
Rivers in the Landscape
Description
Alles über E-Books | Antworten auf Fragen rund um E-Books, Kopierschutz und Dateiformate finden Sie in unserem Info- & Hilfebereich.
Rivers in the Landscape, Second Edition, emphasizes general principles and conceptual models, as well as concrete examples of each topic drawn from the extensive literature on river process and form. The book is suitable for use as a course text or a general reference on rivers. Aimed at advanced undergraduate students, graduate students, and professionals looking for a concise summary of physical aspects of rivers, Rivers in the Landscape is designed to:
* emphasize the connectivity between rivers and the greater landscape by explicitly considering the interactions between rivers and tectonics, climate, biota, and human activities;
* provide a concise summary of the current state of knowledge for physical process and form in rivers;
* reflect the diversity of river environments, from mountainous, headwater channels to large, lowland, floodplain rivers and from the arctic to the tropics;
* reflect the diverse methods that scientists use to characterize and understand river process and form, including remote sensing, field measurements, physical experiments, and numerical simulations;
* reflect the increasing emphasis on quantification in fluvial geomorphology and the study of Earth surfaces in general;
* provide both an introduction to the classic, foundational papers on each topic, and a guide to the latest, particularly insightful and integrative references.
More details
Other editions
Additional editions

Person
ELLEN WOHL is a Professor in the Department of Geosciences at Colorado State University. She has over twenty-five years' experience in teaching fluvial geomorphology at the graduate level in courses with students from the earth sciences, civil engineering, ecology, and other disciplines. She has written several books about rivers for non-technical audiences as well as the more technical books Mountain Rivers, and its second edition, Mountain Rivers Revisited.
Content
Acknowledgements xi
1 Introduction 1
1.1 Connectivity and Inequality 3
1.2 Six Degrees of Connection 8
1.3 Rivers as Integrators 11
1.4 Organization of this Volume 13
1.5 Understanding Rivers 15
1.5.1 The Colorado Front Range 15
1.6 Only Connect 26
2 Creating Channels and Channel Networks 27
2.1 Generating Water, Solutes, and Sediment 27
2.1.1 Generating Water 27
2.1.2 Generating Sediment and Solutes 28
2.2 Getting Water, Solutes, and Sediment Downslope to Channels 30
2.2.1 Downslope Pathways of Water 30
2.2.2 Downslope Movement of Sediment 39
2.2.3 Processes and Patterns of Water Chemistry Entering Channels 42
2.2.4 Influence of the Riparian Zone on Fluxes into Channels 43
2.3 Human Influences on Fluxes from Uplands to Channels 46
2.3.1 Climate Change 46
2.3.2 Altered Land Cover 48
2.3.2.1 Deforestation 48
2.3.2.2 Afforestation 49
2.3.2.3 Grazing 50
2.3.2.4 Crop Growth 50
2.3.2.5 Urbanization 50
2.3.2.6 Upland Mining 51
2.3.2.7 Land Drainage 52
2.3.2.8 Commercial Recreational Property Development 52
2.4 Channel Initiation 53
2.5 Extension and Development of the Drainage Network 57
2.5.1 Morphometric Indices and Scaling Laws 58
2.5.2 Optimality 61
2.6 Spatial Differentiation within Drainage Basins 62
2.7 Summary 64
Part I Channel Processes I 67
3 Water Dynamics 69
3.1 Hydraulics 69
3.1.1 Flow Classification 70
3.1.2 Energy, Flow State, and Hydraulic Jumps 74
3.1.3 Uniform Flow Equations and Flow Resistance 76
3.1.4 Velocity and Turbulence 86
3.1.5 Measures of Energy Exerted Against the Channel Boundaries 93
3.1.6 Numerical Models of Hydraulics 94
3.2 Hydrology 95
3.2.1 Measuring Discharge 95
3.2.2 Indirectly Estimating Discharge 96
3.2.3 Modeling Discharge 103
3.2.4 Flood Frequency Analysis 105
3.2.5 Hydrographs and Flow Regime 106
3.2.6 Other Parameters Used to Characterize Discharge 110
3.2.7 Hyporheic Exchange and Hydrology 110
3.2.8 River Hydrology in Cold Regions 114
3.2.9 Human Influences on Hydrology 115
3.2.9.1 Flow Regulation 115
3.2.9.2 River Corridor Engineering 122
3.2.10 The Natural Flow Regime 123
3.3 Summary 124
Part II Channel Processes II 125
4 Fluvial Sediment Dynamics 127
4.1 The Channel Bed and Initiation of Motion 128
4.1.1 Bed Sediment Characterization 128
