Bedload sediment transport regimes of urban gravel-bed rivers under different management scenarios

Watershed urbanization profoundly alters the hydrologic characteristics of urban rivers compared to their rural counterparts. This change in hydrologic conditions in combination with alterations to the sediment supply regime in urban watersheds leads to adjustments to channel form and the widespread degradation of urban rivers. Urban river management increasingly attempts to balance the societal needs of flood and erosion control, while simultaneously improving the ecological health or waterways. Two common types of river management include stormwater management (SWM), which focuses on the attenuation of urban floods, and in-stream restoration, which attempts to reconstruct stable and ecologically favourable channels. However, current urban river management designs lack consideration of the key process responsible for channel stability and habitat availability: bedload sediment transport. Two reasons for this shortcoming are the lack of bedload sediment data in urban watersheds and the consequent gap in understanding of the bedload transport dynamics of urban rivers. Consequently, the degradation of urban rivers persists. This project investigates bedload transport dynamics in urban rivers with different management scenarios to focus on four themes: (1) how urbanization affects bedload transport dynamics and its relationship to channel morphology, (2) how to best predict bedload transport dynamics in urban rivers, (3) how current urban river management strategies change the transport dynamics of rivers, and (4) how to improve bedload sediment monitoring technology. This project focuses on the grain-scale bedload transport dynamics of coarse material because it links to the morphodynamics and ecological processes of channels, it provides insights on the exact controls and spatial variability of bedload transport, and the responses to individual flood events can be directly measured. The overarching goal of this study is to contribute to improved urban river management strategies that focus on adaptive management and interdisciplinary approaches. Bedload sediment transport was monitored using RFID tracer stones in three streams with different hydrologic settings: rural, urban with no SWM, and urban with SWM. High-resolution water level data confirmed the hydrologic differences expected from the three watershed conditions, as well as channel enlargement characteristic of urban rivers. Results demonstrate that the morphologic differences between the study streams can be linked to changes in the grain-scale bedload transport dynamics of the streams. Bedload transport is accelerated in the urban stream due to an increase in the frequency of bedload mobilization, particularly of coarse sediment sizes. In contrast, SWM hasdecreased the bedload transport to an immobile and armoured state indicative of a competence-limit transport regime. Results are used to make recommendations for improved urban river management. Results from the bedload tracking were used to build predictive models of tracer displacements. A new variable that captures both the mobility and travel length of bed particles is introduced. Several flow metrics developed in the literature in rural and laboratory settings are calculated, and their ability to predict tracer displacements in the three streams is tested. Scaling tracer travel lengths by mean channel width collapses the data into a single, strong relationship with cumulative energy expenditure, providing a single model that can be used across systems with different watershed conditions. To assess the impact of an in-stream riffle-pool channel reconstruction on bedload sediment dynamics, bedload transport and morphologic change was monitored in adjacent unrestored and restored reaches of an urban channel. Results reveal that the restored reach is stable and self- maintaining, mirroring bedform maintenance processes in natural riffle-pool streams. However, the construction is more successful at slowing down the transport of coarse sediment more than fine sediment, leading to a coarse sediment discontinuity that may be contributing to accelerated channel adjustment beyond the limits of the constructed riffle-pool sequences. This project highlights the importance of considering the entire channel corridor when designing and monitoring restoration projects. A large limitation of bedload sediment tracking technology is the inability to determine the vertical position of tracers, which hinders the ability to study vertical mixing and translate tracer data into bedload transport rates. A new Radio Frequency Identification (RFID) bedload tracer stone is presented, along with results of laboratory performance tests. This new bedload tracer improves upon existing bedload sediment monitoring technology by providing the ability to measure the burial depth of tracers without disturbing the bed. An important contribution of this study is the extensive dataset of bedload transport collected in urban rivers. This study attempts to move away from descriptive differences in the characteristics of urban rivers compared to rural streams, and towards a process-level understanding of the anthropogenic effects on river systems. Grain-scale bedload transport theory, developed in rural and laboratory settings, is applied to urban settings to gain insights into the effects of urbanization and common river management strategies on the geomorphic processes of urban rivers. Recommendations for improved urban river management are developed from the results of this thesis

