In addition to its fifty mile network of electric fencing, Jurassic Park’s dinosaur enclosures were also reinforced with moats filled with water. These trenches, according to John Arnold, were always at least twelve feet deep, but, depending on the size of the dinosaurs in captivity, could be up to thirty feet deep.
Source: Jurassic Park, by Michael Crichton, page 131 (Fifth reprint)
