ALBERT

Description: Scientific literature is replete with papers describing advances in applying new technologies to the study of landslides and advances in our understanding of factors affecting landslide occurrence, distribution, and movement. Far fewer papers look at how this knowledge is implemented to achieve landslide risk reduction. State and local governments exercise the greatest control on how landslide risk reduction is accomplished. Data generated from a questionnaire to state geological surveys, review of their agency Web sites, and two case studies demonstrate that progress has been made during the last 20 years in implementing actionable policy changes and programs to achieve a reduction is landslide risk in the United States. Progress is evident from the pivotal role played by state and local government in the areas of: (1) developing guidelines and training, (2) increasing public awareness and education, (3) implementing loss reduction measures, and (4) conducting emergency preparedness, response, and recovery. The number of states requiring registration for practicing geologists has nearly doubled during the last 20 years. This increase was accompanied by a shift from individual state tests as part of determining competency to a uniform national test. During this period, state geological surveys established Web sites as a primary means for promoting public awareness and education about landslide hazards. Measures reducing the impact of landslides have included providing information specific to residents and landowners, as well as supporting land-use planning efforts by local governments. Many state geological surveys are involved with emergency management of landslide hazards.

Description: Watersheds recently burned by wildfires can be susceptible to debris flow, although little is known about how long this susceptibility persists and how it changes over time. We use a compilation of 75 debris-flow response and fire-ignition dates, vegetation and bedrock class, rainfall regime, and initiation process from throughout the western United States to address these issues. The great majority (85 percent) of debris flows occurred within the first 12 months following wildfire, with 71 percent occurring within the first 6 months. Seven percent of the debris flows occurred between 1 and 1.5 years after a fire, or during the second rainy season to impact an area. Within the first 1.5 years following fires, all but one of the debris flows initiated through runoff-dominated processes, and debris flows occurred in similar proportions in forested and non-forested landscapes. Underlying geologic materials affected how long debris-flow activity persisted, and the timing of debris flows varied within different rainfall regimes. A second, later period of increased debris flow susceptibility between 2.2 and 10 years after fires is indicated by the remaining 8 percent of events, which occurred primarily in forested terrains and initiated largely through landslide processes. The short time period between fire and debris-flow response within the first 1.5 years after ignition and the longer-term response between 2.2 and 10 years after fire demonstrate the necessity of both rapid and long-term reactions by land managers and emergency-response agencies to mitigate hazards from debris flows from recently burned areas in the western United States.

Description: During and following wildfires affecting steep mountain slopes, there can be an increase in rockfall activity usually taking the form of individual rocks, and occasionally, groups of rocks rolling, sliding or bouncing downslope. This increase results from removal of stabilizing vegetation, downed wood, and organics within the soil matrix as well as increase in erosional processes such as dry ravel. The hazard posed to vehicles is difficult to assess because of uncertainty manifested in several ways. First, there is uncertainty in defining the road segments that will be impacted by increased rockfall activity. Second, it is difficult to quantify the size, number, and/or travel behavior of rocks which may impact a given road segment. Finally, there is uncertainty as to how long increased rockfall activity may persist after a wildfire. Between 2007 and 2013, some insight into the first two uncertainty issues was provided by observed rockfall on roads within eight different wildfires in California and Idaho. This insight provided an efficient and effective means to prioritize rapid assessment for rockfall hazard for a large number of roads within the 2013 Rim Fire in the central Sierra Nevada, California. Data on the third rockfall uncertainty issue, persistence, was developed for a road on the Olympic National Forest in Washington. Monitoring of rocks accumulating on the road at sixteen sites between July 2006 and April 2007 recorded 3,463 rocks with the number of rocks found to decrease over time.