L'inventaire forestier comme méthode de caractérisation spatiale de l'aléa chute de pierres

The contribution of tree inventories to the spatial characterisation of the rockfall hazard Rockfall is one of the most frequent natural hazards in mountain areas. The characterisation of rockfall activity in terms of frequency, intensity (energy) and dispersion (run-out distance) is essential for risk management, but is extremely complex due to the diffuse nature of this hazard and the gaps in historical records. In this study we show that trees can be reliable bioindicators to reconstruct rockfall activity. Our method is based on the combination of a systematic mapping of all trees (location, breast height diameter, species) and the complete recording of all visible scars. On an area of one hectare in the municipality of Saint-Guillaume (Vercors massif, French Alps) we recorded 793 trees and 2333 scars. The spatial distribution of the tree species and scars was used to locate the most active source areas and the most important rockfall trajectories and to show the decreasing rockfall activity with increasing distance to the source area and thus also the protective effect of the forest. The approach is particularly valuable in areas where historical records are lacking. It can be used in the future to 1) refine hazard zoning and 2) calibrate rockfall models. Thanks to the recorded tree data, the area could also be used as a marteloscope for practicing silvicultural interventions in the rockfall protection forest.

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An approach for evaluating the role of protection measures in rockfall hazard zoning based on the Swiss experience

Natural Hazards and Earth System Science ◽

10.5194/nhess-17-1127-2017 ◽

2017 ◽

Vol 17 (7) ◽

pp. 1127-1144 ◽

Cited By ~ 6

Author(s):

Erika Prina Howald ◽

Jacopo Maria Abbruzzese ◽

Chiara Grisanti

Keyword(s):

Methodological Framework ◽

Protection Measures ◽

Correct Operation ◽

Rockfall Hazard ◽

Step Procedure ◽

Hazard Zoning ◽

Swiss Experience ◽

Federal Guidelines ◽

Rockfall Protection

Abstract. Rockfall hazard zoning is essential for ensuring the safety of communities settled at the toe of potentially unstable slopes. Rockfall hazard zoning can be performed to include the effect of protection measures when land use restrictions might not be enough to mitigate hazards. The real effectiveness of the measures must be assessed to make sure they can play their role, especially in those cases when measures might have been installed at a given site for years. This article focuses on how to evaluate the effectiveness of rockfall protection measures and how hazard zoning can be influenced by their correct operation. The approach presented is divided into four main stages, which include a two-step procedure to evaluate the effectiveness of both existing and new protections. It is based on quite a comprehensive rockfall protection database built for the canton of Vaud in Switzerland, and on the Swiss Federal Guidelines for hazard zoning; however, all the methodological framework proposed and related considerations could be in principle extended to any other regional or national context in which a combination of intensity and frequency is used to assess rockfall hazards.

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Understanding rockfalls along the national road G318 in China: from source area identification to hazard probability simulation

10.5194/nhess-2021-303 ◽

2021 ◽

Author(s):

Lixia Chen ◽

Yu Zhao ◽

Yuanyao Li ◽

Lei Gui ◽

Kunlong Yin ◽

...

Keyword(s):

