So, good news! I finally got that surface to work with my data! Now I can (relatively) accurately model the bedrock surface and have it match reasonably well with the measurements I took in the field. It sort of falls apart after a certain distance upstream, but what can you do?

Also: I have discovered that Retromud is one of the coolest games I have ever played. If you enjoy text based RPGs, I can highly reccommend it!