Debris Floods Research Articles

Imbrication fabric as a diagnostic feature for the genetic classification of gravels deposited by fluid‐gravity versus sediment‐gravity subaerial flows

AbstractGravel transport in subaerial environments occurs through different flows that are conveniently classified as debris flows, debris floods and water flows based on their distinct morpho‐sedimentary dynamics and different implications for geomorphic hazard. Because distinctive features allowing gravelly sedimentary bodies to be ascribed to related genetic process are still a matter of discussion, this study aims to establish whether imbrication fabric represents a sedimentological fingerprint potentially applicable towards a more robust genetic classification of gravels. We analysed the fabric of 1007 imbricated clasts from modern and ancient deposits. Our results highlight statistically significant differences between imbrication fabrics in gravels deposited by different flows. Particles imbricated by water flows are typified by low imbrication angles (median of 35°) and elongated clasts oriented perpendicular to the flow. In contrast, debris‐flow gravels exhibit high imbrication angles (median of 65°) and elongated clasts oriented parallel to the flow. Debris‐flood deposits display elongated clasts both parallel and transverse to the main flow and intermediate values of imbrication angle (median of 47°). We propose that imbrication angles result from the combination of stability‐driven selection—a process acting under tractional transport and promoting the remobilization of high‐angle imbrication fabrics—and shear‐stress‐driven overriding—a mechanism leading to the formation of the higher imbrication angles—with the first dominating in water flows and the latter being effective in mass transport processes. The progressive change in imbrication fabrics from fluid‐gravity to sediment‐gravity flow deposits offers easily quantifiable sedimentological evidence to help in distinguishing genetic processes that contribute to the accumulation of gravels in alluvial and colluvial settings. Analysis of imbrication fabric can add valuable information, particularly as regards the classification of (1) coarse deposits in stratigraphic records and (2) modern debris flood deposits.

The White Hills Gravel of central Victoria: an anomalous Paleogene very coarse-grained fluvial deposit

The White Hills Gravel is the coarsest fluvial gravel within Victoria, southeastern Australia, and outcrops discontinuously across a substantial part (>35 000 km2) of this region. It overlies a major regional unconformity representing >300 Ma, and is dominated by conglomerate (61% of beds), with less abundant sandy lithofacies (36% of beds) and rare mudstones (3% of beds). The sedimentary characteristics of the basal conglomerates (e.g. thick bedding, common boulders, very poor sorting and in places chaotic appearance) indicate deposition by significant paleofloods, including debris floods, within braided streams that had similar flow directions to the modern drainage. Paleohydraulic calculations estimate that the paleofloods had discharges exceeding >7200 m3 s−1, over 25 times the largest recorded floods in the same valleys. These paleofloods were probably caused by exceptionally severe storm systems, consisting of many individual thunderstorms. Deposition of the White Hills Gravel has previously been attributed to the mid-Cretaceous uplift that affected southeastern Australia, but the maximum possible age of the formation (early Paleocene) is too young for this to be a viable explanation. Instead, the White Hills Gravel may have been deposited during a period of increased precipitation at the Paleocene–Eocene Thermal Maximum (ca 56 Ma), when an intensification of the hydrological system generated significant sediment responses within fluvial systems around the world. Modelling indicates that this climatic event had a substantial impact in Victoria, where increases in mean annual precipitation (50–60%) and the most extreme rainfall rates achieved by the strongest storms (60–70%) were some of the largest globally, and frequent and intense Atmospheric Rivers were an important part of the hydrological system. These factors, together with a period of disturbed vegetation cover, resulted in major paleofloods that could have deposited the coarse-grained conglomerates of the White Hills Gravel.

Development and application of an integrated methodology for post‐disaster field investigation of debris floods

AbstractDebris floods commonly occur in steep channels with an abundant sediment supply, and they can cause significant damage, primarily due to their higher sediment concentrations and negative impacts upon bank erosion, deep scouring and aggradation. These key hazards pose challenges for traditional assessment methods, making quantification difficult. This became obvious during a recent catastrophic debris flood that occurred on July 12, 2022, in the Heishuigou catchment (102 km2), northern Sichuan Province, China. In this case study, we developed an integrated methodology for assessing this debris flood event by incorporating field surveys, hydrological and hydraulic modelling and sediment transport calculations. Detailed information such as topographic maps, photographs, deposits, grain size distributions and inundation depths was collected to analyse the material sources, validate the parameters and conduct model calculations. The peak debris flood discharge and the supra‐critical bed shear stress ratios, estimated from hydrological and dynamic models, were incorporated to analyse the debris flood's typology and characterize its destructive mechanisms. The regional frequency–volume relationship established through bedload transport calculations was calibrated using the volume of the deposits determined via field investigation. These methods not only contribute to a comprehensive understanding of debris floods but also provide valuable support for future risk assessments and mitigation designs.

