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Debris flows are major geophysical processes which are able to modify the landscape. Structural sediment connectivity describes the physical coupling of landscape units, and it may be affected by the occurrence of single large-magnitude debris flows and/or by the cumulative changes determined by frequent, small-magnitude events. Understanding the coupling of hillslopes to the main channel during and after debris flows is essential for comprehending catchments sediment transfer at different timescales. Debris flows might provoke sudden changes in the landscape through processes such as bed and bank erosion, overbank deposition and natural dam formation. While debris flows may modify the landscape, their characteristics (e.g., path, runout) are strongly affected by the geomorphological settings. Indeed, there is an interplay between landscape morphology and debris flows, one conditioning the other and vice versa. In this regard, determining how much structural connectivity influences the coupling of debris flow with the channel network remains a challenge. An evaluation of the structural connectivity before and after storm events that triggered debris flow has been carried out on multi-temporal DTMs available for the Stolla basin (Autonomous Province of Bozen-Bolzano, Italian Alps) utilizing the Index of Connectivity (IC) and on a pre-event DTM for the Revolver basin (Santa Catarina state, Southern Brazil). To understand whether the morphological changes caused by the debris flows had an impact on flow routing during the event, some of the debris flow events were simulated by a physically based model. The topographic changes caused by the simulated scenarios have been used to compare pre- vs post-event sediment connectivity.

Coastal erosion has extremely complex reasons and is related to both natural and anthropogenic factors. Sea level changes due to ongoing global climate change and/or soil subsidence are certainly among the most studied natural controlling factors. Nevertheless, anthropogenic causes are probably the most common ones. In fact, the coastal equilibrium is strongly conditioned by the reduction of sediment supply to the coast due to both direct and indirect anthropogenic interventions on river channels and catchments, and the construction of coastal defense and maritime structures, which interfere with the sediment transport towards and along the coast, and control sediment distribution.In this study, the southern Molise coast, located along the central Adriatic coast and extending from the Termoli promontory to the Saccione River mouth, has been investigated. The analyzed coastline has been affected by intense erosion from the 1920s’ onwards, with the destruction first of the Biferno River delta, followed from the mid-1950s onwards by a more extensive retreat that produced an elevated loss of land during approximately the last 65 years. Shoreline retreat mainly affected the coastal segment including the Biferno River mouth, which is characterized by average annual rates of almost -3 m/y in the long-term, but also several other coastal stretches in different periods. To contrast further retreat, rigid coastal defense structures such as groins, adherent and detached breakwaters (both emerged and submerged) were realized over time. Nevertheless, during the last twenty years erosion further accelerated, with maximum annual rates recorded for periods 1998-2004 and 2011-2016, involving increasingly the coastal segments located south of the one that includes the Biferno mouth.An accurate analysis of the mid to short term shoreline evolution, considering the possible role played by the decrease of sediment inputs from the Biferno River, meteomarine forcing and coastal defenses, has been carried out. Direct observations of shoreline variations over time and numerical simulations, performed with the "one-line" numerical model GENESIS, showed that the coast was governed by the wave component 10°N. In fact, the consequent equivalent direction of solid transport, coupled with to a net decrease in sediment inputs from the main rivers and its interference with coastal defenses, has contributed to increase coastal erosion rates, recorded in particular around the Biferno River mouth. Moreover, obtained results show that the bimodality of the wave climate may has significantly influenced the recent beach dynamics with the more inclined wave components (coming from the NW and SE sectors) would be responsible for the genesis of coastal instability which amplifies the erosion phenomena.

