How do I know if and when my pond is overtopping?
How do I know how much of water is overflowing from the pond?
An easy way to tell if your pond is overtopping and when is to graph the flow in vs. flow out along with the pond elevation. This will allow you to see when you pond overtops. In the graph below you can see the outflow from the pond cannot not keep up with the inflow and the pond overtops at 11 hours. After the pond overtops you will see a straight line across in the elevation and flow out on your graph.
To quantify the overflow
What do I do if I'm getting pond or conduit overtopped user notifications?
Modeling surface ponding for overflow above multiple inlets