Procedural foliage volumes can be used to quickly scatter foliage assets on the level
The landscape material has a number of settings. One of them determines the world position of certain procedural layers that are overlaid on top of the painted layers and are defined in a shader Those are “wet sand” and “shore debree” layers for example
These layers are placed procedurally on the top of all of the layers that you painted To control where they appear you have a few sliders in the material instance that are shown below