Soil erosion in Sicily: testing hydro-morphological approaches

I processi di denudazione sulla Terra sono fenomeni naturali di modellazione della sua superficie sotto l'azione di una serie di agenti, tra i quali il deflusso delle acque superficiali svolge un ruolo centrale soprattutto nelle zone climatiche umide. Ogni processo di modellazione è caratterizzato da tre fasi: erosione, trasporto e deposito. Nel caso di fenomeni legati al deflusso dell'acqua, devono essere analizzati in un sistema molto complesso, l’acqua infatti scorre con modalità diverse dai versanti (overland flow) ai ruscelli (rete di drenaggio) ai fiumi (canali). Allo stesso tempo, la litosfera espone al lavoro meccanico dell'acqua diversi tipi di geo-materiali, che vanno da rocce cementate molto resistenti a terreni e detriti molto deboli. Nel caso delle rocce s.s. le differenze in termini di erodibilità sono legate ai processi litogenetici (composizione, tessitura, struttura) e ai successivi fenomeni atmosferici che ne possono modificare lo stato originale. Gran parte della Terra è in realtà "coperta" dai prodotti degli agenti atmosferici o dai depositi dei processi di modellazione (detriti s.s., in geomorfologia). Lo strato mediamente stabile è l'orizzonte di base dove la vegetazione cresce e fissa l'eluvium (suolo s.s., in geomorfologia). I depositi detritici sono il risultato dell'azione erosiva dell'agente modellante e possono avere caratteristiche molto diverse a seconda del processo genetico specifico.Secondo gli elementi molto generali menzionati sopra, l'approccio allo studio dell'erosione mette lo scienziato di fronte a una sfida molto complessa. Tuttavia, un approccio semplificato può fornire strumenti per comprendere e modellare i processi in misura sufficiente per affrontare le esigenze attuali. Infatti, se la logica naturale dei processi di erosione è indiscutibile, gli effetti legati all'incrocio di questi processi e l'attività umana sono di interesse in quanto sono correlati ad alcuni aspetti di rischio. La perdita del suolo è ovviamente una fonte diretta di danni per l'agricoltura e le coltivazioni. Il deterioramento del suolo e dei detriti può provocare fenomeni distruttivi come debris floods e debris flow o ridurre la sezione del canale disponibile sui ponti e riempire i serbatoi artificiali riducendone la loro capacità di stoccaggio.Questa tesi cerca di indagare le problematiche dell'erosione del suolo in Sicilia, focalizzandosi su tre principali approcci.Il primo approccio si basa sull'analisi dei processi di erosione da una prospettiva sperimentale, cercando le relazioni tra la portata liquida e la portata solida, misurati in sezioni fluviali, e le caratteristiche idro-morfodinamiche dei bacini idrologici. In particolare, i dati storici della rete regionale delle stazioni di misura idrometriche sono stati analizzati costruendo le Sediment Rating Curves (SRC), che predicono la concentrazione del sedimento in sospensione (Suspended Sediment Concentration) dalla portata liquida (Q), e analizzando i cicli annuali di isteresi media. Un approccio diverso è stato adottato nel secondo caso sperimentale, in cui SWAT (Soil and Water Assessment Tool), un modello continuo fisicamente basato a scala di bacino e sviluppato dall'USDA-ARS, è stato applicato al bacino del fiume San Leonardo. L'obiettivo di SWAT è determinare in che modo l'uso e la gestione del territorio possano influire sulle portate liquide e sulle portate solide nei bacini idrici. In SWAT, l'erosione e la resa dei sedimenti sono stimati dalla Modified Universal Soil Loss Equation (MUSLE). Mentre la più conosciuta ed applicata USLE (Universal Soil Loss Equation) utilizza la pioggia come indicatore dell'energia erosiva, la MUSLE utilizza la quantità di deflusso funzione delle condizioni di umidità antecedenti e dell'energia delle precipitazioni. Nella terza ed ultima applicazione, la valutazione dell'erosione idrica è stata effettuata nell'ambito di uno studio di vulnerabilità all’erosione costiera per stimare il contributo dell’apporto di sedimento nelle unità fisiografiche costiere siciliane. In particolare, il modello spazialmente distribuito WaTEM/SEDEM è stato utilizzato per valutare il carico sedimentario trasportato nelle zone costiere. Il modello WaTEM/SEDEM è costituito da tre componenti principali: valutazione dell'erosione del suolo, calcolo della capacità di trasporto dei sedimenti e applicazione in un algoritmo di trasporto dei sedimenti. In WaTEM/SEDEM l'erosione del suolo è calcolata con una versione modificata della RUSLE. Una volta che il tasso medio annuale di erosione è noto, l’algoritmo viene utilizzato per trasferire la quantità di suolo prodotta (erosione lorda) dalla sorgente alla rete fluviale in base alla equazione della