I have a base layer that represents an area that has two layers above it, one layer is lakes, the other layer is wooded area. In the image below the layer with the lakes is blue, the layer representing wooded area is green, the pale green is the base which covers the entire area. The pale green represents lowlands, low elevation.
The two images below show the wooded layer and the lakes layer without the pale green base layer. If I set the three layers as shown above the pale green lowlands show through, but, when I add the elevation layer (DEM) the lowlands do not show through. I can add transparency to the DEM but that washes out the colors in the lakes and wooded area.
I would like to use the wooded and lakes layers to create some sort of masked area which represents only the lowlands. Then I will have some options to make the lowlands show through the DEM layer, I might be able to move the lowland layer above the DEM layer or make the color brighter, etc. Any ideas on how to create a layer representing only the pale green areas in the image above? I have used the Feature Outline Masking Tools to mask the contour labels but I don't know if that will work with polygons.