DOCSLIB.ORG

Reading the Recorded History of Soil Mantled Hillslopes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Reading the Recorded History of Soil Mantled Hillslopes READING THE RECORDED HISTORY OF SOIL MANTLED HILLSLOPES By Simon Marius Mudd Dissertation Submitted to the Faculty of the Graduate School of Vanderbilt University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Environmental Engineering May, 2006 Nashville, Tennessee Approved: Professor David J. Furbish Professor James H. Clarke Professor Kaye S. Savage Professor Florence Sanchez To my wife Robin, my mother Monika, and my father Brian ii ACKNOWLEDGMENTS This work was made possible through the financial support of the National Science Foundation, the Florida State University, and Vanderbilt University. I am grateful to my peers, colleagues, and mentors with whom I have had countless hours of discussion about geomorphology that have shaped my ideas about the physics of the Earth’s surface. I wish to give special thanks to the people with whom I have generally looked for beautiful landscapes to work in and understand. These people include (in semi-chronological order) Ian MacMillan, Manny Gabet, Mike Singer, Daniel Malmon, Tom Dunne, Steve Lancaster, Ryosuke Akahori, Jeroen Sonke, Jiun-Yee Yen, Sergio Fagherazzi, Andrea D’Alpaos, Mark Schmeekle, and Kyungsoo Yoo. Finally, and perhaps most significantly, I wish to acknowledge David Furbish, my advisor and mentor. It will be my pleasure to carry on David’s intellectual legacy, and will strive in my career to be his equal in ability and enthusiasm for both teaching and creating knowledge in the field of earth surface processes. iii TABLE OF CONTENTS Page DEDICATION ................................................................................................................ii ACKNOWLEDGMENTS ..............................................................................................iii LIST OF TABLES ...........................................................................................................vii LIST OF FIGURES ..........................................................................................................viii Chapter I. INTRODUCTION .................................................................................................1 1. Overview ...............................................................................................1 2. Components of the Thesis .....................................................................7 3. Summary .............................................................................................14 3. References ...........................................................................................16 II. THE INFLUENCE OF CHEMICAL DENUDATION ON HILLSLOPE MORPHOLOGY .................................................................................................19 Abstract ...................................................................................................19 1. Introduction .........................................................................................20 2. A Depth-Integrated Equation of Hillslope Mass Conservation Incorporating Chemical Denudation and Deposition ..............................25 2.1. Previous Work ......................................................................25 2.2. General Statement of Mass Conservation ............................26 2.3. Depth-Integration of the Statement of Mass Conservation ..28 2.4. Kinematic Conditions at the Soil Surface and the Soil-Bedrock Boundary ........................................................29 2.5. The Depth-Integrated Equation for Mass Conservation of Soil on a Hillslope ............................................................31 2.6. Simplifying Assumptions for Conservation of Mass Equation .......................................................................32 3. The Steady-State, Chemically Denuding Hillslope: 1-D Analysis .....33 3.1. Derivation of Governing Equations .....................................33 3.2. Denudation Rates .................................................................36 3.2.1. Mechanical Denudation Rate ................................36 3.2.2. Chemical Denudation Rate ...................................36 3.3. Curvature, Slope, and Profile of the 1-D Steady- State Hillslope ......................................................................39 iv 3.3.1. Features of the 1-D Steady-State Hillslope ...........40 3.4. Non-Dimensionalization .......................................................43 4. Discussion ............................................................................................46 4.1 Effect of Chemical Weathering on the Morphology of Steady-State Hillslopes .....................................................46 4.2. Conceptual Explanation of the Steady-State Convex-Concave Hillslope ...................................................47 4.3. Conditions for Steady-State Hillslopes with Convex-Concave Profiles .....................................................48 4.4. Transport Ratios for Steady-State Hillslopes With Convex-Concave Profiles ............................................50 4.5. Comparison of Theoretical Transport Ratios with Transport Ratios Calculated From Field Data ......................51 4.6. The Occurrence of Hillslopes with Denudation Ratios Greater Than 0.5 .......................................................54 5. Conclusions .........................................................................................55 Appendix 1 ..............................................................................................56 Appendix 2 ..............................................................................................57 Appendix 3 ..............................................................................................58 6. List of Symbols ...................................................................................60 7. References ...........................................................................................62 III. USING CHEMICAL TRACERS IN HILLSLOPE SOILS TO ESTIMATE THE IMPORTANCE OF CHEMICAL DENUDATION UNDER CONDITIONS OF DOWNSLOPE SEDIMENT TRANSPORT.........................................................68 Abstract ...................................................................................................68 1. Introduction .........................................................................................69 2. A Coupled Model of Hillslope Evolution ...........................................72 2.1. Conservation of Total Soil Mass .........................................72 2.2. Conservation of a Soil Phase ...............................................74 3. A 1-D, Two Phase Model of Hillslope Weathering and Transport ....77 3.1. Simplifying assumptions ......................................................78 3.2. Flux Laws .............................................................................79 3.3. Lagrangian Coordinate System ............................................80 3.4. The Governing Equations for a Hillslope Soil Composed of Two Phases .....................................................81 3.5. Non-Dimensionalization and Scaling ...................................84 4. On the Use of the Two Phase Hillslope System ..................................87 4.1. Steady State Solution of the Two Phase Hillslope Model ....90 4.2. Quantifying the Changes in the Concentration of the Immobile Phase Related to Transient Incision or Deposition .............................................................................99 5. Conclusions ........................................................................................105 Appendix A ............................................................................................107 6. List of Symbols ..................................................................................109 v 7. References ..........................................................................................111 IV. LATERAL MIGRATION OF HILLCRESTS IN RESPONSE TO CHANNEL INCISION IN SOIL MANTLED LANDSCAPES.............................................117 Abstract .................................................................................................117 1. Introduction ........................................................................................118 2. A 1-D Model of Hillcrest Migration ..................................................122 2.1. Governing Equations ...........................................................122 2.2. Scaling and Nondimensionalization of the Governing Equations ...........................................................126 2.3. Dimensionless Governing Equations ..................................128 3. Analytical Solutions of Hillcrest Migration .......................................129 3.1. Hillcrest Offset Due to Channel Elevation Differences at Topographic Steady State ................................................129 3.2. Migrating Hillcrest Due to Steady But Unequal Channel Incision Rates .......................................................135 4. Numerical Simulations of Transient Hillcrest Migration ..................142 4.1. The Effect of Delayed Knickpoint Migration .....................143 4.1.1. Linear Flux Law ..................................................144 4.1.2. Linear-Critical Flux Law .....................................151 4.1.3. Soil Storage and Thickness Effects .....................153 4.2. The Effect of Variations in Amplitude and Frequency of Incision Rates ..................................................................155 5. Conclusions
Load more

Recommended publications
  • Changing Hillslopes : Evolution and Inheritance
    Provided for non-commercial research and educational use only. Not for reproduction, distribution or commercial use. This chapter was originally published in the Treatise on Geomorphology, the copy attached is provided by Elsevier for the author’s benefit and for the benefit of the author’s institution, for non-commercial research and educational use. This includes without limitation use in instruction at your institution, distribution to specific colleagues, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier’s permissions site at: http://www.elsevier.com/locate/permissionusematerial Roering J.J., and Hales T.C. Changing Hillslopes: Evolution and Inheritance; Inheritance and Evolution of Slopes. In: John F. Shroder (Editor-in-chief), Marston, R.A., and Stoffel, M. (Volume Editors). Treatise on Geomorphology, Vol 7, Mountain and Hillslope Geomorphology, San Diego: Academic Press; 2013. p. 284-305. © 2013 Elsevier Inc. All rights reserved. Author's personal copy 7.29 Changing Hillslopes: Evolution and Inheritance; Inheritance and Evolution of Slopes JJ Roering, University of Oregon, Eugene, OR, USA TC Hales, Cardiff University, Cardiff, UK r 2013 Elsevier Inc. All rights reserved. 7.29.1 Introduction 285 7.29.2 Hillslope Evolution
    [Show full text]
  • Beyond the Angle of Repose: a Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California
    Portland State University PDXScholar Geology Faculty Publications and Presentations Geology 2-23-2015 Beyond the Angle of Repose: A Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California Joshua J. Roering University of Oregon Benjamin H. Mackey University of Canterbury Alexander L. Handwerger University of Oregon Adam M. Booth Portland State University, [email protected] Follow this and additional works at: https://pdxscholar.library.pdx.edu/geology_fac David A. Schmidt Univ Persityart of of the W Geologyashington Commons , Geomorphology Commons, and the Geophysics and Seismology Commons Let us know how access to this document benefits ou.y See next page for additional authors Citation Details Roering, Joshua J., Mackey, Benjamin H., Handwerger, Alexander L., Booth, Adam M., Schmidt, David A., Bennett, Georgina L., Cerovski-Darriau, Corina, Beyond the angle of repose: A review and synthesis of landslide pro-cesses in response to rapid uplift, Eel River, Northern California, Geomorphology (2015), doi: 10.1016/j.geomorph.2015.02.013 This Post-Print is brought to you for free and open access. It has been accepted for inclusion in Geology Faculty Publications and Presentations by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. Authors Joshua J. Roering, Benjamin H. Mackey, Alexander L. Handwerger, Adam M. Booth, David A. Schmidt, Georgina L. Bennett, and Corina Cerovski-Darriau This post-print is available at PDXScholar: https://pdxscholar.library.pdx.edu/geology_fac/75 ACCEPTED MANUSCRIPT Beyond the angle of repose: A review and synthesis of landslide processes in response to rapid uplift, Eel River, Northern California Joshua J.
