title: Let's get connected: A new graph theory-based approach and toolbox for understanding braided river morphodynamics

authors: Connor-Streich, Gabriel

subjects: Science & Technology

abstract: Our understanding of braided river morphodynamics has improved significantly in recent years, however, there are still large knowledge gaps relating to both long‐term and event‐based change in braided river morphologies. Furthermore, we still lack methods that can take full advantage of the increasing availability of remotely sensed datasets that are well suited to braided river research. Network analysis based on graph theory, the mathematics of networks, offers a largely unexplored toolbox that can be applied to remotely sensed data to quantify the structure and function of braided rivers across nearly the full range of spatiotemporal scales relevant to braided river evolution. In this article, important commonalities between braided rivers and other types of complex network are described, providing a compelling argument for the wider uptake of complex network analysis methods in the study of braided rivers. We provide an overview of the extraction of graph representations of braided river networks from remotely sensed data and detail a suite of metrics for quantitative analysis of these networks. Application of these metrics as new tools for multiscale characterization of braided river planforms that improve upon traditional, spatially averaged approaches is discussed and potential approaches to network‐based analysis of braided river dynamics are proposed, drawing on a range of different concepts from braided river research and other network sciences. Finally, the potential for using graph theory metrics to validate numerical models of braided rivers is discussed.

text: Let's get connected: A new graph theory-based approach and toolbox for understanding braided river morphodynamics Our understanding of braided river morphodynamics has improved significantly in recent years, however, there are still large knowledge gaps relating to both long‐term and event‐based change in braided river morphologies. Furthermore, we still lack methods that can take full advantage of the increasing availability of remotely sensed datasets that are well suited to braided river research. Network analysis based on graph theory, the mathematics of networks, offers a largely unexplored toolbox that can be applied to remotely sensed data to quantify the structure and function of braided rivers across nearly the full range of spatiotemporal scales relevant to braided river evolution. In this article, important commonalities between braided rivers and other types of complex network are described, providing a compelling argument for the wider uptake of complex network analysis methods in the study of braided rivers. We provide an overview of the extraction of graph representations of braided river networks from remotely sensed data and detail a suite of metrics for quantitative analysis of these networks. Application of these metrics as new tools for multiscale characterization of braided river planforms that improve upon traditional, spatially averaged approaches is discussed and potential approaches to network‐based analysis of braided river dynamics are proposed, drawing on a range of different concepts from braided river research and other network sciences. Finally, the potential for using graph theory metrics to validate numerical models of braided rivers is discussed.

year: 2018

title: Twenty-three unsolved problems in hydrology (UPH)–a community perspective

authors: Blöschl, G

subjects: hydrology

abstract: This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

text: Twenty-three unsolved problems in hydrology (UPH)–a community perspective This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

year: 2019

title: No explanation required: Entrenchment and perception of Māori loanwords in a diachronic newspaper corpus of New Zealand English

authors: Levendis, Katharine Joy

subjects: New Zealand English

abstract: Māori loanwords are uncontestably the most notable feature of New Zealand English (Gordon, 2005; Macalister, 2006b). Although frequencies of Māori loanwords are reported to be increasing in recent years (Macalister, 2006b), and analyses strongly indicate a skew in loanwords across certain topics (Davies & Maclagan, 2006; de Bres, 2006), no studies have yet addressed whether Māori loanword behaviour differs in a corpus restricted to a single topic (with the exception of Calude, Miller, Harper, & Whaanga, Forthcoming). Nor has a thorough diachronic analysis been made on the subject since Davies and Maclagan (2006) and Macalister (2006b). This thesis is concerned with frequency of use and perception of Māori loanwords in a diachronic corpus restricted to a singular theme: te Wiki o te Reo Māori, Māori Language Week. Using a quantitative methodology in a corpus constructed from New Zealand regional and national newspaper articles spanning 2008-2017, average Māori loanword frequencies are found to be almost 5 times that of the most recent comparable diachronic study (Macalister, 2006b), and demonstrate a statistically significant diachronic increase in use. In contrast, the markedness (or translation) of Māori loanwords shows a statistically significant decreasing diachronic trend over the 10-year period. However, practice of marking appears to be affected by user perceptions and intention to educate, and therefore cannot be relied upon as a gauge of loanword entrenchment. Other conventional measures of loanword entrenchment such as frequency, listedness and morphological assimilation are also shown to be unreliable when considered independently from one another, and in cases such as that of New Zealand English where a change from above influenced by social and cultural factors (Māori loanwords functioning as an expression of political attitude and stance) appears to be interfering in loanword use. Measurement of Māori loanword entrenchment cannot be made using the same criteria as loanwords from non-threatened languages, and suggestions are made for the revised criteria for studying loanword entrenchment which takes into account the sociolinguistic context in which the loanwords are used.

text: No explanation required: Entrenchment and perception of Māori loanwords in a diachronic newspaper corpus of New Zealand English Māori loanwords are uncontestably the most notable feature of New Zealand English (Gordon, 2005; Macalister, 2006b). Although frequencies of Māori loanwords are reported to be increasing in recent years (Macalister, 2006b), and analyses strongly indicate a skew in loanwords across certain topics (Davies & Maclagan, 2006; de Bres, 2006), no studies have yet addressed whether Māori loanword behaviour differs in a corpus restricted to a single topic (with the exception of Calude, Miller, Harper, & Whaanga, Forthcoming). Nor has a thorough diachronic analysis been made on the subject since Davies and Maclagan (2006) and Macalister (2006b). This thesis is concerned with frequency of use and perception of Māori loanwords in a diachronic corpus restricted to a singular theme: te Wiki o te Reo Māori, Māori Language Week. Using a quantitative methodology in a corpus constructed from New Zealand regional and national newspaper articles spanning 2008-2017, average Māori loanword frequencies are found to be almost 5 times that of the most recent comparable diachronic study (Macalister, 2006b), and demonstrate a statistically significant diachronic increase in use. In contrast, the markedness (or translation) of Māori loanwords shows a statistically significant decreasing diachronic trend over the 10-year period. However, practice of marking appears to be affected by user perceptions and intention to educate, and therefore cannot be relied upon as a gauge of loanword entrenchment. Other conventional measures of loanword entrenchment such as frequency, listedness and morphological assimilation are also shown to be unreliable when considered independently from one another, and in cases such as that of New Zealand English where a change from above influenced by social and cultural factors (Māori loanwords functioning as an expression of political attitude and stance) appears to be interfering in loanword use. Measurement of Māori loanword entrenchment cannot be made using the same criteria as loanwords from non-threatened languages, and suggestions are made for the revised criteria for studying loanword entrenchment which takes into account the sociolinguistic context in which the loanwords are used.

year: 2018