Too bad they can't drain off some of the water before it builds up to the point where the "dam" collapses. Once the water overtops the "dam", erosion or even total collapse may rapidly ensue, either of which might quickly release damaging amounts of water.

Of course there are "dams" formed by terminal moraines that have stood up to the pressures of dammed waters for centuries. Perhaps this will become a new recreational area. Dunno, but it does sound like an awful lot of debris came off that mountain. That amount of debris might be strong enough to hold back a lot of water provided that the "dam" doesn't get quickly eroded when water finally rises to the level where it overtops the "dam."

Of course, if there's a lot of ice in the debris, then, when the ice melts, it will leave voids, voids that I can only think would destabilize the "dam". Sounds like this might be a good prayer opportunity.

HJ