    [Show full text]
  • Sensitivity Analysis of Pediment Development Through Numerical Simulation and Selected Geospatial Query ⁎ Mark W
    Geomorphology 88 (2007) 329–351 www.elsevier.com/locate/geomorph Sensitivity analysis of pediment development through numerical simulation and selected geospatial query ⁎ Mark W. Strudley , A. Brad Murray Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Science, Center for Nonlinear and Complex Systems, Duke University, USA Received 3 October 2006; received in revised form 29 November 2006; accepted 7 December 2006 Available online 23 December 2006 Abstract Dozens of references recognizing pediment landforms in widely varying lithologic, climatic, and tectonic settings suggest a ubiquity in pediment forming processes on mountain piedmonts worldwide. Previous modeling work illustrates the development of a unique range in arid/semiarid piedmont slope (b0.2 or 11.3°) and regolith thickness (2–4 m) that defines pediments, despite varying the initial conditions and domain characteristics (initial regolith thickness, slope, distance from basin to crest, topographic perturbations, and boundary conditions) and process rates (fluvial sediment transport efficiency and weathering rates). This paper expands upon the sensitivity analysis through numerical simulation of pediment development in the presence of spatially varying rock type, various base level histories, various styles of sediment transport, and various rainfall rates to determine how pediment development might be restricted in certain environments. This work suggests that in landscapes characterized by soil and vegetation types that favor incisive fluvial
    [Show full text]
  • Soil Formation and Transport Processes on Hillslopes Along a Precipitation Gradient in the Atacama Desert, Chile
    Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile by Justine Janet Owen A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Environmental Science, Policy, and Management in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Ronald Amundson, Chair Professor William E. Dietrich Professor Celine Pallud Professor Guillermo Chong Diaz Fall 2009 Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile © 2009 by Justine Janet Owen Abstract Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile by Justine Janet Owen Doctor of Philosophy in Environmental Science, Policy, and Management University of California, Berkeley Professor Ronald Amundson, Chair The climate-dependency of the rates and types of soil formation processes on level landforms has been recognized and documented for decades. In contrast, methods for quantifying rates of soil formation and transport on hillslopes have only recently been developed and the results suggest that these rates are independent of climate. One explanation for this discrepancy is that hillslopes and their soil mantles are dynamic systems affected by local and regional tectonic effects. Tectonics can change local or regional baselevel which affects the hillslope through stream incision or terrace formation at its basal boundary. Another explanation is that in most of the world hillslope processes are biotic, and biota and their effects vary nonlinearly with climate. The effects of both tectonics and life can obscure climatic effects. Recent studies have been made to isolate the climatic effect on hillslope processes, but they are few and focus on humid and semiarid hillslopes.