Slope Angle ◽

Source Area ◽

Field Investigation ◽

Slope Aspect ◽

Multivariate Logistic Regression Model ◽

Potential Hazard ◽

Rockfall Hazard ◽

Source Areas ◽

Slope Structure ◽

National Road

Abstract. Rockfall hazard is frequent along the national road (G318) in west Hubei, China. To understand the distribution and potential hazard probability, this study combines the result of a 3-years engineering geological investigation, statistical modeling, and kinemics-based method to identify risky road sections. Rockfall hazard probability is calculated by integrating spatial, temporal, size probability, and reaching probabilities of source areas. Rockfall source areas are preliminarily identified first by slope angle threshold (SAT) analysis. Random Forest model (RFM) and multivariate logistic regression model (MLRM) are then applied and compared to get the final susceptible source areas, considering eight factors, including slope, aspect, elevation, lithology, joint density, slope structure, land-use type, distance to the road. Temporal and size probability of source areas are separately obtained by Poisson distribution and power-law distribution theory. An important parameter (reach angle) for rockfall trajectory simulation was determined by back analysis in Flow-R and validated by field investigation. The results show good fitness with the measurements by field investigation. In the conditions of 5, 20, and 50 years return period, potential risky road sections are found out under two size scenarios (larger than 1 000 m3, 10 000 m3). This research helps the local government to completely understand the rock falls from source area existence and potential risk to roads.

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An efficient semi-distributed hillslope erosion model for the subhumid Ethiopian Highlands

Hydrology and Earth System Sciences ◽

10.5194/hess-17-1051-2013 ◽

2013 ◽

Vol 17 (3) ◽

pp. 1051-1063 ◽

Cited By ~ 58

Author(s):

S. A. Tilahun ◽

C. D. Guzman ◽

A. D. Zegeye ◽

T. A. Engda ◽

A. S. Collick ◽

...

Keyword(s):

Surface Runoff ◽

Source Area ◽

Sediment Concentration ◽

Erosion Model ◽

Ethiopian Highlands ◽

Source Areas ◽

Blue Nile Basin ◽

Field Evidence ◽

Sediment Loss ◽

Main Variable

Abstract. Erosion modeling has been generally scaling up from plot scale but not based on landscape topographic position, which is a main variable in saturation excess runoff. In addition, predicting sediment loss in Africa has been hampered by using models developed in western countries and do not perform as well in the monsoon climate prevailing in most of the continent. The objective of this paper is to develop a simple erosion model that can be used in the Ethiopian Highlands in Africa. We base our sediment prediction on a simple distributed saturated excess hydrology model that predicts surface runoff from severely degraded lands and from bottom lands that become saturated during the rainy season and estimates interflow and baseflow from the remaining portions of the landscape. By developing an equation that relates surface runoff to sediment concentration generated from runoff source areas, assuming that baseflow and interflow are sediment-free, we were able to predict daily sediment concentrations from the Anjeni watershed with a Nash–Sutcliffe efficiency ranging from 0.64 to 0.78 using only two calibrated sediment parameters. Anjeni is a 113 ha watershed in the 17.4 million ha Blue Nile Basin in the Ethiopian Highlands. The discharge of the two watersheds was predicted with Nash–Sutcliffe efficiency values ranging from 0.80 to 0.93. The calibrated values in Anjeni for degraded (14%) and saturated (2%) runoff source area were in agreement with field evidence. The analysis suggests that identifying the runoff source areas and predicting the surface runoff correctly is an important step in predicting the sediment concentration.

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Spatial heterogeneity of debris-flow watershed

10.5194/egusphere-egu21-14201 ◽

2021 ◽

Author(s):

Yingjie Yao

Keyword(s):

