Soil and Water Bioengineering techniques are a sustainable alternative to civil engineering to prevent erosion processes that threaten streambank stability. These techniques are still poorly developed and documented in subalpine streams, where climatic and hydrological conditions are particularly challenging. It is well known that the success and integration of a SWBE technique is best achieved when it is possible to use indigenous plants and plant material. At the subalpine belt, shrub and tree willows are among the dominant woody species on streambanks. Even if a few past studies claimed that they could play a full role in stabilising the banks of high-elevation streams, their biotechnical characteristics are nearly unknown. The unique information available comes from empirical and not detailed results showing a low resprouting rate of cuttings. Still, no data or information on these capacities are known in the subalpine environment. We conducted an in situ experimental study to assess the cutting capacity of willow species at high elevations to improve SWBE on these streambanks.

Six willow species were selected: three subalpine shrub species (Salix caesia, S.foetida, S.hastata) and three tree species (S.daphnoides, S.myrsinifolia, S.purpurea) presents in both foothill and subalpine belt. The cuttings were planted in three different experimental sites with varied conditions: in Val Thorens at 1 800 m on subalpine grassland habitat and in Lautaret garden at 2 100 m on subalpine tall herb communities and on sand. For each site, 52 cuttings per species were planted in October 2022. In September 2023, at the end of the vegetative period, the recovery rate and the cuttings' aerial growth were assessed. Aerial growth was estimated by biomass dry weight and cumulative stem length.

All recovery rates were above 70%. In Val Thorens, S.purpurea had a recovery rate of 100%, S.hastata 80% and the other species between 88 and 96%. At the Lautaret garden on grassland, the recovery rates, ranged for all species from 71 (S.caesia) to 98% (S.purpurea). The recovery rates in the Lautaret garden on the sand were higher with 100% for S.caesia, S.foetida and S.purpurea and over 88% for the other three species. Despite differences in in situ conditions, all six species had excellent recovery rates for their use in SWBE structures. The willows growing on the sandy substrate at the Lautaret garden showed a higher growth rate. Within sites, there was no significant difference in growth between species. After the first year of growth, these six species seemed suitable for SWBE structures. Recovery rate and aerial growth will be re-estimated in autumn 2024, after the second growing season.

How to cite: Francois, A., Rousset, J., Didier, M., and Evette, A.: Which willows for Soil and Water Bioengineering structures on high-elevation streambank? In situ study of cutting capacity of six species, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16671, https://doi.org/10.5194/egusphere-egu24-16671, 2024.

The integration of urban green space management into erosion control for streambanks and embankments addresses essential environmental challenges by linking urban green spaces (UGS) with natural hazard (NH) mitigation. This strategic approach emphasizes comprehensive management that harmonizes seemingly different domains. At first glance, erosion stabilization measures and UGS appear distinct, yet they address similar processes from different perspectives. Central to this integration is vegetation assessment, vital for functions such as erosion control and urban ecosystem enhancement. Assessing vegetation through field evaluations and remote sensing is key for understanding how it interacts with soil, especially in terms of soil moisture, which is vital for slope stability and drought mitigation. This process is essential for evaluating the health and type of vegetation and its structural characteristics.

Decision-making in system selection and management for erosion control should adopt a lifecycle perspective, encompassing environmental and economic impacts. This includes considerations from material selection to maintenance and eventual decommissioning, aiming for sustainable, cost-effective approaches. Additionally, there is a wealth of knowledge in communal and city green space management that can potentially be adapted and transferred to meet the requirements of erosion control. The choice of vegetation is crucial for decisions in both urban areas and for slope stabilization measures. The role of evapotranspiration in enhancing soil cohesion and reducing erosion risk, especially in urban green spaces (UGS) and nature-based systems, is significant. These methods not only ensure slope stability but also offer urban benefits, like mitigating urban heat island (UHI) effects. In adapting to climate change for effective erosion protection strategies, the key distinction is found in the detailed assessment of specific parameters from UGS and their application to erosion control methods. This focused evaluation ensures that erosion control measures are not only effective but also congruent with the distinct ecological aspects of urban environments. By carefully analyzing factors like vegetation type, soil characteristics, and water management in UGS, these insights become invaluable in strengthening the resilience and adaptability of erosion control strategies. This strategy goes beyond mere soil erosion reduction; it plays a pivotal role in enriching ecosystem capacities. By fostering biodiversity and refining the utility of green spaces, it contributes to the development of landscapes that are both sustainable and better equipped to adapt to climate change. This holistic approach underlines the multi-faceted benefits of integrating green space management into broader environmental resilience planning.

