Geomorphic and Land Management Effects on Channel Altering Events in the Klamath Mountain, Northern California

Channel altering events have many impacts on stream channels and can be the result of debris flows, hyper-concentrated flows or severe flooding. They play a major role in coarse woody debris delivery to fish bearing streams and provide a mix of sediment to the higher order streams. Channel altering events can reduce or even temporarily eliminate riparian vegetation along the stream channel and create changes in the stream bed such as aggradation and degradation. These processes are a natural part of steep, rugged landscapes such as that of the Klamath Mountains and have long-term benefits to the stream systems. The process can be accelerated however, by land management activities or severe wildfire events. Previous investigations have focused on the impacts to landsliding rates as a result of timber harvest, wildfire and forest roads. These studies are limited in spatial extent and have not combined timber harvest, wildfire, forest roads, storm intensity and geomorphic characteristics in the same investigation. In addition, previous studies have not included areas where landslides did not occur for comparison. This study investigates the relationships between landform, timber harvest, forest roads, wildfire, and storm intensity over the Klamath Mountains in Northern California. The study investigates the initiation points of channel altering events that occurred in the flood of December 1996/January 1997. Channel altering event initiation points are the uppermost point of an altered channel segment (highest elevation) as apparent on aerial photos. The initiation points are compared to stratified random points in and near channels where no channel altering event occurred. The initiation points and random points were attributed with information such as aspect, hillslope gradient, elevation, bedrock type, landform, storm intensity and land management practices. A logistic regression analysis will determine if there is a suite of characteristics that separated the initiation points from the random points. This study will provide insight into the characteristics of initiation points of channel altering events which will improve land management practices in the Klamath Mountains.