CONTENTS 



Page 



CONVERSION FACTORS, U.S. CUSTOMARY TO METRIC (SI) 7 



SYMBOLS AND DEFINITIONS 8 



I BACKGROUND 11 



1. Introduction 11 



2. Dimensionless Variables 12 



3. Previous Observations 14 



II EXPERIMENTAL PROGRAM AND PROCEDURES 27 



1. Nature and Scope of the Experiments 27 



2. Ranges of Materials and Variables 30 



3. Referral to Prototype Conditions 38 



III INITIATION OF GRAIN MOTION 39 



1. Determination of the Condition 39 



2. Effects of Surface Compression 39 



3. Results for the Three Sands 40 



4. Applicability of a Shields Criterion 40 



IV EARLY STAGES OF RIPPLE FORMATION 44 



1. Induced and Spontaneous Ripples 44 



2. Observations with Coarse and Finer Sands 44 



3. Rolling-Grain Ripples 45 



4. Initial Ripple Length 47 



V GROWTH AND VARIABILITY OF EQUILIBRIUM RIPPLES 47 



1 . Two- and Three-Dimensional Forms 47 



2. Growth of Two -Dimensional Ripples 52 



3. Equilibrium Two -Dimensional Ripple Profiles 55 



4. End Effects 57 



5. Variability and Hysteresis of Stable Profiles 60 



VI CONDITIONS FOR TWO- AND THREE-DIMENSIONAL BED FORMS 65 



1 . Approach 65 



2. Results 65 



3. Results with Inman's (1957) Sea Floor Data 69 



VII INTERPRETATION OF RESULTS 72 



1. Initiation of Grain Motion and Ripple Formation 72 



2. Growth of Ripples 73 



3. Size and Shape of Stable Ripples 74 



4. Two- and Three-Dimensional Bed Forms 77 



5. Disappearance of Ripples 78 



6. Occurrence of Ripples 80 



VIII SUMMARY 81 



