It appears that the UAE authorities have a pretty full time road block on the Hatta Dubai road as you return back into the UAE heading to Madam. The Big Red Truck and others independently report similar experience to myself where it appears passports or other documents are being checked. In order to avoid a difficult return into the UAE at this location it may be worth carrying your passport.
I was at Hatta yesterday and spoke to the people conducting the checkpoints (there's one at each end of the road, as it enters the UAE, and also one on the Hatta - Ray road - towards the Hatta pools). You will need either your passport with vaild residency visa or your Emirates ID Card. The duration of their presence is not known (probably 'not decided') but expect them to be there irregulalry and for weeks at a time.