Potential Energy ◽

Debris Flow ◽

Spatial Autocorrelation ◽

Gravitational Potential ◽

Source Area ◽

Geospatial Analysis ◽

Gravitational Potential Energy ◽

Source Areas ◽

Hypsometric Analysis ◽

Inflection Points

The intermittent surge is the basic manifestation of viscous debris flow, which emerges universally over the world, especially exemplified by those in Jiangjia Gully (JJG), a valley famous for its high frequency and variety of debris flow surges. It has been found that the surges originate from various sources in the watershed, thus identifying the source areas plays a fundamental role in studying the mechanism and process of surge developing. Advancement of GIS provides an apparent convenience in geospatial analysis of the watershed, which is used as a dominate tool in this paper.In this study the JJG is divided into 97 tributaries (sub-watershed) and the hypsometric analysis is performed for each, from which derive the height of inflection points and the gravitational potential energy, coupled with the fitted parameters of specific power function. Then the morphology parameters, including slope, roundness, vegetation and soil, are revealed in tributaries. Besides, spatial autocorrelation among tributaries is quantified both globally and locally through Moran&#8217;s I and Getis-Ord Gi*, so that the HI spatial distributions are quantified and visualized. In particular, hot spots are conspicuously visible and highlight the geologic meaning of the HI when exploratory spatial data analysis is applied to the data distributions through local indices of spatial autocorrelation.The results show that H-curves approximately present as S-shaped, and the integral values (HI) range from 0.18 to 0.69 and show positive relationship with both gravitational potential energy and the height of the inflection points. By the HI value, the tributaries are identified as in 5 phases of evolution. The younger tributaries (HI>0.49) make up the majority, which are expected to be the main possible sources for debris flows. Additionally, the slope distribution of tributaries all conform to the extreme distribution while the curves for the upstream, where the HI of tributaries generally manifest higher coupled with larger roundness, tends to skew to the right.Finally the correlation between possible sources are explored through geospatial analysis. The spatial association in JJG provides an explanation of the debris flow source areas. Global spatial autocorrelation manifests significantly clustered (Moran&#8217;s I shows 0.449, passing the significance test) while tributaries with high HI value concentrate mainly in the Menqian Valley. Moreover, the drainage form of Menqian Valley represents a large possibility of debris flow source area with the respect of that being in Duozhao Valley.Keywords: debris flow source area; hypsometric analysis; topographical characteristics; spatial autocorrelation; evolutionary phases

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The Occurrence and Risks of Selected Emerging Pollutants in Drinking Water Source Areas in Henan, China

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16214109 ◽

2019 ◽

Vol 16 (21) ◽

pp. 4109 ◽

Cited By ~ 2

Author(s):

Donghai Wu ◽

Ying Zhou ◽

Guanghua Lu ◽

Kai Hu ◽

Jingjing Yao ◽

...

Keyword(s):

Drinking Water ◽

Hazard Index ◽

Source Area ◽

Dry Weight ◽

Water Source ◽

Triphenylphosphine Oxide ◽

Drinking Water Source ◽

Uv Filters ◽

Source Areas ◽

Total Concentrations

The occurrence of organic micropollutants (OMPs) in aqueous environments has potential effects on ecological safety and human health. Three kinds of OMPs (namely, pharmaceuticals, ultraviolet (UV) filters and organophosphate esters (OPEs)) in four drinking water source areas in Henan Province of China were analyzed, and their potential risks were evaluated. Among 48 target chemicals, 37 pollutants with total concentrations ranging from 403.0 to 1751.6 ng/L were detected in water, and 13 contaminants with total concentrations from 326.0 to 1465.4 ng/g (dry weight) were observed in sediment. The aqueous pollution levels in Jiangang Reservoir and Shahe Water Source Area were higher than that in Nanwan Reservoir and Baiguishan Reservoir, while the highest total amount of pollutants in sediment was found in Baiguishan Reservoir. Compared with pharmaceuticals and UV filters, OPEs presented higher concentrations in all investigated drinking water source areas. The highest observed concentration was triphenylphosphine oxide (TPPO, 865.2 ng/L) in water and tripentyl phosphate (TPeP, 1289.8 ng/g) in sediment. Moreover, the risk quotient (RQ) analysis implies that the determined aqueous contaminants exhibited high risks to algae and invertebrates, whereas moderate risk to fish was exhibited. The health risk assessment of aqueous OMPs by means of the hazard index (HI) indicates that the risks to adults and children were negligible. These observations are expected to provide useful information for the assessment of water quality in drinking water sources in Henan, China.

