Backyard on a slope -- drainage problem
I am having an issue with water coming down the hill into my backyard (undermining the small terrace wall) and turning the lower portion of my backyard into a pond.
Last summer I did some digging and found a 4" corrigated pipe that while full of mud, seemed to be part of the problem. I cannot determine if it is draining an adjacent property (homes on hill above my house) or even draining a spring. Since I couldn't find it's source I went ahead and capped it off (affixed cap with silicone) to see if it made a difference. It seems to be helping, but significant moisture can still be seem in the terrace directly in front of the cap. When the house was purchased this was not a problem, only has become an issue within the last year.
I have attached a picture with illustrations showing where water is coming down the hill into my backyard, and where the capped pipe is located. If anyone has any experience with this type of problem, please feel free to provide your comments. Thanks in advance.