Storm & Flood Damage Recovery in Corona, CA

That is the defining local pattern. The canyon concentrates drainage from a large upstream area, so what arrives here is set by rainfall miles away rather than by what fell on your street. A local gauge reading of half an inch is entirely consistent with substantial flow at the canyon mouth. Watching upstream conditions rather than the local forecast gives a much more honest picture of the risk on any given day.

Substantially, and for several years rather than one season. A burn scar sheds water at much higher rates because the vegetation and the soil structure that used to absorb it are gone, and it delivers debris along with the water. Flows that would previously have been routine become damaging. If a fire has burned in the watershed above you, the sensible assumption is that the next few wet seasons behave worse than the historical record suggests.

Yes, because the water here arrives as a moving sheet rather than as a rising pool. Directing that sheet past a building, with grading, a low wall, or protected openings, is achievable in a way that stopping a rising pond is not. Debris is also part of the problem, so keeping the flow path clear of anything it can pick up and pile against the house matters as much as the water itself.