Understanding Tide Basics for Alaska Sea Kayaking Trips
As a kayaker, your safety and comfort hinges on a few key items. One of those is having at least a basic understanding of tides. You must have a tide table for the area you intend to paddle because not knowing what time high and low tides are is like not knowing your own name. Approximately every 6 hours the tide moves from high to low, or low to high and in areas like Prince William Sound, the difference can exceed 20 feet.
You can figure out the volume of water moving each hour if you know the size of the tide. This is important for planning when to leave camp in the morning, how much the water level might change while you’re eating lunch, or if you want to ride the tide in or out of a particular area.
You can read the tide by using the rule of twelfths and adding basic fractions. The rule states that in the first hour after low/high tide the water level will rise/fall by one-twelfth of the total tide swing, in the second hour two-twelfths, and so on according to the sequence – 1 : 2 : 3 : 3 : 2 : 1. How many actual feet of water moving each hour will depend upon the size of the tide.
If it’s a 12-foot tide, during the 1st hour one foot of water moves (1/12), the 2nd-hour 2-feet of water (2/12), and by the end of the 3rd hour you’ll know the tide is 50% out (1/12 + 2/12 + 3/12 = 6/12). The 2nd, 3rd, and 4th hour is when most of the water is moving (2/12 + 3/12 + 3/12 = 8/12 = 2/3rds of the tidal change). The two hours surrounding the high/low tide is what is referred to as the ‘slack tide’, when not much water is moving. (1/12 + 1/12).
Weather also impacts the tides. If there’s a huge wind blowing against the tide, the waves get taller and the going can get tougher so watching weather patterns is important and periodically checking the weather can be valuable if you have the means.