scholarly journals Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil

2021 ◽  
Author(s):  
Victor Carvalho Cabral ◽  
Fábio Augusto Gomes Vieira Reis ◽  
Fernando Mazo D’Affonseca ◽  
Ana Lucía ◽  
Claudia Vanessa dos Santos Corrêa ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rain Gauge ◽  
Peak Discharge ◽  
Hazard Management ◽  
Magnitude Comparison ◽  
Tropical Regions ◽  
Serra Do Mar ◽  
Total Magnitude

AbstractDebris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies, especially in subtropical and tropical regions where debris flows have scarcely been studied when compared to other mass-wasting processes. Thus, this study aims at systematically analyzing the meteorological and geomorphological factors that characterize a landslide-triggered debris flow at the Pedra Branca catchment (Serra do Mar, Brazil), to quantify the debris flow’s magnitude, peak discharge and velocity. A magnitude comparison with empirical equations (Italian Alps, Taiwan, Serra do Mar) is also conducted. The meteorological analysis is based on satellite data and rain gauge measurements, while the geomorphological characterization is based on terrestrial and aerial investigations, with high spatial resolution. The results indicate that it was a large-sized stony debris flow, with a total magnitude of 120,195 m3, a peak discharge of 2146.7 m3 s−1 and a peak velocity of 26.5 m s−1. The debris flow was triggered by a 188-mm rainfall in 3 h (maximum intensity of 128 mm h−1), with an estimated return period of 15 to 20 years, which, combined with the intense accumulation of on-channel debris (ca. 37,000 m3), indicates that new high-magnitude debris flows in the catchment and the region are likely to occur within the next two decades. The knowledge of the potential frequency and magnitude (F–M) can support the creation of F–M relationships for Serra do Mar, a prerequisite for reliable hazard management and monitoring programs.

Magnitude estimation of a landslide-triggered debris flow in the Serra do Mar Mountain Range, Brazil

2020 ◽  
Author(s):  
Victor Carvalho Cabral ◽  
Fernando Mazo D'Affonseca ◽  
Marcelo Fischer Gramani ◽  
Agostinho Tadashi Ogura ◽  
Claudia Santos Corrêa ◽  
...  
Keyword(s):  
Debris Flow ◽  
Magnitude Estimation ◽  
Cross Sections ◽  
Debris Flows ◽  
Mountain Range ◽  
Serra Do Mar ◽  
Solids Concentration ◽  
Geomorphic Features ◽  
Total Magnitude ◽  
Future Events

<p><span>Debris flows represent great hazard to communities and infrastructures, since they move quickly and are very destructive. In Brazil, debris flows mainly occur in the Serra do Mar Mountain Range, where thousands of casualties were reported in the last two decades due to these phenomena. This study aims at estimating the magnitude of a debris-flow event that occurred in Serra do Mar on February 2017, at the Pedra Branca watershed in the State of Paraná. Debris-flow magnitude refers to the volume of material discharged during an event and is an important aspect of debris-flow hazard assessment. The Pedra Branca event was initiated by rainfall-triggered shallow landslides, damaging local oil pipelines and farms. The magnitude estimation is based on the combination of empirically based equations and the geomorphic features of the debris flow, acquired from <em>in situ</em> and aerial investigation. 28 cross-sections were made along the river channel, considering post-event channel width, erosion and accumulation depth, as well as depositional features. Sediment sources and accumulation areas were identified and delimitated based on high-resolution (1:500) aerial drone photographs. The results indicate that the landslides that initiated the event released approximately 26,884.5 m<sup>3</sup> of sediments (V<sub>i</sub>) into the main channel of Pedra Branca and that the volume eroded (V<sub>e</sub>) and accumulated (V<sub>d</sub>) along the channel are, respectively, 82,439 m<sup>3</sup> and 22,012 m<sup>3</sup>. The estimated total solids volume (V<sub>s</sub>) is 87,274 m<sup>3</sup>, assuming that V<sub>s</sub> = V<sub>i</sub> + V<sub>e</sub> - V<sub>d</sub>. Moreover, considering a solids concentration of 57% calculated according to empirically-based equations for Serra do Mar, the debris flow had a total magnitude of 153,113 m<sup>3</sup>. These estimations suggest that the February 2017 debris flow mobilised great volume of material and that 15% of the total volume accumulated on the channel bed, which can be remobilised by future events. Further research on debris-flow dynamics and recurrence at the Serra do Mar Mountain Range is recommended to mitigate future hazards.</span></p>

