I live in Phoenix, Arizona.
I recently purchased a home on a large lot of roughly an acre. A large wash (a dry desert creekbed) is on the property, which sits between my neighbor's lot and the north side of my backyard fence. It's easy to access the wash from the street.
As I've come to discover, the wash is frequently used by people hiking, walking their dogs, etc. as a way to cut through to the neighborhood behind our subdivision (we don't have a HOA). Instead of sticking to walking in the wash, most of these individuals have been walking across my side yard because the terrain is easier to walk on. As a result, there's been a build-up of litter on my side of the wash and I've lost a few plants that have been trampled upon.
Is there anything that I can do to minimize this sort of traffic? Is this traffic even trespassing, as I've heard that washes in Phoenix are public domain? If I put in a ton of cacti as a physical barrier to prevent foot traffic and someone (or their pet) gets injured, am I liable?
Thanks.

