Almost everyone agrees that flooding is bad. Most years it’s the number one natural disaster in the US by dollars of damage. So being able to characterize flood risks is a crucial job of civil engineers.
Engineering hydrology has equal parts statistics and understanding how society treats risks. We need to be prepared for the times when there’s too much water, a flood. Rainfall and streamflow have tremendous variability and it’s the engineer’s job to characterize that so that we can make rational and intelligent decisions about how we develop the world around us.