A rip is a deeper part in a sandbar, beach or beside a groyn. In those deeper parts current can be present which can be dangerous for swimmers. Those so called rip currents are heading into the open sea and cause a lot of incidents and accidents yearly along the coast.
The rip current is caused by the difference in water level after the surfwaves in comparison with the level at open sea. This difference is called set-up. This set-up variies, it will be lower at the rips and higher behind the sand-bars. The effect is a certain flow pattern in and around the rip. In the trogues the current is toward the rip. This is called the long-shore current and is quite good recognisable from the beach. Mostly there is 1 longshore current however 2 might be possible also. The current in the rip at the sand-bar is called the neck of the rip. In the neck of the rip lower or no surf will be present. However depending on tide and waveheight it might be difficult to recognise the neck of the rip. In the neck the current will take the sand away towards the deeper area seawards of the neck. On this way the rip will deepen out and finally fix the rip. These type of rips are called fixed rips.
In the next picture the different currents are shown:
The picture belongs to Rijkswaterstaat. (RIKZ)
Permanent obstacles
If a groyne or peer is build from the beach towards the sea a different type of rip will occur. Because of the tidecurrent or if the wind is paralel to the coast the water is pushed seawards. The effect of this ia that the sand alongside these permanent obstacles will be transported away. A deeper channel is the result. These rips are called permanent rips. They are very dangerous. Never swim at these obstacles even with calm weather they will be dangerous because of the tidal currents. The rips at these permanent objects are called permanent rips.
The fixed rips do appear in all kinds of ways. This makes it difficult to recognise these rips.
Information
What is a rip?
