You could also intentionally have one end of the line supporting the tarp lower than the other by a few inches which tends to cause any water to follow the line to the lowest point at one end, rather than going to the center of the support line (under the tarp) due water/tarp/snow loads causing it to drop off inside under the tarp. It would be wise to use the tie offs on each end when using this method.

As far as the wear and tear on the tarp, the supporting line could be wrapped with a spare blanket or you could also find a way of making / attaching some sort of load spreader under the tarp or on the line itself. Of course this carries its own weight penalty to be dealt with. YMMV

Regards,
Comanche7