I am always fascinated by how fast nature erases what we leave behind, ie Detroit, some areas the asphalt is almost gone :eek
This location was uniquely disappointing as I really wanted to approach the area where the set was, as it is a favorite film of mine, and a beautiful location of which I've wondered for years where it was located. But as mentioned, 1.) it is nearly impossible without significant planning, permissions, and cutting tools, and 2.) even in reaching the exact spot, you "couldn't see the forest for the trees" - it would not have looked the same. I suppose today, the best shots and those that are most representative of the film are those taken from above and outside the actual creek bed arroyo.
Time ravages...
With this hobby of film location "scouting", typically the natural areas generally stay the same, as rocks and earth and such don't change that much over time. The rock Dreyfus hides from the helicopter in Close Encounters is still in the exact spot and still has the same basic lichen pattern on its surface.
Usually it is development that really screws with this hobby - natural areas become developed, or structures seen in film are torn down, remodeled or removed. Case in point; Rhonda's house in Trick r Treat received a complete face-lift in the past year or so and no longer has the "witches cottage" look it had in the film, and the bar Tom Cruise drinks "hemlock" in Top Gun no longer exists where it was on the opposite side of the field at Lindbergh Field, San Diego.
But with this location, being a zone where vegetation thrives and has a source of water - well, we get the point. Though the geological features remain recognizable, the bed and actual filming site is virtually unrecognizable.
Suppose we'd need another 100-year flood, and I'm not certain that is a good thing to hope for...