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Rural Households’ Willingness to Accept Compensation Standards for Controlling Agricultural Non-Point Source Pollution: A Case Study of the Qinba Water Source Area in Northwest China

Water ◽

10.3390/w11061251 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1251 ◽

Cited By ~ 1

Author(s):

Xiaoping Li ◽

Wenxin Liu ◽

Yan Yan ◽

Gongyuan Fan ◽

Minjuan Zhao

Keyword(s):

Rural Households ◽

Source Area ◽

Water Source ◽

Willingness To Accept ◽

Point Source Pollution ◽

Ecological Benefits ◽

Source Areas ◽

Compensation Standard ◽

Non Point Source Pollution ◽

Willingness To Accept Compensation

Agricultural non-point source pollution (ANSP) has become one of the main sources of pollution in water source areas. An effective solution to this problem is the use of ecological compensation to encourage rural households to adopt agricultural pollution control measures. This study aims to answer two questions: How much compensation should be given to encourage rural households in water source areas to participate in ANSP control? What factors will influence their participation? In this study, paddy rice planting in water source area has been used as an example aiming to answer these questions. This study used the random parameter logit (RPL) model with survey data from 632 rural households in the Qinba water source area to empirically analyze rural households’ willingness to accept compensation for ANSP control and the influencing factors of this willingness. From this information, the compensation standards for ANSP control in a water source area were calculated. The results show that (1) compensation had a significant incentive effect on rural households’ willingness to control ANSP. The marginal compensation standard for reducing the use of fertilizer and pesticide was $3.40/ha and $2.00/ha, respectively. The compensation standard for not applying chemical fertilizer and pesticide at all was $540.23/ha. (2) There was heterogeneity in rural households’ preference for ANSP control compensation policies. Rural households characterized by younger residents, higher family income, higher perception of the ecological benefits, and higher perception of government policy were more willing to participate in the compensation policy. It is suggested that rural households showed a strong preference for ANSP control policies by considering both of their economic losses and ecological benefits. Our study contributes to the literature by enriching the evaluation method in providing references for the compensation of ANSP control policies

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Resistance of zircons to U–Pb resetting in a prograde metamorphic sequence of Caledonian age in East Greenland

Canadian Journal of Earth Sciences ◽

10.1139/e85-033 ◽

1985 ◽

Vol 22 (3) ◽

pp. 330-338 ◽

Cited By ~ 37

Author(s):

J. J. Peucat ◽

D. Tisserant ◽

R. Caby ◽

N. Clauer

Keyword(s):

Source Area ◽

Detrital Zircons ◽

Metamorphic Event ◽

Great Resistance ◽

East Greenland ◽

Geological Interpretation ◽

Source Areas ◽

Metasedimentary Rocks ◽

Sedimentary Source

In the Alpefjord area, Caledonian metamorphism from the chlorite zone to the sillimanite zone is seen to cut across the sedimentary pile of the lower Eleonore Bay Group. Zircons have been collected from quartzite layers enriched in heavy minerals.U–Pb zircon dating in the chlorite and the sillimanite zones does not reveal the Caledonian event but, instead, previous episodes at 1100 and 2500 Ma ago. The Caledonian event can be recognized in anatectic gneisses where detrital zircons are surrounded by overgrowths, K–Ar and Rb–Sr methods yield 1030–410 Ma ages on micas, with a positive correlation between the degree of apparent reselling of mica ages and the grade of the Caledonian metamorphism.The following geological interpretation of the age data is proposed. (1) A major metamorphic event occurred around 1100 Ma ago in the source area for the lower Eleonore Bay Group sediments. During this Grenvillian event, Archaean detrital zircons were affected by an episodic lead loss and a muscovite phase recorded the cooling and uplift of a basement source area. (2) Erosion of this source area occurred after 1100 Ma, followed by sedimentation of the lower Eleonore Bay Group [Formula: see text]. The 2500–1100 Ma U–Pb system remained nearly a closed system during Caledonian metamorphism up to and including sillimanite-zone conditions.This example shows the great resistance or inherited zircons to an important secondary Pb loss during Caledonian metamorphism and consequently shows that the lower-intercept ages of zircons from metasedimentary rocks do not always record the last metamorphic event observed in situ, but retain memories of previous geological events in the sedimentary source areas. By contrast, zircons separated from quartzitic xenoliths in migmatitic gneisses have recorded a disturbance in their U–Pb systems that corresponds to Caledonian partial melting.

