TEMPORAL CHANGES IN DEBRIS FLOW SOURCE MATERIAL AND INITIATION MECHANISMS FOLLOWING THE 2016 FISH FIRE IN THE SAN GABRIEL MOUNTAINS, CA, USA

2018 ◽  
Author(s):  
Hui Tang ◽  
◽  
Luke McGuire ◽  
Francis K. Rengers ◽  
Jason W. Kean ◽  
...  
Keyword(s):  
Debris Flow ◽  
Temporal Changes ◽  
Source Material ◽  
San Gabriel Mountains

Time Since Burning and Rainfall Characteristics Impact Post-Fire Debris-Flow Initiation and Magnitude

2021 ◽  
Vol 27 (1) ◽  
pp. 43-56
Author(s):  
Luke A. McGuire ◽  
Francis K. Rengers ◽  
Nina Oakley ◽  
Jason W. Kean ◽  
Dennis M. Staley ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Debris Flow ◽  
Debris Flows ◽  
Numerical Models ◽  
Ground Cover ◽  
Temporal Changes ◽  
Infiltration Capacity ◽  
Rainfall Characteristics ◽  
San Gabriel Mountains ◽  
Fire Debris

ABSTRACT The extreme heat from wildfire alters soil properties and incinerates vegetation, leading to changes in infiltration capacity, ground cover, soil erodibility, and rainfall interception. These changes promote elevated rates of runoff and sediment transport that increase the likelihood of runoff-generated debris flows. Debris flows are most common in the year immediately following wildfire, but temporal changes in the likelihood and magnitude of debris flows following wildfire are not well constrained. In this study, we combine measurements of soil-hydraulic properties with vegetation survey data and numerical modeling to understand how debris-flow threats are likely to change in steep, burned watersheds during the first 3 years of recovery. We focus on documenting recovery following the 2016 Fish Fire in the San Gabriel Mountains, California, and demonstrate how a numerical model can be used to predict temporal changes in debris-flow properties and initiation thresholds. Numerical modeling suggests that the 15-minute intensity-duration (ID) threshold for debris flows in post-fire year 1 can vary from 15 to 30 mm/hr, depending on how rainfall is temporally distributed within a storm. Simulations further demonstrate that expected debris-flow volumes would be reduced by more than a factor of three following 1 year of recovery and that the 15-minute rainfall ID threshold would increase from 15 to 30 mm/hr to greater than 60 mm/hr by post-fire year 3. These results provide constraints on debris-flow thresholds within the San Gabriel Mountains and highlight the importance of considering local rainfall characteristics when using numerical models to assess debris-flow and flood potential.

scholarly journals Temporal changes in the debris flow threshold under the effects of ground freezing and sediment storage on Mt. Fuji

2021 ◽  
Author(s):  
Fumitoshi Imaizumi ◽  
Atsushi Ikeda ◽  
Kazuki Yamamoto ◽  
Okihiro Osaka
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rainfall Threshold ◽  
Temporal Changes ◽  
Frozen Ground ◽  
Sediment Storage ◽  
Cold Regions ◽  
Initiation Zone ◽  
Ground Freezing ◽  
Channel Deposits

Abstract. Debris flows are one of the most destructive sediment transport processes in mountainous areas because of their large volume, high velocity, and kinematic energy. Debris flow activity varies over time and is affected by changes in hydrogeomorphic processes in the initiation zone. To clarify temporal changes of debris flow activities in cold regions, the rainfall threshold for the debris flow occurrence was evaluated in Osawa failure at a high elevation on Mt. Fuji, Japan. We conducted field monitoring of the ground temperature near a debris flow initiation zone to estimate the presence or absence of seasonally frozen ground during historical rainfall events. The effects of ground freezing and the accumulation of channel deposits on the rainfall threshold for debris flow occurrence were analyzed using rainfall records and annual changes in the volume of channel deposits since 1969. Statistical analyses showed that the intensity-duration threshold during frozen periods was clearly lower than that during unfrozen periods. A comparison of maximum hourly rainfall intensity and total rainfall also showed that debris flows during frozen periods were triggered by a smaller magnitude of rainfall than during unfrozen periods. Decreases in the infiltration rate due to the formation of frozen ground likely facilitated the generation of overland flow, triggering debris flows. During unfrozen periods, the rainfall threshold was higher when the volume of channel deposits was larger. Increases in the water content in channel deposits caused by the infiltration of rainfall is likely important for the debris flow occurrence during unfrozen periods. The results suggest that the occurrence of frozen ground and the sediment storage volume need to be monitored and estimated for better debris flow disaster mitigation in cold regions.

