I live on a canal on St. John's River in Florida. I have a metal retaining wall. The yard is sloped toward canal and I have a small deck and 18"x18" block on the ground. Even though I have a drainage pipe to canal, the water (when it rains) has just washed the dirt out from under my deck and also from under the blocks. I now have a big hole under deck and blocks. I don't know what to do. This is a never ending battle. No matter what I do it doesn't work. Please help...