The growing interest of the Earth sciences community in sediment connectivity has led this property to become a key concept for modern geomorphology. At the same time, a great effort has been made to develop new methods to measure it. The increasing availability of high-resolution Digital Elevation Models (DEMs) for different spatial and temporal scales from various sources, such as LiDAR and photogrammetry, has laid the foundations for the development of approaches exploiting DEM derivatives as slope, flow accumulation, and surface roughness through geomorphometry for a (semi)quantitative assessment of sediment connectivity. Among the different methods, the index of sediment connectivity, which aims at depicting spatial connectivity patterns to support the assessment of the contribution of a given part of the catchment as a sediment source and define sediment transfer paths, was particularly successful thanks also to its intrinsic simplicity and the relative ease of computation through the dedicated open-source software application. The index saw many applications in different geographical and environmental contexts and for different study objectives, reflecting the increasing need for an objective characterization of the linkages between landscape units. Traditional applications of the index are based on qualitative and semi-quantitative analyses to investigate hillslope-channel coupling, sediment transfer dynamics, the impact of extreme natural events, and prioritization of sediment source inventories. This work aims at presenting and discussing the main applications of the sediment connectivity index. If the intrinsic limitations of the index are considered, it is demonstrated that the index can provide a spatial characterization of sediment dynamics, thus improving the understanding of geomorphic systems' behavior. A specific focus will be made on the most recent applications that are moving towards a more quantitative approach to identify areas in a catchment that are both susceptible to slope instability/mass movements and connected to a specific target. Although other fields of application can be envisaged, the applications so far implemented deal especially with debris flows, one of the most active processes in supplying sediment to the main river channels. We believe that this kind of approach paves the way for a new generation of susceptibility maps that, encompassing the sediment connectivity concept, can be adopted for a better hazard and risk assessment and, consequently, for improved countermeasures planning.

Debris flows are among the most widespread natural hazards in mountain areas. They play an important role in sediment transfer from low order channel networks to downstream areas and, thus, they can pose a serious threat to infrastructure. For debris flows to be released, in addition to a considerable amount of rainfall, sediment availability and a peculiar morphological setting (e.g. inclined terrain) are required. However, areas prone to trigger debris flows are not always structurally connected to the main channel, and thus do not necessarily provide sediments to the draining channel network. Despite the relatively high number of published research in the fields of debris flow susceptibility mapping and sediment connectivity analyses, to our knowledge, no attempts have yet been made to combine these two aspects, explicitly by means of data-driven procedures.This work builds upon a novel data-driven approach developed by Steger et al. (under review), which allows to categorize areas based on both aspects, debris flow release susceptibility and structural connectivity. The original method was tested within three mountain catchments in the South Tyrolean Alps (max area 140 km²). This study aims at upscaling this approach at the regional scale and to this end, the whole South Tyrolean Dolomites (1,120 km²) has been selected as study area. In summary, the methodical framework comprised (i) modelling of debris flow release susceptibility using an interpretable machine learning algorithm (generalized additive model) and derivation of a quantitative threshold (susceptible vs. not-susceptible areas), (ii) training a logistic regression model to calculate the probability of an area being structurally connected in terms of debris flow release and subsequent thresholding (connected vs. disconnected areas), and (iii) combination of both previously generated and validated binary maps to create a joint susceptibility-connectivity map.The results are represented via a variety of maps and associated statistics. It is shown that only 1.7% of the Dolomites were determined to be both susceptible to debris flow initiation and structurally connected to a target channel system, whereas areas that are susceptible but disconnected cover 8.2% of the whole study area. 16.5% of the area represents hillslopes that are potentially connected to the river network but result not susceptible in terms of debris flow release.The straightforward implementation of this approach allows it to be an effective tool to assist hazard mapping and management. This study shows that the presented method provides spatial information useful to preliminary identify areas of interest for connected debris flows at the regional scale, but at the same time, it also highlights the need for further ground truth data to validate the results quantitatively beyond single catchment analyses.Stefan Steger, Vittoria Scorpio, Francesco Comiti, Marco Cavalli. Data-driven modelling of joint debris flow release susceptibility and connectivity. Earth Surface Processes and Landforms. Under review.

Debris flow processes are known to contribute substantial amounts of sediment to the fluvial system in mountainous areas, such as the Alps. In fact, debris flow release areas represent relevant sediment sources that should be taken into account when mitigating flood hazards for lower order streams. However, terrain that frequently produces debris flows is not necessarily connected to the channel network while structurally connected areas may often not produce debris flows. Therefore, the relevance of an area to contribute debris flow material to a channel mainly depends on the co-occurrence of two aspects: a high debris flow susceptibility which coincides with a high structural sediment connectivity.In this work, we present a novel data-driven approach that allows to identify areas that are both, susceptible to debris flow initiation and structurally connected to the main channel network. The methodology was developed for a debris flow prone basin located in the Dolomites (Italy) and further tested for other catchments that exhibit different geomorphological settings.The methodical approach was based on the manual mapping of event-specific connected and disconnected debris flows areas that allowed to (i) calibrate a statistically based debris flow release susceptibility model and (ii) to derive quantitative thresholds for the previously derived connectivity index map (IC). The joined results reflect debris flow connectivity-susceptibility maps that were evaluated from numerous perspectives, including the evaluation of the spatial transferability of the approach.We present (i) quantitative IC index thresholds that allow to discriminate connected from disconnected debris flow release areas, (ii) well-performing debris flow release susceptibility models and (iii) joint debris flow connectivity-susceptibility maps that allow identifying zones that are differently relevant in terms of debris flow connectivity. Issues related to the geomorphic plausibility of the results and the spatial transferability of the approach are discussed. The proposed approach requires few basic input data sets and therefore will be applied over vast areas with similar geomorphological settings.

