I have looked through as much Cisco, and other, documentation as I could find on the subject, but I couldn't find a solid answer on this question.
The default action for an interface that exceeds the configured storm-control level is to drop the traffic. However, what happens to an interface when you configure one of the optional behaviors?
It would seem that the traffic would continue to be dropped, in addition to the configured behavior. But I can't find evidence of this. Here I've configured a storm-control action of 'trap', along with rise and fall thresholds.
storm-control action trap
storm-control broadcast level 40.00 30.00
storm-control multicast level 40.00 30.00
storm-control unicast level 40.00 30.00