Was Colorado, America, flash flood resulted from heavy rain only? I believe, though rain could be a factor, the 14-September-2013 Boulder Creek Colorado flash flood was rather a change in river fluid, maybe some cold an hot areas etc made water chemistry flow raised from deep earth.
The flooding places which geographically are rich in river water in general will not have frequent Earthquakes, deep water probably represents a good chemistry to suspend earthquakes.
Could be worse with a big flash flood. The death toll for such a flood is luckily low.
In another continent, in Trabzon city with high human population, in August 1998; a smaller river, a smaller river creek flash flood, not because of heavy rain, raised, killed at least 30-50 people in a night and immediately disappeared as the 'Flash' word describes.