Observations and Analyses of the 9 January 2018 Debris-Flow Disaster, Santa Barbara County, California

2021 ◽  
Vol 27 (1) ◽  
pp. 3-27
Author(s):  
Jeremy T. Lancaster ◽  
Brian J. Swanson ◽  
Stefani G. Lukashov ◽  
Nina S. Oakley ◽  
Jacob B. Lee ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Atmospheric Conditions ◽  
Santa Barbara ◽  
Debris Removal ◽  
Fire Debris ◽  
Santa Barbara County ◽  
Coastal Land

ABSTRACT The post–Thomas Fire debris flows of 9 January 2018 killed 23 people, damaged 558 structures, and caused severe damage to infrastructure in Montecito and Carpinteria, CA. U.S. Highway 101 was closed for 13 days, significantly impacting transportation and commerce in the region. A narrow cold frontal rain band generated extreme rainfall rates within the western burn area, triggering runoff-driven debris flows that inundated 5.6 km2 of coastal land in eastern Santa Barbara County. Collectively, this series of debris flows is comparable in magnitude to the largest documented post-fire debris flows in the state and cost over a billion dollars in debris removal and damages to homes and infrastructure. This study summarizes observations and analyses on the extent and magnitude of inundation areas, debris-flow velocity and volume, and sources of debris-flow material on the south flank of the Santa Ynez Mountains. Additionally, we describe the atmospheric conditions that generated intense rainfall and use precipitation data to compare debris-flow source areas with spatially associated peak 15 minute rainfall amounts. We then couple the physical characterization of the event with a compilation of debris-flow damages to summarize economic impacts.

scholarly journals Peak Discharge and Hydrograph Assessments Induced by Heavy Rainfall Events Using Tank Model

2018 ◽  
Vol 207 ◽  
pp. 02001
Author(s):  
Yen-Kun Hsu ◽  
Szu-Hsien Peng ◽  
Chiao-Wen Tsai
Keyword(s):  
Debris Flow ◽  
Flow Simulation ◽  
Rain Gauge ◽  
Peak Discharge ◽  
Soil Horizon ◽  
Tank Model ◽  
Rainfall Events ◽  
The Mean ◽  
Heavy Rainfall Events ◽  
Better Than

Tank Model is a kind of simulation of rainfall movement in soil horizon. With the runoff and piping rate, the peak discharge could be effectively calculated. Having 17 rain gauge stations in 13 debris flow events during 1996-2010 as the studied cases, the peak discharge at 12 control points along Chenyulan River is simulated. Furthermore, the data in Neimaopu discharge station is established parameters of Tank Model to estimate the peak discharge in Shenmu Village. By comparing with the parameters of Shueili Station and Japanese Granite, the mean error of the parameter in this study is 51.0%, which is better than those of Japanese Granite 189% and Shueili discharge stations 251%. The parameter in this study appears the highest in allowance analysis, showing that it is more suitable for simulating the peak discharge than the other two. In spite that the percentage of the three parameters is still low, Shenmu Village could be ignored as it locates in the sub-basin of Chenyulan River with few factors. The parameters of Tank Model are applied to transform average rainfall into hydrograph so as to solve the problem of no discharge records when analysing the areas with various debris flow simulation programs.

scholarly journals Augmentation and Use of WRF-Hydro to Simulate Overland Flow- and Streamflow-Generated Debris Flow Hazards in Burn Scars

