Debris Flow Phenomena Research Articles

Assessment of geo-disaster in the snowmelt season considering climate changes

In this study, we reproduced avalanches and debris flow phenomena using the debris flow analysis tool, iRIC Morpho2DH, and laboratory-test apparatus. In the laboratory tests, we reproduced aggregates of snow, water, and soil that form during avalanches and debris flows using a pot mill turntable. Consequently, the possibility of forming aggregates of snow, water, and soil during debris flow phenomena was analyzed. Evaluation of avalanche and debris flow phenomena during the snowmelt season was conducted by considering the characteristics of these aggregates. Based on the results, the validity of the analysis method for the Nozuka disaster in Japan was examined. Moreover, the risks associated with future avalanches and debris flow phenomena under changing climatic conditions were studied using the Policy Decision making for Future climate change (d4PDF) database.

Slump-flow channel test for evaluating the relations between spreading and rheological parameters of sediment mixtures

Understanding debris flow phenomena and modeling them effectively requires accurate estimation of their rheological parameters. This study introduces a simple approach defined as the “slump-flow channel test”, which employs a horizontal rectangular channel to evaluate these parameters. The results of slump-flow channel tests indicate that the spreading parameters (spread length, angle of reach, and time to final spread) of sediment mixtures are strongly influenced by their sediment fractions and rheological properties. An empirical analysis of the temporal evolution of the spread length and spread velocity was carried out employing both experimental and simulation results. The numerical simulation of the slump-flow channel tests was performed using the Flow-3D software. Both experimental and simulation results demonstrate that the spreading and the rheological parameters of sediment mixtures exhibit strong correlations and this implies that the rheological parameters of sediment mixtures can be evaluated indirectly using a simple slump-flow channel test.

The Emerging Widespread Debris Flow Disasters in Tropical Terrain of Peninsular Malaysia: Understanding the Risk and Policy Intervention

Several widespread debris flow disasters stroke Peninsular Malaysia in between 2021 and 2022, scattered across the country. It was the first time for this hazard being nationally recognised as a type of geological disaster in the country. Debris flow disaster is not a new phenomenon. It had been recorded since 1995, however, in the past they were isolated incidents and did not attract much attention. The recent widespread debris flow disasters started in Gunung Jerai, Kedah on 18 August 2021; followed by similar incidents but in 3 different states concurrently in (1) Bentong, Pahang, (2) Hulu Langat, Selangor, and (3) Jelebu, Negeri Sembilan on 18 December 2021; Kenyir, Terengganu on 27 February 2022; and finally at Gunung Inas, Kedah on 4 July 2022. These disasters sparked numerous technical and social issues where heated debates on whether they were purely due to natural processes or caused anthropogenic activities. Previously, debris flow phenomena in Malaysia were so rare, that the term ‘debris flow’ was not familiar to the lay public. The term of “debris flow” was often disregard or used interchangeable with ‘water surge’ phenomena by the media and public, especially for sudden sediment water surge from hilly upstream after intense rainfall at hillside river catchment areas, normally occurs during the monsoon season. The ordinary water surge has significantly lesser level of destruction and momentum as compared to a debris flow with higher debris-type sediments. This paper discusses the emerging issues of debris flow in Malaysia and some initiatives being carried out in in facing the geohazard. The Department of Mineral and Geoscience Malaysia and a team of local geohazard experts have taken the lead to carry out studies to understand the sudden emergence of widespread and cascading debris flow events in Malaysia. As a result, proposal on policy intervention was put forward to the relevant government ministries; post-disaster programme has been continuously carried out to educate the communities on the geological disaster risks through community-based disaster risk management (CBDRM).

The Rosetta Stone Project – Integrating experimental results on debris flow mechanics across the scales: Next results

We present the combined efforts of a research network designed to address the many challenges in the experimental modelling of debris flow phenomena. The approach has been to use apparatuses of different functional arrangement and at different scale with identical and commonly sourced flow materials from the highly idealised (dry, coarse and uniform) to the highly complex (well graded, segregating, fluid saturated). Here we briefly present some key findings of the network and point to the research questions that are currently being addressed. This complementary view of experimental debris flows helps to constrain methodological artefacts/scale effects and to identify key processes responsible for the diverse appearance and often high mobility of debris flows.

