Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 25, 2007) Vita. Includes bibliographical references.

The scour experiments on the bare root-free and root-permeated soils indicated that for each soil, critical tractive force (CTF) linearly increases with both root density and vane shear strength. However, for both soilsq CTF was mainly related to vaneýshear strengthp indicating the potential importance of soil shear strength as an index of scour erodibility of cohesive channel bank materials. The analysis of the relative effects of the grass vegetation parameters on scour resistance confirmed the dominance of vegetation shoots relative to the roots in resisting scour in-non-bending vege- tation. The results showed that it is the initial introduction of vegetation into bare (root-free) bank conditions that produces the greatest increase in scour resistance and that subsequent increases in vegetation density bring about relatively lower increases in scour resistance. However, in all the vegetation densities studied, root- permeated so-ils contributed significantly to scour resistance in low flows especially through low vegetation densities. Compared to root- free soil conditions, sandy clay loam soils permeated with 1.8 g/CM3 of roots increased their scour resistance by more than 400%. Althgouh these results may only be indicative of the low flow depths as would exist in shallow grassed channels commonly used for agricultural run- off drainage, they nevertheless highlight the importance of root density in contributing to the total flow resistance of grassed channel banks. The bank stability analysis indicated that for low channel banks (1.5m high), grass roots can stabilise banks with even vertical slopes against toe and slope vailures. For high (2.25m) and vertical bank conditions, the results indi- cate that the effects of increases in root density may need to be com- plemented by bank shaping in order to achieve stability. The scour and bank stability findings indicate that the three most important charac- teristics for the selection of grass vegetation for bank protection are quick establishmentg the development of a stiff shoot system and a strong root mat.

The geomorphic and geochemical characteristics of landscapes impose a physical template on the establishment and development of ecosystems. Conversely, vegetation is a key geomorphic agent, actively involved both soil production and sediment transport. The evolution of hillslopes and the ecosystems that populate them, are thus intimately coupled; their co-dependence potentially has a profound impact on the way in which landscapes respond to environmental change. This thesis explores how rates of erosion, integrated over millennia, impact on the structural characteristics of the mixed conifer forest that presently mantles this landscape, the development of the underlying soils and emergence of bedrock. The focus for this investigation is the Feather River Region in the northern Sierra Nevada in California, a landscape characterised by a striking geomorphic gradient accompanied by spatial variations in erosion rate spanning over an order of magnitude, from 20 mm ka-1 to over 250 mm ka-1. Using LiDAR data to quantify forest structure, I demonstrate that increasing rates of erosion drive a reduction in canopy height and aboveground biomass. Subsequently, I exploit a novel method to map rock exposure, based on a metric of topographic roughness, to show that as erosion rates increase and soil thickness consequently decreases, the degree of bedrock exposed on hillsides increases. Importantly, this soil-bedrock transition is gradual, with rapidly eroding hillslopes frequently possessing a mosaic of bedrock outcrop and intermittent soil mantle. Both the ecological and geomorphic trends are shown to be impacted by the underlying bedrock, which provides an additional source of heterogeneity in the evolution of the Feather River landscape. The negative correlation between AGB and erosion rate has potential implications for soil production. Using a simple hillslope model I show that if this decrease in AGB is associated with a drop in biotic soil production, then feedbacks between soil thickness and biotic soil production are capable of generating a complex response to geomorphic forcing, such that hillslopes possess multiple stable states: for intermediate rates of erosion, equilibrium hillslopes may be either soil mantled or bedrock. Hillslope evolution in these simulations is path dependent; once exposed at the surface, significant patches of bedrock exposure may persist over a wide range of incision rates.

Soil erosion is a global problem, affecting much of the world’s agricultural land. As the world’s population increases, the pressures placed upon the land resource to provide space for food production, leisure, housing and industrial facilities also increases. Thus it is vital that the land resource is as productive as possible. As soil erosion is the major cause of soil degradation globally, it is vital that methods for accurately monitoring the degree of erosion from a site, and the effectiveness of any remediation attempts are available. Reported here is the development of a novel soil erosion particle tracer, based upon a lanthanide chelate complex doped silica particle. The luminescent lanthanide chelate complexes were comprised of 2-thenoyltrifluoroacetone (TTA) and 2-pyridinol-1-oxide (2PO) coordinated with either trivalent europium or terbium ions. These complexes were then doped into silica sol-gel particles using a core shell technique. This method resulted in the synthesis of two luminescent soil tracers, targeted to two of the key eroded soil fractions; fine silt (63-250 μm) and clay (< 1.2 μm). The behaviour of the tracers was analysed within three different soils obtained from the Glensaugh research station. They retained their luminescence when mixed with soil, and could be detected at concentrations of 10 mg tracer / kg soil using a standard benchtop fluorescence spectrometer (Perkin Elmer LS55B). Scanning electron micrographs indicated that the tracer particles interacted with the soil particles, whilst soil sedimentation experiments demonstrated that the tracer particles had a similar sedimentation pattern to natural soil particles. Soil microbial respiration studies were performed for the tracers and showed that the tracers did not significantly impact the soil microbial population. Studies of the luminescence stability of the tracer in soil over time showed that the tracer could be detected in the soil for one season (approximately 3 months). A prototype rainfall simulator, designed to simulate the kinetic energy of raindrops on the surface of the soil, was developed, and used during a series of rainfall simulation experiments. These simulations were performed at two different rainfall intensities (30 and 90 mm.h-1) and both of these conditions resulted in movement of the tracer particles within the plot. This movement was both horizontal, in overland flow over the plot surface, and vertical, through the plot. The pattern of tracer movement reflected that of the soil mass moved, and as such indicated that the tracers exhibited similar transport behaviour during the erosion simulations performed. These initial simulations demonstrated that the tracers can be detected at low concentrations within the soil using standard laboratory equipment, and that they move with the eroded soil particles during simulated soil erosion experiments. As such, these tracers are excellent candidates for further study in larger scale erosion events.

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Thesis (M.Eng. (Hons.)) -- University of Western Sydney, 2003. / "Thesis submitted for the degree of Masters of Engineering (Honours) Environmental Engineering" Includes bibliography.

Thesis (doctoral)--Wageningen University, 2004. / Includes bibliographical references.