Wednesday, August 25, 2010

Tide tables

So now we understand what causes tides, it's time to look at how this information breaks down into effects for us paddlers.

First lets look at a tide table for an area near where I learned to paddle, Port Jefferson on Long Island, New York for Monday the 30th day of August 2010.

It lists four tides in this order, HIGH, LOW, HIGH, LOW. Because we have four tides a day and two of them are highs, and two lows, they occur in that order HIGH, LOW, HIGH, LOW. The first high is at 3:19am and has a height of 6.3 feet. 6.3 feet above what, you may ask? 6.3 feet above mean low tide, which means the average low tide. The next tide, a low is at 9:20 am - almost exactly 6 hours later and is 1.0 feet high, again above mean low tide. Next is a high tide at 3:31pm with a height of 6.9 feet followed by a low at 10:01 at 0.8 feet. Four tides of different heights all approximately 6 hours apart. This tide table has a tidal range of about 7 feet. From a low low of 0.8 to a high high of 6.9 feet. 7.1 feet to be precise.

The tides occurred in this order:
Low High - meaning the lower of the two high tides
High Low - the higher of the two low tides
High High - the higher of the two high tides
Low Low - the lower of the two low tides

I mentioned before that when traveling in a kayak, my first concern is being able to get off the water. I would rather be off the water and wish I was on the water, then on the water and wish I was off. But once I am off the water, I need to be able to camp. I don't want to set up a tent and wake up in the middle of the night floating in my sleeping bag with my kayak washed away. So I use this tide information when picking a campsite. I want to make sure that I am camped above the high high tide line, and then I want my kayak to be above the tent. This assures that if my tide calculations are wrong I will know when my tent floods, and before my kayak floats away. And remember we are talking about tides, which are the vertical movement of water - not horizontal. So when I am finding a campsite - with this tide table - the tent needs to be at least 7 vertical feet above the low tide line. On a steep beach that usually isn't too far. On flatter beach, that can be a great distance.

Lets look at one more tide chart, this time for a place I have been lucky enough to paddle out of on numerous occasions. Whittier Alaska. This one for August 6th 2010. The first tide, 1:58 am at 12.3 feet Followed by 8:32 at -1.1 feet. Then 2:57pm at 11.0 feet, and finally 8:35pm at 2.2 feet

1:58am 12.3 feet is the high high
8:32am -1.1 feet is the low low
2:57pm 11 feet is the low high
8:35 pm 2.2 feet is the high low

There is a tidal range 13.4 feet, think about having to find a campsite 14 feet above the low tide! I say low tide, because if you come ashore at low tide, that is how far you will have to travel. But most people will come ashore between tides. Rarely have I ever arrived at my home for the day at high tide. So really what we need to do is find the last high tide, figure out how high the highest tide will be during our stay, find that spot on the beach, and camp above it.

That is our next lesson.

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