    [Show full text]
  • Shallow Landslides As Drivers for Slope Ecosystem Evolution And
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by ResearchOnline@GCU Shallow landslides as drivers for slope ecosystems evolution and biophysical diversity Gonzalez-Ollauri, Alejandro; Mickovski, Slobodan B. Published in: Landslides DOI: 10.1007/s10346-017-0822-y Publication date: 2017 Document Version Publisher's PDF, also known as Version of record Link to publication in ResearchOnline Citation for published version (Harvard): Gonzalez-Ollauri, A & Mickovski, SB 2017, 'Shallow landslides as drivers for slope ecosystems evolution and biophysical diversity', Landslides, vol. 14, no. 5, pp. 1699-1714. https://doi.org/10.1007/s10346-017-0822-y General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Take down policy If you believe that this document breaches copyright please view our takedown policy at https://edshare.gcu.ac.uk/id/eprint/5179 for details of how to contact us. Download date: 29. Apr. 2020 Original Paper Landslides Alejandro Gonzalez-Ollauri I Slobodan B. Mickovski DOI 10.1007/s10346-017-0822-y Received: 19 July 2016 Accepted: 22 March 2017 Shallow landslides as drivers for slope ecosystem © The Author(s) 2017 evolution and biophysical diversity This article is published with open access at Springerlink.com Abstract Shallow landslides may be seen as local disturbances that Shallow landslides increase the openness (Odum 1969) of the foster the evolution of slope landscapes as part of their self- landscape by displacing the topsoil and established vegetation regulating capacity.
    [Show full text]
  • Soil Formation and Transport Processes on Hillslopes Along a Precipitation Gradient in the Atacama Desert, Chile
    UC Berkeley UC Berkeley Electronic Theses and Dissertations Title Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile Permalink https://escholarship.org/uc/item/0wm2q0dx Author Owen, Justine J. Publication Date 2009 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile by Justine Janet Owen A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Environmental Science, Policy, and Management in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Ronald Amundson, Chair Professor William E. Dietrich Professor Celine Pallud Professor Guillermo Chong Diaz Fall 2009 Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile © 2009 by Justine Janet Owen Abstract Soil Formation and Transport Processes on Hillslopes along a Precipitation Gradient in the Atacama Desert, Chile by Justine Janet Owen Doctor of Philosophy in Environmental Science, Policy, and Management University of California, Berkeley Professor Ronald Amundson, Chair The climate-dependency of the rates and types of soil formation processes on level landforms has been recognized and documented for decades. In contrast, methods for quantifying rates of soil formation and transport on hillslopes have only recently been developed and the results suggest that these rates are independent of climate. One explanation for this discrepancy is that hillslopes and their soil mantles are dynamic systems affected by local and regional tectonic effects. Tectonics can change local or regional baselevel which affects the hillslope through stream incision or terrace formation at its basal boundary.
    [Show full text]
  • Weathering Front.Pdf
    Earth-Science Reviews 198 (2019) 102925 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Weathering fronts T ⁎ Jonathan D. Phillipsa,c, , Łukasz Pawlikb, Pavel Šamonilc a Earth Surface Systems Program, Department of Geography, University of Kentucky, Lexington, KY 40508, USA b Faculty of Earth Sciences, University of Silesia, ul. Będzińska 60, 41-200 Sosnowiec, Poland c The Silva Tarouca Research Institute, Department of Forest Ecology, Lidická 25/27, Brno 602 00, Czech Republic ARTICLE INFO ABSTRACT Keywords: A distinct boundary between unweathered and weathered rock that moves downward as weathering pro- Weathering profile ceeds—the weathering front—is explicitly or implicitly part of landscape evolution concepts of etchplanation, Regolith triple planation, dynamic denudation, and weathering- and supply-limited landscapes. Weathering fronts also fl Multidirectional mass uxes figure prominently in many models of soil, hillslope, and landscape evolution, and mass movements. Clear Critical zone transitions from weathered to unweathered material, increasing alteration from underlying bedrock to the Soil evolution surface, and lateral continuity of weathering fronts are ideal or benchmark conditions. Weathered to un- Hillslope processes weathered transitions are often gradual, and weathering fronts may be geometrically complex. Some weathering profiles contain pockets of unweathered rock, and highly modified and unmodified parent material at similar depths in close proximity. They also reflect mass fluxes that are more varied than downward-percolating water and slope-parallel surface processes. Fluxes may also be upward, or lateral along lithological boundaries, structural features, and textural or weathering-related boundaries. Fluxes associated with roots, root channels, and faunal burrows may potentially occur in any direction.