Life cycle assessment of green–grey coastal flood protection infrastructure: a case study from New Orleans

The study compared the life cycle environmental impacts of three coastal flood management strategies: grey infrastructure (levee), green–grey infrastructure (levee and oyster reef), and a do-nothing scenario, considering the flood damage of a single flooding event in the absence of protection infrastructure. A case study was adopted from a New Orleans, Louisiana residential area to facilitate the comparison. Hazus software, design guidelines, reports, existing projects, and literature were utilized as foreground data for modelling materials. A process-based life cycle assessment was used to assess environmental impacts. The life cycle environmental impacts included global warming, ozone depletion, acidification, eutrophication, smog formation, resource depletion, ecotoxicity, and various human health effects. The ecoinvent database was used for the selected life cycle unit processes. The mean results show green–grey infrastructure as the most promising strategy across most impact categories, reducing 47% of the greenhouse gas (GHG) emissions compared to the do-nothing strategy. Compared to grey infrastructure, green–grey infrastructure mitigates 13%–15% of the environmental impacts while providing equivalent flood protection. A flooding event with a 100-year recurrence interval in the study area is estimated at 34 million kg of CO2 equivalent per kilometre of shoreline, while grey and green–grey infrastructure mitigating such flooding is estimated to be 21 and 18 million kg, respectively. This study reinforced that coastal flooding environmental impacts are primarily caused by rebuilding damaged houses, especially concrete and structural timber replacement, accounting for 90% of GHG emissions, with only 10% associated with flood debris waste treatment. The asphalt cover of the levee was identified as the primary contributor to environmental impacts in grey infrastructure, accounting for over 75% of GHG emissions during construction. We found that there is an important interplay between grey and green infrastructure and optimizing their designs can offer solutions to sustainable coastal flood protection.

Bivariate analysis of short-duration extreme rainfalls. Application to the study of the debris floods (alluviums) in the Funchal region (Madeira Island)

Intense rainfalls and debris floods are familiar occurrences in Madeira Island (Portugal); but, understanding how intense rainfall relates to this type of floods is limited. This research seeks to characterise extreme rainfall events measured at the Funchal rain gauge station and to analyse their relationship with the region’s debris flood records. Contrary to other studies, a multivariate approach was performed to describe those relationships. To identify the extreme hourly rainfall events, the annual maximum series (AMS) technique was applied to a record of hourly time-series data covering a period of 34 years. By applying bivariate copula analysis to coupled AMS and cumulative rainfall series, joint and conditional return periods were calculated. The results suggested that the extreme rainfall events causing debris flood events tend to have higher return periods than those with no debris flow generation. The exceptionality of the late February 2010 deadly event is reaffirmed. This work assists our understanding as to how intense rainfall events relate to debris flood events, and shows the benefit of copulas in providing new insights in hydrologic studies.

Modeling Multiphase Debris Floods Down Straight and Meandering Channels

Natural debris floods travel in straight and meandering courses. The flow behaviour greatly depends on the volume fractions of solid and fluid, as well as on their dynamic interactions with the channel geometry. For the quasi three-dimensional simulations of flow dynamics and mass transport of these floods through meandering and straight channels, we employ a two-phase debris flow model to carry out simulations for debris floods within straight and sine-generated meandering channels of different amplitudes. The results for different sinuous meandering paths are compared with that in the straight one in terms of phase velocity, downslope advection and dispersion, depths of the maxima, deposition of mass, position of front and rear parts of the solid and fluid phases, and also the flow dynamics out of the conduits. The results reveal the slowing of the flow and increase of momentary deposition of the mixture mass in the vicinity of the bends along with the increasing sinuosity. The numerical experiments are useful to better understand the dynamics of debris floods down meandering channels as seen in the natural paths of the rivers as well as already existing channels like episodic rivers in hilly regions. The results can be extended to propose some appropriate mitigation strategies.

