Any time we get significant rainfall here in GA my pond turns itself inside out and pushes most of the water out of the pond. It only happens when there is a lot of rain so maybe 3-5 times a year. So far it's happened twice in 2025, so I wonder if it is getting worse. It is very squishy and feels like trapped air under the liner. I am meeting with contractors to address drainage as it does run down hill and my entire back yard get wet. I met with one drainage pro today and he could not explain what was happening, but maybe water was somehow coming off the hill and getting behind the liner. Any one dealt with this before?
Firstly you definitely need to keep looking for a Qualified pro.
Building berms around the pond/ building up the sides keeping run off from getting to the pond is a must. Whether the water goes under the liner or into the pond is baddddd. Unless you live on cape cos and you have nothing but sand and the water will drain away long before it can build up pressure.
Three options the first was just mentioned second is to dig down on the sides of the pond down toward the bottom in the spot where you always see the hippo start first. Get to the bottom along the side" this is after you drain the pond" and install pipe pretty much any pipe that will not crush in backfilling. Pipe goes to the bottom but sits in a pocket of stone that will not plug up the pipe . This creates a path of least resistance. A place for the water to rise instead of raising your liner within the pond. You can do this in several spots around the pond.
Lastly is dig a pit again next to the liner. Make a larger pit so you can make a sump area for lots of water to drain into a bucket surrounded by stone and a sump pump. This should get at least a foot deeper than your pond.
Good luck.