How to cite: Obriejetan, M. and Krexner, T.: From Parks to Banks: Aligning Nature-Based Urban Green Space Assessment with Erosion Protection Goals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18351, https://doi.org/10.5194/egusphere-egu24-18351, 2024.

The use of vegetation is a sustainable technique to mitigate the risk of landslides and erosion phenomena. Literature agrees that roots improve soil shear strength properties. The reinforcement of roots on soils is complex and depends on their morphological and mechanical characteristics and the stresses that develop at the soil–root interface. In this regard, many models have been produced in literature to infer the increase in soil shear/tensile strength due to roots. Among them, soil hydraulic state was poorly considered.

Large cell triaxial consolidated drained compression tests and tensile tests were carried out to explore the mechanical effects of vegetation on a compacted soil at low confining stresses and at different hydraulic states (identified in terms of suction and degree of saturation). Root features were thoroughly assessed for each soil specimen and were correlated, jointly with soil hydro-mechanical states, to the two soil reinforcement mechanisms observed (roots breakage and slippage). Different stress-strain responses were observed during the mechanical tests, depending on soil initial suction. Strain spatial distributions during tensile tests were observed by an advanced imaging technique (Particle Image Velocimetry): roots contributed to redistribute the tensile stresses over larger soil volumes. A combination of two literature reinforcement models was adopted to interpret the results: one model to consider root tensile strength full exploitation and breakage, and the other to predict friction forces at the soil–root interface during root slippage. The correlation coefficients of these two models were calibrated based on this experimental campaign.

Fraccica, A., Romero Morales, E. E., & Fourcaud, T. (2019). Multi-scale effects on the hydraulic behaviour of a root-permeated and compacted soil. In IS-Glasgow 2019–7th International Symposium on Deformation Characteristics of Geomaterials (pp. 1-5). EDP Sciences.

Fraccica, A., Romero, E., & Fourcaud, T. (2022). Tensile strength of a compacted vegetated soil: Laboratory results and reinforcement interpretation. Geomechanics for Energy and the Environment, 30, 100303.

Fraccica, A., Romero, E., & Fourcaud, T. (2023). Large cell triaxial tests of a partially saturated soil with vegetation. In E3S Web of Conferences (Vol. 382, p. 05005). EDP Sciences.

Fraccica, A., Romero, E., & Fourcaud, T. (2024). Effects of vegetation growth on soil microstructure and hydro-mechanical behaviour. Géotechnique (accepted)

Oorthuis, R., Hürlimann, M., Fraccica, A., Lloret, A., Moya, J., Puig-Polo, C., & Vaunat, J. (2018). Monitoring of a full-scale embankment experiment regarding soil–vegetation–atmosphere interactions. Water, 10(6), 688.

How to cite: Fraccica, A., Romero, E., and Fourcaud, T.: Exploring stress-paths and vegetation reinforcement mechanisms in a compacted soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19887, https://doi.org/10.5194/egusphere-egu24-19887, 2024.

Nowadays there is a high demand on engineering solutions considering not only technical aspects but also ecological and aesthetic values. Soil and water bioengineering (SWB) is a construction technique that uses biological components for hydraulic and civil engineering solutions. In general it pursues the same objectives as conventional civil engineering structures. In this context SWB techniques are often used as standalone solutions or in combination with conventional engineering structures.

