Regarding your mention of Monster Thunderstorms. In my many explorations of Granite Mountains behind our home, I have found a number of areas, near the bottom of canyons coming out of the higher hills in the Granites, where there are large piles of rounded rocks, pilled up on either side of the runoff channel, which look to be indicative of massive runoff coming out of the hills, runoff of such volume, that its way beyond any precipitation, be it thunderstorm or otherwise, that we are accustomed to. I have seen those same canyons, after very strong thunderstorms, and the runoff has been very minimal, since the water really sinks fast into those hills of rocks, cracks and sand. The size of the downpours necesary to make those piles of rocks, had to be immense indeed.