Physical and Environmental Geography Commons^™

River Confinement And Braiding Loss In Canterbury Region, Aotearoa New Zealand, Victoria Barlow, Peter Ashmore

Geography & Environment Publications

In relation to the wider concern that rivers in Aotearoa New Zealand have been narrowed by river control and land-use encroachment, and that iconic braided patterns are being lost, nine braided rivers from the Canterbury region were studied to compare river width, pattern type and braiding intensity between the mid-1900s and the present based on mapping from aerial images. Channel narrowing occurred along >90% (~490km) of the length of the rivers studied, 375km of which were historically braided. In total, the rivers narrowed by an average of 43% (48% for braided reaches). Coinciding with narrowing, braided reaches lost 1.3 channels, …

Power And Politics: The Case Of Urbanization And River Channel Change, Peter Ashmore

Geography & Environment Presentations

Gradual urbanization of a watershed in Toronto, Canada, over 60+ years resulted in major channel changes. The temporal and spatial extent of channel widening are predictable from new analysis tracking changes in total stream power along the river system as urban land cover extended across the watershed, and also produced very high energy large flood events responsible for major channel change. The analysis is a geomorphically-satisfying, quasi-experimental test of theory of river channel change. But it misses important elements of the full trajectory of change that are not physically predictable. Treating urbanization as a neutral physical variable of changing watershed …

Evaluating River Morphology Change With A Geomorphic Form Variation Approach, Corey Dawson, Peter Ashmore, Robert Corry

Geography & Environment Publications

Geomorphic river design strives for natural resilience by encouraging geomorphic form complexity and morphological processes linked to greater habitat diversity. Increasing availability of high-resolution topographic data and spatial feature mapping methods provide advantages for morphological analysis and river restoration planning. We propose and evaluate an approach to quantifying topographic variability of geomorphic form and pixel-level surface roughness resulting from channel planform geometry differences using spatially continuous variety computation applied to component metrics including flow direction, aspect and planform curvature. We define this as the geomorphic form variation (GFV) approach and found it scalable, repeatable and a multi-stage analytical metric for …

What Braiding Reveals About River Morphology, Bedload And Channel Change, Peter Ashmore

Geography & Environment Presentations

Braided rivers can appear to be outliers in the range of river morphological types with unique dynamics and processes. Analysis shows that they have systematic structure, dynamics and response to external change that have properties relevant to the continuum of channel morphology. Rapid morphological change in real time creates a system in which bedload transport is strongly morphologically driven, which leads to thinking about bedload thresholds in terms of morphological change rather than grain scale dynamics. Occurrence and complexity of braiding respond to total stream power, and channel pattern is therefore partly an effect of river size. Braided rivers have …

What Braiding Reveals About River Morphology, Bedload And Channel Change, Peter Ashmore

Geography & Environment Publications

Braided rivers can appear to be outliers in the range of river morphological types with unique dynamics and processes. Analysis shows that they have systematic structure, dynamics and response to external change that have properties relevant to the continuum of channel morphology. Rapid morphological change in real time creates a system in which bedload transport is strongly morphologically driven, which leads to thinking about bedload thresholds in terms of morphological change rather than grain scale dynamics. Occurrence and complexity of braiding respond to total stream power, and channel pattern is therefore partly an effect of river size. Braided rivers have …

Braiding, Peter Ashmore

Geography & Environment Publications

Braided rivers have multiple, unstable channels and ephemeral bars formed by intense bed-load transport, and active channel processes. They occur in a range of environments associated with high-energy, coarse bedded rivers with limited riparian vegetation, and relatively high sediment supply. The occurrence in some regions is strongly modified by human activity. Empirical and rational analysis of regime conditions and in-channel process mechanisms can predict occurrence of braiding, considering by the problem of gradual transitions between channel pattern types, transient flood influence and vegetation effects. Braided rivers have hydraulic geometry relations similar to those of single-thread channels as well as systematic …

