RECENT NON-ERUPTIVE DEBRIS FLOWS AT MT. HOOD, OREGON

Mt. Hood is a large glaciated Pleistocene volcano in the northern Oregon Cascade Range. Due to its location, size, eruptive history, and age, Mt. Hood has nearly ideal conditions for the generation of debris flows: steep slopes, confined channels, abundant loose material, and seasonal infusions of large amounts of water. Over the last six years the frequency of large-scale non-eruptive debris flows at Mt. Hood has increased from previous years. These debris flows have destroyed or threaten state highways and bridges and Forest Service roads, bridges, culverts, campgrounds, trailheads, and trails. Factors contributing to the increased frequency include a possible cyclical shift in the Pacific Northwest from a “drier” climate to a “wetter” climate and continuing glacial retreat. More large debris flows are expected in the next several years.