinga Waiora (HPW) Implementation Framework; the study presents lessons learnt in addressing health inequities following this framework. METHODS: The partnership involved a university research team and a Māori community health provider. They engaged with other stakeholders and several cohorts of Māori men through a co-design process to adapt a 12-week lifestyle intervention. The co-design process was documented through meeting notes and interviews with partners. Two cohorts participated in separate single group pre-intervention/post-intervention designs with multi-method data collection. Key outcome measures included weight loss, self-reported health, physical activity, and nutrition. Post-intervention data collection included qualitative data. RESULTS: The co-design process resulted in a strong and engaged partnership between the university team and the provider. There were significant challenges in implementing the intervention including having two additional partner organisations dropping out of the partnership just after the initial implementation phase. However, a flexible and adaptable partnership resulted in developing two distinct lifestyle interventions run with 32 Māori men (in two different cohorts of 8 and 24). All but one in the first cohort completed the programme. The first cohort had a modest although statistically insignificant improvement in weight loss (d = 1.04) and body mass index (BMI; d = 1.08). The second cohort had a significant reduction in weight loss (d = 1.16) and BMI (d = 1.15). They also had a significant increase in health-related quality of life (d = 1.7) and self-rated health (d = 2.0). CONCLUSION: The HPW Framework appears to be well suited to advance implementation science for Indigenous communities in general and Māori in particular. The framework has promise as a policy and planning tool to evaluate and design interventions for chronic disease prevention in Indigenous communities. Despite this promise, there are structural challenges in developing and implementing interventions to address health inequities. TRIAL REGISTRATION: Retrospectively registered, Australia New Zealand Clinical Trials Registry, ACTRN12619001783112.

year: 2020