    [Show full text]
  • On the Main Components of Landscape Evolution Models
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 17 June 2019 doi:10.20944/preprints201906.0161.v1 Review On the main components of landscape evolution models Michael Nones 1 1 Department of Hydrology and Hydrodynamics, Institute of Geophysics, Polish Academy of Science, Warsaw, Poland; [email protected] * Correspondence: [email protected]; Tel.: +48226915776 Abstract: Currently, the use of numerical models for reproducing the landscape evolution of a river basin is part of the day-by-day research activities of fluvial engineers and geomorphologists. However, despite landscape modelling is based on a rather long tradition, and scientists and practitioners are trying to schematize the processes involved in the evolution of a landscape since decades, there is still the need for improving both the knowledge of the physical mechanisms and their numerical coding. The present review focuses on the first aspect, discussing the main components of a landscape evolution model and their more common schematizations, presenting possible open questions to be addressed towards an improvement of the reliability of such kind of models in describing the fluvial geomorphology. Keywords: numerical modelling; landscape evolution; surface processes; river networks 1. Introduction This paper reviews the state-of-art in computational models of landscape evolution, focusing on the main processes typically schematized in numerical codes that can be applied for describing terrains shaped by a combination of fluvial and hillslope processes. Indeed, nowadays numerical models represent an indispensable tool for assisting geomorphologists in reproducing the diversity, origins and dynamics of surface landscapes, combining a quantitative characterization of terrain with various theories describing the continual modification of topography by the manifold processes that sculpt it [1].
    [Show full text]
  • Numerical Modelling of the Climate Control on Hillslope Erosion
    Université de Liège - Université de Grenoble Numerical modelling of the climate control on hillslope erosion Model development and application to the Last Glacial-Interglacial Cycle in NW Europe Thèse réalisée par Benoît Bovy sous la direction de Alain Demoulin (Université de Liège, UGPQ) et Jean Braun (Université de Grenoble, ISTerre) pour l’obtention du titre de Docteur en sciences de l’Université de Liège et Docteur de l’Université de Grenoble (spécialité : Terre, Univers, Environnement) Jury composé de : M. Niels Hovius (Lecturer, University of Cambridge, Rapporteur), M. Arjun Heimsath (Associate Professor, Arizona State University, Rapporteur), M. Louis François (Chargé de cours, Université de Liège, Président), M. Stéphane Bonnet (Maître de Conférences, Université de Toulouse 3, Examinateur), M. Yves Cornet (Chargé de cours, Université de Liège, Examinateur), M. Jean Braun (Professeur, Université de Grenoble, Co-directeur de thèse), M. Alain Demoulin (Maître de recherches FNRS, Université de Liège, Co-directeur de thèse) Résumé Modélisation numérique du contrôle climatique sur l’érosion des versants. Développement d’un nouveau modèle et application au dernier cycle glaciaire- interglaciaire dans le Nord-Ouest de l’Europe. L’évolution des versants est le résultat de l’action combinée des processus d’altération et de transport sédimentaire. Même si il est généralement admis que l’efficacité de ces processus varie en fonction du climat, la quantification de l’influence climatique sur l’érosion des versants reste encore peu développée aujourd’hui. S’inscrivant dans cette problématique, notre étude est consacrée au développement d’un nouveau modèle numérique d’érosion des versants, ay- ant pour objectif de mieux représenter, à différentes échelles de temps, les multiples aspects du contrôle climatique sur les processus de transport de sol.
    [Show full text]
  • Fire and the Evolution of Mountainous Landscapes 1
    Fire and the evolution of mountainous landscapes Joshua J. Roering* Molly Gerber Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA ___________ * email: [email protected] ph: 541-346-5574 fax: 541-346-4692 ABSTRACT Recent burns in the western United States attest to the significant geomorphic impact of fire in mountainous landscapes, yet we lack the ability to predict and interpret fire-related erosion over millenial timescales. A diverse set of geomorphic processes is often invoked following fire; the magnitude of post- fire erosional processes coupled with temporal variations in fire frequency dictate the extent to which fires affect sediment production and landscape evolution. In the Oregon Coast Range (OCR), several models for long-term rates of soil production and transport have been tested and calibrated, although treatment of fire-related processes has been limited. Following recent fires in the OCR, we observed extensive colluvial transport via dry ravel, localized bedrock emergence due to excess transport, and talus-like accumulation in adjacent low-order valleys. Soils exhibited extreme but discontinuous hydrophobicity and no evidence for rilling or gullying was observed. Using a field-based dataset for fire- induced dry ravel transport, we calibrated a physically-based, transport model which indicates that soil flux varies nonlinearly with gradient. The post-fire critical gradient (1.03), which governs the slope at which flux increases rapidly, is lower than the previously estimated long-term value (1.27), reflecting the reduction of slope roughness from incineration of vegetation. Using a high-resolution topographic dataset generated via airborne laser swath mapping, we modeled the spatial pattern of post-fire and long-term erosion rates.
