This small design is basically an elaborate cover representing a desert scene solely for the home owners viewing pleasure.
As you'll see in the photos of this finished project, this desert scene has a lot of character. And we also managed to incorporate a lot of different elements and textures without looking shabby. The key here is that the majority of the elements are just different shades and textures of the same element. Rock.
The curved fake river bed has visual function in the design process. The curves give this small area a percieved distance and makes it feel larger.
Try to imagine this desert scene design with the river bed coming straight out to the end. Not only would it lose interest but would also seem smaller. For more on creating illusions and designing small spaces see Small Gardens.