Found a few refs for th ground in you're scene




this one show what looks like gravel, but i'm just now realizing is the heavy ripple from the barrage of water droplets.

Interestingly enough they had a huge mechanical (anamatronic) Trex for the scene, and the were actually dumping tons of water on the set, and onto this huge robot, so after every half hour or so they had to stop filming, and wipe down/dry out the big guy, this took closer to an hour and a half. This movie (and scene) also had some groundbreaking CG creatures in it, in the long shots when he's walking around hes completely CG.

They though about using stop motion, and more specifically a modified version of it with some heavy motion blur, they called it GO-motion. But pretty close to the last minute they decided to use CG, and since they already hired the clay posing guy (who was like really good or something) they built this mini robot thing with cervos and wires and such shaped like the trex that was actually used as input for the cg creatures animation!