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Determination of the rockfall source in an urban settlement area by using a rule-based fuzzy evaluation

Natural Hazards and Earth System Science ◽

10.5194/nhess-6-941-2006 ◽

2006 ◽

Vol 6 (6) ◽

pp. 941-954 ◽

Cited By ~ 19

Author(s):

H. Aksoy ◽

M. Ercanoglu

Keyword(s):

Field Studies ◽

Fuzzy Evaluation ◽

Hazard Map ◽

Initiation Mechanism ◽

Urban Settlement ◽

Rule Based ◽

Rockfall Hazard ◽

Source Areas ◽

The City

Abstract. The evaluation of the rockfall initiation mechanism and the simulation of the runout behavior is an important issue in the prevention and remedial measures for potential rockfall hazards in highway protection, in forest preservation, and especially in urban settlement areas. In most of the studies in the literature, the extent of the rockfall hazard was determined by various techniques basing on the selection of a rockfall source, generally defined as zones of rock bodies having slope angles higher than a certain value, proposed by general practice. In the present study, it was aimed to carry out a rule-based fuzzy analysis on the discontinuity data of andesites in the city of Ankara, Turkey, in order to bring a different and rather systematic approach to determine the source areas for rockfall hazard in an urban settlement, based on the discontinuity and natural slope features. First, to obtain rock source areas (RSAs), data obtained from the field studies were combined with a rule-based fuzzy evaluation, incorporating the altitude difference, the number of discontinuities, the number of wedges and the number of potential slides as the parameters of the fuzzy sets. After processing the outputs of the rule-based fuzzy system and producing the linguistic definitions, it could be possible to obtain potential RSAs. According to the RSA maps, 1.7% of the study area was found to have "high RSA", and 5.8% of the study area was assigned as "medium RSA". Then, potential rockfall hazard map was prepared. At the final stage, based upon the high and medium RSAs, 3.6% of the study area showed "high rockfall potential", while areal distribution of "medium rockfall potential" was found as 7.9%. Both RSA and potential rockfall hazard map were in accordance with the observations performed in the field.

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Jurassic-Cretaceous paleogeography of Central-West Parnaiba Basin, NE Brazil - stratigraphy and sedimentary provenance of detrital zircons

10.5194/egusphere-egu2020-22505 ◽

2020 ◽

Author(s):

André Pereira de Assis ◽

Kelly Aparecida Caldas da Cruz ◽

Renata da Silvia Schmitt ◽

Silvia Regina de Medeiros

Keyword(s):

