i saw a tut somewhere about this...for the life of me i can't find the site it was on. I do remember the person said he went to a beach that had firm sand, walked on it for a few steps then took a photo of the footprints. he then imported the image into PS and made a greyscale from it then imported the greyscale image into bryce terrain editor...now this is going from memory so i hope i got it correct for you..

I have opinions of my own -- strong opinions -- but I don't always agree with them.