The mod comes with the major storm depth curves for the US.
Type I - Pacific Southwest/AK/HI
Type IA - Pacific Northwest
Type II - Noncoastal US
Type III - East & Gulf Coasts

You can add your own depth curves as long as it follows the exact format of the others.

1. First exit the game.
2. The mod adds a file at C:\Program Files
(x86)\Steam\steamapps\common\Cities_Skylines\RFDepthCurves.csv on most computers. Open this file excel. If you don't have excel you can also use a text editor, but it will be much harder to work with.
3. Start a new column and add the name of your curve. (Do not use any commas)
4. The time in row 2 (Time = 0) must equal 0
5. Input/Paste the depth values for each of the Time increments from (Time = 3 to
Time = 1437) Each depth value must be greater than the depth value in the previous row but 0 < x < 1
6. The Time in row 482 (Time = 1440) must equal 1.
7. Save and exit the file.

If you start the game with the file still open the mod will crash.
If you didn't enter your values correctly the mod will not accept your custom depth curve.

Good Luck!