The Prediction of Debris Flow Based on Eruption and Rainfall Event for River Infrastructure Mitigation: Study Case Opak River, Sleman Regency

Mount Merapi is a volcano active in Indonesia. The eruption that occurred in 2010 was a major eruption with a return period of 100 years. Dominant debris to the Opak – Gendol Watershed; the biggest debris flood occurred in 2010 – 2011. One of the disaster mitigations on the Opak River is the Sabo Dam infrastructure. Currently, in the upper reaches of the Opak River, there are 5 Sabo Dams. In 2022, 2 additional Sabo Dams were built, namely OP RRC4 and OP RRC3a. This study will be used modelling 2D HEC-RAS Non-Newtonian before the construction of 2 Sabo Dams and after the construction of 2 Sabo Dams with river geometry measured in 2020 and flood discharge as measured from rainfall triggering debris flow on 03 January 2011, from this rainfall a 6-hour rain distribution was carried out using the PSA coefficient to be input in the HEC-HMS, the hydrological parameters used on 03 January 2011, were used to calculate the Q100 flood discharge. The results of modelling at the observation point using the Q100 showed that the elevation of the debris flow after the presence of the new Sabo Dam series could be reduced by up to 47.21 %, Sabo Dam effectively reduces the rate of debris flow to reduce the potential debris flood.

The Effect of Sabo Works Design and River Improvement on the Magila River with Consideration on Morphological Changes Influenced by Debris Flow Events

The morphological changes of a river due to debris flow are essential considerations in understanding the dynamics of a river. The Magila River, located in the Sigi Regency, Central Sulawesi Province, is a small river with an area of approximately 125 hectares, but the average riverbed slope exceeds 10%. This river faced water damage issues, such as debris floods on December 12, 2019, and overflowing floods on October 11, 2022. Based on the ongoing mitigation (Sabo Works and River Improvement), an analysis of flow modeling through HEC-RAS software with non-Newtonian parameters is also being conducted. Simulations are performed on both the existing river scenario and the design river scenario. The flood and sediment transport simulations indicate that the capacity of the existing river is insufficient to accommodate the planned 100-year return period flood discharge, leading to overflow in several river sections with a maximum inundation height of 42.80 centimeters. The river also tends to experience riverbed degradation, triggering landslide events. In contrast, in the design river, overflow in river sections is reduced, although some areas still experience inundation with a maximum height of 18 centimeters. The river morphology in this scenario is more stable, with a balanced level of degradation and aggradation. The conclusion of this research indicates that a series of ongoing mitigation efforts needs to be expanded to minimize the risk of floods but is already optimal in maintaining river morphology stability. The research findings are expected to be beneficial in maximizing the management of the Magila River.

Stability analysis of rainfall-induced landslides: A case study of a hilly area in Bangladesh

Rainfall-induced landslides stand as the prevailing geohazard in tropical and subtropical regions. The ongoing global climatic changes have introduced a wave of anomalous rainfall events across the world. These abnormal weather patterns have triggered numerous landslide incidents, resulting in significant loss of life and property. To develop early warning systems for such threats to people in mountainous areas of Chittagong, Bangladesh, it requires an in-depth understanding of the geo-environmental properties of soil slopes under heavy rainfall. Historical records reveal that rainfall in total exceeding 150–250 mm has resulted in both localized slope collapses and debris floods. When it rains heavily, rainwater infiltrates initially unsaturated slopes, elevating the degree of saturation while decreasing soil suction. Consequently, the reduced shear strength along the critical slip surface diminishes the factor of safety (FoS), and slope failure occurs. As a result, studies of soil-water characteristics have been conducted, followed by laboratory testing at the impacted sites, and the study found that rainfall and soil type (fine-grained silt) were the most critical factors behind landslides. The mechanism of slope failure is also demonstrated using a simple numerical infiltration model and a slope stability equation. The soil characteristics, the saturated volumetric water content (θs), closely match the field water holding capacity (θf), with a minor difference of 4-8%, and the drainage condition at the bottom of the slope appear to be important factors. Application of these test results to an early warning system for landslides and flash floods is finally demonstrated based on some simplifying assumptions.