Empowering The Human-Nature Bond, Lightning Talk (7 Min), Valeria Widjaja

GIS Day

What is land? Is it dirt, the Earth, property, a resource? But rarely we ask who is land? When we change the question, it changes the way we think about land. It transforms the way we make decisions about how we might protect land. Through the Deshkan Ziibi Conservation Impact Bond, this story map explores how Carolinian Canada, Chippewas of the Thames First Nations, VERGE Capital, Ivey Business School, Thames Talbot Land Trust, and 3M are striving to heal the landscape. Overall, this story map visualizes both the human-nature and human-human relationships being facilitated by the bond. Learn the about …

Bed Particle Displacements And Morphological Development In A Wandering Gravel-Bed River, Ryan Mcqueen, Peter Ashmore, T Millard, N Goeller

Geography & Environment Publications

Bed particles were tracked using passive integrated transponder tags in a wandering reach of the San Juan River, British Columbia, Canada, to assess particle movement around three major bars in the river. In-channel topographic changes were monitored through repeat LiDAR surveys during this period and used in concert with the tracer data set to assess the relationship between particle displacements and changes in channel morphology, specifically, the development and re-working of bars. This has direct implications for virtual velocity and morphologic based estimates of bedload flux, which rely on accurate estimates of the variability and magnitude of particle path lengths …

When You Preach Water And You Drink Wine: Exploring The Implementation, Use And Management Of Wash In Healthcare Facilities In Kisumu County, Thelma Zulfawu Abu, Susan J. Elliott, Diana Karanja

Africa Western Collaborations Day 2020 Abstracts

No abstract provided.

Short Communication: Challenges And Applications Of Structure-From-Motion Photogrammetry In A Physical Model Of A Braided River, Peter Ashmore, Pauline Leduc, Sarah Peirce

Geography & Environment Publications

For extending the applications of structure-from-motion (SfM) photogrammetry in river flumes, we present the main challenges and methods used to collect a large dataset ( > 1000 digital elevation models, DEMs) of high-quality topographic data using close-range SfM photogrammetry. Automatic target detection, batch processing, and considerations for image quality were fundamental to the successful implementation of the SfM technique on such a large dataset, which was used primarily for capturing details of gravel-bed braided river morphodynamics and sedimentology. While the applications of close-range SfM photogrammetry are numerous, we include sample results from DEM differencing, which was used to quantify morphology change …

Evolution Of Grain Size Distributions And Bed Mobility During Hydrographs In Gravel-Bed Braided Rivers, Sarah Peirce, Peter Ashmore, Pauline Leduc

Geography & Environment Publications

Evolution of bed material mobility and bedload grain size distributions under a range of discharges is rarely observed in braiding in gravel-bed rivers. Yet, the changing of bedload grain size distributions with discharge is expected to be different from laterally stable, threshold, channels on which most gravel bedload theory and observation are based. Here, simultaneous observations of flow, bedload transport rate, and morphological change were made in a physical model of a gravel-bed braided river to document the evolution of grain size distributions and bed mobility over three experimental event hydrographs. Bedload transport rate and grain size distributions were measured …

The Variability In The Morphological Active Width: Results From Physical Models Of Gravel‐Bed Braided Rivers, Sarah Peirce, Pauline Leduc, Peter Ashmore

Geography & Environment Publications

The morphological active width, defined as the lateral extent of bed-material displacement over time, is a fundamental parameter in multi-threaded gravel-bed rivers, linking complex channel dynamics to bedload transport. Here, results are presented from 5 constant discharge experiments, and three event hydrographs, covering a range of flow strengths and channel configurations for which morphological change, bedload transport rates, and stream power were measured in a physical model. Changes in channel morphology were determined via differencing of photogrammetrically-derived digital elevation models (DEMs) of the model surface generated at regular intervals over the course of ~115 hours of experimental runs. Independent measures …

Expanding The "Active Layer", Peter Ashmore, Sarah Peirce, Pauline Leduc

Geography & Environment Publications

Church and Haschenburger (2017) make helpful distinctions around the issue of defining the active layer, with which we agree. We propose expanding discussion and definition of the ”active layer” in fluvial bedload transport to include the concept of the “morphological active layer”. This is particularly applicable to laterally unstable rivers (such as braided rivers) in which progressive morphological change over short time periods is the process by which much of the bedload transport occurs. The morphological active layer is also distinguished by variable lateral and longitudinal extent continuity over a range of flows and transport intensity. We suggest that the …

