Combining spatial modelling and regionalization of rainfall thresholds for debris flows hazard mapping in the Emilia-Romagna Apennines (Italy)

Landslides ◽  
2021 ◽  
Author(s):  
Ciccarese G. ◽  
Mulas M. ◽  
Corsini A.
Keyword(s):  
Debris Flows ◽  
Spatial Modelling ◽  
Hazard Mapping ◽  
Rainfall Thresholds

Uncertainty in debris flow rainfall thresholds

2021 ◽  
Author(s):  
Matteo Berti ◽  
Alessandro Simoni
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Measurement Errors ◽  
Critical Conditions ◽  
Model Parameters ◽  
Average Intensity ◽  
Rainfall Thresholds ◽  
Sources Of Uncertainty ◽  
Time Space ◽  
Physically Based

<p>Rainfall is the most significant factor for debris flows triggering. Water is needed to saturate the soil, initiate the sediment motion (regardless of the mobilization mechanism) and transform the solid debris into a fluid mass that can move rapidly downslope. This water is commonly provided by rainfall or rainfall and snowmelt. Consequently, most warning systems rely on the use of rainfall thresholds to predict debris flow occurrence. Debris flows thresholds are usually empirically-derived from the rainfall records that caused past debris flows in a certain area, using a combination of selected precipitation measurements (such as event rainfall P, duration D, or average intensity I) that describe critical rainfall conditions. Recent years have also seen a growing interest in the use of coupled hydrological and slope stability models to derive physically-based thresholds for shallow landslide initiation.</p><p>In both cases, rainfall thresholds are affected by significant uncertainty. Sources of uncertainty include: measurement errors; spatial variability of the rainfall field; incomplete or uncertain debris flow inventory; subjective definition of the “rainfall event”; use of subjective criteria to define the critical conditions; uncertainty in model parameters (for physically-based approaches). Rainfall measurement is widely recognized as a main source of uncertainty due to the extreme time-space variability that characterize intense rainfall events in mountain areas. However, significant errors can also arise by inaccurate information reported in landslide inventories on the timing of debris flows, or by the criterion used to define triggering intensities.</p><p>This study analyzes the common sources of uncertainty associated to rainfall thresholds for debris flow occurrence and discusses different methods to quantify them. First, we give an overview of the various approaches used in the literature to measure the uncertainty caused by random errors or procedural defects. These approaches are then applied to debris flows using real data collected in the Dolomites (Northen Alps, Itay), in order to estimate the variabilty of each single factor (precipitation, triggering timing, triggering intensity..). Individual uncertainties are then combined to obtain the overall uncertain of the rainfall threshold, which can be calculated using the classical method of “summation in quadrature” or a more effective approach based on Monte Carlo simulations. The uncertainty budget allows to identify the biggest contributors to the final variability and it is also useful to understand if this variability can be reduced to make our thresholds more precise.</p><p> </p>

Rainfall thresholds for the occurrence of debris flows in the Jiangjia Gully, Yunnan Province, China

2015 ◽  
Vol 195 ◽  
pp. 335-346 ◽  
Author(s):  
Jianqi Zhuang ◽  
Peng Cui ◽  
Gonghui Wang ◽  
Xiaoqing Chen ◽  
Javed Iqbal ◽  
...  
Keyword(s):  
Debris Flows ◽  
Yunnan Province ◽  
Rainfall Thresholds ◽  
Jiangjia Gully

Modeling debris flows in volcanic terrains for hazard mapping: the case study of Ischia Island (Italy)

Landslides ◽  
2014 ◽  
Vol 12 (5) ◽  
pp. 831-846 ◽  
Author(s):  
M. Nocentini ◽  
V. Tofani ◽  
G. Gigli ◽  
F. Fidolini ◽  
N. Casagli
Keyword(s):  
Debris Flows ◽  
Hazard Mapping ◽  
Ischia Island ◽  
Volcanic Terrains

Debris flows rainfall thresholds in the Apennines of Emilia-Romagna (Italy) derived by the analysis of recent severe rainstorms events and regional meteorological data

Geomorphology ◽  
2020 ◽  
Vol 358 ◽  
pp. 107097 ◽  
Author(s):  
Giuseppe Ciccarese ◽  
Marco Mulas ◽  
Pier Paolo Alberoni ◽  
Giovanni Truffelli ◽  
Alessandro Corsini
Keyword(s):  
Debris Flows ◽  
Meteorological Data ◽  
Rainfall Thresholds

scholarly journals Quantitative Analysis of the Effects of an Earthquake on Rainfall Thresholds for Triggering Debris-Flow Events

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuang Liu ◽  
Kaiheng Hu ◽  
Qun Zhang ◽  
Shaojie Zhang ◽  
Xudong Hu ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rainfall Intensity ◽  
Focal Depth ◽  
Rainfall Threshold ◽  
Effective Rainfall ◽  
Rainfall Thresholds ◽  
Jiuzhaigou Earthquake ◽  
The Wenchuan Earthquake ◽  
The Moment

The impacts of destructive earthquakes on rainfall thresholds for triggering the debris flows have not yet been well investigated, due to lacks of data. In this study, we have collected the debris-flow records from the Wenchuan, Lushan, and Jiuzhaigou earthquake-affected areas in Sichuan Province, China. By using a meteorological dataset with 3 h and 0.1° resolutions, the dimensionless effective rainfall and rainfall intensity-duration relationships were calculated as the possible thresholds for triggering the debris flows. The pre- and post-seismic thresholds were compared to evaluate the impacts of the various intensities of earthquakes. Our results indicate that the post-quake thresholds are much smaller than the pre-seismic ones. The dimensionless effective rainfall shows the impacts of the Wenchuan, Lushan, and Jiuzhaigou earthquakes to be ca. 26, 27, and 16%, respectively. The Wenchuan earthquake has the most significant effect on lowering the rainfall intensity-duration curve. Rainfall threshold changes related to the moment magnitude and focal depth are discussed as well. Generally, this work may lead to an improved post-quake debris-flow warning strategy especially in sparsely instrumented regions.

