Abstract
Future trends in debris flow activity are constructed based on bias-corrected climate change projections using two meteorological proxies: daily precipitation and Convective Available Potential Energy (CAPE) combined with specific humidity for two Alpine areas. Along with a comparison between proxies, future number of days with debris flows are analyzed with respect to different regional and global climate models, Representative Concentration Pathways (RCPs), and area for quantile mapping. Two different base periods are also analyzed, as debris flows were observed on only 6 (17) days between 1950 and 1979, yet on 18 (49) days between 1980 and 2009 for Fella River, NE Italy (Barcelonnette, SE French Alps). For both areas, future climate projections vary between no change up to an increase of 6.0 % per decade in days with debris flow occurrences towards the end of 21st century. In Barcelonnette, the base period and proxy have a bigger impact on the future number of debris flow days than the climate model or RCP used. In Fella River, the base period, RCP, and proxy used define the future range. Therefore the selection of proxy, base period and downscaling technique should be carefully considered for future climate change impact studies concerning debris flow activity and associated fast-moving landslides.
Highlights
Debris flows are a common mass movement hazard in mountainous areas, with extreme rainfall the most common trigger for fatal debris flows (Dowling and Santi 2014), snowmelt can contribute in spring
This study examines the role of meteorological proxy on future debris flows using precipitation, and Convective Available Potential Energy (CAPE) combined with humidity, to capture instability and moisture needed to sustain deep convection
Using the rain-proxy results in a higher future debris flow activity compared to the QCAPE-proxy
Summary
Debris flows are a common mass movement hazard in mountainous areas, with extreme rainfall the most common trigger for fatal debris flows (Dowling and Santi 2014), snowmelt can contribute in spring. It is likely that increases in extreme rainfall will alter debris flow frequency (Winter et al 2010). Different meteorological proxies have been used for debris flow occurrence. Other meteorological proxies for debris flow occurrence can account for deficiencies in precipitation records, either without (Turkington et al 2014) or alongside rainfall (Paranunzio et al 2015; Rulli et al 2007). Previous work demonstrated that atmospheric variables, such as specific humidity (Q) combined with atmospheric instability through Convective Available Potential Energy (CAPE), can be used as proxies for debris flow occurrence, especially for those triggered by intense convective rainfall unrecorded by a rain gauge (Turkington et al 2014)
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