Baronnies Provençales Regional Nature Park Pilot Action Region: The Benefit of Large-Scale Rockfall Modelling for Developing Efficient Forest-Based Integrative Management of an Alpine Territory

The choice of a natural risk prevention strategy must be considered at the scale of a territory in order to take into account all its components. Since 2015, France has developed integrated natural risk management (INRM) approaches in Alpine territories. The challenge of INRM lies in the definition and implementation of innovative projects for initiating synergies with respect to natural risks while seeking to increase resilience through the new and different involvement of the territorial actors. The Baronnies Provençales Regional Nature Park is one of the pilot territories for the operational implementation of this approach, with a particular focus on forest-based solutions. For this reason it has been chosen as the French Pilot Action Region (PAR) of the Interreg Alpine Space project GreenRisk4Alps. In this article we present an example of good practice related to the benefit of large-scale rockfall risk modeling, the analysis of potential cascading effects and the added value of a territorial perspective

Assessing wildfires effects on the protection capability of forests against rockfalls in the French Alps

Les chutes de blocs constituent un aléa naturel majeur dans les Alpes françaises en raison de leur probabilité d'occurrence spatiale et temporelle très élevée. Les forêts peuvent constituer une solution naturelle et efficace pour atténuer ce phénomène tout en protégeant les populations et leurs infrastructures. Cependant, ce service écosystémique peut être perturbé par d'autres aléas naturels comme les feux de forêts, susceptibles d'être plus fréquents et intenses dans le contexte actuel et futur de changements climatiques.Cette thèse propose ainsi d'évaluer les effets des incendies sur la capacité de protection des forêts contre les chutes de blocs dans les Alpes françaises.Une méthodologie pour évaluer la capacité de protection d'une forêt contre les chutes de blocs est d'abord développée et consiste à utiliser des simulations de propagation de chutes de blocs réalisées sur 3886 placettes forestières des Alpes françaises pour calculer trois indicateurs quantitatifs évaluant la réduction de la fréquence (BARI), de l'intensité (MIRI) et la réduction globale (ORPI) de l'aléa chutes de blocs dues à la présence d'une forêt. Ces indicateurs sont utilisés pour identifier les variables forestières prépondérantes pour évaluer la capacité de protection : la longueur boisée sur le versant, la surface terrière et le diamètre moyen. Les peuplements présentant une distribution hétérogène des diamètres et composés de plusieurs essences offrent généralement une meilleure protection que les peuplements monospécifiques et réguliers, soulignant ainsi l'influence de la diversité forestière. Cette thèse montre ainsi que les taillis présentent les capacités de protection les plus élevées, suivis par les futaies feuillues et les futaies mixtes ; les peuplements résineux venant en dernier.Les évolutions spatiales et temporelles des conditions climatiques favorables aux incendies, étudiées sur la période 1959-2015, révèlent un contraste majeur entre les Alpes du Sud qui ont connu une forte augmentation (en intensité, fréquence, durée et saisonnalité) surtout à haute altitude, et les Alpes du Nord, où une légère hausse est observée à basse altitude, mais aucune tendance significative n'est observée à haute altitude. Ces résultats sont ensuite utilisés pour définir trois types de feux (d'hiver, d'été moyen et d'été très sec) pour lesquels la mortalité post-incendie est étudiée à l'échelle de l'arbre et du peuplement forestier. Ces analyses montrent que seuls les feux d'été sont susceptibles d'affecter significativement les peuplements, en particulier à basse altitude où les peuplements feuillus (notamment les taillis) dominent.L’effet des incendies sur la capacité de protection des forêts est évalué en comparant les simulations de propagation de chutes de blocs sans feu aux simulations après chaque type de feu pour lesquelles les arbres avec une forte probabilité de mortalité post-feu ne sont pas pris en compte. Les valeurs de ORPI pour chaque placette forestière et chaque type de feu sont ainsi calculées et comparées au scénario de référence sans feu, permettant ainsi d'évaluer quantitativement la réduction de la capacité de protection. Les peuplements de basse altitude, soumis à des conditions climatiques plus chaudes et sèches, présentent des réductions de la capacité de protection après des feux d'été de l'ordre de 60 à 100 %. Il s'agit principalement de taillis et de futaies feuillues. À plus haute altitude, la réduction est de l'ordre de 30 à 65 %.En conclusion, ce travail de thèse propose une méthode originale pour quantifier la capacité de protection d'une forêt contre les chutes de blocs avant et après un incendie et alimente les connaissances sur ces deux aléas naturels et les risques associés. L'analyse multi-aléas conduite en fin de thèse permet d'appréhender les effets cascades potentiels à l'échelle du peuplement forestier et de quatre territoires bioclimatiquement homogènes des Alpes françaises.Rockfalls are a major natural hazard in the French Alps due to their high probability of spatial and temporal occurrence. Forests constitute an efficient nature-based solution to mitigate this hazard while protecting human lives and assets. However, this ecosystem service may be disrupted by others natural hazards such as wildfires likely to be more frequent and intense in the current and future context of climate changes.This PhD thesis proposes to assess the effects of fires on the protection capability of forests against rockfalls in the French Alps.A methodology to evaluate the protection capability of a forest against rockfalls is first developed. It consists in modeling rockfalls propagations on 3886 forest plots taken in the French Alps to calculate three quantitative indicators that assess the reduction of the frequency (BARI), the intensity (MIRI) and the overall reduction (ORPI) of rockfalls due to the presence of a forest. These indicators are used to identify the predominant forest variables for assessing the protective effect: the length of forest along the slope, the basal area and the mean diameter. Forest stands with a heterogeneous distribution of diameters and made up of several tree species generally offer a better protection than monospecific and regular stands, thus underlining the influence of forest diversity. This work shows that coppices have the highest protection capabilities, followed by hight stands dominated by deciduous species and mixed stands; coniferous stands coming last.Spatio-temporal trends in fire weather in the French Alps are investigated over the period 1959-2015 and reveal a major contrast between Southern Alps which experienced a strong increase (in intensity, frequency, duration and seasonality) especially at high elevation, and Northern Alps, where a slight increase at low elevation and no significant trends at high elevation are observed. These results are then used to define three types of fires (winter, summer, and dry summer) for which post-fire tree mortality is studied at the tree and forest stands levels. These analyses show that only summer fires are likely to significantly affect the forest ecosystems, particularly at low elevations where deciduous stands (especially coppice) dominate.The effect of fires on the protection capabilities of forests is assessed by comparing rockfalls propagation simulations without fire to simulations after each type of fire in which the trees with a high post-fire mortality are not taken into account. The ORPI values for each forest plot and fire type are thus calculated and compared to the reference scenario without fire thus making it possible to quantitatively assess the reduction of the protection capabilities. Low elevation stands, subject to warmer and drier climatic conditions, show reductions of the protective effect in the range 60-100%. It mainly concerns coppices and deciduous stands. At high elevation, the reduction is in the range 30- 65%.In conclusion, this PhD thesis proposes an original method to quantify the protection capabilities of a forest against rockfalls before and after a fire and improve the knowledge of these two natural hazards and their associated risks. The multi-hazard analysis conducted at the end of the thesis makes it possible to understand the potential cascading effects in the main forest types and for four bioclimatically homogeneous territories of the French Alps

