Dubai does have heavy rainfall periodically and I have seen the under passes flooded and cars floating around bumping into the underside of over bridges. The problem is, as other have posted, that the ever present sand blocks the drains and unless they are cleared out which they are not, then when the deluge comes you end up with the flooding witnessed this week. However I have to say the UK is equally bad at this if you look at the flooding that occurs on certain sections of our roads and motorways, caused by the same issue, and we have no excuse as we do get rain often, but just seem inept at maintaining things these days.
Cheers
Mr Mac