Monday, February 22, 2016

How far inland will sea level rise come

And inch of sea level rise can have a greater impact than many might think. It depends on the slope of the land by the water. The more slowly the land rises, the greater the impact will be.
(This analysis is for a situation where there there is not a cliff.)

If you remember your geometry, the tangent of an angle is computed from a right angle. It is the length of the side opposite the angle divided by the non-hypotenuse side beside the angle.

For a brush up, and a neat interactive tool for computing the sin, cos, & tan of an angle, see

If X is the amount of sea level rise, and A is the angle of rise of the land, the amount inland that the water would come would = X / (tan A).
The less the slope, the farther inland the sea will intrude.
(For us math nerds, we might multiply by (cot A) instead of dividing by (tan A).

So with a one inch rise in sea level, and a slope of 10°,
the sea would intrude by 1 in. / (tan 10°) = 1 in / .176 = 5.68 inches.

If the slope is 5°, the sea will intrude 1/0.087 = 11.49 times as far as the sea level rise.
If the slope is 15°, the sea will intrude 1/0.268 = 3.73 times as far as the sea level rise.

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