Currently, existing assessment methods for SWB structures are evaluating technical and economic aspects. In a modern engineering approach, additionally, environmental impacts should be considered. Therefore, the Institute of Soil Bioengineering and Landscape Construction aims at developing an Environmental Life Cycle Assessment (LCA) model for this special field of soil bioengineering and river restoration. Different studies were carried out to assess the carbon footprint of various SWB structures mainly with the popular impact category Global Warming Potential (GWP). The life cycle itself can be divided into four phases: the product phase, the construction phase, the use phase and the end of life phase. For the presented case studies the system boundary is defined as cradle to gate (until the construction is finished), except for one case study where the use phase is analysed (including the maintenance and conservation work as well as the potential positive effects resulting from the living plants).

The results show that SWB construction sites are able to perform better in terms of carbon emissions than conventional construction sites, but they even cause negative effects on the environment. Apart from that, SWB structures are able to compensate emissions from construction by absorbing carbon through growing vegetation in the use stage. Therefore, a holistic approach starting in the planning stage can help to optimize processes throughout the life cycle and to minimize the environmental burdens. The case studies show that the application of an LCA model is not only important in terms of engineering effects but also provides transparency for the responsible planners and stakeholders, by pointing out the total consumption of resources in all phases and components.

How to cite: von der Thannen, M. and Rauch, H. P.: Life Cycle Assessment of soil and water bioengineering structures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8218, https://doi.org/10.5194/egusphere-egu24-8218, 2024.

In physics-based models for regional landslide susceptibility, the slope stability is most sensitive to the changes of both soil and root cohesion, thus a stochastic approach for these variables is preferred. Root cohesion (RC) is frequently oversimplified and assumed constant and uniform across the landscape. However, the assumption of a constant RC may be inappropriate because root distribution varies spatially with forest characteristics and temporally with tree growth.

Root biomass (RB) is a parameter used to partly quantify the amount of carbon sequestered in forest soils and therefore some empirically based functions (Marklund, 1988) exist to estimate RB from forest characteristics (size and species) in Norway. In turn, RB can be correlated to the reinforcement provided by roots, and can be included in slope stability models as an additional RC term.

This study presents an expeditious estimation of spatially variable RC from RB maps. The resulting maps can be used as input to shallow landslide susceptibility models at regional scale.

The method uses the formula proposed by Hwang et al. (2015), which derives the basal root cohesion from the original W&W model as proportional to the root biomass per ground area, and the density of the roots. The assumptions of the method are the following:

• Basal RC is used to account for the role of forests on regional scale landslide susceptibility and hazard analysis.
• RC increase is directly proportional to RB.
• Only the roots with a diameter below 5 mm are concurring to the additional RC, thus only a percentage of the total root underground biomass as calculated for purposes of carbon sequestration is considered.

The method was applied for Norwegian forests consisting primarily of Pine (Pinus sylvestris), Spruce (Picea abies), and Birch (Betula pendula and pubescens) trees.

The RB maps were obtained by models produced by the Norwegian Institute of Bioeconomy Research (NIBIO), which use a mixture of airborne LIDAR and satellite imagery to characterise the above ground forest characteristics nationally (Astrup et al. 2019), then use the empirical functions to estimate RB. The surface resolution is 16 m².

The study area is located in Sunnfjørd, precisely in Jølster, where several rainfall-induced landslides occurred in July 2019, causing damages to local infrastructure.

Estimates of RC from RB are compared with empirical data from the literature for similar species in forests outside Norway, showing reasonable consistency in the values ranges obtained. Further validation is needed with empirical data from Norwegian forests.

This study provides a simple yet computationally efficient estimation of root cohesion from RB maps, which can be used to supply parameters for models accounting for the effect of vegetation on landslide susceptibility at regional scale. In the future, it will be necessary to develop more precise relationships of fine root biomass to above ground forest characteristics with respect to changing soil properties.

References:

Astrup et al. (2019). https://doi.org/10.1080/02827581.2019.1588989

Hwang et al. (2015). https://doi.org/10.1002/2014JG002824

Marklund, L.G. (1988) Biomassafunktioner för tall, gran och björk i Sverige = Biomass functions for pine, spruce and birch in Sweden. Umeå: Sveriges lantbruksuniversitet, Institutionen för skogstaxering.

