title: Three-dimensional numerical simulation of mixing patterns at open channel confluences

authors: Aghazadegan, Ali

abstract: Open channel confluences, where two streams or rivers converge, play a crucial role in hydraulic engineering and river dynamics. These confluences are characterized by complex hydrodynamics influenced by the discharge ratios of merging water bodies. This study investigated the mixing structure at open channel confluences using three-dimensional numerical modeling. A comprehensive three-dimensional numerical model was developed and validated against a dataset obtained from controlled laboratory experiments. This dataset incorporated three-dimensional time-averaged velocity measurements. The skew-induced and stress-induced equation systems were adopted as the core governing equations, providing a framework for simulating various scenarios. A total of ten different cases were analyzed. The results highlighted the effect of discharge ratios on turbulence, lateral and vertical vorticities, and the distribution of mixing, which intensified with higher magnitudes of discharge ratios. The mixing structure, driven by velocity gradients and vorticity, revealed the significant role of lateral and vertical vorticities in determining hydrodynamic behaviors and mixing distributions at confluences. Specifically, the momentum ratio of incoming flows governed the spatial evolution of mixing processes. This study revealed that the distribution of mixing served as a key indicator for identifying the formation of mid-channel scours. High normalized velocities induced toward the left bank led to the superelevation of the water surface, enhancing the potential for bed material and the formation of significant scour holes beneath the elevated water surface. This novel approach provides a deeper understanding of the mixing patterns at confluences, particularly in scenarios with equilibrated discharge ratios but in different magnitudes.

text: Three-dimensional numerical simulation of mixing patterns at open channel confluences Open channel confluences, where two streams or rivers converge, play a crucial role in hydraulic engineering and river dynamics. These confluences are characterized by complex hydrodynamics influenced by the discharge ratios of merging water bodies. This study investigated the mixing structure at open channel confluences using three-dimensional numerical modeling. A comprehensive three-dimensional numerical model was developed and validated against a dataset obtained from controlled laboratory experiments. This dataset incorporated three-dimensional time-averaged velocity measurements. The skew-induced and stress-induced equation systems were adopted as the core governing equations, providing a framework for simulating various scenarios. A total of ten different cases were analyzed. The results highlighted the effect of discharge ratios on turbulence, lateral and vertical vorticities, and the distribution of mixing, which intensified with higher magnitudes of discharge ratios. The mixing structure, driven by velocity gradients and vorticity, revealed the significant role of lateral and vertical vorticities in determining hydrodynamic behaviors and mixing distributions at confluences. Specifically, the momentum ratio of incoming flows governed the spatial evolution of mixing processes. This study revealed that the distribution of mixing served as a key indicator for identifying the formation of mid-channel scours. High normalized velocities induced toward the left bank led to the superelevation of the water surface, enhancing the potential for bed material and the formation of significant scour holes beneath the elevated water surface. This novel approach provides a deeper understanding of the mixing patterns at confluences, particularly in scenarios with equilibrated discharge ratios but in different magnitudes.

year: 2025

title: The ecology of community environmental groups: Integrating restoration, partnerships and citizen science

authors: Peters, Monica Annabel

subjects: conservation

abstract: New Zealand is facing a biodiversity crisis as forest and wetland habitat loss continue, and the quality of freshwater declines. But in recent years, a grassroots, nationwide network of community environmental groups has been expanding its contribution to restoring, protecting and enhancing these terrestrial and aquatic habitats. At the same time, government agencies are becoming increasingly reliant on voluntary community input to enhance conservation outcomes and to manage freshwater values. Globally, volunteer participation in environmental monitoring (citizen science) is recognised as an important mechanism for producing robust data that contributes to research, management and policy development, and for enhancing scientific and environmental literacy. New Zealand, however, lags far behind international efforts in acknowledging the value of, and uses for, the type of data that community groups undertaking environmental restoration may generate. Furthermore, strategies and policies around supporting community data generation as well as use have not yet been developed at a government level.  

This study sought to address this shortcoming by investigating characteristics of New Zealand community environmental groups and their projects, partnerships between groups and their project supporters, and the current and potential roles of environmental monitoring by these groups (i.e., citizen science). Data to inform this investigation was gathered using an online questionnaire sent to 540 community environmental groups across New Zealand, and 34 semi-structured interviews with project partners (e.g., resource managers and scientists),  including nine interviews with members of four well–established (>10 y) community environmental groups. Qualitative data from the questionnaire and interviews were analysed using inductive and deductive thematic analysis, and quantitative data from the questionnaire were analysed for frequency counts, chi-square significance and Random Forest modelling. 