capacità di trasporto (TC in Mg yr-1).Denudation processes on Earth are intricate and natural modeling phenomena of its surface under the action of a set of agents, among which water runoff surface plays a central role in humid climatic areas. Each modeling process is marked by erosion s.s., transport, and deposit stages, which in the case of runoff water-related phenomena, have to be analyzed in a very complex system. In fact, running water flows with different modes from hillslopes (overland flow) to streams (drainage network) to rivers (channel). At the same time, the lithosphere is exposed to the mechanic work of running water with very different types of geo-materials, ranging from very (too) resistant cemented rocks to very weak soils and debris. In the case of rocks s.s., differences in terms of erodibility are linked to the lithogenetic processes (composition, texture, structure) and to subsequent weathering phenomena, which can modify the original status in the outcropping horizon volumes. A large part of the Earth is actually “covered” by the products of weathering processes or the deposits of the modeling processes (debris s.s., in geomorphology). The moderately stable weathered layer is the base horizon where vegetation grows and fixes the eluvium (soil s.s., in geomorphology). Debris deposits are the result of the erosive action of the modeling agent and can have very different characteristics according to the specific genetic process.According to the general elements above, approaching the study of erosion poses the scientist in front of a very intricate challenge. However, a simplified approach can furnish tools for understanding and modeling the processes to an extent suitable enough to face the current requirements. In fact, if the natural rationale of erosion processes is out of doubt, the effects of mixing these processes and human activity are of interest as some risk aspects are related. Soil loss is obviously a direct source of damage for agriculture and farming. Deteriorating soil and debris can result in destructive phenomena such as debris floods and debris flow, reducing the available channel section at bridges, or filling artificial reservoirs, reducing their storage capacity.This thesis tries to investigate water erosion issues in Sicily, with a specific focus on three main adopted approaches.The first approach is based on the analysis of the erosion processes from an experimental perspective, searching relations between the measured flow of water and sediment through a stream or fluvial section and the subtending hydro-morphodynamic, which merge in two time changing measured parameters all the effects of the interplay between rainfall/temperature forcing and slope, stream, and channel response.In particular, the available historical data of the hydrometric gauge stations' regional network are analyzed by modeling Sediment Rating Curves (SRCs), which predict the Suspended Soil Concentration (SSC) from the water discharge (Q) and analyzing the mean hysteresis annual loops. A different approach was adopted in the second experimental case, where SWAT (Soil and Water Assessment Tool), a physically-based continuous model for catchment scale simulations developed by the USDA-ARS, was applied to the San Leonardo River basin. SWAT's objective is to determine how land use and management can affect water, sediment, and agricultural chemical yields in ungauged watersheds. In SWAT, erosion and sediment yield are estimated from the Modified Universal Soil Equation (MUSLE). While the USLE uses rainfall as an indicator of erosive energy, MUSLE uses the amount of runoff, which should improve the sediment yield prediction because runoff is a function of antecedent moisture conditions as well as rainfall energy. Therefore, differently from USLE, delivery ratios are not needed with MUSLE because the runoff factor represents energy in detaching and transporting sediment.In a third application, water erosion assessment is carried out in the framework of a coastal erosion study to estimate the contribution of soil delivery at the coastal physiographic units in the advancement/retreatment stages. In particular, the spatially distributed model WaTEM/SEDEM is used to evaluate the sediment load carried to the coastal areas. The WaTEM/SEDEM model consists of three main components: soil erosion assessment, sediment transport capacity calculation, and sediment routing. Soil erosion is predicted with a modified version of RUSLE for 2-dimensional landscapes. Once the mean annual erosion rate is known at each grid cell, a routing algorithm is used to transfer the displaced soil amount (gross erosion) from the source to the river network according to the transport capacity (TC in Mg yr-1)

