Introduction

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On many beaches all over the world, rip currents are known as a serious hazard to beach users. These seaward-directed currents typically pull swimmers offshore. Intuitively the swimmers try to fight the current until they become exhausted and need to be saved by lifeguards. So far, rip current research has been concentrated on swell wave-dominated coasts (such as the US coast, Australian coast and the French and British Atlantic coast). Swell waves are generated by wind at a long distance from a beach and therefore have a longer wavelength with more impact on currents near the shore

Little research has been undertaken in locally-generated wind-sea dominated environments such as the Dutch coast. Furthermore, the influence of obliquely incident waves and resultant long shore currents on rip current initiation and strength is not fully understood. Still, rip currents cause problems also in the Netherlands where dozens of people need to be saved each year, sometimes even on a single day.

The Surf lifesavers of the Reddingsbrigade in Egmond aan Zee have identified a strong rip current as the largest risk for swimmers at this beach. This rip current is located in a channel that interrupts the sand bar just north of the surf lifesaver station. In the summer of 2010, the surf lifesavers attributed the rescue of 16 people to this rip current. This implicates that the amount of rescues was again, like in 2009, above average (Jaarverslag, 2010). The surf lifesavers have identified a need to further minimise this risk.

It is suggested that improved insight in the near shore hydrodynamics at Egmond may provide useful information to assess where and when dangerous conditions could be expected.