Flood Debris Quantification and Comparison Based on the Removal and Disposal Operation: Postdisaster Study of Beaumont, Texas Following Hurricane Harvey

Accurate forecasts and estimates of disaster debris are critical for effective debris management planning. However, detailed postdisaster waste data to validate and improve debris predictions is often unavailable. In this study, a postdisaster waste dataset collected in Beaumont, Texas, following widespread flooding from Hurricane Harvey that included debris tonnages and coordinate locations of each debris removal in residential areas was investigated. The dataset was utilized to quantify the amount of debris produced, identify the factors that influenced debris generation in different areas of the city, and compare Beaumont debris tonnages to predictive models. The study found that the type of flooding (riverine versus urban) had the highest influence on debris generation. Riverine flooded areas generated twice the debris tonnage as urban flooded areas. Elevation appeared to influence debris generation when considered with the type of flooding. FEMA’s correlation for flooded personal property was within the same magnitude of debris quantities, while other methods significantly overpredicted debris quantities (up to one order of magnitude) due to their generality. However, they can be adapted for flood-generated debris. Urban flooding is an increasingly prevalent issue following a natural hazard and generates considerable amounts of debris, but is not addressed in current disaster management plans. Estimation methods that consider urban flooding should be developed.

Torrential Hazards’ Mitigation Measures in a Typical Alpine Catchment in Slovenia

Different sediment-related disasters due to torrential hazards, such as flash floods, debris flows, and landslides, can occur in an Alpine torrential catchment. When protecting infrastructure and human lives, different structural and non-structural protection measures can be used to mitigate permanent and future risks. An overview of the mitigation measures constructed near the Krvavec ski resort in northwest Slovenia (Central Europe) is presented. In May 2018, an extreme debris flood occurred in this area, causing significant economic damage. After the May 2018 event, different field investigations (i.e., geological and topographic surveys) and modeling applications (e.g., hydrological modeling, debris flow) have been conducted with the purpose of preparing the required input data for the design of protection measures against such disasters in future—due to climate change, more disasters are expected to happen in this torrential watershed. The mitigation includes the restoration of local streams, the construction of a large slit check dam for sediment retention, the construction of several smaller check dams and the construction of 16 flexible net barriers with an estimated ~8000 m3 retention volume for controlling in-channel erosion in steep torrential streams. Additionally, in order to observe and monitor potential future extreme events, an extensive monitoring system has been established in the investigated area. This monitoring system will cover measurements of flexible net corrosion, the estimation of concrete abrasion at check dams, periodical geodetic surveys using small drones (UAV), hydro-meteorological measurements using rainfall gauges and water level sensors. The recent extreme floods of August 2023 also hit this part of Slovenia, and this combination of technical countermeasures withstood the event and prevented large amounts of coarse debris from being transported to the downstream section and devastating infrastructure, as was the case in May 2018 during a less extreme event. Therefore, such mitigation measures can also be used in other torrential catchments in the Alpine environment.

Modeling and mapping the environmental impact of debris flow hazard on alluvial fans for sustainable development in Bangga and Poi Villages, Sigi, Central Sulawesi

On September 28, 2018, an Mw 7.5 Palu earthquake triggered massive landslides upstream, followed by 24 debris flood events that spread to 15 villages in Sigi from September 2018 to December 2021. Debris flow and flash floods on alluvial fans inundated lowland communities, causing severe property destruction and structural damage to bridges and roadways and resulting in an estimated 900 damaged houses. Understanding their historical occurrence is essential to sustainable fan development and minimizing their threat to infrastructure and human life due to their severe geohazard potential. Poi and Bangga Villages were affected by the disastrous debris flood in Sigi Regency, Central Sulawesi. This study aimed to create a landslide inventory map, a back-analysis model, and a damage and loss assessment (DaLAs) to evaluate the potential hazard and environmental impacts of debris flow on Sigi’s alluvial fans. The result of landslide mapping showed more than 400 mapped landslides within Bangga Village in various sizes and a massive landslide within Poi Village were digitized. Then, the back-analysis model overpredicted flow direction due to vegetation, infrastructure, and road information not covered by the digital elevation model (DEM). Finally, DaLAs shows the losses caused by damaged buildings were estimated at around 65.7 and 7.4 billion rupiah in Bangga and Poi Villages, respectively.

