Geophysical Surveys of Debris Flow Susceptible Areas; Implications for Risk Perception
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Understanding how an individual cognizes and processes geophysical information pertinent to natural hazards can further enhance geophysical imaging in becoming more reliable and beneficial to the public. It has long been debated to what degree an individual’s perception of the risk associated with natural disasters changes with the level of exposure to relevant scientific evidence and the manner in which the information is communicated by experts. Debates on this topic have circled around climate change, natural hazard preparedness, and health risks. One situation that lends itself to studying the public perception of the information content in geophysical images is debris flow hazard in inhabited mountainous regions, as such flows have an immediate impact on human life, property and amenity values. Geophysical mapping was performed along the Front Range in Boulder County, Colorado, to provide information about the potential for new additional debris flows in light of the September 2013 flooding episodes, which brought a State of Emergency to Boulder County. The geophysical maps provided subsurface images of geotechnical proxies that are herein interpreted in terms of debris flow susceptibility along a given profile. We acquired two along-slope and two down-slope electrical resistivity tomography (ERT) profiles for assessment of potential slope failure. The ERT images suggest a complex subsurface heterogeneity characterized by shallow localized channels of high hydraulic conductivity constrained by surrounding areas of low hydraulic conductivity. Understanding the geotechnical implications of these subsurface structures gives better insight into the apparent risk of future rainfall-induced debris flows in this specific area. The geophysical information ideally would be widely communicated to the public and local stakeholders for risk assessment and mitigation purposes. In this study, instead we have used a small informal focus group approach which has provided a crude indication of the potential response of the public and stakeholders to the information content revealed in the ERT images pertaining to Boulder county debris flow-susceptible slopes. Particularly, we monitored changes in expressed risk perception as various levels of scientific information were systematically revealed to the focus group. The focus group study is a precursor to a larger study in understanding how the general public perceives geophysical information regarding natural hazards and its implications for hazard mitigation.
Tebo, Daniel Theodore (2016). Geophysical Surveys of Debris Flow Susceptible Areas; Implications for Risk Perception. Master's thesis, Texas A & M University. Available electronically from