So this thing is mostly a show of the organizers having failed infrastructure, having failed to deal with relatively low rain and not having sensible sanitation infrastructure, as well as having a focus on car travel instead of public transport to the event area? I do get that in the desert your storm water takes time to get into the ground, but what you describe is not that big a problem, if you have the means to deal with it.

Rainfall reports from the National Weather Service suggest up to 0.8 inches of rain fell in the area from Friday morning through Saturday morning – approximately two to three months of rainfall for that location this time of year. Even small rainfall totals can lead to flooding in the dry Nevada desert.

Flood watches were in effect in northeast Nevada, to the east of Black Rock City. Those watches noted individual storms were producing up to one inch of rainfall, but higher totals — as much as 3 inches — would be possible through the weekend.

The festival, which began in 1986, is held each summer in Black Rock City – a temporary metropolis that is erected annually for the festival. The city comes complete with planning services, emergency, safety and sanitary infrastructure.

Doesn't seem to be "complete with sanitary and safety infrastructure". If you wouldn't do it in a desert you could also ensure good seepage, and using other kind of toilets would've reduced the problem with the toilets. All in all an example of US individualism in planing for communal events.

eeeehhhh...

I think they site that Burning Man is at is technically in a basin or valley between some mountain ranges, so that 2cm of rain collects from miles around and comes flowing right down to them. Nobody is getting drowned or anything, there aren't any wadis near enough to where Burning Man's at, but I could believe that for a while there was 10 or 20 cm of standing water for a few hours.