Passive seismology and deep structure in central Italy

n the last decade temporary teleseismic transects have become a powerful tool for investigating the crustal and upper mantle structure. In order to gain a clearer picture of the lithosphere-asthenosphere structure in peninsular Italy, between 1994 and 1996, we have deployed three teleseismic transects in northern, central, and southern Apennines, in the framework of the project GeoModAp (European Community contract EV5V-CT94–0464). Some hundreds of teleseisms were recorded at each deployment which lasted between 3 and 4 months. Although many analyses are still in progress, the availability of this high quality data allowed us to refine tomographic images of the lithosphere-asthenosphere structure with an improved resolution in the northern and central Apennines, and to study the deformation of the upper mantle looking at seismic anisotropy through shear-wave splitting analysis. Also, a study of the depth and geometry of the Moho through the receiver function technique is in progress. Tomographic results from the northernmost 1994 and the central 1995 teleseismic experiments confirm that a high-velocity anomaly (HVA) does exist in the upper 200–250 km and is confined to the northern Apenninic arc. This HVA, already interpreted as a fragment of subducted lithosphere is better defined by the new temporary data, compared to previous works, based only on data from permanent stations. No clear high-velocity anomalies are detected in the upper 250 km below the central Apennines, suggesting either a slab window due to a detachment below southern peninsular Italy, or a thinner, perhaps continental slab of Adriatic lithosphere not detectable by standard tomography. We found clear evidence of seismic anisotropy in the uppermost mantle, related to the main tectonic processes which affected the studied regions, either NE–SW compressional deformation of the lithosphere beneath the mountain belt, or arc-parallel asthenospheric flow (both giving NW–SE fast polarization direction), and successive extensional deformation ( E–W trending) in the back-arc basin of northern Tyrrhenian and Tuscany. Preliminary results of receiver function studies in the northern Apennines show that the Moho depth is well defined in the Tyrrhenian and Adriatic regions while its geometry underneath the mountain belt is not yet well constrained, due to the observed high complexity.Published479-4934T. Sismicità dell'ItaliaJCR Journa

An Approach for the Validation of a Coastal Erosion Vulnerability Index: An Application in Sicily

In recent decades, coastal erosion phenomena have increased due to climate change. The increased frequency and intensity of extreme events and the poor sediment supply by anthropized river basins (dams, river weirs, culverts, etc.) have a crucial role in coastal erosion. Therefore, an integrated analysis of coastal erosion is crucial to produce detailed and accurate coastal erosion vulnerability information to support mitigation strategies. This research aimed to assess the erosion vulnerability of the Sicilian coast, also including a validation procedure of the obtained scenario. The coastal vulnerability was computed by means of the CeVI (Coastal Erosion Vulnerability Index) approach, which considers physical indicators such as geomorphology and geology, coastal slope, sea storms, wave maxima energy flux and sediment supply to river mouths. Each indicator was quantified using indexes which were assessed considering transects orthogonal to the coastline in 2020. These transects were clustered inside natural compartments called littoral cells. Each cell was assumed to contain a complete cycle of sedimentation and not to have sediment exchange with the near cells. Physical parameters were identified to define a new erosion vulnerability index for the Sicilian coast. By using physical indexes (geological/geomorphological, erosion/sediment supply, sea storms, etc.), the CeVI was calculated both for each littoral cell and for the transects that fall into retreating/advancing coastal areas. The vulnerability index was then validated by comparing CeVI values and the coastline change over time. The validation study showed a direct link between the coastline retreat and high values of CeVI. The proposed method allowed for a detailed mapping of the Sicilian coastal vulnerability, and it will be useful for coastal erosion risk management purposes