2021 ◽  
Author(s):  
Chuxuan Li ◽  
Alexander L. Handwerger ◽  
Jiali Wang ◽  
Wei Yu ◽  
Xiang Li ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Hydrological Modeling ◽  
Overland Flow ◽  
New Physics ◽  
Reanalysis Data ◽  
Peak Discharge ◽  
Burn Scar ◽  
Big Sur ◽  
Discharge Volume

Abstract. In steep wildfire-burned terrains, intense rainfall can produce large volumes of runoff that can trigger highly destructive debris flows. The ability to accurately characterize and forecast debris-flow hazards in burned terrains, however, remains limited. Here, we augment the Weather Research and Forecasting Hydrological modeling system (WRF-Hydro) to simulate both overland and channelized flows and assess postfire debris-flow hazards over a regional domain. We perform hindcast simulations using high-resolution weather radar-derived precipitation and reanalysis data to drive non-burned baseline and burn scar sensitivity experiments. Our simulations focus on January 2021 when an atmospheric river triggered numerous debris flows within a wildfire burn scar in Big Sur – one of which destroyed California’s famous Highway 1. Compared to the baseline, our burn scar simulation yields dramatic increases in total and peak discharge, and shorter lags between rainfall onset and peak discharge. At Rat Creek, where Highway 1 was destroyed, discharge volume increases eight-fold and peak discharge triples relative to the baseline. For all catchments within the burn scar, we find that the median catchment-area normalized discharge volume increases nine-fold after incorporating burn scar characteristics, while the 95th percentile volume increases 13-fold. Catchments with anomalously high hazard levels correspond well with post-event debris flow observations. Our results demonstrate that WRF-Hydro provides a compelling new physics-based tool to investigate and potentially forecast postfire hydrologic hazards at regional scales.

Consideration of the Validity of Debris-flow Bulking Factors

2017 ◽  
Vol 23 (4) ◽  
pp. 291-298
Author(s):  
Holly Brunkal ◽  
Paul Santi
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Rainfall Intensity ◽  
Peak Discharge ◽  
Data Set ◽  
Burned Areas ◽  
The Given ◽  
Basin Area ◽  
Bulking Factor ◽  
Significant Underestimation

Abstract Compilation of a database of debris-flow peak discharges (Q) allowed for a comparison with the expected basin discharge, as computed using the rational equation, Q=CIA. The observed values of Q for debris flows in unburned and burned areas were divided by the computed Q values of runoff using the rational method. This ratio is the bulking factor for that debris-flow event. Unburned and burned basins constitute two distinct populations; analysis shows that the bulking factors for burned areas are consistently higher than those for unburned basins. Previously published bulking factors for unburned areas fit the data set in about 50 percent of the observed cases in our compiled data set. Bulking factors for burned areas that were found in the published literature were well below the observed increases in peak discharge in over 50 percent of the cases investigated. If used for design purposes, these bulking factors would result in a significant underestimation of the peak discharge from a burned basin for the given rainfall intensity. Peak discharge bulking rates were found to be inversely related to basin area.

scholarly journals Characteristics of a Debris Flow Disaster and Its Mitigation Countermeasures in Zechawa Gully, Jiuzhaigou Valley, China

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1256 ◽  
Author(s):  
Xing-Long Gong ◽  
Kun-Ting Chen ◽  
Xiao-Qing Chen ◽  
Yong You ◽  
Jian-Gang Chen ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Peak Discharge ◽  
Dam Failure ◽  
Check Dam ◽  
Jiuzhaigou Earthquake ◽  
Property Losses ◽  
Jiuzhaigou Valley ◽  
Engineering Projects ◽  
Debris Flow Disaster