scholarly journals Temporal changes in the debris flow threshold under the effects of ground freezing and sediment storage on Mt. Fuji

2021 ◽  
Vol 9 (6) ◽  
pp. 1381-1398
Author(s):  
Fumitoshi Imaizumi ◽  
Atsushi Ikeda ◽  
Kazuki Yamamoto ◽  
Okihiro Ohsaka
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rainfall Threshold ◽  
Temporal Changes ◽  
Frozen Ground ◽  
Sediment Storage ◽  
Cold Regions ◽  
Initiation Zone ◽  
Ground Freezing ◽  
Channel Deposits

Abstract. Debris flows are one of the most destructive sediment transport processes in mountainous areas because of their large volume, high velocity, and kinematic energy. Debris flow activity varies over time and is affected by changes in hydrogeomorphic processes in the initiation zone. To clarify temporal changes in debris flow activities in cold regions, the rainfall threshold for the debris flow occurrence was evaluated in Osawa failure at a high elevation on Mt. Fuji, Japan. We conducted field monitoring of the ground temperature near a debris flow initiation zone to estimate the presence or absence of seasonally frozen ground during historical rainfall events. The effects of ground freezing and the accumulation of channel deposits on the rainfall threshold for debris flow occurrence were analyzed using rainfall records and annual changes in the volume of channel deposits since 1969. Statistical analyses showed that the intensity–duration threshold during frozen periods was clearly lower than that during unfrozen periods. A comparison of maximum hourly rainfall intensity and total rainfall also showed that debris flows during frozen periods were triggered by a smaller magnitude of rainfall than during unfrozen periods. Decreases in the infiltration rate due to the formation of frozen ground likely facilitated the generation of overland flow, triggering debris flows. The results suggest that the occurrence of frozen ground and the sediment storage volume need to be monitored and estimated for better debris flow disaster mitigation in cold regions.

Predicting locations of post-fire debris-flow erosion in the San Gabriel Mountains of southern California

2015 ◽  
Vol 77 (2) ◽  
pp. 1305-1321 ◽  
Author(s):  
J. E. Gartner ◽  
P. M. Santi ◽  
S. H. Cannon
Keyword(s):  
Debris Flow ◽  
Southern California ◽  
San Gabriel Mountains ◽  
Fire Debris

Emergency Assessment of Postfire Debris-Flow Hazards for the 2009 Station Fire, San Gabriel Mountains, Southern California

2009 ◽  
Author(s):  
Susan H. Cannon ◽  
Joseph E. Gartner ◽  
Michael G. Rupert ◽  
John A. Michael ◽  
Dennis M. Staley ◽  
...  
Keyword(s):  
Debris Flow ◽  
Southern California ◽  
San Gabriel Mountains

scholarly journals Impact of Short-term Temporal Changes in Volcanic Ash Fall on Rainfall Threshold for Debris Flow Occurrence in Sakurajima, Japan

2014 ◽  
Vol 7 (3) ◽  
pp. 75-84
Author(s):  
Hiroshi KISA ◽  
Takao YAMAKOSHI ◽  
Tadanori ISHIZUKA
Keyword(s):  
Debris Flow ◽  
Volcanic Ash ◽  
Rainfall Threshold ◽  
Temporal Changes ◽  
Short Term ◽  
Ash Fall

Temporal changes in conversational interactions induced by the presence of a simultaneous conversation

2011 ◽  
Author(s):  
J. Villegas ◽  
V. Aubanel ◽  
M. Cooke
Keyword(s):  
Temporal Changes ◽  
Conversational Interactions
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