Assessment of economic efficiency indicators of environmental protection measures during the construction of hydraulic engineering structures

In order to ensure the integral management of water and land resources during the implementation of environmental protection engineering measures, as well as to solve ecological problems, a macroeconomic approach directed at the final results is necessary. The traditional "narrow" economics of nature use is viewed as a single cycle of water and land resources and production waste and pollution, with insufficient attention paid to the economy itself ("black box"). For purposeful use of macroeconomics, it is necessary to build a vertical of natural productivity of each natural resource (chain), which will connect the primary natural factors with the production of final products. An effective concept of the rationalization of nature use and environmental protection against debris-flow phenomena and the matching economic mechanism of nature use in sectors and complexes can be developed and realized only after the development of the concept of development of the sector complexes and the whole economy. Regional features of the formation of the economic mechanism of nature use are important. The assessment of economic efficiency indicators of environmental protection measures during the construction of hydraulic engineering structures is discussed. The value of efficiency obtained by environmental activities is considered by the criteria for evaluating the efficiency of the investment project, where this criterion is called net discounted income, net discounted value, or modern net income. Functional-value analysis of environmental impact during the construction of hydraulic engineering structures, including the construction of high dams, for the realization of the analytical stage, a functional model is built based on the orography of the social-ecological-economic system. Based on theoretical and field scientific studies, the economic efficiency of the innovative debris-flow control structure has been established, the numerical value of which is equal to 16.15 USD per 1 longitudinal meter of the structure.

Rainstorm Magnitude and Debris Flows in Pyroclastic Deposits Covering Steep Slopes of Karst Reliefs in San Martino Valle Caudina (Campania, Southern Italy)

Debris flows that have occurred in the area of San Martino Valle Caudina (Campania, Southern Italy) are described by geomorphological and hydrological analyses, focusing on the recent event of December 2019. This area can be considered a key example for studying debris-flow phenomena involving the pyroclastic mantle that covers the karstified bedrock along steep slopes. A hydrological analysis of the time series of the maximum annual rainfall, of durations of 1, 3, 6, 12 and 24 h, was carried out based on a new approach to assess rainstorm magnitude. It was quantified by measuring the deviation of the rainfall intensity from the normal conditions, within a specified time period. As the time series of annual maxima are typically skewed, a preliminary transformation is needed to normalize the distribution; to obtain the Z-value of the standard normal distribution, with mean µ = 0 and standard deviation σ = 1, different probability distribution functions were fitted to the actual data. A specific boxplot was used, with box width Z = ±1 and whiskers length Z = ±2. The deviations from these values provide the performance of the distribution fits. For the normalized time series, the rates shown by the trends and relative significance were investigated for the available time series of 11 rain gauges covering the Western–Central Campania region. The most critical condition for the debris-flow initiation appears to occur when a severe or extreme rainfall has a duration ≥ 12 h. The trend analysis did not detect statistically significant increases in the intensity of the rainfall of duration ≥ 6 h.

Role of the Rheological Parameters in Debris Flow Modelling

Nowadays, the debris flow model has become an essential part of risk analysis and impact engineering. Coupled with field observations and historical records, these models have proven powerful tools to understand the behaviour of debris flow in complex terrain. However, their application poses several new challenges to scholars and engineers. A detailed understanding of the debris flow phenomena requires a sound knowledge of the shallow water equation and rheological model used to simulate the debris flow hazard. In this study, important rheological models used to analyse the debris flow process and their limitations have been highlighted. Furthermore, the suitability of the Voellmy-Salm rheological model has been studied for 2D pyroclastic flow taking different combinations of the coefficient of friction namely coulomb friction coefficient \\i,and turbulent coefficient of friction £ using IMEX SFLOW 2D dynamic continuum model. It was found that velocity and runout distances are significantly influenced by the variation of the coefficient of the turbulent friction © at a large scale. It is then concluded that the identification of a suitable rheological model is necessary to simulate the precise behaviour of complex and heterogeneous debris flow

Parametric Study of an Alpine Wet Debris Flow Event (Novalesa, Torino, Italy) Applying The Finite Volume Method (FVM). Comparison with Available Experimental Data

The Marderello torrent, located at an altitude ranging from 3538m to 900 m above sea level (Novalesa, Cenischia Valley, in Province of Turin) is known for its peculiar capability to generate, with relative frequency, important mud flows and debris (muddy debris flow). Accordingly, the CNR-IRPI (National Research Council) of Turin, since more than twenty years ago, selected this site in order to carry out field observations and measurements campaign. In this paper the muddy-debris flow event, occurred and monitored on July 22, 2016, was considered. The simulation of debris flow phenomena was performed by a 2D Finite Volume Method, solving PDE (Partial Differential Equation) based on the shallow-water approach, through a commercial numerical software. The mathematical-numerical model, beside hydrodynamic model, may also include solid transport and movable river bottom, not explored yet at this stage of the research. First of all, a morphological vectorial model of the basin under study was created and implemented as inputs. The inflow boundary conditions, deriving from the hydrogram consisting of values measured at the monitoring gauge were considered. Several parametric analyses were performed in order to individuate the best values fitting the experimental data concerning the estimated height of the front over time. To this purpose, different available rheological options such as Turbulent-Coulomb, Turbulent-Yield, Turbulent-Coloumb-Yield, and Full Bingham were selected and tested. The comparison with the values collected by the monitored event allowed to define the best values of the parameters to be used. The selected approach and the related model construction can be considered useful and suitable tools in order to study and to simulate this kind of phenomena.

