Environmental Science

... John F. Stamm*, Shawn M. Chartrand*, Stacey Porter*, Dipankar Sen** ... Cross hatched area is McClellan Ranch, light green pattern (solid) downstream of McClellan Ranch is Blackberry Farms Golf Course. Arrows show locations of trenches. ...

Step-pool channels are a ubiquitous element of mountain watersheds. As communities continue to expand into the mountainous regions of the world, an increased understanding of step-pool properties and characteristics is essential to support informed land-use decisions. A surge in recent research has explored fundamental characteristics of step-pools in part from the perspective of utilizing step-pools in stream restoration or stabilization efforts. Much of this research has focused on applying hydraulic and energy theory to elucidate controls on step-pool geometry. These approaches are based on the concept that step-pool form evolves to provide a maximum resistance to flow. We describe a new perspective on step-pool geometric scaling. Our work suggests that step-pool geometry is the result of interactions between channel geometry and step-pool hydraulics, notably head loss through the step-pool reach. We will illustrate that at the reach level of organization, the ratio of bankfull w...

How do gravel bed pool‐riffle streams adjust to changing upstream water and bedload sediment supplies, and what analysis techniques can help to effectively identify how change occurs? Here, we use a mixture of field and experimental data to examine these problems and apply a suite of traditional and novel analysis approaches to highlight dynamics which might otherwise go undetected. Eleven years of monitoring channel morphology in a small forested watershed indicate that pool‐riffles persist through large changes in upstream water and bedload supply and that bed architecture relief is correlated to flow magnitude. A flume experiment consisting of eight runs was conducted to examine the field case in more detail. The experimental design splits the eight runs into four runs of relatively high water and sediment supply and four of relatively low water supply, with no upstream sediment supply. Experimental results corroborate the field‐based measurements of pool‐riffle persistence, which is due to a coupling between downstream width variations, and spatial patterns of flow velocity and bedload transport. More specifically, measurements made during the flume experiments along a prominent pool‐riffle pair indicate that temporal and spatial changes to topography, flow hydraulics, and bed surface sediment texture are more rich and nuanced than existing generalizations offer. For example, clustering analysis completed using self‐organizing maps indicates that sediment sorting between pools and riffles is not simply a binary type response of finer versus coarser described by some characteristic grain size.

Osinski2, A. M. Jellinek3, S. M. Chartrand4 1School of Earth and Space Exploration, Arizona State University, Tempe, US ([email protected]), 2Department of Earth Sciences/Institute for Earth and Space Exploration, University of Western Ontario, London, Canada, 3Department of Earth, Ocean, and Atmospheric Science, University of British Columbia, Vancouver, Canada, 4School of Environmental Science, Simon Fraser University, Vancouver, Canada.

It is common for mountain riverbeds to exhibit a repetitive pattern of topographic lows and highs known respectively as pools and riffles. Pool-riffle structures are ecologically important because salmon rely on them for birth, growth and regeneration, and they are physically important because pool-riffles are observed across diverse landscape settings. A common physical characteristic of pool-riffles is that pool spacing is proportional to channel width, for longitudinal bed slopes that vary by two-orders of magnitude. Furthermore, field, numerical and laboratory based studies observe that pools are colocated with points of channel narrowing, and riffles with points of widening. What is not known, however, is how downstream changes of channel width give rise to, and maintain pool-riffles. The goal of my thesis is to address this knowledge gap, and to specifically build physical understanding for the observed spatial correlation between channel width and pool-riffle architecture. I ...

Abstract. Bedload transport of sediment mixtures in mountain streams is challenging to predict, with implications for understanding how rivers form and respond to environmental change. Experimental work shows that collective particle entrainment is an important contributing mechanism of bedload transport, but questions remain. We use four different time series of experimental sediment flux for granular particles 4–32 mm in diameter to indirectly examine the role of collective mobilization. Flux was measured at a fixed position in space using an imaging light table. The light table provides a flux measurement that is sampled at a resolution of 1 Hz, and for total time durations ranging from 75 to 240 min. Experimental conditions include periods of statistical steady-state, and transient adjustments due to changes of the upstream supply of water and sediment. We find that despite the contrasting experimental conditions, the time series encode a consistent transport behaviour within th...

R. Osinski2, A. M. Jellinek3, S. M. Chartrand4 1School of Earth and Space Exploration, Arizona State University, Tempe, US ([email protected]), 2Department of Earth Sciences/Institute for Earth and Space Exploration, University of Western Ontario, London, Canada, 3Department of Earth, Ocean, and Atmospheric Science, University of British Columbia, Vancouver, Canada, 4School of Environmental Science, Simon Fraser University, Vancouver, Canada.

This repository provides raw data and python 3 scripts to reproduce figures and analysis provided in a journal publication by the first two authors. The raw data is in the form of fractional particle flux [particles per second], for six different grain size fractions. The data were measured during a flume experiment completed at the University of British Columbia, and reported by Chartrand et al., 2018; 2019. See the READ_ME.txt file in this repository for more details about the data and python 3 scripts.<br>

This is a simple 1D probabilistic model of riverbed sediment mobility. It is based on the work of Wiberg and Smith, 1987 (WRR) and Kirchner et al., 1990 (Sedimentology). The model consists of a master script and three functions called by the master script.