Holding ballast or bark in place

Hi there, we live in an area with a lot of trees and we want to replace some soil beds with either round washed ballast or bark pieces. I need a way of keeping them all in place with some sort of resin or adhesive as when I leaf blow in Autumn I don't want to lose and move this aswell.

There is quite a large area in total so has anyone got any ideas....I don't even know what to google as a starting point and garden centres don't sell this type of adhesive or resin....

Thanks in advance