How to cite: Capobianco, V., Palau Berastegui, R., McLean, P., Hoffstad Reutz, E., DiBiagio, A., Piciullo, L., and Gilbert, G.: A method to derive spatially variable root cohesion maps from underground biomass maps for regional landslide susceptibility models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15976, https://doi.org/10.5194/egusphere-egu24-15976, 2024.

In the course of climate change, the framework conditions for agricultural production will change significantly. The ability of the soil to absorb water quickly and efficiently while at the same time storing as much water as possible for plants to use is a prerequisite for maintaining future agricultural production potential.

The aim of this study was to investigate the application of recycled brick sand in agricultural soils with regard to its water absorption and storage capacity and thus to improve the efficiency of water utilisation. The influence of different precipitation intensities on the water storage capacity was analysed.

In order to determine the influence of brick sand on the soil water balance, an experiment was carried out with nine small lysimeter systems. The lysimeters were all filled with soil samples from a vineyard in eastern Austria, whose soil has a high sand fraction and low clay mineral content. Three lysimeters were used as a reference and contained no brick sand. In three others, a mixture of soil sample and 10 % brick sand was used and in three others a mixture of soil sample and 30 % brick sand was applied. A 3-phase test was then carried out. The first phase was used to set a volumetric water content that was as constant as possible in all samples. The second phase was the simulation of a 10-millimetre precipitation event, followed by the third phase, the simulation of a 20-millimetre precipitation event. During the precipitation simulation, the amount of water corresponding to the precipitation intensity was applied to the lysimeter systems and the volumetric water content of the samples was recorded. Control values were determined using soil moisture sensors.

The results showed that the addition of brick sand enabled the soil to store more water over time than the sample without brick sand. The simulations also showed that the amount of brick sand added made a difference in how the water storage capacity changed. Shortly after the rainfall simulation, the lysimeters with 30 % brick sand were able to store the water better. Towards the end of the precipitation simulation, the difference in stored water between the lysimeters with 30 % brick sand content and those with 10 % brick sand content became smaller, and in the 20 millimetre rainfall simulation, the lysimeters with 10 % brick sand content stored more water from halfway through the observation period. The results showed that the use of brick sand as a measure to improve the soil water balance has a high potential, however, the amount of brick sand applied must be adapted to the soil to be treated. These adjustments concern parameters such as grain size distribution and pore distribution, as these have a decisive influence on the water storage capacity.

How to cite: Mähr, A., Rauch, H. P., Eitzinger, J., Weihs, P., and Hörbinger, S.: Effect of brick sand on the soil water balance in permeable soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20297, https://doi.org/10.5194/egusphere-egu24-20297, 2024.

Bank erosion is essential for the proper functioning of rivers and the preservation of their freedom space. However, when the assets are at risk, it is sometimes necessary to implement protective structures along the banks. Unlike civil engineering, soil and water bioengineering techniques offer the advantage of addressing various ecosystem services, thereby contributing to environmental preservation while protecting against erosion. Despite these advantages, the development of such techniques is hampered by a lack of understanding regarding their failure modes. Scour was identify as a factor of failure for 45% of cases of mechanical destruction on bioengineering structure. This is why accurate prediction of scour depths is a predominant factor for a successful design. In order to reduce the scope of the study, this work focuses on bend scour, where stresses on the outer bank are often significant. A review of existing literature was conducted to gain a deeper understanding of available methods for estimating this depth. Twelve empirical formulas for bend scour predication were identified and their domain of validity gathered. All these formulas were developed between 1930 and 2006 and some links between them were highlighted. Depending on the country in which they were developed, the news ones were often inspired from the old ones and used a part of the same dataset. Fifty natural bend were visited on ten lowland or piedmont rivers. Topographical and granulometric measurements were performed to compare the scour depths derived from literature formulas with field values. Some formulas appear to stand out due to their general tendency to overestimate depths or their precision under specific application conditions. Despite the limitations of the study, these results provide an initial overview of the trends for each formula, making it easier to understand the most appropriate conditions of application for each of them.