An Approach for the Validation of a Coastal Erosion Vulnerability Index: An Application in Sicily

In recent decades, coastal erosion phenomena have increased due to climate change. The increased frequency and intensity of extreme events and the poor sediment supply by anthropized river basins (dams, river weirs, culverts, etc.) have a crucial role in coastal erosion. Therefore, an integrated analysis of coastal erosion is crucial to produce detailed and accurate coastal erosion vulnerability information to support mitigation strategies. This research aimed to assess the erosion vulnerability of the Sicilian coast, also including a validation procedure of the obtained scenario. The coastal vulnerability was computed by means of the CeVI (Coastal Erosion Vulnerability Index) approach, which considers physical indicators such as geomorphology and geology, coastal slope, sea storms, wave maxima energy flux and sediment supply to river mouths. Each indicator was quantified using indexes which were assessed considering transects orthogonal to the coastline in 2020. These transects were clustered inside natural compartments called littoral cells. Each cell was assumed to contain a complete cycle of sedimentation and not to have sediment exchange with the near cells. Physical parameters were identified to define a new erosion vulnerability index for the Sicilian coast. By using physical indexes (geological/geomorphological, erosion/sediment supply, sea storms, etc.), the CeVI was calculated both for each littoral cell and for the transects that fall into retreating/advancing coastal areas. The vulnerability index was then validated by comparing CeVI values and the coastline change over time. The validation study showed a direct link between the coastline retreat and high values of CeVI. The proposed method allowed for a detailed mapping of the Sicilian coastal vulnerability, and it will be useful for coastal erosion risk management purposes

A regional approach for exploring the relation between sediment transport and coastal erosion in Sicily

To study on a regional basis, the relation between fluvial sediment delivery and coastal erosion, the historical record of coastline migration of Sicily was analyzed with respect to the estimated sediment delivery to the coast obtained from the spatially distributed sediment delivery WaTEM/SEDEM model. The latter was directly acquired from the ESDAC database as a 25 m pixel layers, being based on the combination between the RUSLE model and a transport capacity routing algorithm. At the same time, the coastline-evolution (accretion/retreatment) data for 1960/1994 and 1994/2012 intervals were processed. This dataset, provided by ISPRA (Italian Institute for Environmental Protection and Research), is made by vectorial polygons, corresponding to erosion or accretion areas obtained by the intersection between two coastlines. The dataset contains polygons related to the 1960-1994 and 1994-2012 periods. Once a common baseline was extracted from 2019 satellite images, 22 Physiographic Units (PU) were identified. The PU was defined based on geomorphologic criteria and by assuming a null net sediment budget (null sediment transport between two PU neighboring). Each coastal PU was connected to its contributing fluvial basins, also assigning the expected sediment delivery at the coastline. To perform the analysis, cross profiles along the coastline were generated and intersected with the polygons, calculating a response value, in terms of retreatment or accretion, to each of the cross-profile centroids. Finally, for each PU, the cumulated variations were computed. PUs with significant cumulative variations (more than 2 km) in at least one of the two epochs were identified and three different patterns were detected: accretion/retreatment, retreatment/accretion, and retreatment/retreatment. The response observed for the different PUs was then analyzed considering estimated sediment delivery, recognizing coherent (large sediment delivery = accretion) and incoherent (large sediment delivery = retreatment) behaviors, which have been interpreted as controlled by the history of soil/coastal erosion management practices. In particular, in spite of a very high expected sediment delivery, more than three-quarters of the Powered by TCPDF (www.tcpdf.org) Tyrrhenian coast resulted as affected by a marked retreat in 60-94 (same tens of meters) and a moderate accretion in 94-12, as the result of extensive coastal works which have been realized to mitigate coastal erosion

Susceptibility analysis for seismically-induced landslides: application to the 2001 earthquakes in El Salvador (C.A.)

