The dam was built. Y the state of Oklahoma as part of the caddo creek watershed project in 1966. The state evaluates their dams and places them on status and my dam is on "no worry" status. The dam appears really well made, has a good wide spillway and has a very nice drainage structure that keeps the pool well below spillway level. During the storms in 2015 the previous owners said it reached the spillway once, and the previous owners to them said it hit spillway once or twice. So yes, large watershed, but the design of the system is different reservoirs collect and slowly drain downstream and don't inundate the caddo which would inundate lake Texoma. Had never heard of the system until looking at this property.
So to answer your question, the drainage system is a nice concrete structure but the spillway is grass. It is a well designed dam/structure that I don't expect to fail anytime soon.