On 8 August 2017, an Ms 7.0 earthquake struck Jiuzhaigou Valley, triggering abundant landslides and providing a huge source of material for potential debris flows. After the earthquake debris flows were triggered by heavy rainfall, causing traffic disruption and serious property losses. This study aims to describe the debris flow events in Zechawa Gully, calculate the peak discharges of the debris flows, characterize the debris flow disasters, propose mitigation countermeasures to control these disasters and analyse the effectiveness of countermeasures that were implemented in May 2019. The results showed the following: (1) The frequency of the debris flows in Zechawa Gully with small- and medium-scale will increase due to the influence of the Ms 7.0 Jiuzhaigou earthquake. (2) An accurate debris flow peak discharge can be obtained by comparing the calculated results of four different methods. (3) The failure of a check dam in the channel had an amplification effect on the peak discharge, resulting in a destructive debris flow event on 4 August 2016. Due to the disaster risk posed by dam failure, both blocking and deposit stopping measures should be adopted for debris flow mitigation. (4) Optimized engineering countermeasures with blocking and deposit stopping measures were proposed and implemented in May 2019 based on the debris flow disaster characteristics of Zechawa Gully, and the reconstructed engineering projects were effective in controlling a post-earthquake debris flow disaster on 21 June 2019.

scholarly journals Debris flows in the Eastern Italian Alps: seasonality and atmospheric circulation patterns

2014 ◽  
Vol 2 (12) ◽  
pp. 7197-7224 ◽  
Author(s):  
E. I. Nikolopoulos ◽  
M. Borga ◽  
F. Marra ◽  
S. Crema ◽  
L. Marchi
Keyword(s):  
Debris Flow ◽  
Atmospheric Circulation ◽  
Debris Flows ◽  
Large Scale ◽  
Rain Gauge ◽  
Italian Alps ◽  
Synoptic Pattern ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Synoptic Forcing

Abstract. The work examines the seasonality and large-scale atmospheric circulation patterns of debris flows in the Trentino-Alto Adige region (Eastern Italian Alps). Analysis is based on classification algorithms applied on a uniquely dense archive of debris flows and hourly rain gauge precipitation series covering the period 2000–2009. Results highlight the seasonal and synoptic forcing patterns linked to debris flows in the study area. Summer and fall season account for 92% of the debris flows in the record, while atmospheric circulation characterized by Zonal West, Mixed and Meridional South, Southeast patterns account for 80%. Both seasonal and circulation patterns exhibit geographical preference. In the case of seasonality, there is a strong north–south separation of summer–fall dominance while spatial distribution of dominant circulation patterns exhibits clustering, with both Zonal West and Mixed prevailing in the northwest and central east part of the region, while the southern part relates to Meridional South, Southeast pattern. Seasonal and synoptic pattern dependence is pronounced also on the debris flow triggering rainfall properties. Examination of rainfall intensity–duration thresholds derived for different data classes (according to season and synoptic pattern) revealed a distinct variability in estimated thresholds. These findings imply a certain control on debris-flow events and can therefore be used to improve existing alert systems.

scholarly journals Impact of rainfall spatial aggregation on the identification of debris flow occurrence thresholds

2017 ◽  
Author(s):  
Francesco Marra ◽  
Elisa Destro ◽  
Efthymios I. Nikolopoulos ◽  
Davide Zoccatelli ◽  
Jean Dominique Creutin ◽  
...  
Keyword(s):  
Debris Flow ◽  
Early Warning ◽  
Debris Flows ◽  
Spatial Organization ◽  
Radar Data ◽  
Rain Gauge ◽  
Spatial Aggregation ◽  
Scale Parameters ◽  
The Impact ◽  
Triggering Rainfall

Abstract. The systematic underestimation observed in debris flows early warning thresholds has been associated to the use of sparse rain gauge networks to represent highly non-stationary rainfall fields. Remote sensing products permit concurrent estimates of debris flow-triggering rainfall for areas poorly covered by rain gauges, but the impact of using coarse spatial resolutions to represent such rainfall fields is still to be assessed. This study uses fine resolution radar data for ~ 100 debris flows in the eastern Italian Alps to (i) quantify the effect of spatial aggregation (1–20-km grid size) on the estimation of debris flow triggering rainfall and on the identification of early warning thresholds and (ii) compare thresholds derived from aggregated estimates and rain gauge networks of different densities. The impact of spatial aggregation is influenced by the spatial organization of rainfall and by its dependence on the severity of the triggering rainfall. Thresholds from aggregated estimates show up to 8 % and 21 % variations in the shape and scale parameters respectively. Thresholds from synthetic rain gauge networks show > 10 % variation in the shape and > 25 % systematic underestimation in the scale parameter, even for densities as high as 1/10 km−2.

