CalTopo doesn't put anything on a map. They just display map layers like the USGS topo and people put whatever they want on them. You're most likely just looking at someone else's map. You need to do a lot more research on the area and don't put much weight on someone else's map to get you around. Look at trail guides for the area and get a book or something. You're going to be in and out of streams frequently. I'm not even sure what you mean by the route north to Mamie Creek area. The only part of the route going north to Mamie Creek (coming from Hwy 12) is pretty much in a swift, cold stream the entire time. That's Death Hollow itself. The driest part of the route is where the BMT leaves Death Hollow and heads either west to Escalante or East to the Boulder Air Strip, depending on the route you're choosing. Anyway, like Art said, you really need to do a LOT more research. Read everything you can, then ask questions.