Several days ago, Sapporo saw a disastrous amount of rainfall, something that would happen only once in a few decades. Around the same time Kanto and Tohoku regions experienced heavy rain and flood damage as well. Rivers flooded and houses were soaked, but fortunately there was no major body count. In that respect, we were very lucky in comparison to Hiroshima, where rainfall-induced landslides hit residential areas just recently.
The Sapporo case was notable in that evacuation advisories were issued in a large scale targeted at some 800,000 people. It was four, five in the morning when almost half the city was advised to evacuate, with cell phones generating unfamiliar alarm sound, followed by schools all around town closed the next day.
During and after the rain, I heard quite a few people complaining about the alarm hindering their sleep. Having to work next day with little sleep, in the end the damage level did not require waking up even, blah, blah.
Still, I highly regard the governmental efforts to ring the bell.
Just to make it clear, the alarm was not randomly going off. It was provided in an well-organized manner, with fine area designations and clear points about what to watch out for, cliffs, rivers, etc. It must have been based on the groundwork laid over the past years including provision of hazard maps and whatnot.
Humans are fairly powerless in the face of natural disasters. In a situation not seen in decades, it does make sense to at least get ready to evacuate. If it ends up in vain, you can later laugh off this one time you were so worried it was ridiculously lame. To do that, or anything, you need to survive.
On the technical side, I don’t think you can have ultimately accurate damage forecasts anyway. The rain is not falling in the same pattern as the last time. And there is no telling what may happen to houses built, renovated, deteriorated over the course of that few decades, let alone housing areas developed in a new area.
Thus, a well-made warning system usually goes off more frequently, to some extent, than the occurrence of actual disasters. If you criticize the inconvenience by focusing on the false alarm cases, it is not a good way to run the system. If you see the cry wolf story from the boy’s viewpoint, well surely the moral of the story is that you shouldn’t tell lies. But that can’t be the only thing we can learn from it.