Preface vii
1. Introduction 1
Brief History 1
Runoff Mechanisms 3
Engineering and Scientific Approaches to Hydrology 4
Objective and Scope of this Work 5
2. Basic Porous Media Hydraulics 7
Capillary Properties of Soil Water 7
Porous Media 9
Darcy's Law 12
Hydraulic Characteristics of Porous Media 13
Steady Flow Soil Water Relations 14
Functional Representation of Hydraulic Characteristics 18
3. Some Essentials of One-Dimensional Porous Media Dynamics 25
Introduction 25
Absorption: Gravity-Free Intake 27
Infiltration: Vertical Flow 31
Mathematical Approximations for Soil Water Flow 34
Approximations for Soil Hydraulic Characteristics 36
4. A Realistic Integrable Nonlinear Model for Transient Unsaturated Flow 41
Introduction 41
Integrable Forms of Richards' Equation' 43
Solution of Nonlinear Diffusion Equation 46
Required Forms for Soil Characteristics 49
Solution of the Integrable Form 55
Discussion and Summary 60
5. Absorption and Infiltration Relations and the Infiltrability-Depth
Approximation 63
Introduction 63
Absorption 65
Infiltration 73
Stability of Flux-ConcentrationR elation 85
6. Infiltrability Models: Comparisons and Application 97
Introduction 97
Timing of Pending 98
Time Explicit Approximations 108
Applying the Infiltrability Models to Variable Rainfall Patterns 114
7. Applying Infiltration Models in Layered Soils and Redistribution Cases 119
Introduction 119
Redistribution and Reinfiltration 119
Layered Soils 122
8. Field Measurements of Infiltration Parameters 135
Introduction 135
Drip Infiltrometers 136
Ring Infiltrometers 138
Permeameters 141
9. Infiltration and Runoff on a Hillslope 159
Introduction 159
General Surface Flow and Infiltration Interaction 160
Effect of Surface Relief on Surface Water Losses 162
Infiltration Heterogeneity and Runoff 164
Appendices 185
I. Derivation of the Infiltration Integral from Richards' Equation 185
II. Attenuation of Characteristic Kinematic Shock in Soil Water Flow 187
III. Finite Difference Solution Method for Richards' Equation 190
List of Symbols and Abbreviations 199
References 203
Index 211