Earth Science Education #7. GeoTrails: Accessible Online Tools for Outreach and Education

As geoscientists, we must prioritize improving our ability to communicate science to the public. Effective geoscience communication enables communities to understand how geological processes have shaped our planet and make informed decisions about Earth’s future. However, geoscience research outputs have traditionally been published in peer-reviewed journals and presented at academic conferences. Consequently, essential information about local geology is rarely available in accessible, open access, and engaging formats. Here, we propose virtual field trips, or ‘GeoTrails’, as a possible solution to address the disconnect between geoscience research and public knowledge by improving our communication to the public. This initiative is largely driven by undergraduate students, who identify points of geological interest along selected hiking trails, write concise descriptions derived from scientific sources (e.g. longer peer-reviewed articles and government reports), and collect field data (e.g. 3-D LiDAR models, drone photography) to illustrate the characteristics of these geological features. The goal of the project is to communicate the importance of local geology on our environment and to raise awareness of how changing climates could affect us in the future; this information can empower communities to make better, more informed planning decisions. The creation of GeoTrails along the Niagara Escarpment offers a promising strategy to highlight the role of geoscientists and to engage the public in our ongoing research that aims to showcase Canada’s geoheritage.En tant que géoscientifiques, nous devons donner la priorité à l’amélioration de notre capacité à communiquer la science au public. Une communication efficace des géosciences permet aux communautés de comprendre comment les processus géologiques ont façonné notre planète et de prendre des décisions éclairées sur l’avenir de la Terre. Cependant, les résultats de la recherche en géosciences ont traditionnellement été publiés dans des revues à comité de lecture et présentés lors de conférences académiques. Par conséquent, les informations essentielles sur la géologie locale sont rarement disponibles sous des formats accessibles, en libre accès et attrayants. Dans cette optique, nous proposons des excursions virtuelles, ou « GeoTrails », comme solution possible pour combler le fossé entre la recherche en géosciences et la connaissance du public en améliorant notre communication avec celui-ci. Cette initiative est en grande partie menée par des étudiants de premier cycle, qui identifient des points d’intérêt géologiques le long de sentiers de randonnée sélectionnés, rédigent des descriptions concises basées sur des sources scientifiques (par exemple, des articles à comité de lecture plus longs et des rapports gouvernementaux) et collectent des données sur le terrain (par exemple, des modèles LiDAR 3-D, des photographies par drone) pour illustrer les caractéristiques de ces caractéristiques géologiques. L'objectif du projet est de communiquer l'importance de la géologie locale sur notre environnement et de sensibiliser aux façons dont les changements climatiques pourraient nous affecter à l'avenir; cette information peut permettre aux communautés de prendre des décisions de planification meilleures et plus éclairées. La création de GeoTrails le long de l'escarpement du Niagara offre une stratégie prometteuse pour mettre en valeur le rôle des géoscientifiques et pour engager le public dans notre recherche en cours qui vise à présenter le patrimoine géologique du Canada

The effects of channel morphology on the mobility and dispersion of sediment in a small gravel-bed stream