scholarly journals Mechanisms of Initiation, Runout, and Rainfall Thresholds of Extreme-Precipitation-Induced Debris Flows

2021 ◽  
Author(s):  
Srikrishnan Siva Subramanian ◽  
Ali. P. Yunus ◽  
Faheed Jasin ◽  
Minu Treesa Abraham ◽  
Neelima Sathyam ◽  
...  
Keyword(s):  
Debris Flow ◽  
Extreme Precipitation ◽  
Debris Flows ◽  
Maximum Velocity ◽  
Rainfall Threshold ◽  
Rainfall Thresholds ◽  
Long Runout ◽  
Loss Of Life ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Abstract The frequency of unprecedented extreme precipitation events is increasing, and consequently, catastrophic debris flows occur in regions worldwide. Rapid velocity and long-runout distances of debris flow induce massive loss of life and damage to infrastructure. Despite extensive research, understanding the initiation mechanisms and defining early warning thresholds for extreme-precipitation-induced debris flows remain a challenge. Due to the nonavailability of extreme events in the past, statistical models cannot determine thresholds from historical datasets. Here, we develop a numerical model to analyze the initiation and runout of extreme-precipitation-induced runoff-generated debris flows and derive the Intensity-Duration (ID) rainfall threshold. We choose the catastrophic debris flow on 6 August 2020 in Pettimudi, Kerala, India, for our analysis. Our model satisfactorily predicts the accumulation thickness (7 m to 8 m) and occurrence time of debris flow compared to the benchmark. Results reveal that the debris flow was rapid, traveling with a maximum velocity of 9 m/s for more than 9 minutes. The ID rainfall threshold defined for the event suggests earlier thresholds are not valid for debris flow triggered by extreme precipitation. The methodology we develop in this study is helpful to derive ID rainfall thresholds for debris flows without historical data.

Rainfall thresholds of the debris flows based on various rainfall intensity types in Beijing

2021 ◽  
Author(s):  
Haizhi Wang ◽  
Qingli Zeng ◽  
Bing Xu ◽  
Luqing Zhang
Keyword(s):  
Debris Flows ◽  
Rainfall Intensity ◽  
High Water ◽  
Rainfall Threshold ◽  
Limited Information ◽  
Rainfall Thresholds ◽  
Occurrence Time ◽  
Water Flows ◽  
Average Rainfall ◽  
Concert Works

Abstract Empirical rainfall thresholds derived from various types of rainfall intensities have widely used in characterizing rainfall conditions that cause debris flows and landslides. However, few works have studied the differences among these various thresholds, due to limited information on the instantaneous intensity triggering debris flows. The detail records of the storms on 21 July, 2012, 20 July, 2016, and 16 July, 2018, together with the occurrence time of debris flows, provide an opportunity to evaluate the thresholds based on various rainfall intensities. Based these data, a new rainfall threshold of debris flows is derived from the instantaneous rainfall intensity in Beijing. At the same time, the thresholds based on average rainfall intensities as used in most previous studies, including the average over the periods from the beginnings of rainfall to the occurrences of the debris flows and over the whole period of the rainstorms, are reconstructed. The result shows that the instantaneous rainfall threshold has a higher ability in separating the rainstorms inducing from those without reducing debris flows than those derived from average intensities, indicating a high accurate of the instantaneous threshold. Our data also indicate that the debris flows in Beijing should be triggered by the concert works of rainfall intensity and cumulative precipitation. Only when enough water to infiltrate, saturate, mobilize the debris sediments, and sufficient high water flows and surges caused by intensive storms to incorporate and retain the mobilized sediments, are satisfied simultaneously do the debris flows occur.

Global warming, slope stability, and the dynamization of geological hazards in high mountain regions: a case study from the Eastern Alps.

2021 ◽  
Author(s):  
Sara Savi ◽  
Francesco Comiti ◽  
Manfred Strecker
Keyword(s):  
Slope Stability ◽  
Debris Flows ◽  
Slope Instability ◽  
Medium Size ◽  
Hazard Mapping ◽  
High Mountain ◽  
Permafrost Degradation ◽  
Mountain Regions ◽  
Extreme Precipitation Events ◽  
Altitudinal Shift

<p>In recent decades, slope instability in high-mountain regions has often been linked to the increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small to medium-size rockfalls and debris flows in a small catchment of the Italian Alps (Sulden/Solda basin). We found that rockfall events have been increasing since the 1990s, whereas debris flows have increased only since 2010. The current warming trend of mountain regions such as the Southern Alps is leading to an increased elevation of rockfall detachment areas (altitudinal shift of ca. 300-400 m in the study site), mostly controlled by frost-cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity-duration rainfall distribution. The possible occurrence of a debris-flow event in this environment may be additionally influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden basin (above ca. 2500 m asl), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 1990s and that an increase in rockfalls and debris flows during spring and summer can be observed. Our study thus confirms that “forward-looking” hazard mapping should be undertaken in these increasingly frequented areas of the Alps, as these environmental changes have elevated the overall hazard level in these high-elevation regions.</p>

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