Most pond disasters are caused by the pond owner. They are due to a lack of pond education or just plain stupidity. I had clients who did not know how to reset a GFI, clients that did not listen to me and used every chemical they could find to get clear water and in doing so, killed every plant and fish in the pond.
But most of all, I had clients who did not keep an extra bottle of dechlorinator in the house for those times when they started to top off the pond and left the water running.
One of my long term clients, a well known politician here in New Orleans, turned his water on and then left town for the weekend. Flooded his yard and flooded the entire street corner. When the water was threatening the neighbors front doors, somebody called me, suspecting the pond had somehow fallen apart. I drove over and turned off the water. And charged him a whopping service call just because he deserved it.