Wow, avalance, tnat sounds like a frustrating situation. Let me share a small story about an experience I had at Frenchman Coulee. I came up to a route on Sunshine Wall and someone had left their top rope. It was a little annoying, but it wasn't a big deal. I asked the people in the immediate area if it was their rope, but no one was around to claim it so I just climbed past it. The owner came back while I was almost to the anchors and he wanted to pull his rope down. I told him that I would prefer it if he would wait until I was at the anchors. So I climbed up and since I was right there, I dropped their rope down for them and then brought their anchors for them. Once down, the guy thanked me and we started talking. In the conversation I mentioned that it wasn't good to leave a top rope unattended on a popular route. The guy said something about climbing with a group of people and that they were planning to come back to the route. I might have been too nice, but I was glad I acted the way I did because when I pulled my rope it got stuck half-way down, and the guy let me use his rope to climb back up to retrieve mine.
Now if I had yelled at the guy when he came back or if I had just pulled his rope down when I was wanting to climb, the whole situation would have been changed. He might have gotten defensive, and it might have turned into a negative confrontation. I think the key to the situation, in my case, was that I was willing to talk to the guy about leaving a rope. Maybe he will think about leaving his rope unattended next time. Maybe not. But I had a fun day climbing.