Saturday, 1 November 2008

Samui's low tides...

I read on a Samui Internet forum recently, about a group of holidaymakers who were trying to wring refunds out of their travel agent because the beach, a key attraction in their choice of hotel in North Chaweng, didn't exist for the duration of their stay. The tide had receded some 300m behind a rocky reef leaving only a strip of sand and unappetizing puddle-filled mudflat, studded with rocks and broken coral.

It was their reported claim that the sea didn't return from beyond the reef for over a week that got me wondering what malevolent forces could conspire to neutralize the gravitational affect of the Moon and Sun. The answer is surprisingly simple if you understand how tides are created. Depending on their positioning relative to each other, the gravitational attraction of the Moon and Sun can produce spring tides (from the verb [to jump], not the season) or neap tides. Both have an affect on the extent that tides come in or go out.

But important to the issue of the reported static low tide, the tides in the Gulf of Thailand are Diurnal. We have a single high tide and a single low tide per lunar day. This means that unlike anywhere in Europe or, in fact, most of the World, in a 24 hour period the tide will rise and fall only once instead of twice, and herein lies the answer - the high tide could have occured at night or early morning, unobserved by guests during a short holiday.

The diurnal tidal range (the difference in height between high and low waters over a full day) varies in a two-week cycle. The complainant guests probably arrived at that lunar phase which ended with a spring low tide and entered the neap tide cycle. The changing distance of the Moon from the Earth also affects tide heights.

The photo below shows the lowest that the water ever recedes opposite Baan Bophut, and why we don't have any problem advertising ourselves as a 'Beach' hotel. We've always got plenty of it.

The sea opposite Baan Bophut snapped in mid-July, the lowest tides of the year. The reef, seen from the air is hardly noticeable from the beach. Still good swimming to the side or beyond the reef.

As an avid reader of guest opinions on Tripadvisor and other review sites, I've noticed that the reverse complaint is frequently made, that small beaches can 'disappear' during a period of very high tides. This is simply the reverse of the natural phenomenon described above.

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