Abstract. The two primary causes of surf zone injuries (SZIs)
worldwide, including fatal drowning and severe spinal injuries, are rip
currents (rips) and shore-break waves. SZIs also result from surfing and
bodyboarding activity. In this paper we address the primary environmental
controls on SZIs along the high-energy meso–macro-tidal surf beach coast of
southwestern France. A total of 2523 SZIs recorded by lifeguards over 186 sample days
during the summers of 2007, 2009 and 2015 were combined with measured and/or
hindcast weather, wave, tide, and beach morphology data. All SZIs occurred
disproportionately on warm sunny days with low wind, likely because of
increased beachgoer numbers and hazard exposure. Relationships were
strongest for shore-break- and rip-related SZIs and weakest for surfing-related SZIs, the latter being also unaffected by tidal stage or range.
Therefore, the analysis focused on bathers. More shore-break-related SZIs
occur during shore-normal incident waves with average to below-average wave
height (significant wave height, Hs = 0.75–1.5 m) and around higher water
levels and large tide ranges when waves break on the steepest section of the
beach. In contrast, more rip-related drownings occur near neap low tide,
coinciding with maximised channel rip flow activity, under shore-normal
incident waves with Hs >1.25 m and mean wave periods longer
than 5 s. Additional drowning incidents occurred at spring high tide,
presumably due to small-scale swash rips. The composite wave and tide
parameters proposed by Scott et al. (2014) are key controlling factors
determining SZI occurrence, although the risk ranges are not necessarily
transferable to all sites. Summer beach and surf zone morphology is interannually highly
variable, which is critical to SZI patterns. The upper beach
slope can vary from 0.06 to 0.18 between summers, resulting in low and high
shore-break-related SZIs, respectively. Summers with coast-wide highly
(weakly) developed rip channels also result in widespread (scarce) rip-related drowning incidents. With life risk defined in terms of the number of
people exposed to life threatening hazards at a beach, the ability of
morphodynamic models to simulate primary beach morphology characteristics a
few weeks or months in advance is therefore of paramount importance for predicting
the primary surf zone life risks along this coast.
A FIELD STUDY OF WAVES IN THE NEARSHORE ZONE