The geodynamic context in which El Salvador is located, made of a convergent structure characterized by the interaction among six different plates, together with the lithological characteristics of the outcropping rocks and soils (mainly corresponding to deeply weathered acid pyroclastites, basic effusive rocks and volcanic ashes), are responsible for the very high seismically- induced landslide susceptibility of the country. These predisposing factors were decisive on the occurrence of thousands of seismically-induced landslides caused by two huge earthquakes on 13th January and 13th February 2001, which triggered thousands of landslides in the country. In particular, the February event (6.6M, onshore and intraplate at a depth of 10 km) triggered 5,371 landslides in an area of around 300km2. These gravitational phenomena took the form of debris slides, earth slides and debris flows and affected several inhabited areas damaging infrastructures and crops and causing, respectively 844 and 315 fatalities. Thanks to aerial photos taken soon after the days following both the two earthquakes and made available by the CNR (Centro Nacional de Registros - Instituto Geográfico y del Catastro Nacional), associated landslide maps have been prepared, where each phenomenon is represented by a landslide polygon and its LIP (Landslide Identification Point), located in the crown of the landslide. In particular, static landslide susceptibility models were prepared for the Ilopango (1594 landslides in an area of around 40km2) and the San Vicente (1602 landslides in an area of around 108 km2) sectors, by regressing the spatial distribution of the 13th February seismically-induced landslides on a set of explanatory variables obtained by a geologic map and a 10m pixel DTM (Digital Terrain Model). At the same time, shaking-dependent models were prepared by including also PGA (Peak Ground Acceleration) and the epicentral distance (ED) among the predictors. For both the two areas a marked increase of performance was observed (AUC from 0.70 to 0.75, for Ilopango, from 0.73 to 0.77, for San Vicente) from the static to the shaking-dependent models, highlighting the role of the seismic acceleration in the triggering of the landslides both in activating the susceptible sites and in lowering the score threshold for slope failures occurrences. Besides, for the Ilopango sector, a rainfall-induced susceptibility model was also prepared, exploiting a landslide inventory available for the 2009 IDA/12E storm events. The obtained score was then Powered by TCPDF (www.tcpdf.org) combined with PGA and ED to predict the spatial distribution of the seismically induced landslides, obtaining a higher performance than the relative basic model (AUC = 0.75). The results obtained from the research demonstrate suggest the possibility to couple the susceptibility scores obtained from static modelling to the expected mechanical shaking for the seismically-induced susceptibility assessment. The whole modelling was carried out by applying MARS (Multivariate Adaptive Regression Splines) analysis through RStudio and SAGA GIS freeware software

Predicting Earthquake-Induced Landslides by Using a Stochastic Modeling Approach: A Case Study of the 2001 El Salvador Coseismic Landslides

In January and February 2001, El Salvador was hit by two strong earthquakes that triggered thousands of landslides, causing 1259 fatalities and extensive damage. The analysis of aerial and SPOT-4 satellite images allowed us to map 6491 coseismic landslides, mainly debris slides and flows that occurred in volcanic epiclastites and pyroclastites. Four different multivariate adaptive regression splines (MARS) models were produced using different predictors and landslide inventories which contain slope failures triggered by an extreme rainfall event in 2009 and those induced by the earthquakes of 2001. In a predictive analysis, three validation scenarios were employed: the first and the second included 25% and 95% of the landslides, respectively, while the third was based on a k-fold spatial cross-validation. The results of our analysis revealed that: (i) the MARS algorithm provides reliable predictions of coseismic landslides; (ii) a better ability to predict coseismic slope failures was observed when including susceptibility to rainfall-triggered landslides as an independent variable; (iii) the best accuracy is achieved by models trained with both preparatory and trigger variables; (iv) an incomplete inventory of coseismic slope failures built just after the earthquake event can be used to identify potential locations of yet unreported landslides

