Robertson, B.; Hall, K.; Nistor, I.; Zytner, R., and Storlazzi, C., 2015. Remote sensing of irregular breaking wave parameters in field conditions.
The analysis of wave breaking in shallow water has been ongoing for almost 150 years. Numerous research papers have been published that approximate both the local conditions and geometric characteristics of breaking waves. However, much of this knowledge is based on laboratory results or limited field investigations because traditional methods of extracting breaking wave measurements from the surfzone are expensive, dangerous, and feature low-resolution data. Unfortunately, laboratory studies are prone to scaling and friction effects that introduce unwanted variability in the data. This study presents a novel, safe, and low-cost method of extracting relevant breaking-wave properties from irregular waves in the surfzone, using optical and in situ measurement systems. Published, contradictory breaking-water depth definitions are compared, and the water depth at the wave-trough depth, corrected for optical offsets using a still-water correction of one-third of the wave height, is found to exhibit the least variability. A new, effective seafloor-slope definition, based on individual, breaking wavelength-to-depth ratios, was found to increase predictive ability over previously variable seafloor slope extraction methods. Collected field data are compared against established breaking-wave height formulas with the general exponential form consistently finding the best correlation. Finally, an optimized breaking-wave height-prediction method finds a root mean square relative error of just 1.672% within the ranges of the measured data set. Irregular waves investigated on an individual wave basis are shown to follow regular wave-breaker height and depth prediction methods.