Spatio-temporal trends in fire weather in the French Alps

International audienceThe Alpine area is particularly sensitive to climatic and environmental changes that might impact socio-ecosystems and modify the regime of natural hazards. Among them, wildfire is of major importance as it threatens both ecosystems and human lives and infrastructures. Wildfires result from complex interactions between available vegetation fuels, climate and weather, and humans who decide of the land use and are the main source of fire ignitions. The changes in fire weather during the past decades are rather unknown in the French Alps especially due to their complex topography. Moreover, local institutions and managers wonder if the ongoing climate changes might increase fire risk and affect the environmental quality and the different ecosystem services provided by the mountain forests. In this context, we used the national forest fires database together with daily meteorological observations from 1959 to 2015 to investigate the changes in wildfire danger in the French Alps. We analysed the spatial and temporal variations in terms of intensity, frequency, seasonality and window of opportunity of two fire weather indices: the fine fuel moisture code (FFMC) and the fire weather index (FWI) that measure the daily water content of vegetation and the potential intensity of fires, respectively. Our results showed a major contrast between Southern Alps with a high fire weather danger on average and a significant increase in the past decades, and Northern Alps with low to moderate danger on average that increased only at low elevations. This study contributes to the understanding of the consequences of ongoings climate changes on wildfires in the French Alps. It produced high resolution results that account for the topographic and climatic variability of the area. Finally, the maps of the different fire weather components have practical implications for fire management and modelling and for preventing indirect effects of fires on ecosystems and human assets

Vulnerability of forest ecosystems to fire in the French Alps

Forest fires are expected to be more frequent and more intense with climate change, including in temperate and mountain forest ecosystems. In the Alps, forest vulnerability to fire resulting from interactions between climate, fuel types, vegetation structure, and tree resistance to fire is little understood. This paper aims at identifying trends in the vulnerability of Alpine forest ecosystems to fire at different scales (tree species, stand level and biogeographic level) and according to three different climatic conditions (cold season, average summer and extremely dry summer). To explore Alpine forest vulnerability to fire, we used surface fuel measurements , forest inventory and fire weather data to simulate fire behaviour and ultimately post-fire tree mortality across 4438 forest plots in the French Alps. The results showed that cold season fires (about 50% of the fires in the French Alps) have a limited impact except on low elevation forests of the Southern Alps (mainly Oak, Scots pine). In average summer conditions, mixed and broadleaved forests of low elevations suffer the highest mortality rates (up to 75% in coppices). Finally, summer fires occurring in extremely dry conditions promote high mortality across all forest communities. LowS. Dupire Univ

