1,721,142 research outputs found
A test of transferability for landslides susceptibility models under extreme climatic events: application to the Messina 2009 disaster
No full textA model building strategy is tested to assess the susceptibility for extreme
climatic events driven shallow landslides. In fact, extreme climatic inputs such as storms
typically are very local phenomena in the Mediterranean areas, so that with the exception
of recently stricken areas, the landslide inventories which are required to train any stochastic
model are actually unavailable. A solution is here proposed, consisting in training a
susceptibility model in a source catchment, which was implemented by applying the binary
logistic regression technique, and exporting its predicting function (selected predictors
regressed coefficients) in a target catchment to predict its landslide distribution. To test the
method, we exploit the disaster that occurred in the Messina area (southern Italy) on 1
October 2009 where, following a 250-mm/8-h storm, approximately two thousand debris
flow/debris avalanches landslides in an area of 21 km2 triggered, killing 37 people and
injuring more than 100, and causing 0.5 M € worth of structural damage. The debris flows
and debris avalanches phenomena involved the thin weathered mantle of the Varisican low
to high-grade metamorphic rocks that outcrop in the eastern slopes of the Peloritani
Mounts. Two 10-km2-wide stream catchments, which are located inside the storm core
area, were exploited: susceptibility models trained in the Briga catchment were tested
when exported to predict the landslides distribution in the Giampilieri catchment. The
prediction performance (based on goodness of fit, prediction skill, accuracy and precision
assessment) of the exported model was then compared with that of a model prepared in the
Giampilieri catchment exploiting its landslide inventory. The results demonstrate that the
landslide scenario observed in the Giampilieri catchment can be predicted with the same
high performance without knowing its landslide distribution: we obtained, in fact, a very poor decrease in predictive performance when comparing the exported model to the native
random partition-based model
Analisi della suscettività al dissesto idrogeologico del bacino del T. Roglio (Val d’Era – Toscana): confronto tra analisi di regressione logit e analisi cart per la determinazione delle unità di risposta all’erosione.
No full textIdentification, characterisation and analysis of the Oltrepo Pavese calanchi in the Northern Apennines (Italy)
No full textBadlands are characteristic erosional forms distributed along the entire Apennines. In the Italian context badland areas are called “calanchi”, the plural of the word “calanco”. In this paper we present the first calanchi inventory map of the Oltrepo Pavese area, Northern Apennines (Italy). In total 263 calanchi were mapped using remote sensing techniques like Orthophotos, Google Earth images, as well as field recognition. Moreover, calanchi were characterised from a geomorphologic, geologic and a morphometric point of view. The calanchi of the Oltrepo Pavese have been categorised in two geomorphological classes based on process related morphologies. In the study area calanchi mainly occur in soft sedimentary bedrock materials such as melanges, marls, claystones, and interstratified rocks. The results show that calanchi formations are often related to faults and tectonic lineaments present in the study area. Moreover, we analyse a 5 m cell size Digital Terrain Model to detect correlations between calanchi and morphometric indices. The calanchi, defined and categorised for the first time in the study area, show typical morphometric characteristics of Apennine calanchi forms and features. In particular, they occur on concave south-facing slopes on soft bedrock formations. Finally, a multitemporal air photo interpretation over a 40 years period indicated a general decrease in calanchi areas. The area reduction is mainly correlated to intensive land use changes combined with variations of precipitation pattern. The revegetation trend was also confirmed by NDVI analysis based on Landsat satellites images. The calanchi were digitized and stored in a GIS database providing the information for future quantitative modelling assessments
Spatial prediction of soil organic carbon: Combining machine learning with residual kriging in an agricultural lowland area (Lombardy region, Italy)
No full text'The stolen space': A history of channelization, reduction of riverine areas and related management issues. The lower Scrivia River case study (NW Italy)
No full textIn this research, we present the lower Scrivia River planform changes occurred from 1878 to 2016. furthermore, we illustrate the channelization-works development and the land-use changes registered close to the riverbed after the 1950s. The Scrivia River is among the most relevant right-bank tributaries of the Po River; it is about 90 km long and origins from the Ligurian-Piedmontese Appennines. The study reach is about 16 km long, close to the Po River, and generally shows a single-thread, sinuous and deep-incised channel. Nowadays the lower Scrivia River presents many bank retreat processes that involve surrounding areas, creating serious management issues. The aim of this research is to outline in detail the active-channel morphological evolution over the last 100-150 years, and characterize channelization and riverscape changes, with a specific focus on the occupation of the areas of fluvial pertinence. A quantitative multi-temporal analysis supported by field surveys and based on historical maps, aerial photographs and satellite images was performed in a GIS environment through automated and semi-automated procedures. The active channel experienced a well-defined sequence of morphological evolutionary phases. They were substantially characterized by a gradual increase of the active-channel stability and a reduction of the active-channel width, up to the end of the 20th century. Since the 2000s, morphological evolutionary trends have changed. Anthropic pressures on the river system, and in particular bank protections, are documented to have played a key role in driving the active-channel changes, and consequently, the near-riverbed land-property and land-use changes. In this respect, on the basis of cadastral data, the past legal framework is also identified as a relevant conditioning factor of the river-corridor morphological evolution. The ongoing dynamics most probably represent the morphological response to the documented, severe anthropic alterations, and are currently raising serious management issues
Prediction of soil erosion and mass wasting processes in southern Tuscany using gradient boosting
No full textMORPHOMETRIC ANALYSIS TO EXPLORE THE SURROUNDINGS OF THE MELKA KUNTURE PREHISTORIC SITE
No full textThe area of Melka Kunture (central Ethiopia) is one of
the most important clusters of Paleolithic sites in Eastern
Africa. The archaeological record spans from ca. 1.7 Ma
onwards, with a number of stratified occurrences of Oldowan,
Acheulean, Middle Stone Age and Late Stone Age
industries, together with faunal remains and human fossils.