Using Public Landslide Inventories for Landslide Susceptibility Assessment at the Basin Scale: Application to the Torto River Basin (Central-Northern Sicily, Italy)

In statistical landslide susceptibility evaluation, the quality of the model and its prediction image heavily depends on the quality of the landslide inventories used for calibration. However, regional-scale inventories made available by public territorial administrations are typically affected by an unknown grade of incompleteness and mapping inaccuracy. In this research, a procedure is proposed for verifying and solving such limits by applying a two-step susceptibility modeling procedure. In the Torto River basin (central-northern Sicily, Italy), using an available regional landslide inventory (267 slide and 78 flow cases), two SUFRA_1 models were first prepared and used to assign a landslide susceptibility level to each slope unit (SLU) in which the study area was partitioned. For each of the four susceptibility classes that were obtained, 30% of the mapping units were randomly selected and their stable/unstable status was checked by remote analysis. The new, increased inventories were finally used to recalibrate two SUFRA_2 models. The prediction skills of the SUFRA_1 and SUFRA_2 models were then compared by testing their accuracy in matching landslide distribution in a test sub-basin where a high-resolution systematic inventory had been prepared. According to the results, the strong limits of the SUFRA_1 models (sensitivity: 0.67 and 0.57 for slide and flow, respectively) were largely solved by the SUFRA_2 model (sensitivity: 1 for both slide and flow), suggesting the proposed procedure as a possibly suitable modeling strategy for regional susceptibility studies

Cucire L’immaginario. Arte e moda alla prova dell’ibridazione dei linguaggi

Since the first cover of the magazine «Artforum» dedicated to the fashion designer Miyake, the relationship between fashion design and contemporary art has had several unexpected outocomes and collaborations. Through the study of some occasions in which the mutual alliance between contemporary art and fashion design has been institutionalized and presented to the general public, this essay aims to analyse the assimilation of the couturier to the role of the artist. But, what happens when either haute couture or contemporary art give way to new forms of art and fashion dominated by the global market

Rapid response to the earthquake emergency of May 2012 in the Po Plain, northern Italy

Rapid-response seismic networks are an important element in the response to seismic crises. They temporarily improve the detection performance of permanent monitoring systems during seismic sequences. The improvement in earthquake detection and location capabilities can be important for decision makers to assess the current situation, and can provide invaluable data for scientific studies related to hazard, tectonics and earthquake physics. Aftershocks and the clustering of the locations of seismic events help to characterize the dimensions of the causative fault. Knowing the number, size and timing of the aftershocks or the clustering seismic events can help in the foreseeing of the characteristics of future seismic sequences in the same tectonic environment. Instrumental rapid response requires a high degree of preparedness. A mission in response to a magnitude (ML) 6 event with a rupture length of a few tens of kilometers might involve the deployment within hours to days of 30-50 seismic stations in the middle of a disaster area of some hundreds of square kilometers, and the installation of an operational center to help in the logistics and communications. When an earthquake strikes in a populated area, which is almost always the case in Italy, driving the relevant seismic response is more difficult. Temporary station sites are chosen such as to optimize the network geometry for earthquake locations and source study purposes. Stations have to be installed in quiet, but easily reachable, sites, and for real-time data transmission, the sites might need to have optical intervisibility. The operational center can remain in a town if there is one within the damaged area, and it should coordinate the actions of the field teams and provide information to colleagues, the Civil Protection Authorities and the general public. The emergency system should operate as long as the seismic rate remains high; the duration of any mission might also depend on the seismic history of the area involved. This study describes the seismic response following the May 20, 2012, ML 5.9 earthquake in northern Italy, which included rapid deployment of seismological stations in the field for real-time seismic monitoring purposes, the coordination of further instrumental set-ups according to the spatial evolution of the seismic sequence, and data archiving