    [Show full text]
  • Effects of Large Deep-Seated Landslides on Hillslope Morphology, Western Southern Alps, New Zealand
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, F01018, doi:10.1029/2004JF000242, 2006 Effects of large deep-seated landslides on hillslope morphology, western Southern Alps, New Zealand Oliver Korup1 Received 28 September 2004; revised 21 October 2005; accepted 12 December 2005; published 14 March 2006. [1] Morphometric analysis and air photo interpretation highlight geomorphic imprints of large landslides (i.e., affecting 1km2) on hillslopes in the western Southern Alps (WSA), New Zealand. Large landslides attain kilometer-scale runout, affect >50% of total basin relief, and in 70% are slope clearing, and thus relief limiting. Landslide terrain shows lower mean local relief, relief variability, slope angles, steepness, and concavity than surrounding terrain. Measuring mean slope angle smoothes out local landslide morphology, masking any relationship between large landslides and possible threshold hillslopes. Large failures also occurred on low-gradient slopes, indicating persistent low- frequency/high-magnitude hillslope adjustment independent of fluvial bedrock incision. At the basin and hillslope scale, slope-area plots partly constrain the effects of landslides on geomorphic process regimes. Landslide imprints gradually blend with relief characteristics at orogen scale (102 km), while being sensitive to length scales of slope failure, topography, sampling, and digital elevation model resolution. This limits means of automated detection, and underlines the importance of local morphologic contrasts for detecting large landslides in the WSA. Landslide controls on low-order drainage include divide lowering and shifting, formation of headwater basins and hanging valleys, and stream piracy. Volumes typically mobilized, yet still stored in numerous deposits despite high denudation rates, are >107 m3, and theoretically equal to 102 years of basin-wide debris production from historic shallow landslides; lack of absolute ages precludes further estimates.
    [Show full text]
  • Canons of Landscape Evolution
    BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 64. PP. 721-762.10 FIGS. 4 PLS. JULY 1963 CANONS OF LANDSCAPE EVOLUTION BY LESTER C. KING ABSTRACT The manner in which epigene landscapes evolve is examined and discussed. Slope flattening as a general process of landscape evolution is rejected, and with it Davis' concept of the peneplain. Landscape evolu- tion by scarp retreat and pedimentation is accepted, and several of its consequences are examined. The opinions derived are expressed at the end of the paper as a series of canons of landscape development CONTENTS TEXT Figure Page Page 4. Elements of a hillside slope 728 Historical approach 721 5. Effect of structure on hillslopes 729 Acknowledgment 722 Statement of the problem 723 6. Development of rock floors under humid Nature of hillslopes 725 climate 737 Evolution of hillslopes according to W. M. 7. Continued development of rock floors under Davis 725 humid climate 737 Hillslope elements 728 8. Late stage of the cycle of erosion under Pedimentation 730 humid controls according to W. M. Present hypothesis of hillslope evolution 732 Davis 738 Convexity of upper slopes 735 9. Standard conception of a peneplain 739 Hornologies between tie landscapes of humid- 10. Landscape profiles under arid, semiarid, temperate, semiarid, and arid regions 736 and humid influences 741 Peneplain versus pediplain 738 Plate Facing page "Normality" in landscape 740 Epigene cycle of erosion 742 1. Erosional surfaces and scarps in South Africa 744 Dating of land surfaces 745 2. Erosional features of granite terrains, Quantitative methods of landscape study 746 Southern Africa 744 Canons of landscape evolution 747 3.
    [Show full text]