Flume Tests On Fluvial Erosion Mechanisms In Tillbed Channels, L Pike, Peter Ashmore, S Gaskin

Geography & Environment Publications

Semi-alluvial stream channels eroded into till and other glacial sediments are common in areas of extensive glacial deposition such as the Great Lakes region and northern interior plains of North America. The mechanics of erosion and erosional weakness of till results in the dominance of fluvial scour and mass erosion due to spontaneous fracture at planes of weakness under shearing flow. There have been few controlled tests looking at erosional mechanisms and resistance of till in river channels.We subjected small blocks of till to unidirectional flows in a laboratory flume to measure the threshold shear stress for erosion and observed …

Transforming Toronto's Rivers: A Socio-Geomorphic Perspective, Peter Ashmore

Geography & Environment Publications

No abstract provided.

Morpho-Sedimentary Characteristics Of Proximal Gravel Braided River Deposits In A Froude-Scaled Physical Model, Peter Ashmore, Tobias Gardner, Pauline Leduc

Geography & Environment Publications

A Froude‐scaled physical model of a proximal gravel‐bed braided river was used to connect the river morphological characteristics, and sedimentary processes and forms, to deposit geometry. High resolution continuous three‐dimensional topographic data were acquired from sequential photogrammetric digital elevation models paired with grain‐size surface maps derived from image analysis of textural properties of the surface. From these data, the full three‐dimensional development of the braided river deposit and grain‐size sorting patterns was compiled over an experimental time period of 41 h during which the model river reworked a large portion of the braided channel. The minimum surface of the deposit …

The Relationship Between Particle Travel Distance And Channel Morphology: Results Fromphysicalmodels Of Braided Rivers, Alan Kasprak, Joseph Wheaton, Peter Ashmore, James Hensleigh, Sarah Peirce

Geography & Environment Publications

Channel form and sediment transport are closely linked in alluvial rivers, and as such the development of a conceptual framework for the downstream controls on particle mobility and likely deposition sites has immense value in terms of the way we understand and predictively model rivers. Despite the development of conceptual models which frame flood-scale particle transport distance (termed path length) as a function of channel bar locations, an understanding of the controls on such path lengths in braided rivers remains especially elusive, in large part due to the difficulty in explicitly linking morphology and particle transport distances in the field. …

Implications Of Global Peak Population For Canada's Future, Alain P. Bélanger, Barry Edmonston, Kevin Mcquillan, Benoît Laplante, Sharon M. Lee, Martin Cooke, Don Kerr

Population Change and Lifecourse Strategic Knowledge Cluster Discussion Paper Series/ Un Réseau stratégique de connaissances Changements de population et parcours de vie Document de travail

In “Imagining Canada’s Future” the Social Science and Humanities Research Council (SSHRC) engaged various stakeholders to help establish six Future Challenge Areas. This report elaborates on the capacity of the Canadian research community with regard to the Future Challenge Area on “What might the implications of global peak population be for Canada?” It provides answers to sub-questions associated with this theme, namely: (1) What do we need to understand in order to effectively nurture the next generations? (2) What might Canadian families look like in five, 10, and 20 years, and how might they measure their well-being? (3) Life cycle …

Blogging: An Exercise In Communicating Science To The Public, Beth J. Hundey

Technology in Education Symposium (TIES)

No abstract provided.

A Case Study In Collaborative Mind-Mapping With Lucidchart, Beth J. Hundey

Technology in Education Symposium (TIES)

This two-day event on March 27 & March 28 featured:

• research paper presentations,
• lightning rounds,
• hands-on workshops,
• posters and demonstrations, and
• a student panel on the uses of instructional technology.

TIES 2.0 is open to faculty, librarians, staff, postgrads, and graduate students from across all disciplines at Western and its affiliates.

Participants heard and saw how instructors and others employ technology to engage students and enrich learning, and to connect with others from across the campus who are exploring the potential of instructional technology and online education.