Rivers are the great 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.
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.
Table of Contents:
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
About the Author :
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.