In mountain environments, the coupling of hillslopes processes with the channel network during extreme events is of great importance for rivers dynamics, as debris flows and landslides are among the most important sources of sediments. The Stolla Creek (40 km drainage area, South Tyrol, Italy) is a confined and partly confined mountain channel that was affected by an extreme flood in August 2017, followed by a smaller event in August 2020. The geomorphic effects of the two floods were investigated both in the main channel and over the entire basin with the aim to assess the impacts of the lateral sediment connectivity to the channel response and to the event-scale sediment export. An integrated approach was applied, including radar rainfall estimation, hydrologic-hydraulic analysis, analysis of morphological changes and sediment delivery to the stream network. Hillslope and channel processes were mapped and characterized by using geomorphological analysis of multitemporal orthophotos and Digital Terrain Models. Debris-flow connectivity to the main channel was derived by combining field evidence and GIS-based analysis. The 2017 flood was caused by rainfall with a short duration (6 h) and a rainfall intensity exceeding 45 mm/h. More than 600 debris flows were triggered in the Stolla basin, and the main channel experienced widening (width ratio between 1.3 and 4.9) through bank erosion and overbank deposition. Widening was accompanied by aggradation in the river corridor up to 1.2 m or incision down to -2.2 m. The 2020 flood was characterized by lower rainfall intensity (max 17 mm/h) and a longer duration (48 h), and debris flows were not triggered. The moderate magnitude of the 2020 flood peak did not lead to channel widening, but marked bed incision (up to -1.4 m) occurred in the reaches where aggradation took place during the 2017 event. In both flood events, limited volumes of sediments were exported from the catchment outlet. Overall, our results highlight how structural connectivity at the basin scale determines the potential sediment cascades linking hillslopes to channels but time-varying functional connectivity - driven by hydrological drivers as rainfall intensities and durations - eventually control the actual sediment transport effectiveness both on hillslopes and along the channel.

This work presents the results of the basin-scale analysis of sediment connectivity between hillslopes and the main channel during an extreme event in a mountain catchment. The Stolla basin (South Tyrol, Italy) was affected by a high-magnitude event in August 2017, during which the channel experienced widening and bed level changes and more than 600 debris flows, and landslides occurred in the basin.Hillslope and channel processes were mapped and characterized by using geomorphological analysis of orthophotos and pre- and post-event Digital Terrain Models (DTMs). Mass wasting process connectivity was derived by combining field survey evidence and GIS analysis. The coupling between the debris flows and landslides and the main channel was also evaluated by applying the Index of sediment connectivity (IC) by Cavalli et al. (2013). Binary logistic regression and the receiver operating characteristic curve was used to define thresholds that allow to discriminate connected from disconnected debris flows and landslides, based on IC values with respect to the main channel of the Stolla stream.First results indicate that the Stolla’s post-event channel width was up to five times the pre-event width. Channel widening occurred mainly through bank erosions, removals of riparian vegetation and over bank depositions. Widening appeared to be accompanied by channel bed aggradation up to 1 m or incision up to -2 m. Depending on the morphological characteristics of the channel and of the valley, sediments were eroded from the banks, from the bed or were delivered by connected debris flows, landslides, and toe erosion processes. Statistical analyses indicate a high efficiency of the logistic regression model and the associated threshold to separate connected from disconnected debris flows and landslides using the IC as a predictor variable.

The lower Calore and middle Volturno valleys preserve stratigraphical and morphological evidence and tephrostratigraphic markers particularly suitable for reconstructing the long-term geomorphological evolution of the central-southern Apennines. Aim of our study is to identify the main steps of the Quaternary landscape evolution of these valley systems and to improve knowledge about the relationships between fluvial processes and tectonics, volcanic activity, climatic and human influences. To this purpose, we carried out an integrated geomorphological and chrono-stratigraphical analysis of identified fluvial landforms and related deposits, integrated by 230Th/234U datings on travertines from the Telese Plain area. The study highlighted in particular: (1) fluvial sedimentation started in the Middle Pleistocene (~650 ka) within valleys that originated in the lower Pleistocene under the control of high-angle faults, (2) extensional tectonics acted during the Middle and Upper Pleistocene, driving the formation of the oldest fluvial terraces and alluvial fans, and persisted beyond the emplacement of the Campanian Ignimbrite pyroclastic deposits (~39 ka), and (3) from the late Upper Pleistocene onwards (&lt, 15 ka), the role of tectonics appears negligible, while climatic changes played a key role in the formation of three orders of valley floor terraces and the youngest alluvial fans.