Debris flows in the Hrubý Jeseník Mountains, Bohemian Massif, Czech Republic

ABSTRACTDebris flows in mountainous areas have a deep geomorphic impact on slope dynamics. Their activity corresponds with heavy rainfall events. The estimation of these events depends not only on meteorological prediction but also on the knowledge of their spatial occurrence. As debris flows usually occur in the same paths with different frequencies during the Quaternary period, spatial data are needed to obtain more detailed information about debris flow phenomena. This was the reason for the creation of the presented map of debris flow features in the Hrubý Jeseník Mts. A total of 95 debris flow paths and 47 debris flow accumulations (including lobes or levees) have been mapped in the field. A comprehensive spatial database of debris flow features is shown in the map, which could be helpful for future research of Quaternary geomorphic evolution of the landscape and for forest management and state administrative authorities in future planning.

Hydraulic Physical Model of Debris Flow for Malaysia Case Study

In the recent decade, several debris flow events occurred and caused hundreds of deaths, missing or injury and damaged many facilities. In addition to causing significant morphological changes along riverbeds and mountain slopes, these flows are frequently reported to bring about extensive property damage and loss of life. Debris flow phenomena occasionally occur in Malaysia and numbers of death reported cause by this event. In order to investigate the debris flow and its deposition process, experiments were conducted at the School of Civil Engineering Laboratory, Universiti Sains Malaysia. The models consists of three main parts which are water tank, rectangular flume and deposition board. A high speed video camera (HSVC) had been placed nearly downstream of the rectangular flume to capture the movement characteristics of particle grain. From this study, the characteristics of particle routing segregation can be understand clearly, therefore this input will be a very useful information to other researchers for further investigation in terms of knowledge sharing between researchers. Catastrophic cause by debris flow event can be minimized therefore in term of economy losses can be reduce and human life can be safe.

Simulative modeling of the soil erosion processes

Abstract In order to visualize the negative consequences of soil erosion processes running in Georgia, namely in the Gldaniskhevi ravine within the territory of Tbilisi, research field integrated polygon has been arranged on the eroded slope chosen beforehand. At the control area of polygon 24 field experiments have been carried out to study the dynamics of the formed erosion processes under the different intensity precipitation conditions, whereby scour parameters were being measured (average depth – h, average width – b, B). For estimating the exactness of calculations done on the results of measurings accomplished with the purpose to definite the intensity of soil erosion processes, the method of least squares have been used, on the base of which contour dependence between investigated parameters and therefore validity of the accomplished researches have been ascertained. Simulative modeling of the soil erosion processes has been accomplished by means of special computer programs, which has shown, that during 167 days at the control area of the field polygon the eroded slope gulleying processes have been significantly strengthened, that nowadays can be also noticed on the slopes outside the polygon, on account of which can be concluded, that in order, to prevent expected landslide and debris flow phenomena in the river Gldaniskhevi ravine, implementation of urgent effective anti-erosive measures is needed.

A probabilistic multidimensional approach to quantify large wood recruitment from hillslopes in mountainous-forested catchments

Large wood (LW) plays a key role in physical, chemical, environmental, and biological processes in most natural and seminatural streams. However, it is also a source of hydraulic hazard in anthropised territories. Recruitment from fluvial processes has been the subject of many studies, whereas less attention has been given to hillslope recruitment, which is linked to episodic and spatially distributed events and requires a reliable and accurate slope stability model and a hillslope-channel transfer model.The purpose of this study is to develop an innovative LW hillslope-recruitment estimation approach that combines forest stand characteristics in a spatially distributed form, a probabilistic multidimensional slope stability model able to include the reinforcement exerted by roots, and a hillslope-channel transfer procedure. The approach was tested on a small mountain headwater catchment in the eastern Italian Alps that is prone to shallow landslide and debris flow phenomena. The slope stability model (that had not been calibrated) provided accurate performances, in terms of unstable areas identification according to the landslide inventory (AUC = 0.832) and of LW volume estimation in comparison with LW volume produced by inventoried landslides (7702 m3 corresponding to a recurrence time of about 30 years in the susceptibility curve). The results showed that most LW potentially mobilised by landslides does not reach the channel network (only about 16%), in agreement with the few data reported by other studies, as well as the data normalized for unit length of channel and unit length of channel per year (0–116 m3/km and 0–4 m3/km y−1).This study represents an important contribution to LW research. A rigorous and site-specific estimation of LW hillslope recruitment should, in fact, be an integral part of more general studies on LW dynamics, for forest planning and management, and positioning in-channel wood retention structures.

