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Full-Text Articles in Physical Sciences and Mathematics
Remains Of The 19th Century: Deep Storage Of Contaminated Hydraulic Mining Sediment Along The Lower Yuba River, California, Tyler Nakamura, Michael Bliss Singer, Emmanuel Gabet
Remains Of The 19th Century: Deep Storage Of Contaminated Hydraulic Mining Sediment Along The Lower Yuba River, California, Tyler Nakamura, Michael Bliss Singer, Emmanuel Gabet
Faculty Publications
Since the onset of hydraulic gold mining in California’s Sierra Nevada foothills in 1852, the environmental damage caused by displacement and storage of hydraulic mining sediment (HMS) has been a significant ecological problem downstream. Large volumes of mercury-laden HMS from the Yuba River watershed were deposited within the river corridor, creating the anthropogenic Yuba Fan. However, there are outstanding uncertainties about how much HMS is still contained within this fan. To quantify the deep storage of HMS in the Yuba Fan, we analyzed mercury concentrations of sediment samples collected from borings and outcrops at multiple depths. The mercury concentrations served …
Particle Transport Over Rough Hillslope Surfaces By Dry Ravel: Experiments And Simulations With Implications For Nonlocal Sediment Flux, Emmanuel Gabet, Morgan Mendoza
Particle Transport Over Rough Hillslope Surfaces By Dry Ravel: Experiments And Simulations With Implications For Nonlocal Sediment Flux, Emmanuel Gabet, Morgan Mendoza
Faculty Publications
Past studies of hillslope evolution have typically assumed that soil creep processes are governed by a linear relationship between local hillslope angle and transport distance. The assumption of “linear diffusion” has fallen out of favor because, when coupled with an expression of mass continuity, it yields unrealistic hillslope profiles. As a consequence, a better understanding of the mechanics of sediment transport is needed. Here we report results from a series of flume experiments performed to investigate sediment transport by dry ravel, a common soil creep process in arid and semiarid environments. We find that, at gentle slopes, transport distances follow …
Bedrock Erosion By Root Fracture And Tree Throw: A Coupled Biogeomorphic Model To Explore The Humped Soil Production Function And The Persistence Of Hillslope Soils, Emmanuel Gabet, Simon Mudd
Bedrock Erosion By Root Fracture And Tree Throw: A Coupled Biogeomorphic Model To Explore The Humped Soil Production Function And The Persistence Of Hillslope Soils, Emmanuel Gabet, Simon Mudd
Faculty Publications
In 1877, G. K. Gilbert reasoned that bedrock erosion is maximized under an intermediate soil thickness and declines as soils become thinner or thicker. Subsequent analyses of this “humped” functional relationship proposed that thin soils are unstable and that perturbations in soil thickness would lead to runaway thinning or thickening of the soil. To explore this issue, we developed a numerical model that simulates the physical weathering of bedrock by root fracture and tree throw. The coupled biogeomorphic model combines data on conifer population dynamics, rootwad volumes, tree throw frequency, and soil creep from the Pacific Northwest (USA). Although not …
Bedrock Channel Geometry Along An Orographic Rainfall Gradient In The Upper Marsyandi River Valley In Central Nepal, William Craddock, Douglas Burbank, Bodo Bookhagen, Emmanuel Gabet
Bedrock Channel Geometry Along An Orographic Rainfall Gradient In The Upper Marsyandi River Valley In Central Nepal, William Craddock, Douglas Burbank, Bodo Bookhagen, Emmanuel Gabet
Faculty Publications
Pronounced rainfall gradients combined with spatially uniform exhumation of rocks at Quaternary timescales and uniform rock strength make the upper Marsyandi River valley in central Nepal a useful natural laboratory in which to explore variations in bedrock channel width. We focus on small catchments (0.6–12.4 km2) along a more than tenfold gradient in monsoon rainfall. Rainfall data are gathered from a dense weather network and calibrated satellite observations, the pattern of Quaternary exhumation is inferred from apatite fission track cooling ages, and rock compressive strength is measured in the field. Bedrock channel widths, surveyed at high scour indicators, scale as …
A Stochastic Sediment Delivery Model For A Steep Mediterranean Landscape, Emmanuel Gabet, Thomas Dunne
A Stochastic Sediment Delivery Model For A Steep Mediterranean Landscape, Emmanuel Gabet, Thomas Dunne
Faculty Publications
It is a truism in geomorphology that climatic events operate on a landscape to drive sediment transport processes, yet few investigations have formally linked climate and terrain characteristics with geomorphological processes. In this study, we incorporate sediment transport equations derived from fieldwork into a computer model that predicts the delivery of sediment from hillslopes in a steep Mediterranean landscape near Santa Barbara, California. The sediment transport equations are driven by rainstorms and fires that are stochastically generated from probability distributions. The model is used to compare the rates and processes of sediment delivery under two vegetation types: coastal sage scrub …
Sediment Transport By Dry Ravel, Emmanuel Gabet
Sediment Transport By Dry Ravel, Emmanuel Gabet
Faculty Publications
Dry ravel is a general term that describes the rolling, bouncing, and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes. During fires, particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation. On a daily basis, particles may be mobilized by bioturbation and by small landslides. Experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface. This equation is further elaborated to produce a nonlinear slope-dependent …