What drives major channel widening in mountain rivers during floods? The role of debris floods during a high-magnitude event

Our capability to accurately predict at the local scale the morphological changes in a mountain river affected by a severe flood is currently limited. Given the importance of including geomorphological hazards in flood risk evaluation, some improvements in this direction are required. In fact, on the basis of the controlling factors typically considered in the literature, that are the unit stream power (ωpk) and the confinement index (CI), a relatively broad spectrum of width ratios (WR = ratio between channel width after a flood and channel width before a flood) occurring in response to major floods is commonly observed in streams. We extended previous research focused on parameters that influence the morphological response of a channel to a severe flood by investigating the role played by the type of sediment transport process that occurs in a mountain river. In particular, we explored whether a relationship exists between debris flood (i.e. a condition characterised by extremely high bedload) and intense channel widening. The case study was the Cordevole River (the Dolomites, Italy) and four of its tributaries, which were affected by the severe flooding induced by the Vaia storm in October 2018. WR was determined at the sub-reach scale, and ωpk was calculated with consideration for the flood peak discharge ascertained via hydrological modeling. Despite the significant relationships found among WR, ωpk and CI, 21 sub-reaches (out of 144) of the studied stream network widened intensely reaching a WR higher than approximately 4, often to a substantially larger extent than predicted by statistical models. Such sub-reaches were certainly or probably affected by debris floods, leading us to infer that debris floods can induce widening processes that are more intense than those occurring in response to water flows. Having said that, debris floods do not automatically imply very intense widening. In addition to hydraulic and morphological constraints, the sediment transport processes possibly taking place at a sub-reach of a mountain river should be regarded as another driver of channel modifications during high-magnitude hydrological events.

MAMODIS - A low-cost monitoring system for debris flows based on infrasound and seismic signals

The automatic detection of sediment related disasters like landslides, debris flows and debris floods, gets increasing importance for hazard mitigation and early warning. Past studies showed that such processes induce characteristic seismic signals and acoustic signals in the infrasonic spectrum which can be used for event detection. The presented system MAMODIS (MAss MOvement Detection and Identification System) is a detection system for debris flows, debris floods and avalanches based on a combination of infrasound and seismic signals. The detection system consists of one infrasound sensor, one geophone and a microcontroller, where a specially designed detection algorithm is executed. This algorithm reliably detects events in real time directly at the sensor site. The setup can be easily installed beside a torrent or an avalanche path and therefore can be used as a low-cost and practicable solution for early warning. In addition, this system offers first information of the process-type and a rough estimation of the peak discharge and the total volume for debris flows and debris floods. These values are calculated from the infrasound and seismic signals. Currently the system is installed on several test sites in Austria, Switzerland and Italy.

Log Crib Check Dam Performance under Multiple Debris-Flow Loadings – East Gate Landslide, British Columbia, Canada

Check dams are used in gullies to prevent vertical downcutting of the thalweg. Check dams built as log crib structures are common in steep creeks prone to floods or debris floods. Recent experience with performance of log crib check dams subject to debris flow loadings is less common, as those check dams are often made from reinforced concrete, steel or masonry. This paper summarizes our experience with six log crib check dams built in a gully at East Gate Landslide, between Revelstoke and Golden, BC, Canada. The log crib check dams are subjected to multiple debris flow events every year. The project started as a pilot study and the design is adjusted before the next construction season, based on performance experience with previously built structures.

Characteristics of July 2019 Cherna Mesta River flash flood

One of the biggest rivers in the southern part of the Balkan peninsula – the Mesta River is wellknown for frequent flash floods, especially in the upper river course. As a result of severe storms and related heavy rain in mid-July 2019, the Cherna Mesta River flooded, and this resulted in heavy damage to the road infrastructure and water-supply systems. All data indicate that this was not a usual water flood, instead at peak flow, the river carried a huge amount of gravel. Our mapping of erosional and depositional features related to the 2019 event, as well as geomorphological analysis, allows for distinguishing distinct sectors along the river valley. Most hazards are defined in the lower reaches of the Cherna Mesta River, where the processes of channel aggradation and lateral erosion are pronounced. The field analysis of the flood-related deposits indicates the operation of debris flood and hyperconcentrated and water flood processes.

