Pitman, S.J. and Lee, D., 2019. Determining the accuracy of visual wave height observations and the perception of surfzone hazards made by lifeguards. Journal of Coastal Research, 35(4), 776–783. Coconut Creek (Florida), ISSN 0749-0208.

In deciding whether the water at the beach is safe to enter, one key parameter on which people base their assessment is the size of breaking waves. To understand the accuracy with which wave height can be visually estimated, this study utilises 1566 observations of wave height made by New Zealand's Surf Life Saving Northern Region's lifeguards over a 3-year period across 15 sites. Lifeguard observations were compared against hindcast wave data for each of the times and locations logged by the lifeguards. Across the entire data set, spanning wave heights of 0–5 m, there was consistent underprediction of the breaking wave height (mean – 0.48 m). The magnitude of underprediction was greatest for large surf, where waves between 3 and 4 m were underestimated by 1.75 m on average. This study showed that for small waves, lifeguards on the calmer east-coast beaches were more accurate in their estimation, whereas lifeguards from the west coast significantly underestimated smaller waves. West-coast lifeguards regularly deal with surf in excess of 3 m, and therefore they may perceive far less risk from these small waves, leading to significant underestimation. This study shows an inherent bias for underprediction of wave height by a large number of experienced observers, which implies that there may be a tendency to underpredict the degree of hazard during rescue situations. Furthermore, there are implications for the general public's ability to make informed assessments of hazard when entering the water.