How to cite: Fructus, N., Leblois, S., Piton, G., Recking, A., and Evette, A.: Literature review and empirical analysis of bend scour formulas., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3879, https://doi.org/10.5194/egusphere-egu24-3879, 2024.

Fascines are Soil and Water Bioengineering techniques for erosion control and slopes stabilisation. As Nature-based solutions, these age-old and highly adaptable techniques generally rely on the installation of living willow bundles fixed to either dead or living stakes. Fascines are the most widely used techniques to protect riverbanks toe in France; they are also implemented on slopes, and gullies making wide their possible use. They are often employed as part of a combination of techniques to meet specific local needs. Despite the common implementation of fascines, no guidelines cover the entire diversity of fascines. The technical guideline proposed describes the full scope of possibilities fascines offer, their advantages and disadvantages and technical details and specifications of implementation. Drawing on a foundation of technical literature, historical documentation, research experiments, and empirical knowledge, the guide delves into no fewer than 112 references. The objective is to enhance the use, success, and overall confidence in fascine-based techniques.

This guide presents comprehensive information on no fewer than 12 fascine techniques that have transcended through the ages, originating from structures dating back over 2,000 years in China and continuing to be relevant in the contemporary world.  Although fascines may seem simple and are known for their high mechanical strength, these techniques require high expertise to ensure lasting resistance and satisfactory plant growth. Several critical factors contribute to the success and durability of these structures, including the choice of plant species, the quality of planting materials, the nature of soil contact, and the positioning of the bundle relative to infiltration or groundwater levels. Application methods vary based on the specific technique and context: Fascines can be alive or inert; placed parallel or perpendicular to the slope; they come in different diameters with one or multiple bundles and can be used as barriers or drains. The most illustrative example is the implementation of fascines along the toe of the bank, which stands as the most widely used technique. For this approach, bundles should measure between 100 and 300 cm in length, with a diameter ranging from 15 to 50 cm. Branches should have a minimum diameter of 2 cm and a length of approximately one meter.

This technical support is intended for designers, river managers, technicians, and the general public, providing precise technical recommendations for the successful creation of fascines, from materials to maintenance, as well as implementation methods and environmental conditions appropriate to this type of structures.

How to cite: Didier, M., Evette, A., Schmitt, E., Leblois, S., Jaymond, D., Evette, J.-B., Mira, E., Raymond, P., Frossard, P.-A., and Vivier, A.: Enhancing fascine techniques for slopes erosion control: A comprehensive technical guide, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15564, https://doi.org/10.5194/egusphere-egu24-15564, 2024.

Integrating Soil and Water Bioengineering (SWBE) and Nature-Based Solutions (NBS) represents a historical and advanced approach to addressing complex environmental issues. In particular, SWBE, as NBS, solutions aim to mitigate the occurrence and propagation of hydrogeological hazards. Techniques involving plants, and locally available materials, like timber and stone, have characterized land management since past times, guided by practical experience and necessity. In recent decades, we started rediscovering these techniques by including them in the definition of SWBE.

This study explores the current knowledge and perceptions of practitioners, such as engineers, architects, geologists, agronomists-foresters, and naturalists, regarding practices defined as SWBE by recent legislation and scientific literature. A questionnaire will be distributed through different communication channels to achieve this goal, mainly targeting the professional association of interest. The questionnaire consists of three sections: i) collecting the stakeholders’ biographical information, ii) investigating knowledge of the basic concepts and interpretation of SWBE and NBS techniques, and iii) discussing critical issues, possible improvements, and future perspectives in applying SWBE and NBS.

The results of this study provide a framework that leads to a deeper understanding of how SWBE and NBS are understood outside the academic environments, fostering more significant interaction between technical application and theoretical development. Analyzing similarities and divergences between the state of the art, current practices, and stakeholder perceptions is crucial, thus helping identify gaps and bringing out new frontiers of innovation within SWBE.

How to cite: Pini, S. and Preti, F.: Innovations in Soil Water Bioengineering: A Stakeholder Perception Assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18452, https://doi.org/10.5194/egusphere-egu24-18452, 2024.