However, the archaeological sites are affected by present
day processes. These processes are mainly triggered by the
climatic conditions and specific Paleo-landscape forms
and features in the nearer surroundings of Melka Kunture
and the upper Awash catchment. Hence, the main aims
and objectives of this study are the assessment of the present
day geomorphological and hydrological processes as
well as the detection of Paleo-landscape pattern.
Based on fieldwork, aerial photo interpretation and a detailed
DEM analysis we derived a geomorphological map
of the Melka Kunture area. Furthermore, we assessed the
major landscape forming process using physically based
models and a detailed Terrain Analysis. For this study
we utilized the SRTM-X with 25m resolution and ALOS/
PRISM DEM with 10m resolution.The study reveals the spatial distribution of present day
landscape forming processes. Especially surface runoff
and soil erosion processes were analysed in detail. Moreover,
we identified evidences for specific Paleo-landscape
pattern in the surroundings of Melka Kunture. In
part these features can be explained with tectonic activity,
on the other hand they indicate specific pattern of
the Paleo-drainage network
Assessing landscape features and geomorphic processes influencing sediment dynamics in a geomorphologically highly active Mediterranean agroecosystem: The upper Val d'Arda case study (Northern Apennines, Italy)
No full textThe management of Mediterranean Agroecosystems is crucial to prevent or mitigate sediment-related threats like soil erosion, water quality issues, and reservoir sedimentation. Hence, the identification of type, extent, and location of sediment sources and sinks, in relation to geological and landscape features, is a key prerequisite for identifying erosion hot spot areas and assessing sediment dynamics at catchment scale. This study was carried out in the upper Val d'Arda catchment (Northern Apennines, Italy). We applied geomorphological field mapping together with multi-temporal photointerpretation, GIS-based hydrological modelling, terrain analysis and photogrammetry. Our approach was aimed at exploring the main landscape features, as well as identifying the variety of processes influencing sediment dynamics. In this poorly studied area, we identified a high heterogeneity in terms of type and extent of sediment sources and related processes. Landslides are the most common processes contributing to the sediment yield. Their morphogenesis, extent and location are controlled mainly by lithology and topography. Large ancient earthflows have been the most important geomorphic factor in shaping the landscape, strongly influencing the surficial drainage pattern and the morphological evolution of the main fluvial systems. Upland rill-interrill erosion is another main sediment source, particularly on arable lands. Piping and gullying locally contribute to the development of badlands, and have a high potential for soil loss and sediment production. Finally, fluvial processes significantly contribute to the sediment yield with several active fluvial erosion scarps and bank erosion source areas. Alluvial sediments are locally stored in transient landforms such as bars or more permanent sinks such as floodplains or river terraces. Our study shows that an integrated methodology based on fieldwork, geomorphological mapping, GIS applications and proximal sensing methods is an effective approach to characterize complex geomorphic systems in the Northern Apennines
Assessment of gully erosion in relation to lithology in the southwestern Zagros Mountains, Iran using ASTER data, GIS and stochastic modeling
No full textSoil erosion in arid areas is a major environmental threat. Gullies, as one of the most intensive soil erosion processes, are very common in the southwest of Iran. Lithology, vegetation density and climate change, as well as land use and land cover change are effective drivers of soil loss in general, and gully erosion in particular. The overall objective of this research is to assess the relation between, lithology and the spatial distribution of gullies in the Mazayjan basin. Data were collected by field survey, interpreting aerial photos and analyzing ASTER multispectral images. Modeling of spatial gully susceptibility was performed with a GIS-based statistical mechanics approach (Maxent). The analysis of ASTER bands ratios yields valuable results in terms of the mineral differentiation of the Zagros Mountain substrates and hence, can be utilized as a tool for lithological mapping. Additionally, the statistical mechanics approach used to assess the relation between existing gully locations and the combinations of lithologic predictor variables show that gullies have a high probability in areas showing substrates with high amounts of salt, gypsum and marl, especially in the plain areas. The model performance shows a very high accuracy both for train and test data. The spatial prediction highlights concentrated gully erosion in areas with aeolian sediments on top of alluvial substrates
Short-term GIS analysis for the assessment of the recent active-channel planform adjustments in a widening, highly altered river: The Scrivia river, Italy
No full textFrom the 1990s onwards several Italian rivers have experienced a recent phase characterized by active-channel widening and, generally, by bed-level stability or slight aggradation. However, its triggering factors and its diffusion, along with the relationship between active-channel planform dynamics and vertical adjustments, are still quite debated and only few studies are available. This research deals with the active-channel planform changes occurred along the Scrivia River floodplain reach (NW Italy) over the period 1999-2019 and it aims at investigating in detail the ongoing geomorphological processes under the river management perspective. The study is based on a quantitative multitemporal analysis of aerial photographs and satellite images performed in a GIS environment and supported by field surveys. The outcomes revealed a generalized trend of gentle active-channel widening together with widespread bank instability and several (26% of total banks) intense and localized bank retreats involving both the modern floodplain and the recent terrace. In the investigated 20-year period, the active-channel area has increased by 22.7% (from 613.6 to 753.0 ha), its mean width by 25% (from 151.5 to 189.3 m), whereas no relevant length variations have been noticed. These morphological dynamics have been more or less pronounced both at reach scale and over time. The extreme floods occurred in the investigated period can be considered the most important triggering factor of the active-channel planform changes, most probably together with an increase of the reach-scale unit stream power due to changes in the channel geometry occurred over the 20th century
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