Most groups surveyed were in existence for ≥ 6 y, small (up to 20 participants), and comprised older participants, aged 51-65 y. Groups reported focussing their restoration efforts on a variety of ecosystem types including forests (64%), streams (42%) and freshwater wetlands (33%), which were mostly situated on agency-owned or administered land (68%, n=290). Over two-thirds of groups combined environmental actions (particularly weed and pest control, and native tree planting), with advocacy and educational activities. The vast majority (93%, n=295) of groups relied on their project partners for support (e.g., site visits, funding and technical support), and reported a need for ongoing support in the future. Groups managing larger areas (≥ 8.1 ha), with medium to high partner support, and working on Department of Conservation or private land were more likely to be conducting their own monitoring. Their data were primarily used to support funding applications (63%; n=151), inform project restoration management, and share results with resource management agencies (both 60%; n=151), and for educational purposes (48%; n=157). Conducting water quality monitoring emerged as a strong area of interest for future work, though groups reported a lack of funding and people (both 45%; n=98), as well as technical skills (31%) as the largest challenges they faced for establishing new monitoring programmes generally. Project partners expressed concern over data quality and highlighted a lack of institutional systems for using community-generated data. 

This study provides insights into the methods used by groups to address environmental degradation in New Zealand and the contextual factors that shape their project activities. Enduring partnerships are critical, and more strategic approaches that are designed to support groups and their projects in the long-term are required. Both restoration and citizen science activities by groups are generally carried out independently of other groups, highlighting the need for improved networks between groups and with key agency project partners in order to: (1) achieve stronger conservation outcomes; (2) quantify restoration gains, and (3) improve the efficiency and efficacy of the limited resourcing available. At the same time, expectations of enhancing groups’ conservation and citizen science outputs must be balanced with the voluntary nature of community groups.

text: The ecology of community environmental groups: Integrating restoration, partnerships and citizen science New Zealand is facing a biodiversity crisis as forest and wetland habitat loss continue, and the quality of freshwater declines. But in recent years, a grassroots, nationwide network of community environmental groups has been expanding its contribution to restoring, protecting and enhancing these terrestrial and aquatic habitats. At the same time, government agencies are becoming increasingly reliant on voluntary community input to enhance conservation outcomes and to manage freshwater values. Globally, volunteer participation in environmental monitoring (citizen science) is recognised as an important mechanism for producing robust data that contributes to research, management and policy development, and for enhancing scientific and environmental literacy. New Zealand, however, lags far behind international efforts in acknowledging the value of, and uses for, the type of data that community groups undertaking environmental restoration may generate. Furthermore, strategies and policies around supporting community data generation as well as use have not yet been developed at a government level.  

This study sought to address this shortcoming by investigating characteristics of New Zealand community environmental groups and their projects, partnerships between groups and their project supporters, and the current and potential roles of environmental monitoring by these groups (i.e., citizen science). Data to inform this investigation was gathered using an online questionnaire sent to 540 community environmental groups across New Zealand, and 34 semi-structured interviews with project partners (e.g., resource managers and scientists),  including nine interviews with members of four well–established (>10 y) community environmental groups. Qualitative data from the questionnaire and interviews were analysed using inductive and deductive thematic analysis, and quantitative data from the questionnaire were analysed for frequency counts, chi-square significance and Random Forest modelling. 

Most groups surveyed were in existence for ≥ 6 y, small (up to 20 participants), and comprised older participants, aged 51-65 y. Groups reported focussing their restoration efforts on a variety of ecosystem types including forests (64%), streams (42%) and freshwater wetlands (33%), which were mostly situated on agency-owned or administered land (68%, n=290). Over two-thirds of groups combined environmental actions (particularly weed and pest control, and native tree planting), with advocacy and educational activities. The vast majority (93%, n=295) of groups relied on their project partners for support (e.g., site visits, funding and technical support), and reported a need for ongoing support in the future. Groups managing larger areas (≥ 8.1 ha), with medium to high partner support, and working on Department of Conservation or private land were more likely to be conducting their own monitoring. Their data were primarily used to support funding applications (63%; n=151), inform project restoration management, and share results with resource management agencies (both 60%; n=151), and for educational purposes (48%; n=157). Conducting water quality monitoring emerged as a strong area of interest for future work, though groups reported a lack of funding and people (both 45%; n=98), as well as technical skills (31%) as the largest challenges they faced for establishing new monitoring programmes generally. Project partners expressed concern over data quality and highlighted a lack of institutional systems for using community-generated data. 