Sylvaccess – A Model for Automatically Mapping Accessibility to Forests

Identifier et caractériser les conditions d’accès aux ressources forestières sont des points stratégiques pour assurer leur gestion durable et multifonctionnelle. Le modèle Sylvaccess présenté dans cet article permet de cartographier automatiquement l’accessibilité des forêts en fonction des principaux systèmes de débardage actuellement utilisés en France : le tracteur forestier (ou débusqueur), le porteur forestier et le débardage par câble. Le modèle s’appuie sur des sources d’information spatiale et des paramètres techniques propres à chaque système de débardage. Il offre aussi la possibilité d’intégrer des obstacles physiques ou environne- mentaux dans l’analyse. Les résultats du modèle sont utilisables pour de nombreuses applications forestières allant de l’aménagement et de la planification des opérations d’exploitation jusqu’à la comparaison et la sélection de projets de desserte.Identifying and characterizing the conditions of access to the forest resources are strategic to managing them sustainably and on a multifunctional basis. The Sylvaccess model presented in this article is designed to automatically map the accessibility of forests for the three main logging techniques currently used in France: skidder, forwarder and cable yarder. The model is based on spatial information and specific parameters of each logging technique. It can also integrate physical or environmental obstacles in the analysis. The outputs of the model can be used for many applications ranging from forest management and planning of logging operations to the comparison and selection of new forest roads projects

Predicting load path and tensile forces during cable yarding operations on steep terrain

<p>Cable yarding systems constitute an adapted solution for steep-slope harvesting in mountain forests. However, it requires many specific skills for both forest managers and operators. The objectives of this research were to: (1) develop a <i>CableHelp</i> model for the set-up of cable yarding systems where inputs are operational field data and outputs are load path and tensile forces, and (2) to validate it with field experiments. The results show a high accuracy between the data predicted by the model and field measurements. Furthermore, this work stresses the importance of taking into account both the mainline effect and the friction between skyline and intermediate supports to properly calculate the skyline tension and load path. The <i>CableHelp</i> model shows great adaptability and ensures highly accurate predictions for any position on the line profile and for different configurations: single-span or multiple-span profiles, uphill or downhill yarding and for different kinds of carriage. A direct application of this research is to optimize the set-up of cable lines in order to reduce equipment wear, as well as operating cost, while respecting operator safety.</p

The protective effect of forests against rockfalls across the French Alps: Influence of forest diversity

International audienceThe role of forests in the mitigation of natural hazards has been repeatedly demonstrated. The protective effect of mountain forests against rockfalls has especially been pointed out because it can constitute a natural and cost-effective protection measure in many situations. However, this particular ecosystem service may substantially differ according to the structure and the composition of the forest. Until now, the rockfall protection capability has always been studied at a local scale with only few forest types. Moreover, the comparison of the protective effect of the different forest types studied remains difficult because different methods and indicators were used. For the same reasons, it is not possible to draw conclusions about the influence of biological and structural diversities on the protection capabilities of forests from former works. The aims of this study were (1) to quantitatively assess the protective effect of forests at the French Alps scale and build a classification based on the protection capability, (2) to compare the protective effect of the different forest types present in the French Alps and (3) to analyse the relations between the protective effect and the forest diversity in terms of stand structure and tree composition. For this purpose, the model Rockyfor3D was used to simulate the propagation of rocks on 3886 different forest plots spread over the whole French Alps. Quantitative indicators characterizing the protective effect of each forest plot were then calculated from the simulation results and used to perform the different analyses. Our results emphasized the importance of taking into account the length of forest in the maximum slope direction for an accurate assessment of the protective effect. Thus, the minimum length of forest to get a reduction of 99% of the rockfall hazard was chosen as indicator to compare protective effect between forests. Using this indicator, half of the French Alpine forests presented a high level of protection after a short forested slope (190 m). A decreasing gradient in the protection capabilities was observed from forest types dominated by broadleaved species to those dominated by conifer species. Moreover, considering an equivalent proportion of conifers, stands dominated by shade-tolerant tree species showed better ability to reduce rockfall hazard. Finally, our study highlighted that a high biodiversity and a structural heterogeneity within the forest have a positive effect on the reduction of rockfalls hazard

