You might look at some "silt fence" if you still have some more big rains coming.
You can probably find it in your area for $0.25-0.30 per lineal foot. In a clean, flat line across the face of your dam it can be installed very quickly. If you slow the velocity of the water running down the slope, you will significantly reduce the amount of erosion it can cause.
Good luck on filling up your pond with GENTLE rains!