4.1.2 Entrainment of Noncohesive Sediment 129
4.1.2.1 Forces Acting on a Grain 131
4.1.2.2 Grain Properties 133
4.1.2.3 Turbulence 134
4.1.2.4 Biotic Processes 134
4.1.3 Erosion of Cohesive Beds 135
4.1.3.1 Erosion of Bedrock 135
4.1.3.2 Erosion of Cohesive Sediment 139
4.2 Sediment Transport 139
4.2.1 Dissolved Load 139
4.2.1.1 Nitrogen 141
4.2.1.2 Carbon 141
4.2.1.3 Trace Metals 143
4.2.1.4 Other Environments 144
4.2.2 Suspended Load 144
4.2.3 Bed Load 151
4.2.3.1 Bed Load in Channels with Coarse-Grained Substrate: Coarse Surface Layer 152
4.2.3.2 Bed Load in Channels with Coarse-Grained Substrate: Characteristics of Grain Movements 154
4.2.3.3 Bed Load in Channels with Coarse-Grained Substrate: Controls on Bed-Load Dynamics 156
4.2.3.4 Estimating Bed-Load Flux 158
4.2.3.5 Field Measurements of Bed Load 161
4.3 Bedforms 163
4.3.1 Readily Mobile Bedforms 163
4.3.2 Infrequently Mobile Bedforms 167
4.3.2.1 Particle Clusters 167
4.3.2.2 Transverse Ribs 167
4.3.2.3 Steep Alluvial Channel Bedforms 168
4.3.2.4 Step-Pool Channels 169
4.3.2.5 Pool-Riffle Channels 171
4.3.2.6 Bars 175
4.3.3 Bedforms in Cohesive Sediments 175
4.4 In-Channel Depositional Processes 176
4.5 Downstream Trends in Grain Size 178
4.6 Bank Stability and Erosion 179
4.7 Sediment Budgets 184
4.8 Human Influences on Sediment Dynamics 189
4.9 The Natural Sediment Regime 193
4.10 Summary 194
Part III Channel Processes III 197
5 Large Wood Dynamics 199
5.1 The Continuum of Vegetation in River Corridors 199
5.2 Recruitment of Wood to River Corridors 201
5.3 Wood Entrainment and Transport 203
5.4 Wood Deposition 207
5.5 Wood Storage 208
5.6 Wood Interactions with Water and Sediment 212
5.7 Human Influences on Wood Dynamics 215
5.8 The Natural Wood Regime 216
5.9 Summary 218
6 Channel Forms 219
6.1 Cross-Sectional Geometry 220
6.1.1 Bankfull, Dominant, and Effective Discharge 220
6.1.2 Width-to-Depth Ratio 222
6.1.3 Hydraulic Geometry 223
6.1.3.1 At-A-Station Hydraulic Geometry 223
6.1.3.2 Downstream Hydraulic Geometry 225
6.1.4 Lane's Balance 226
6.1.5 Complex Response 228
6.1.6 Channel Evolution Models 228
6.2 Channel Planform 231
6.2.1 Straight Channels 232
6.2.2 Meandering Channels 233
6.2.3 Wandering Channels 238
6.2.4 Braided Channels 239
6.2.5 Anabranching Channels 244
6.2.6 Compound Channels 246
6.2.7 Karst Channels 246
6.2.8 Continuum Concept 246
6.2.9 River Metamorphosis 247
6.3 Confluences 250
6.4 Bedrock Channels 254
6.5 River Gradient 255
6.5.1 Longitudinal Profile 257
6.5.2 Stream Gradient Index 261
6.5.3 Knickpoints 262
6.6 Adjustment of Channel Form 265
6.6.1 Extremal Hypotheses of Channel Adjustment 266
6.6.2 Nonlinear Behavior and Alternative States 267
6.6.3 Geomorphic Effects of Floods 268
6.7 Human Influences on Channel Form 270
6.8 Summary 276
7 Extra-Channel Environments 277
7.1 Floodplains 277
7.1.1 Floodplain Functions 278
7.1.2 Floodplain Hydrology 281
7.1.3 Depositional Processes and Floodplain Stratigraphy 281
7.1.4 Erosional Processes and Floodplain Turnover Times 287
7.1.5 Downstream Trends in Floodplain Form and Process 289
7.1.6 Classification of Floodplains 290
7.1.7 Human Influences on Floodplains 290
7.2 Terraces 291
7.2.1 Terrace Classifications 292
7.2.2 Mechanisms of Terrace Formation and Preservation 295
7.2.3 Terraces as Paleoprofiles and Paleoenvironmental Indicators 297
7.3 Alluvial Fans 300
7.3.1 Erosional and Depositional Processes 302
7.3.2 Fan Geometry and Stratigraphy 303
7.3.3 Mapping, Studying, and Living on Fans 305
7.4 Deltas 306
7.4.1 Processes of Erosion and Deposition 308
7.4.2 Delta Morphology and Stratigraphy 309
7.4.3 Paleoenvironmental Records 312
7.4.4 Deltas in the Anthropocene 313
7.5 Estuaries 314
7.6 Summary 316
8 Rivers in the Landscape 319
8.1 Rivers and Topography 319
8.1.1 Tectonics, Topography, and Large Rivers 321
8.1.2 Indicators of Relations Between Rivers and Landscape Evolution 323
8.1.3 Tectonic Influences on River Geometry 323
8.1.4 Effects of River Incision on Tectonics 324
8.1.5 Bedrock-Channel Incision and Landscape Evolution 325
8.2 Climatic Signatures 328
8.2.1 High Latitudes 328
8.2.2 Low Latitudes 331
8.2.3 Warm Drylands 333
8.3 Spatial Differentiation Along a River 336
8.4 Connectivity 338
8.5 River Management in an Environmental Context 342
8.5.1 Reference Conditions 342
8.5.2 Restoration 344
