How to lower certain parts of a layout in layout generator.

So I’m still very new to World Machine, but I’ve been working on a landscape for a team using World Machine Pro, they already have a drawn map so I’ve used the map and layout generators to make each piece of land. problem I’m running into is that part of the land is higher, other parts are lower, with a waterfall feature in the center. You can see it in the attachment, the map has a waterfall area, and parts of the land are lower. How do I get that layout to lower in certain areas to water level while keeping a high cliff in other spots? Thanks for any help.

and this is the map, working on the Eden Region

you can draw your map in photoshop and import into WM. Use perlin generator for more details or erosion device and also use the imported map as a mask.