Detrital Zircon ◽

Source Area ◽

Depositional Environments ◽

Detrital Zircons ◽

Hypersaline Lake ◽

Red Sandstone ◽

Source Areas ◽

Aeolian Dunes ◽

Marine Ingression ◽

And Shifts

The Phanerozoic Parna&#237;ba Basin occupies 600.000km&#178; in northeast Brazil, covering cratons and Neoproterozoic belts. Its Central-West region is mostly represented by the Jurassic-Cretaceous Sequence (Mosquito, Corda Graja&#250;, Cod&#243; and Itapecuru formations) recording magmatic events from the Central Atlantic Magmatic Province, with depocenters migrations and shifts on depositional environments related to Pangea breakup.&#160; This work discusses the Jurassic-Cretaceous siliciclastic units testing possible sedimentary source areas with U-Pb and combined Lu-Hf data on detrital zircons, using LA-ICP-MS. The basalts from Mosquito Formation are dated at +/- 198Ma and the Cod&#243; Formation present accurate Aptian fossil data. This formation records a hypersaline lake system, succeeded by a transgression that represents pioneer marine ingression within an intracontinental rift. The other units (Corda, Graja&#250; and Itapecuru) are constituted by siliciclastic sediments involved in intracontinental sub-environments. The Corda Formation consists of aeolian system, sand sheets and wadis deposited in a desertic setting. The contact between the subsequent Graja&#250; Formation is abrupt, represented, at the base, by thick coarse braided river facies grading laterally and upwards to ephemeral channels in association with low amplitude Aeolian dunes, evidencing still arid conditions. Interlayered beds of fluvial and aeolian sandstones within lacustrine deposits, indicates that Cod&#243; and Graja&#250; formations consists the same seasonal fluvial-lacustrine system. The last Itapecuru Formation, is represented by a thick red sandstone succession deposited in a deltaic system. Paleocurrents measurements below Cod&#243; Formation (i.e. Corda and lower Graja&#250;) points a W-NW sense of direction, whereas paleocurrents above Cod&#243; Formation (i.e. upper Graja&#250; and Itapecuru) presents a regional sense to E-NE. Detrital zircons geochronology analysis helped to identify the source area of sediments through the comparison of the main ages of possible uplifted tectonic terranes. The preliminary results revealed that sandstones below Cod&#243; Formation shows a major Neoproterozoic population (56, 41% to 40%) with age peaks at 583 and 628 Ma; and also Paleoproterozoic (43, 48% to 35,05%); Archean (4,35%) and Paleozoic (2,61%) populations. Sandstones above Cod&#243; Formation, also show a Neoproterozoic major detrital zircon population (40% to 37,12%) with 625, 665 and 783 Ma age peaks. Two other populations are present: Paleoproterozoic (22.68% to 20%) with peaks at 1749 and 1881 Ma, and Archean (24,45% to 15,47%). This last source has a greater contribution than in the formations below the Cod&#243; maker. We envisaged that the shift from W-NW to E-NE sandstones paleocurrent is coherent with the rise on Archean contribution, possibly related to the Amazon Craton to the West. In addition, the youngest Phanerozoic detrital zircons obtained in all samples are minor (6,66% to 6,18%). The integration of field stratigraphic analysis, paleocurrents and detrital zircon provenance studies corroborate to the hypothesis that Cod&#243; Formation must represent a Cretaceous stratigraphic datum for the transition of a rift and post-rift phase, thus the change of source areas is consistent. The authors acknowledge support from Shell Brasil Petroleo Ltda. and ANP (Brazil&#8217;s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation (Technichal Cooperation #20.219-2).

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Numerical Simulation on Ghosting Fire in the Confined Underground Space

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.2667 ◽

2014 ◽

Vol 580-583 ◽

pp. 2667-2670

Author(s):

Pei Hong Zhang ◽

Xiao Wei Lu ◽

Xiao Ming Zhang

Keyword(s):

Heat Release ◽

Heat Release Rate ◽

Release Rate ◽

Source Area ◽

Confined Space ◽

Source Areas ◽

Fire Source ◽

Underground Fire ◽

Two Parameters ◽

Air Vent

The phenomenon of ghosting fire development in underground confined space is simulated to analyze the impacts of ghosting fire generation via some conditions -- different air vent sizes and different fire source areas. FDS is used to establish a physical model of underground fire laboratory in Northeastern University, the simulation is conducted by setting two parameters, the air vent size and the fire source area. The fire heat release rate, temperature, concentration of CO, O2 are measured to analyze the case of ghosting fire generation in underground confined space with different air vent sizes and different fire source areas. It’s most likely to generate ghosting fire when the simulating parameter is that the air vent size is 0.4m × 0.4m and the fire source area is 0.96m2. The conclusion is that increasing the air vent size is not a simple ascending and descending relationship with the occurrence time and duration time of the ghosting fire. Increasing the fire source area can improve the fire heat release rate effectively, and promote the formation of ghosting fire.

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