This study provides insights into the methods used by groups to address environmental degradation in New Zealand and the contextual factors that shape their project activities. Enduring partnerships are critical, and more strategic approaches that are designed to support groups and their projects in the long-term are required. Both restoration and citizen science activities by groups are generally carried out independently of other groups, highlighting the need for improved networks between groups and with key agency project partners in order to: (1) achieve stronger conservation outcomes; (2) quantify restoration gains, and (3) improve the efficiency and efficacy of the limited resourcing available. At the same time, expectations of enhancing groups’ conservation and citizen science outputs must be balanced with the voluntary nature of community groups.

year: 2016

title: Outcomes in different ethnic groups of New Zealand patients with screen-detected vs. non-screen-detected breast cancer.

authors: Lawrenson, Ross

subjects: Breast screening

abstract: OBJECTIVE: To compare characteristics and survival of New Zealand European, Māori, and Pacific women with screen-detected vs. non-screen-detected breast cancer. 
METHODS: Women aged 45-69 diagnosed with invasive breast cancer between January 2005 and May 2013 were identified from the Waikato and Auckland Breast Cancer Registries. Patient demographics and tumour characteristics were described by detection mode and ethnicity. Kaplan-Meier method was used to estimate the five-year breast cancer-specific survival of women with stage I-III breast cancer by ethnicity and detection mode. 
RESULTS: Women with screen-detected cancers were older, had smaller tumours, fewer stage IV (0.8% vs. 7.6%), fewer high grade (16.8% vs. 39.0%), and fewer lymph node positive diseases (26.3% vs. 51.5%) than women with non-screen-detected cancers. There were more Luminal A (70.0% vs. 54.0%), fewer human epidermal growth factor receptor 2 positive non-Luminal (4.4% vs. 8.8%), and fewer triple negative cases (7.0% vs. 13.8%) in screen-detected than non-screen-detected cancers. If not screen detected, 22.7% of breast cancers in Pacific women were stage IV compared with 2.4% if screen detected. If not screen detected, the five-year breast cancer-specific survival was 91.1% for New Zealand European women, 84.2% for Māori women, and 80.2% for Pacific women (p-value <0.001). For screen-detected breast cancer, survival between different ethnic groups was similar.
CONCLUSIONS: Breast cancers detected through screening are diagnosed at an earlier stage and have a greater proportion of subtypes, with better outcome. Variations in survival for Māori and Pacific women are only found in women with non-screen-detected breast cancer.

text: Outcomes in different ethnic groups of New Zealand patients with screen-detected vs. non-screen-detected breast cancer. OBJECTIVE: To compare characteristics and survival of New Zealand European, Māori, and Pacific women with screen-detected vs. non-screen-detected breast cancer. 
METHODS: Women aged 45-69 diagnosed with invasive breast cancer between January 2005 and May 2013 were identified from the Waikato and Auckland Breast Cancer Registries. Patient demographics and tumour characteristics were described by detection mode and ethnicity. Kaplan-Meier method was used to estimate the five-year breast cancer-specific survival of women with stage I-III breast cancer by ethnicity and detection mode. 
RESULTS: Women with screen-detected cancers were older, had smaller tumours, fewer stage IV (0.8% vs. 7.6%), fewer high grade (16.8% vs. 39.0%), and fewer lymph node positive diseases (26.3% vs. 51.5%) than women with non-screen-detected cancers. There were more Luminal A (70.0% vs. 54.0%), fewer human epidermal growth factor receptor 2 positive non-Luminal (4.4% vs. 8.8%), and fewer triple negative cases (7.0% vs. 13.8%) in screen-detected than non-screen-detected cancers. If not screen detected, 22.7% of breast cancers in Pacific women were stage IV compared with 2.4% if screen detected. If not screen detected, the five-year breast cancer-specific survival was 91.1% for New Zealand European women, 84.2% for Māori women, and 80.2% for Pacific women (p-value <0.001). For screen-detected breast cancer, survival between different ethnic groups was similar.
CONCLUSIONS: Breast cancers detected through screening are diagnosed at an earlier stage and have a greater proportion of subtypes, with better outcome. Variations in survival for Māori and Pacific women are only found in women with non-screen-detected breast cancer.

year: 2019