Citizens in urban areas face many pressures and the goal should be to develop plans and implement actions to improve their living environment by providing clean air, clean water but also recreation and relaxation areas. Urban riparian areas can support such services for its citizens; thus, efforts should be made to either establish new ones or conserve the already existing ones. The aim of this study was to utilize new technologies that should enhance the assessment of the current conditions of urban riparian areas. Such datasets should help land and water managers develop better plans to mitigate the anthropogenic pressures that these areas face. In addition, these datasets can showcase the main anthropogenic pressures of the study area and allow to recommend proper nature-based solutions and their optimal placement. The case study was the Agia Varvara Park of Drama city in Greece. The Park is a unique riparian area with litter one of the main problems in its water bodies. The innovative tools used were unmanned aerial vehicles with high resolution regular and thermal cameras, unmanned underwater vehicles. In addition, a GPS tracker, was also used to record the potential movement route of litter and a sonar device to develop cross-sections of Agia Varvara’s stream. The produced orthomosaics, digital surface models, cross-section and litter route showcased that litter traps could be a suitable nature-based solution. In addition, the optimal location for litter trap placement was determined. This simple measure could sustainably minimize litter pollution in the Park.

How to cite: Zaimes, G., Iakovoglou, V., Koutalakis, P., and Gkiatas, G.: Utilizing new technologies and nature-based solutions for sustainable urban riparian area management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3627, https://doi.org/10.5194/egusphere-egu24-3627, 2024.

Land degradation, e.g. shallow landslides, with correlated soil loss and nutrient loss, is a significant environmental problem for the agroecosystems, especially where farming is carried out on sloping soil (e.g. vineyards, olive groves, etc.).Due to climate change and consequent increase on extreme weather events, these processes are likely to become more widespread, thus leading to significant land abandonment.Another factor affecting land degradation concerns soil tillage by agricultural machinery, which, if uncontrolled, can accelerate the development of these processes.Land degradation is also dangerous for rural communities because of its rapidity of initiation and development and the lack of warning signs for its detection. It is therefore necessary to apply in agroecosystems effective solutions for disaster risk reduction (DRR) which, at the same time, are of low environmental impact and economically sustainable. Nature-based Solutions (NbS) can help address all these challenges as they are widely recognized by the scientific community and are often funded by countries or the union of countries, such as the European Union or the United Nations. However, NbS are still poorly applied by farmers and local governments, favoring gray infrastructure measures that are sometimes ineffective at achieving land degradation neutrality.

The aim of this work is to produce an inventory of the Nature-based Solutions applied in vineyards in an Apennine area of Northern Italy in order to verify, at the slope scale, their effectiveness in the mitigation of shallow landslides. The study area is represented by a sector of Oltrepò Pavese, one of the most important agricultural and viticultural regions in Italy.In the last 15 years, more than 2000 shallow landslides were triggered in consequence of intense rainfall events, with a density of distribution which reached more than 40% of the territory cultivated with grapevines. The work is carried out in the context of a PhD project, financed with PNRR (National Recovery and Resilience Plan) and cofounded by seven municipalities, stakeholders of the project. The final aim of the PhD projectis to identify the most suitable NbS for the studied area, in terms of technical and economical suitability. The scientific research results will be incorporated within the municipal planning tools and rural police regulation in order to prevent shallow landslides.

How to cite: Gambarani, A., Vercesi, A., Bordoni, M., Giarola, A., Vivaldi, V., and Meisina, C.: Nature-based Solutions in vineyards of Oltrepò Pavese (Northern Italy): state of the art and analysis of their effectiveness in shallow landslide mitigation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17275, https://doi.org/10.5194/egusphere-egu24-17275, 2024.

