The 2012 work was done by the owner / an amature. However, the overflow feature worked as designed skirting the dam and routing the water around and below. It's just a lower grass exit edge but it provides relief.
Excellent. That is the proper design. If it does begin eroding during a major flood, it will NOT cut out your dam.
Make sure you inspect the emergency spillway every year and after every overflow event. One of the keys to its design function is to have the crest of the emergency spillway be perfectly level. If it develops a low or cut spot, that area will channel a fast flow of water during the next flood event.
