Linking Mesoscale Meteorology With Extreme Landscape Response: Effects of Narrow Cold Frontal Rainbands (NCFR). Issue 10 (8th October 2020)

• Record Type: Journal Article
• Authors: Collins, Brian D.; Oakley, Nina S.; Perkins, Jonathan P.; East, Amy E.; Corbett, Skye C.; Hatchett, Benjamin J.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-10-08
• Subjects: landslide -- landscape response -- mesoscale -- narrow cold frontal rainband -- California -- Sierra Nevada; Geomorphology -- Periodicals; 551.3
• DOI: 10.1029/2020JF005675
• Languages: English
• ISSNs: 2169-9003

Abstract

Abstract: Landscapes evolve in response to prolonged and/or intense precipitation resulting from atmospheric processes at various spatial and temporal scales. Whereas synoptic (large‐scale) features (e.g., atmospheric rivers and hurricanes) govern regional‐scale hydrologic hazards such as widespread flooding, mesoscale features such as thunderstorms or squall lines are more likely to trigger localized geomorphic hazards such as landslides. Thus, to better understand relations between hydrometeorological drivers and landscape response, a knowledge of mesoscale meteorology and its impacts is needed. Here we investigate the extreme geomorphic response associated with one type of mesoscale meteorological feature, the narrow cold frontal rainband (NCFR). Resulting from low‐level convergence and shallow convection along a cold front, NCFRs are narrow bands of high‐intensity rainfall that occur in midlatitude areas of the world. Our study examines an NCFR impacting the Sierra Nevada foothills (California, USA) that initiated over 500 landslides, mobilized ~360, 000 metric tons of sediment to the fluvial system (as much as 16 times the local annual sediment yield), and severely damaged local infrastructure and regional water transport facilities. Coupling geomorphological field investigations with meteorological analyses, we demonstrate that precipitation associated with the NCFR was both intense (maximum 15 min intensity of 70 mm/hr) and localized, resulting in a highly concentrated band of shallow landsliding. This meteorological phenomenon likely plays an important role in landscape evolution and hazard initiation. Other types of mesoscale meteorological features also occur globally and offer new avenues for understanding the effects of storms on landscapes. Plain Language Summary: Major storms can cause extreme and hazardous landscape disturbances, but links between storm conditions and landscape response such as erosion and landslides remain poorly constrained. This is partly due to the lack of attention generally given to the finer‐scale details of storms. We examined one type of atmospheric feature that is common in western North America (as well as in other regions), the narrow cold frontal rainband, and studied its effects on the landscape. In 2018, one such event in the Tuolumne River watershed, California, caused more than 500 landslides in a narrow area, moving more sediment in one day than the river would normally transport in a year. We find that landscape change, including potentially hazardous events such as landslides, can be driven primarily by fine‐scale rainfall patterns rather than by the larger‐scale storm conditions. More integration between weather and landscape scientists can advance knowledge of how storms influence landscapes and produce hazards, especially during extreme events. Key Points: Mesoscale atmospheric processes such as narrow cold frontal rainbands play key roles in triggering landscape responses One such event in the Tuolumne River canyon, California, generated >500 landslides and 1.5–16 times the usual annual sediment yield Predictions of extreme, hazardous landscape response will benefit by incorporating mesoscale atmospheric processes driving intense rainfall