Our motivation is to explain how severe bank slides, such as those following natural disasters, can be sustainably reintegrated into the river ecosystem in a modern, contemporary manner through the application of NbS and combined techniques. Our purpose is to explain the needs of an integrated engineering approach to find out the causes of streambank slides before works start. We point out the workflow of NbS reconstruction process by determining an efficient analysing stage, a construction stage and a monitoring stage. We show three realized examples of steep bank reintegration situated in high flow regime. Our conclusions show that reintegration into the river landscape of violent bank slides near residential areas and infrastructure with NbS techniques is feasible. The prerequisites, however, are a sufficient root cause analysis by an integrated engineering approach, and good training and experience of the hired construction companies during construction stage. In addition, clients need to throw out some of their old ideas of exclusively mineral and similar attachment techniques. This presentation serves as a demonstration of the potential of sustainable NbS steep bank revegetation for infrastructure protection, based on geotechnical analysis using examples realized in France between 1999 and 2022.

How to cite: Peklo, K.: Nature based Solutions and combined techniques in the immediate vicinity of infrastructure and residential areas -  Case studies of steep bank stabilizations in the Garonne water catchment area in France realized between 1999 and 2022, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5718, https://doi.org/10.5194/egusphere-egu24-5718, 2024.

The note focuses on a preliminary study of the effects of deforestation on the activation of debris flow. The area of interest is located in Nottoria, at the south of Norcia (Perugia, Italy). In 2012, after an intense thunderstorm, a debris flow occurred involving the village. The mobilized debris is mainly made of blocks of limestone channelling into the main road and then pouring into the valley lateral to the village. The debris reached in some point 1m of thickness while, in some areas, deep erosion due to water runout was significant. The debris consists of calcareous pebbles of varying sizes diffused in a marly-clayey matrix. Another debris flow was recorded in 2015. The main causes have been attributed to intense rainfalls involving valleys characterized by the outcrop of limestones intensely fractured. This information has been confirmed by the inspection of the Regional Geological Map (1:10000). The figure below shows the accumulation area, the propagation channel, and the source areas of the debris flow. Highly fractured side cliffs in which vegetation has grown were observed. Debris flow polygon has been imported from IdroGEO database (ISPRA).

A recent survey has revealed the presence of tall beeches and oaks. Furthermore, evidence of deforestation is clear in the area of possible triggering of debris. It is interesting to note that different deforestation parcels were generated between 2005 and 2011, while the debris flows occurred in 2012 and 2015. Moreover, from a recent survey, there appear to be potential source zones upstream of the phenomenon mapped in the official databases (IdroGeo, ISPRA).

A preliminary study has been undertaken to highlight the effects of deforestation occurring near the trigger zone. The research aims at investigating the role of vegetation in shallow slope stability or, from another point of view, the effect of deforestation in slope instability.  In-situ investigation has been planned, consisting of a geo-electric survey. Geophysical surveying techniques has been proved to be useful for predicting matric suction values through the relationships among soil porosity, saturation degree and electrical resistivity.

A laboratory investigation on physical properties of debris will be carried out in the geotechnical laboratories of ISPRA and University of Perugia. The need to set up specific in situ instrumentation to detect roots geometry, typology and depth is recognized, with the goal of quantifying the hydro-mechanical effects of roots on the material shear strength through in situ tests (e.g. direct shear apparatus, corkscrew, prospecting based on sound signal propagation).

There is no proof of debris re-activation after the seismic event of 30 October 2016 M_w 6.5 Norcia earthquake, 4 years later the occurrence of the first debris flow and 1 year later the second one. This point requires further investigation. The beneficial (or not) contribution of vegetation along the debris flow channel needs to be carefully modelled in order to design safe countermeasures for the mitigation of hydrogeological and seismic risk.

References

IdroGEO, https://idrogeo.isprambiente.it/ (website accessed on 09/01/2024).

Umbria Region, Geological Map (Carta geologica dell’Umbria - Dataset - Open Data Umbria regione.umbria.it).

Geological Survey of Umbria Region (https://www.regione.umbria.it/-/cartografia-geologica)

How to cite: Lepri, A., Fraccica, A., Cencetti, C., and Cecconi, M.: A preliminary study on the possible effect of deforestation in debris flows deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15726, https://doi.org/10.5194/egusphere-egu24-15726, 2024.