8.5.3 Instream, Channel Maintenance, and Environmental Flows 350
8.5.4 River Health 353
8.6 Rivers with a History 355
8.7 The Greater Context 357
References 361
Index 491
1
Introduction
Rivers are the shapers of terrestrial landscapes. Very few points on Earth above sea level do not lie within a drainage basin. Even points distant from the nearest channel are likely to be influenced by that channel. Tectonic uplift raises rock thousands of meters above sea level. Precipitation falling on the uplifted terrain concentrates into channels that carry sediment downward to the oceans and influence the steepness of adjacent hill slopes by governing the rate at which the landscape incises. Rivers migrate laterally across lowlands, creating a complex topography of terraces, floodplain wetlands, and channels. Subtle differences in elevation, grain size, and soil moisture across this topography control the movement of ground water and the distribution of plants and animals.
Investigators have begun to quantify the extent to which rivers influence the surrounding landscape. Stream ecologists ask, "How wide is a stream?" and address the question by using isotopic signatures to analyze food web data indicating exchanges of matterand energy between aquatic and terrestrial biotic communities (Muehlbauer et al. 2014). Geomorphologists ask, "How large is a river?" and address the question by defining signatures - emergent properties of sets of processes acting on a river landscape - and envelopes - the dynamic penetration of a signature across the landscape (Gurnell et al. 2016b). In each case, the answer is, "Wider and larger than surface appearances might suggest."
Throughout human history, people have settled disproportionately along rivers, relying on them for water supply, transport, fertile agricultural soils, waste disposal, and food from aquatic and riparian organisms. People have also devoted a tremendous amount of time and energy to altering river process and form. We are not unique in this respect: ecologists refer to various organisms, from beaver to some species of riparian trees, as ecosystem engineers in recognition of their ability to alter their environment. Humans are unique, however, in the extent to and intensity with which we alter rivers. In many cases, river engineering has unintended consequences, and effectively mitigating these consequences requires that we understand rivers in the broadest sense, as shapers and integrators of landscape.
Geomorphologist Luna Leopold once described rivers as the gutters down which flow the ruins of continents (Leopold et al. 1964). His father, Aldo Leopold, described the functioning of an ecosystem as a "round river," to emphasize the cycling of nutrients and energy. Rivers can be thought of as having a strong unidirectional and linear movement of water, sediment, and other materials. Rivers can also be thought of as more broadly connected systems with bidirectional fluxes of energy and matter between the channels of the river network and the greater environment. This volume emphasizes the latter viewpoint.
Rivers are not simply channels. Various phrases have been used to describe the integrated system of channels, floodplain, and underlying hyporheic zone, including "the river system," "the fluvial system," "the river ecosystem," and "the river corridor." Regardless of the exact words used, the intent is to recognize that the active channel is integrally connected to adjacent surface and subsurface areas by fluxes of material and organisms. The three legs of the tripod of physical inputs that support a river corridor are inputs of water, sediment, and large wood from adjacent uplands. Although large wood has received less attention than water and sediment inputs, the historical abundance of large wood in regions with forested uplands or floodplains, along with observations of the geomorphic effects of large wood in the few remaining natural river corridors, indicates that large wood significantly influences river process and form. The material inputs of water, sediment, and wood are redistributed within the river corridor, stored for varying lengths of time, and eventually transported to the ocean, to another long-term depositional environment (e.g. alluvial fan or delta), or - for water - back to the atmosphere or ground water.
