This year has been rough for lack of rain but this all actually started last year. Even when we have had a few decent rain events water has been unable to really soak into the soil due to it being hydrophobic.
The rain event has dropped about 5 inches (may be more) over about 18 hours and was just what we needed. The swales continue to do exactly what they were designed to do. When we get something like this we put that water into the ground, not down the ditch on the side of the road.