A combined triggering-propagation modeling approach for the assessment of rainfall induced debris flow susceptibility

Rainfall-induced shallow slides can evolve into debris flows that move rapidly downstream with devastating consequences. Mapping the susceptibility to debris flow is an important aid for risk mitigation. We propose a novel practical approach to derive debris flow inundation maps useful for susceptibility assessment, that is based on the integrated use of DEM-based spatially-distributed hydrological and slope stability models with debris flow propagation models. More specifically, the TRIGRS infiltration and infinite slope stability model and the FLO-2D model for the simulation of the related debris flow propagation and deposition are combined. An empirical instability-to-debris flow triggering threshold calibrated on the basis of observed events, is applied to link the two models and to accomplish the task of determining the amount of unstable mass that develops as a debris flow. Calibration of the proposed methodology is carried out based on real data of the debris flow event occurred on 1 October 2009, in the Peloritani mountains area (Italy). Model performance, assessed by receiver-operating-characteristics (ROC) indexes, evidences fairly good reproduction of the observed event. Comparison with the performance of the traditional debris flow modeling procedure, in which sediment and water hydrographs are inputed as lumped at selected points on top of the streams, is also performed, in order to assess quantitatively the limitations of such commonly applied approach. Results show that the proposed method, besides of being more process-consistent than the traditional hydrograph-based approach, can potentially provide a more accurate simulation of debris-flow phenomena, in terms of spatial patterns of erosion and deposition as well on the quantification of mobilized volumes and depths, avoiding overestimation of debris flow triggering volume and, thus, of maximum inundation flow depths.

Recent damaging events on alluvial fans along a stretch of the Tyrrhenian coast of Calabria (southern Italy)

Debris flow and flood phenomena constitute the main natural hazards on alluvial fans. These processes, often occurring during intense rainfall events, may put many communities living on fan surfaces at high risk. This article focuses on an area along the Tyrrhenian coast of Calabria (southern Italy) where a set of mountain front alluvial fans has developed on the narrow coastal plain. This area has been heavily exploited, and tourism constitutes an important source of income. Rainfall events occurring in 2009, 2010 and 2011, albeit not significantly intense, induced debris flows endangering the population and damaging private property and infrastructures. The analysis highlighted that in the study area the risk due to debris flow and the vulnerability of the area have increased as a consequence of both the reactivation of construction processes in the alluvial fan feeder basin and the intense development of human activities in the same areas. The construction of protection facilities and the loss of the historical accounts of past catastrophic events have encouraged this development. Given the characteristics of the study area, the choice and design of the most appropriate measures need particular attention.

Some key topographic and material controls on debris flows in Scotland

Debris-flow phenomena were investigated at six study sites across upland Scotland using a combination of laboratory and field-based analyses. In agreement with previous research, higher spatial frequencies of debris-flow paths were measured in areas underlain by coarse-grained intrusive igneous and arenaceous sedimentary bedrocks compared with metamorphic and extrusive igneous geologies. A strong relationship between critical state friction angle of sampled initiation zone soils and spatial frequency of debris-flow paths suggests that this trend is attributable to generally lower shear strengths in sandier hillslope material generated from coarser grained bedrocks. Topographic controls on debris-flow susceptibility are demonstrated by higher numbers of debris-flow paths at sites with persistently steep upper slopes (≥30°) and a higher occurrence of potential initiation zones. Strong correlation between debris-flow magnitude and slope length shows that longer mass movements tend to produce higher volumes of material and terminal deposits that travel further at the slope foot. In the cases studied here this reflects greater opportunity for accumulation of fresh material during the transport phase, particularly in the case of long channelized flows. The highest levels of hazard are likely to occur where these topographic and material characteristics conducive to heightened susceptibility and magnitude coincide.