Each of the primary inputs to a river corridor can be described in terms of natural regimes that occur in the absence of human alterations in land cover, river form, flow regulation, and the water table, and in terms of altered regimes associated with human activities. The natural flow regime can be characterized with respect to magnitude, frequency, duration, timing, and rate of rise and fall of water discharge (Poff et al. 1997). Human alterations of the flow regime can be quantified using indicators of hydrologic alteration (Richter et al. 1996; Poff et al. 2010). The natural sediment regime can be characterized with respect to inputs, outputs, and storage of sediment (Wohl et al. 2015b). Because records of sediment flux analogous to those of gaged stream discharge do not exist, human alterations of the sediment regime can be inferred from the occurrence of sustained changes in river process and form that result from altered sediment dynamics. The natural wood regime can be characterized with respect to magnitude, frequency, duration, timing, rate, and mode of wood recruitment, transport, and storage within river corridors (Wohl et al., 2019). As with sediment, insufficient systematic records exist of wood flux in the absence of human influences to quantify changes in the natural wood regime, but the effect of human influences can be inferred from sustained changes in river process and form (e.g. Collins et al. 2012).
The details of how materials from uplands enter a river corridor and move through it are partly governed by the spatial context of the corridor (Figure 1.1). Context here includes valley geometry (downstream gradient, valley-bottom width relative to active channel width), position in the network, base-level stability, and substrate erosional resistance (Wohl 2018a). Valley geometry influences the energy available for changes in river form and the space available to accommodate change. Steep river reaches typically correspond to relatively narrow valleys and coarser sediment or bedrock (Livers and Wohl 2015). Lower-gradient reaches are more likely to have wide valley bottoms relative to channel width, as well as floodplains or secondary channels. Position in the network can influence the sensitivity of a river corridor to fluctuations in relative base level: commonly, the lower portions of a river network are more likely to incise in response to relative base-level fall or aggrade in response to relative base-level rise. Base-level stability influences river corridor configuration in that a river reach may be incising or aggrading irrespective of inputs of water, sediment, and large wood because of base-level instability (e.g. Schumm 1993). Substrate erosional resistance describes the ability of the channel and floodplain substrate to resist erosional changes. Resistance derives from substrate composition (grain size, stratigraphy, bedrock lithology; e.g. Finnegan et al. 2005) and from the presence of riparian vegetation (e.g. Gurnell 2014).
Figure 1.1 Schematic illustration of the primary inputs to river corridors (water, sediment, large wood) and the context in which they interact with one another and with the river form to create the integrative river corridor characteristics listed in the lower portion of the figure. (See color plate section for color representation of this figure).
Human activities can modify inputs and context. Although people typically do not alter the actual valley geometry, they do commonly alter the effective valley geometry by building levees, regulating flow and reducing flood peaks, or stabilizing the banks, each of which limits the interactions between channel and floodplain. Analogously, construction of grade controls or dams affects local base-level stability, and land drainage or bank stabilization modifies substrate erosional resistance.
Interactions between inputs and valley context create the characteristics of the river corridor listed in the lower row of Figure 1.1: spatial heterogeneity, nonlinear behavior, connectivity, resilience, and integrity. Connectivity and nonlinear behavior are introduced in this first chapter. The other concepts are covered in subsequent ones.
1.1 Connectivity and Inequality
Contemporary research and conceptual models of river form and process increasingly explicitly recognize the important of connectivity. Connectivity, sometimes referred to as coupling (e.g. Brunsden and Thornes 1979), is multifaceted. Hydrologic connectivity can refer to the movement of water down a hillslope in the surface or subsurface, from hillslopes into channels, or along a channel network (Pringle 2001; Bracken and Croke 2007). River connectivity refers to water-mediated fluxes within the channel network (Ward 1997). Sediment connectivity can refer to the movement, or storage, of sediment down hillslopes, into channels, or along channel networks (Harvey 1997; Fryirs et al. 2007a,b; Kuo and Brierley 2013; Bracken et al. 2015). Biological connectivity refers to the ability of organisms or plant propagules to disperse between suitable habitats or between isolated populations for breeding. Landscape connectivity can refer to the movement of...
System requirements
File format: ePUB
Copy protection: Adobe-DRM (Digital Rights Management)
System requirements:
- Computer (Windows; MacOS X; Linux): Install the free reader Adobe Digital Editions prior to download (see eBook Help).
- Tablet/smartphone (Android; iOS): Install the free app Adobe Digital Editions or the app PocketBook before downloading (see eBook Help).
- E-reader: Bookeen, Kobo, Pocketbook, Sony, Tolino and many more (not Kindle).
The file format ePub works well for novels and non-fiction books – i.e., „flowing” text without complex layout. On an e-reader or smartphone, line and page breaks automatically adjust to fit the small displays.
This eBook uses Adobe-DRM, a „hard” copy protection. If the necessary requirements are not met, unfortunately you will not be able to open the eBook. You will therefore need to prepare your reading hardware before downloading.
Please note: We strongly recommend that you authorise using your personal Adobe ID after installation of any reading software.
For more information, see our ebook Help page.