ABSTRACT
Rip current and other surf zone hazards can be reduced through better knowledge of a threat level at a given time and location and by improving the response capabilities of individuals at risk. The presence of lifeguards substantially reduces such risks, but lifeguards cannot be present at all locations where swimmers and surf zone hazards coexist. Present approaches to quantify these threats involve broad-based prediction
Introduction ............................................................................................................ 107 Better Rip Current Predictive Models .................................................................... 108
Role of Tides in Three Existing Prediction Methods ........................................ 108 Processes Associated with Formation of Rip Current Channels ....................... 109 Rip Current Channel Formation ........................................................................ 109 Rip Current Channel Maintenance .................................................................... 113
Stability of Waders in Surf Zones .......................................................................... 115 General Notes .................................................................................................... 115 Wader Stability against Currents ....................................................................... 115 Wader Stability against Wave-Induced Water Particle Velocities ..................... 117
Improving Detection and Prediction of Rip Currents ............................................ 117 Better Detection of Rip Currents through Thermal Remote Sensing ............... 118 Need for Including Spatial Information in Rip Current Prediction................... 118
Up-to-Date Advisories ........................................................................................... 118 Personal Responsibility and Education .................................................................. 119 Legal Dilemma ....................................................................................................... 119 Conclusions ............................................................................................................ 119 References .............................................................................................................. 119 Appendix A: Stability of Waders in Seaward-Directed Steady Currents ............... 120
Introduction ....................................................................................................... 120 Idealized Wader Concept................................................................................... 120 Submerged Weight in Surf Zone ....................................................................... 120 Current Forces on Individual ............................................................................. 120 Limiting Water Depth for Stability ................................................................... 121 Characteristics Considered ................................................................................ 121
Appendix B: Stability of Waders in Oscillatory Wave Currents ............................ 122
methods and a review of the rip current history at a particular site; swimmer education could presumably reduce the threat. This chapter focuses on several approaches to reducing rip currents hazards:
• Rational accounting for the quantitative effects of bar height • Improved understanding of the stability of individuals against currents and
waves in the surf zone • Better detection of rip currents for daily quantišcation and calibration of rip
current prediction systems • Fine tuning of existing broad-based prediction systems • More effective application of present and future advisory systems • Emphasizing personal responsibility for water safety
Valuable rip current predictive models were šrst developed by Lushine (1991) and modišcations for local application and incorporation of more complete wave information were introduced by Lascody (1998) and Engle (2003), respectively. The essential ingredients of these models include weighting factors for wave height, winds, tides, and rip current persistence. The role of tides leading to a suggested additional parameter is examined below.
