On extracting sediment transport information from measurements of luminescence in river sediment

📝 Abstract

Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here, we attempt to estimate sediment transport rates using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model based on conservation of energy and sediment mass to explain the patterns of luminescence in river channel sediment from a first-principles perspective. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The parameters from the model can then be used to estimate the time-averaged virtual velocity, characteristic transport lengthscales, storage timescales, and floodplain exchange rates of fine sand-sized sediment in a fluvial system. The values obtained from the luminescence method appear to fall within expected ranges based on published compilations. However, caution is warranted when applying the model as the complex nature of sediment transport can sometimes invalidate underlying simplifications.

💡 Analysis

Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here, we attempt to estimate sediment transport rates using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model based on conservation of energy and sediment mass to explain the patterns of luminescence in river channel sediment from a first-principles perspective. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The parameters from the model can then be used to estimate the time-averaged virtual velocity, characteristic transport lengthscales, storage timescales, and floodplain exchange rates of fine sand-sized sediment in a fluvial system. The values obtained from the luminescence method appear to fall within expected ranges based on published compilations. However, caution is warranted when applying the model as the complex nature of sediment transport can sometimes invalidate underlying simplifications.

📄 Content

On extracting sediment transport information from measurements of luminescence in river sediment Harrison J. Gray1,2*, Gregory E. Tucker2, Shannon A. Mahan1, Chris McGuire3, Edward J. Rhodes3,4 1 Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Geological Sciences, University of Colorado – Boulder, CO 2 U.S. Geological Survey Luminescence Geochronology Laboratory, Denver Federal Center, Denver, CO 3 Department of Earth, Planetary, and Space Sciences, University of California Los Angeles, Los Angeles, CA 4Department of Geography, University of Sheffield, Sheffield, S10 2TN, United Kingdom *corresponding author: harrison.gray@colorado.edu

KEY POINTS  We develop a model coupling sediment transport of fine sand and luminescence, in order to explain the patterns of luminescence observed in river sediment  The model successfully reproduces the patterns of luminescence measurements in river systems  Best-fit values from the model produce sediment transport information for fine sand within orders of magnitude from other river systems

ABSTRACT Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here, we attempt to estimate sediment transport rates using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model based on conservation of energy and sediment mass to explain the patterns of luminescence in river channel sediment from a first- principles perspective. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The parameters from the model can then be used to estimate the time- averaged virtual velocity, characteristic transport lengthscales, storage timescales, and floodplain exchange rates of fine sand-sized sediment in a fluvial system. The values obtained from the luminescence method appear to fall within expected ranges based on published compilations. However, caution is warranted when applying the model as the complex nature of sediment transport can sometimes invalidate underlying simplifications.

INTRODUCTION The rate of sediment transport by rivers is a key variable in understanding the evolution of landscapes [Tucker and Hancock, 2010], the behavior of rivers [van Rijn, 1993], the lifespan of reservoirs [Syvitski et al., 2005; Papanicolaou et al., 2008], and the impacts of development on sedimentation [Syvitski, et al., 2005]. Surprisingly, we have little ability to quantify sediment transport rates beyond hard-to-constrain analytical models and time-consuming tracer experiments [Haschenburger and Church, 1998; Martin and Church, 2004; Bradley and Tucker, 2012 and references therein]. This knowledge gap reflects a lack of reliable field data with which to calibrate models, and uncertainties in the travel velocities and exchange rates of various grain sizes throughout a river system [Papanicolaou et al., 2008]. For this reason, it is important to explore possible connections between geomorphic process and material properties that may act as a proxy for these processes.

One such material property, luminescence, displays changes within river systems which may provide a means to obtain sediment transport information. Luminescence arises as a property of certain silicate minerals wherein bonding electrons excited by ionizing radiation become trapped in defects in a mineral’s crystal lattice [Rhodes, 2011]. The trapped electrons occupy energy levels between the valence and conduction bands and remain stable until a source of energy such as heat or sunlight gives the electrons the energy needed to escape the trap, travel through the crystal (e.g., via the conduction band), and recombine with a radiative hole center, releasing photons in the process [Rhodes, 2011]. The emission of these photons due to energy from visible light is termed Optically Stimulated Luminescence (OSL) [Huntley et al., 1985]. A new method developed for potasssium-feldspar minerals uses infra-red light at a series of elevated temperatures and is termed post-Infrared Stimulated Luminescence (pIRIR) [Thomsen et al., 2008; Buylaert et al., 2009]. When pIRIR is measured at a series of elevated temperatures, different luminescence signals with different bleaching rates can be measured by a technique known as Multiple-Elevated-Tempurature post-infrared infrared stimulated luminescence (MET- pIRIR; Li and Li, 2011). The measurement of luminescence has been exploited as a geochronometer by the geo

This content is AI-processed based on ArXiv data.