If the area to the right of the damn is earth and not bedrock it will fail. I hope it is bedrock.
In two lakes near me and they are big lakes, Stillhouse and Belton, the emergency spillway is several hundred yards wide and cut into the bedrock. In the last 35 years both have been utilized twice. The flow into the lake exceeded the capacity of the damns to release water and the lakes rose. Everything was okay as the emergency spillways worked as designed. On most occasions the Corp of engineers get it right. They did not in New Orleans and the Katrina Hurricane.