The role of channel morphology in sediment transport is poorly understood due to the complexity of the interactions between morphology, sediment characteristics and flow. A better understanding of the ways in which channel morphology affects sediment transport at all scales and under varying flow conditions can improve predictions of channel behavior and provide insights for better stream restoration applications. This study aimed to capture the effects of morphology on bed mobility and sediment dispersion in a small gravel-bed stream through the use of a 10 year tracer dataset. The characterization of bed mobility and sediment dispersion conducted at three spatial scales (the reach, morphological unit and local scale), revealed the importance of scale when examining the role or morphology on sediment transport. East Creek was found to be in conditions of marginal sediment transport, remaining near the critical conditions for sediment mobilization the majority of the time, and falling within a low sediment transport regime common in small gravel-bed streams. Both bed mobility and tracer travel distances increased with increasing flow conditions, and measures of cumulative flow energy had stronger relations to both variables than peak discharge. Grain size was not found to play no role in bed mobility or travel distance in East Creek. At the reach scale, morphology did not affect bed mobility, and influenced the travel distance of tracers only during high flows, or when averaged over long time periods. Although burial rates were high, burial depths were shallow, and burial showed no relation to flow or mobility. At the morphological unit scale, differences were observed in the rate of increase of bed area under mobility with increasing flow between reaches and between morphological units. Finally, at the local scale, bed mobility was highly localized and sporadic. Results of this study allow for the description of the role of morphology on bed mobility and sediment dispersion in a low sediment transport regime and throughout various spatial and temporal scales. Further research opportunities include the exploration of the role of morphology on bed mobility and sediment dispersion in a variety of morphological and sediment transport settings.Arts, Faculty ofGeography, Department ofGraduat

Enlargement and evolution of a semi-alluvial creek in response to urbanization

International audienc

Earth Science Education 7. GeoTrails: Accessible Online Tools for Outreach and Education

As geoscientists, we must prioritize improving our ability to communicate science to the public. Effective geoscience communication enables communities to understand how geological processes have shaped our planet and make informed decisions about Earth’s future. However, geoscience research outputs have traditionally been published in peer-reviewed journals and presented at academic conferences. Consequently, essential information about local geology is rarely available in accessible, open access, and engaging formats. Here, we propose virtual field trips, or ‘GeoTrails’, as a possible solution to address the disconnect between geoscience research and public knowledge by improving our communication to the public. This initiative is largely driven by undergraduate students, who identify points of geological interest along selected hiking trails, write concise descriptions derived from scientific sources (e.g. longer peer-reviewed articles and government reports), and collect field data (e.g. 3-D LiDAR models, drone photography) to illustrate the characteristics of these geological features. The goal of the project is to communicate the importance of local geology on our environment and to raise awareness of how changing climates could affect us in the future; this information can empower communities to make better, more informed planning decisions. The creation of GeoTrails along the Niagara Escarpment offers a promising strategy to highlight the role of geoscientists and to engage the public in our ongoing research that aims to showcase Canada’s geoheritage.En tant que géoscientifiques, nous devons donner la priorité à l’amélioration de notre capacité à communiquer la science au public. Une communication efficace des géosciences permet aux communautés de comprendre comment les processus géologiques ont façonné notre planète et de prendre des décisions éclairées sur l’avenir de la Terre. Cependant, les résultats de la recherche en géosciences ont traditionnellement été publiés dans des revues à comité de lecture et présentés lors de conférences académiques. Par conséquent, les informations essentielles sur la géologie locale sont rarement disponibles sous des formats accessibles, en libre accès et attrayants. Dans cette optique, nous proposons des excursions virtuelles, ou « GeoTrails », comme solution possible pour combler le fossé entre la recherche en géosciences et la connaissance du public en améliorant notre communication avec celui-ci. Cette initiative est en grande partie menée par des étudiants de premier cycle, qui identifient des points d’intérêt géologiques le long de sentiers de randonnée sélectionnés, rédigent des descriptions concises basées sur des sources scientifiques (par exemple, des articles à comité de lecture plus longs et des rapports gouvernementaux) et collectent des données sur le terrain (par exemple, des modèles LiDAR 3-D, des photographies par drone) pour illustrer les caractéristiques de ces caractéristiques géologiques. L'objectif du projet est de communiquer l'importance de la géologie locale sur notre environnement et de sensibiliser aux façons dont les changements climatiques pourraient nous affecter à l'avenir; cette information peut permettre aux communautés de prendre des décisions de planification meilleures et plus éclairées. La création de GeoTrails le long de l'escarpement du Niagara offre une stratégie prometteuse pour mettre en valeur le rôle des géoscientifiques et pour engager le public dans notre recherche en cours qui vise à présenter le patrimoine géologique du Canada