Debris flow magnitude estimation based on infrasound and seismic signals

2020 ◽  
Author(s):  
Andreas Schimmel ◽  
Matteo Cesca ◽  
Pierpaolo Macconi ◽  
Velio Coviello ◽  
Francesco Comiti
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Warning System ◽  
Early Warning Systems ◽  
Peak Discharge ◽  
Detection Methods ◽  
Mountain Areas ◽  
Detection And Identification ◽  
European Mountain ◽  
The Alps

<p>With the rapid socio-economic development of European mountain areas, the automatic detection and identification of mass movements like landslides, debris flows, and avalanches become more and more important to mitigate related risks by means of early warning systems. Past studies showed that such processes induce characteristic seismic and acoustic signals, the latter mostly in the infrasonic spectrum which can thus be used for event detection. Several investigations have already addressed signal processing and detection methods based on seismic or infrasound sensors. However, for developing an efficient warning system, not only the detection of events is important but also the identification of the event type (e.g. debris flow vs debris flood) and the estimation of its magnitude. So far, no method for such objectives has been developed which is based on the combination of both seismic and infrasonic signals.</p><p>This work presents a first approach to identify debris flows and debris floods magnitude based on the integration of infrasound and seismic data. First analysis shows that, for peak discharge, the use of infrasound amplitudes with a power curve fitting offers a good approach for finding an initial relationship between the recorded signals and this event parameter. For an estimation of the total volume, the discharge calculated with the relationship for peak discharge is integrated over the entire detection time of an event. Calculation of the peak discharge based on infrasound data offers a good approximation, but, for the calculation of the total volume, this method shows still a wide variance.</p><p>The method will be applied to seismic and infrasound data collected on three different test sites in the Alps: Gadria (South Tyrol, Italy), Lattenbach (Tyrol, Austria), and Cancia (Belluno, Italy).</p>

scholarly journals Acoustic module of the Acquabona (Italy) debris flow monitoring system

2005 ◽  
Vol 5 (2) ◽  
pp. 211-215 ◽  
Author(s):  
A. Galgaro ◽  
P. R. Tecca ◽  
R. Genevois ◽  
A. M. Deganutti
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Regression Line ◽  
Front Velocity ◽  
Peak Discharge ◽  
Physical Parameters ◽  
Flow Depth ◽  
Ground Vibrations ◽  
Mountain Areas ◽  
Flow Monitoring

Abstract. Monitoring of debris flows aimed to the assessment of their physical parameters is very important both for theoretical and practical purposes. Peak discharge and total volume of debris flows are crucial for designing effective countermeasures in many populated mountain areas where losses of lives and property damage could be avoided. This study quantifies the relationship between flow depth, acoustic amplitude of debris flow induced ground vibrations and front velocity in the experimental catchment of Acquabona, Eastern Dolomites, Italy. The analysis of data brought about the results described in the following. Debris flow depth and amplitude of the flow-induced ground vibrations show a good positive correlation. Estimation of both mean front velocity and peak discharge can be simply obtained monitoring the ground vibrations, through geophones installed close to the flow channel; the total volume of debris flow can be so directly estimated from the integral of the ground vibrations using a regression line. The application of acoustic technique to debris flow monitoring seems to be of the outmost relevance in risk reduction policies and in the correct management of the territory. Moreover this estimation is possible in other catchments producing debris flows of similar characteristics by means of their acoustic characterisation through quick and simple field tests (Standard Penetration Tests and seismic refraction surveys).

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