I’m in Douglass, so pretty close to you. You won’t have to worry much about shrink/swell clay in Rusk County. We have enough East TX sand mixed in to keep it from drying out and leaving a gapping crack.

Main thing to worry about is adequate emergency spillway width, and do something to carry the spring water so it isn’t going over your emergency spillway constantly. I’m convinced that continuous low-flows over a spillway can be just as dangerous as sporadic high flows. I would advise you to install a pipe to carry the continuous low flows, and keep them off your spillway.