Studies of Flexible Barriers Under Debris Flow Impact: An Application to an Alpine Basin

The aim of this paper is to analyze the most relevant aspects that influence the interaction between debris flow phenomena and protection barriers. The volume of the debris and its lithological nature are conditioning the barrier size and strength. This system is often complicated by environmental and climate influences that need to be taken into consideration as well; therefore, a correct design of a protection barrier system in an alpine basin is a complex procedure that needs to be rationalized. This paper will concentrate on the barrier dimension design proposing a rational scheme of study of the global problem. The application to an Alpine basin is reported.

A numerical model for the simulation of debris flow triggering, propagation and arrest

In this paper, it is described the development and the assessment of a 1D numerical procedure for the simulation of debris flow phenomena. The procedure focuses on: (1) the rainfall triggering, and the effects induced on slope stability by both rainfall infiltration and groundwater dynamics; (2) the possible inception of debris flows during the propagation phenomenon itself, due to the actions exerted on the slope by the already triggered flowing masses; (3) the propagation phenomenon over complex topographies; (4) the non-Newtonian internal dissipative processes that develop within the sediment–water mixture; (5) the effects induced by the evolution of the boundaries where the propagation phenomenon occurs; (6) the run-out and arrest phenomena. In order to show the performance and capabilities of the model, the results of its application to an analytic test and to laboratory experimental tests are first analyzed, and finally, the application to a plausible debris flow scenario, taken from a real case study, is discussed.

One-dimensional Simulation of Debris-flow Inception and Propagation

The paper describes the development and the assessment of a numerical model for the simulation of debris flow phenomena. Aiming at this, after having considered the causes of triggering, this work focuses on the simulation of propagation characteristics of the masses mobilized, taking into account both the actual internal dissipative processes characterizing the sediment-water mixture and the effects induced by the modification of the boundaries where the flow takes place. The propagation model implemented is based on the one-dimensional hyper-concentrated shallow flows equations, suitable to take into account also the solid and fluid mass exchanges with the bottom. This system of non-linear partial differential equations is integrated by means of a one-dimensional finite volume scheme, second-order accurate in space and time. In order to show the performance and capabilities of the model, the results of its application to a laboratory dam-break experiment are analysed, and finally the application to a real-world test-case is discussed.

Classification of debris flow phenomena in the Faroe Islands

Landslides and debris flow phenomena in particular constitute a threat to human activities in the Faroe Islands. As a contribution to ongoing landslide risk management research, this paper proposes a classification scheme for debris flow phenomena in the Faroe Islands. The scheme, produced through a multidisciplinary study involving geomorphological fieldwork and qualitative collection of indigenous landslide knowledge, presents physical characteristics to classify debris flow phenomena into groups named with Faroese terms. The following landslide definitions are proposed. Brekku-skriðulop (English translation: hillslope debris flow): a very rapid to extremely rapid non-channelised downslope movement of remoulded colluvium and eventually fragmented rock, initiated as a debris slide in colluvial soil (type 1) or from rock fall (type 2). Áar-skriðulop (English translation: channelised debris flow): a very rapid to extremely rapid channelised downslope movement of remoulded colluvium and/or talus/fluvial material and eventually fragmented rock, initiated as a debris slide in colluvial soil (type 1), from rock fall (type 2) or from mobilisation of talus/fluvial material (type 3). The scheme, which is compatible with international landslide classification systems, significantly increases the knowledge of debris flow phenomena and promotes a consistent terminology of these within the Faroe Islands.

Water storage mapping of pyroclastic covers through electrical resistivity measurements

The knowledge of the geological setting of pyroclastic covers and their water content distribution represents crucial information for stability analyses of slopes potentially subject to debris-flow phenomena. The study we here present would provide a contribution to this issue by means of an approach based on electrical resistivity measurements. Specifically, we describe the results of high-resolution 2D resistivity surveys carried out in a test area on Sarno Mountains (Campania Region – Southern Italy), where shallow landslides involving pyroclastic soils periodically occur triggered by critical rainfall events. We discuss the results in relation to the geology of the area in order to locate characteristic horizons of pyroclastic soils below the ground surface. Then, on the basis of a laboratory characterization of pyroclastic samples collected from the same test area at representative depths, we provide an estimation of the soil water content distribution in the field. Finally, we analyze temporal variations of the soil water content distribution by comparing the data of two surveys carried out in the autumnal and spring seasons , respectively. ► Water is the main driver of pyroclastic debris-flow phenomena. ► We examine changes of soil water content in the field using electrical resistivity tomography. ► Empirical relationships between soil resistivity and effective saturation are found. ► Geoelectric monitoring can identify the thickness of pyroclastic layers in saturated condition.