The Impact of Sediment Supply on the Initiation and Magnitude of Runoff‐Generated Debris Flows. Issue 14 (9th July 2020)

• Record Type: Journal Article
• Authors: Tang, Hui; McGuire, Luke A.; Kean, Jason W.; Smith, Joel B.
• Is Part Of: Geophysical research letters. Volume 47:Issue 14(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-07-09
• Subjects: debris flow -- rainfall intensity‐duration thresholds -- Chalk Cliffs -- sediment supply -- grain size -- numerical model; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL087643
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Rainfall intensity‐duration (ID) thresholds are commonly used to assess the potential for runoff‐generated debris flows, but the sensitivity of these thresholds to sediment supply, which can change rapidly with time, is relatively unexplored. Furthermore, debris flows often self‐organize into distinct surges, but the factors controlling the magnitude and frequency of these surges, including sediment supply and grain size, are poorly constrained. We use a combination of numerical modeling and debris flow monitoring data from Chalk Cliffs, Colorado, USA, to explore how sediment supply influences rainfall ID thresholds for debris flows and surge properties. Results suggest that rainfall ID thresholds only become sensitive to sediment supply below a sediment thickness threshold. Surge magnitude is a nonmonotonic function of sediment supply (i.e., channel bed sediment thickness and grain size) with the largest surges tending to form at intermediate values of sediment availability with intermediate grain sizes. Key Points: Rainfall intensity‐duration thresholds are sensitive to sediment supply below a critical sediment thickness The critical value of sediment thickness depends on the grain size of the sediment source The largest surges tend to form at intermediate values of sediment availability