Riprap around the abutments. This is decomposed granite. I went to my local Lowes and in the area with the paving stones are bags of ‘paver base’. This is the layer under paving stones. It’s decomposed granite .. and I paid $3.98 for 50-lbs. Hard to beat that!
Once it’s where you like it you set it with white glue and water per the normal method of securing scenery materials.
The abutment has been dry-brushed with light colors to blend in the darker areas I had before. That water is only acrylic paint and a clear polycrylic. It has no depth. The appearance is just from paint.