 Among the difficulties associated with filming in Scotland was the  amount of rain that fell during the shoot. During the breaks in  filming, helicopters delivered large bags of gravel to the set in  order to prevent it from washing out. Many of the filmmakers were  concerned as to how this would affect the look of the film, although  director Alfonso Cuarón (qv) and cinematographer  Michael Seresin (qv) insisted that it was the best look that they  could have come up with.