Debris Torrents and Professional Responsibilities

There have been several debris torrents down steep cracks along Howe Sound, near Vancouver, British Columbia, Canada. A debris torrent is a rapid surge of water, mud, and rocks down a steep creek. Debris torrents only occur under special circumstances and are not yet fully understood, although knowledge about them has been growing rapidly. The way in which the professionals who are responsible for public safety responded to the growing knowledge about debris torrents and the risks that they pose is examined. Civil engineers are used to uncertainty and deal with it by using a variable safety factor that depends on the level of uncertainty and the sequences of failure. This approach worked well in the case of the Howe Sound debris torrents, but did not in those cases where the engineers felt little sense of direct responsibility.