Novel quantitative indicators to characterize the protective effect of mountain forests against rockfall

International audienceNatural hazards are frequent in mountain areas where they regularly cause casualties and damages to human infras-tructures. Mountain forests contribute in mitigating these hazards, in particular rockfalls. Assessing the protective effect of a forest against rockfall is a difficult task for both forest managers and rockfall experts. Accurate and simple tools are therefore required to efficiently evaluate the level of protection that results from the presence of forest. This study defines three novel indicators to quantify the protective effect of forests against rockfalls, regarding 1) the reduction of the frequency of rockfalls, 2) the reduction of their maximum intensity, and 3) the combination of the reduction of the frequency and the energy of the rocks. The first two indicators are relevant for rockfall experts whereas the third is mostly interesting for foresters as it summarizes the protective effect of forest. The Rockyfor3D model was adapted and used to simulate rockfalls propagation on 3886 different forest stands located in all the French Alps. The results of the simulations were used to calculate the three indicators for each forest stand. Finally, the relations between the forest structures and compositions and the indicators values were investigated. Our principal result shows that only three forest characteristics are required to accurately predict the indicators and evaluate the protective level of a forest against rockfall. The two first variables correspond to the basal area and the mean diameter at breast height (DBH) of the forest stand which are two parameters commonly used by forest managers. The third characteristic is the length of forest in the maximum slope direction which can be computed with a geographic information system (GIS). The method proposed in this study is easily reproducible and is suitable to evaluate the protective effect of European mountain forests at different scales. At local scale, the proposed indicators can enrich rockfall studies in which forests are usually set aside to simplify the evaluation. Moreover, the indicators may find direct applications with foresters by allowing them to identify the protective level of their forest and consequently to adapt their management. Finally, the indicators are convenient to perform spatial analysis and produce maps of the protective effect of mountain forests that could find many applications in land settlement or evaluation of ecosystem services

Chronique de jurisprudence de droit privé du patrimoine

Entre le 1er octobre 2020 et le 15 janvier 2021, la production jurisprudentielle en droit patrimonial a été plutôt dense. Sans révolutionner la matière, la Cour de cassation apporté d’utiles précisions sur les méthodes de calcul du profit subsistant (Civ. 1re, 14 oct. 2020, n° 19-13.702) et de l’indemnité de réduction (Civ. 1re, 4 nov. 2020, n° 19-10.179). Elle aussi rappelé quelques évidences visiblement oubliées telles que la possibilité de prescrire contre un titre (Civ. 3e, 17 déc. 2020, n° 18-24.434) et l’obligation de restituer les sommes ayant fait l’objet d’un quasi-usufruit (Civ. 1re, 4 nov. 2020, n° 19-14.421). Le droit ancien fait aussi quelques apparitions. L’on regardera avec un peu de nostalgie l’arrêt du 16 décembre 2020 relatif à la charge de la preuve d’une donation rémunératoire entre époux dans le contentieux de la révocabilité post-divorce (n° 19-13.701) et avec circonspection l’arrêt du 18 novembre 2020 dans lequel la Première chambre civile s’entête à qualifier la clause de contribution quotidienne aux charges du mariage de présomption irréfragable (n° 19-15.353). I. Régimes matrimoniaux A. Régime primaire Retour sur la nature de la présomption d’acquittement quotidien des charges du mariage I – Le renforcement de la cohérence de la construction jurisprudentielle II – Une solution décevante au regard du droit de la preuve B. Qualification des biens C. Pouvoirs des époux, gage des créanciers D. Liquidation du régime matrimonial Récompenses : détermination du profit subsistant en présence d’un bien partiellement aliéné La donation chassée par la collaboration conjugale excédant l’obligation contributive aux charges du mariage II. Libéralités A. Donations Les délicates règles de preuve en matière de don manuel et de vices du consentement B. Legs C. Testaments D. Contrats de service gratuit III. Assurance-vie Forme de la désignation bénéficiaire : quelle valeur accorder à la lettre type non signée ? IV. Succession A. Ouverture de la succession Demande de fixation d’une créance et opération de partage B. Liquidation de la succession Paiement de l’indemnité de réduction : nécessité d’une revalorisation Opposition d’intérêts et règlement d’une succession : retour sur un concept-clé du droit des mineurs I – Un rappel : une opposition d’intérêts souverainement appréciée par les juges du fond II – Une confirmation : une conception large de la notion d’opposition d’intérêts V. Droit des biens A. Classification des biens B. Propriété individuelle Le rappel d’une évidence : la prescription trentenaire peut toujours être opposée à un titre, même régulièrement publié C. Démembrements de propriété Quasi-usufruit sur comptes bancaires : analyse et conséquences D. Propriété collective E. Autres droit