I am mapping a lake where I can directly measure the elevation of the shoreline from a benchmark. It's spring and the lake is 3 to 4 feet above normal lake level.

This has allowed me to map areas that are normally flooded in the spring, but become just a streambed later in the season as the water level drops.

My question is about the sign of the offset. I am assuming that a positive number is used for flooding, and a negative offset is used for low water conditions. Is that correct?

It seems that I get non-sensical numbers applying an offset in these very shallow waters, again it's dry land in August (summer in Northern Hemisphere).

Happy to learn how others handle this high water/shallow bay situation.