CONTENTS 



Page 



CONVERSION FACTORS, U.S. CUSTOMARY TO METRIC (SI) 12 | 



SYMBOLS AND DEFINITIONS 13 



CHAPTER 1. INTRODUCTION 21 i 



I 



CHAPTER 2. PHYSICAL DESCRIPTION OF NEARSHORE CURRENTS 23 



I Field Observations 23 



1 . Measurements of Mean Values 23 



2. Space Variations of Longshore Currents 26 



3. Time Variations 30 



II Laboratory Observations 34 



1 . Summary of Data 34 



2. Laboratory Boundary and Scale Effects 36 



III Forcing Functions and Mechanisms 41 



1. Forces Causing Currents in Alongshore Direction 41 



2. Mechanisms Causing Nearshore Circulations and Rip Currents.... 45 



IV Instrumentation and Measurements 53 



1 . Velocity Instruments 54 



2 . Measurement Systems 58 



3. Wave Direction 60 



4. Laboratory Systems » 62 



V Summary 62 



CHAPTER 3 . THEORETICAL DESCRIPTION 64 



I Historical Summary 64 I 



1. Before 1967 64 ' 



2. Modern Approaches 65 | 



I 



II Principles of Radiation Stress 66 



1 . Progressive Waves in Uniform Water Depths 66 ; 



2 . Other Waveforms 72 



III Mean Water Level Changes 72 



1 . Normal Wave Incidence 72 



2 . Oblique Wave Incidence 76 



3. Other Factors 77 i 



i 



IV Longshore Currents 78 i 



1 . Conservation Law Balances 80 I 



2. Original Model 82 j 



3. Modified Models 89 j 



4. Surf Zone Empiricism 107 , 



5. Nonuniform Longshore Current Profiles 112 | 



