Heaven forbid that I had to make that decision but it is what I would do. Test the backup system in a real world scenario. Problem is it failed.
But, it only failed long enough to determine that it was failing and that there might be ways to bolster it so that it won't fail too quickly in the future. Oh, and it failed long enough to move almost 200,000 people out of their homes temporarily.
I disagree... if you wanted to test it, you test it with snowmelt and a fully intact primary spillway. The dam is how many decades old? They decided to test it only when the realized they were in over their heads. Having said that, can’t turn back the clock 10 years to test it under ideal conditions... they were extremely worried about the primary spillway and decided to give it a go.