Monitoring the role of soil hydrologic conditions and rainfall for the triggering of torrential flows in the Rebaixader catchment (Central Pyrenees, Spain)

Torrential flows (debris flows and debris floods) are mainly triggered by precipitation and soil hydrological processes. Most early warning systems in torrential catchments are rainfall-based. However, this approach can result in frequent false positives, due to its pure black-box nature, in which soil water conditions are neglected. We aim to contribute to the understanding of the conditions required for triggering torrential flows by considering also in situ measurements of soil water content. Herein, monitoring data of 12 years of rainfall and torrential flow occurrence (2009–2020) and 8 years of soil hydrologic conditions (2013–2020) in the Rebaixader catchment (Central Pyrenees, Spain) are analyzed. The dataset includes more than 1000 rainfall events and 37 torrential flows. First, rainfall thresholds using maximum rainfall intensity (Imax) and mean intensity (Imean) are defined. For the 2013–2020 dataset, which includes 15 torrential events, the Imean threshold predicted 2 false negatives and 73 false positives (positive predictive value, PPV, of 15.1%) and the best Imax threshold predicted also 2 false negatives but only 11 false positives (PPV of 54.2%). However, our observations confirmed quantitatively that the lower is the soil moisture the higher is the rainfall intensity to trigger torrential flows. Then, we combined Imax and volumetric water content at 15 and 30 cm depth to define a hydro-meteorological threshold. This latter threshold reduced false negatives to 1 and false positives to 8 and increased the PPV to 63.6%. These results confirm that soil hydrological conditions are key factors for torrential flow triggering and may improve early-warning predictions.

Analisis Karakteristik Hujan Ekstrim Menggunakan Model Iklim di Wilayah Gunung Merapi

Extreme rainfall is one of the trigger factors for debris floods in stratovolcanos. It caused by volcanic materials will be easily eroded in large quantity with surface water flow as the result of extreme rainfall. Extreme rainfall is avnatural phenomenon which is often related with climate change. In the future, changes in extreme rainfall characteristics may occur. Therefore, it’s necessary to conduct extreme rainfall analysis for historical and future periods. In this study, the characteristics of rainfall analyzed were the variability of extreme rain as shown by trend analysis of extreme rain indices namely RTOT. Hourly rainfall data at eight rain stations used as input. Future rainfall data was projected using the global climate model CanESM2 (RCP4.5 and RCP8.5 and downscaling process using Statistical Downscaling Model (SDSM). Comparison of the projection rainfall with historical rainfall shows a different trend at each station. Increasing trend occurred at four stations including Plosokerep, Pucanganom, Sopalan, and Talun stations, with the highest increasing trend occurring at Sopalan stations. In addition, there was also a decreasing trend that occurred at Ngandong station for both scenarios and at Sorasan station in the RCP8.5 scenario. The Jrakah and Randugunting stations show a steady trend.

Failure process of a lateral slope deposit and its effect on debris flood formation

Failure process of a lateral slope deposit and its effect on debris flood formation

Modeling of individual debris flows based on DEMNAS using Flow-R: A case study in Sigi, Central Sulawesi

On 2018 September 28, 18:03 a local time (10:03 am UTC), the Mw 7.5 earthquake with a focal depth of about 20 km devastated the Palu region in Central Sulawesi, Indonesia resulting in a catastrophic disaster and many casualties. The Palu earthquakes triggered widespread landslides upstream, contributing to the sizeable material volume accumulated in rivers and mountain slopes. After the Palu earthquake, from September 28, 2018, until December 2021, at least 24 events of debris floods have occurred, which have spread to 15 villages. As of late, the empirical debris flow model Flow-R, software for susceptibility mapping of debris flows at a regional scale, was published. While Flow-R's applicability on a regional scale has been confirmed in several studies, the calibrated case using back-analysis of individual debris flow events in Indonesia based on DEMNAS with a spatial resolution of 8.3 m has never been conducted. Local debris flows modeling using Flow-R was evaluated with three well-documented debris flow events on the break slopes on the west and east sides of the Palu Valley. Quantitative analysis was carried out in this study to assess the accuracy, positive predictive value, and negative predictive value of models. First, the result shows the individual back-analysis model of debris flows found good agreement between debris-flow paths predicted and documented debris flow path extent. However, the parameters for rheological properties and erosion rate required in the software are limited. Second, the quantitative analysis shows accuracy, positive, and negative predictive value, which varies considerably. Based on the study, Flow-R is not suitable for comprehensive hazard mapping but provides a direct information about possible run-outdebris flow paths. Furthermore, lateral spreading and friction of Flow-R model results can be used to calibrate the process with rheological properties and erosion rate in other numerical modeling software, either for forward or back analysis.