For eight rivers situated from northern to southern Italy, the evolutionary trajectories since the middle 19th century and the key controlling factors of channel adjustments were reconstructed using a combined diachronous-synchronous approach, integrating data from catchment- to reach-scale. The analysis takes advantage of multi-temporal GIS analysis of maps, aerial photographs, and orthophotos, and data from literature, archives, and official surveys of population and agrarian censuses. The main aims were to link historical channel responses to human and climate disturbances evidencing regional scale similarities and dissimilarities and to explain the role of upland and floodplain land use changes in the interpretation of channel adjustments. From the middle 19th century to the 1950s, both channel widening and narrowing were observed. These processes were related to land use disturbances (e.g., afforestation versus deforestation) acting at both reach and catchment scales. From the 1950s to 1970s, channel narrowing in some rivers accelerated simultaneously with forests encroachment on fluvial corridors and human abandonment of intense floodplain uses, before the action of any other factors. In southern Italian rivers, channel adjustments were more intense and occurred later than in northern ones, but they remained more active once adjustment ended. Even though these rivers underwent a rural decline, their floodplains were little colonized by mature forests, probably because of drier climatic conditions exacerbated by dewatering due to channel incision. This also means that upland afforestation, with its effects on bedload delivery, was a more critical driver in controlling narrowing than floodplain afforestation, as in this southern context we do not observe floodplain afforestation but grazing expansion. When forest can establish along the channel, as seen on the Volturno River, narrowing is even more important. River widening in the early 2000s–2010s did not compensate for longer term narrowing, demonstrating a shift in river responsiveness that was partly due to upland and floodplain afforestation inducing higher channel resistance to bank erosion and bedload deficit. Such morphological evolution was also observed in Southeastern France, but occurred a bit earlier, with stronger similarities with northern Italy and the Apennines. These drivers of change must not be underestimated in geomorphic diagnosis, even if they are more difficult to assess.

Sediment dynamics of proglacial streams are strongly connected to meltwater contributions, supply and activation of sediments from subglacial and periglacial reservoirs. In this context, the present study investigates and compares these dynamics at two proglacial streams with respect to discharge, bedload rates, suspension, and runoff generation. The study area is the upper Solda-Sulden catchment in the Eastern Italian Alps (14 km² drainage area, 38 % of glacier cover, elevation range between 2225 and 3905 m a.s.l.).From June to September 2017, 2018, and 2019, two proglacial streams from the Eastern Solda-Sulden glacier (almost without debris-cover) and the Western Solda-Sulden glacier (heavily debris-covered) were monitored. We performed bi-weekly to monthly sampling of bedload (by Bunte samplers), suspended sediment content (SSC), stable water isotopes (δ2H and δ18O), and electrical conductivity (EC). During each sampling event, we measured water stages and carried out discharge measurements derived from salt dilution method. Meteorological data were measured at the Madritsch automatic weather station at 2825 m a.s.l. and at a temporary weather station installed on the Western Sulden glacier at about 2625 m a.s.l..At the Eastern Sulden proglacial stream, we collected 32 bedload samples, which correspond to about 32 kg. The discharge during sampling ranged from 0.03 m3 s-1 to 2.1 m3 s-1 and led to bedload rates ranging between 0.002 kg min-1 m-1 and 6.7 kg min-1 m-1 in August 2018. At the Western Sulden proglacial stream, total weight of bedload samples amounted to about 332 kg (n = 56). The minimum and maximum discharge measured were 0.27 m3 s-1 to 4.7 m3 s-1, respectively. Bedload rates were much higher than those at the previous stream and ranged from 2 x 10-4 m3 s-1 to a maximum bedload rate of 248 kg min-1 m-1 in July 2019. Tracer-based runoff calculations (using δ2H) estimated up to 65 % ± 12 of ice melt contribution during the highest bedload rates, indicating that bedload rates were strongly controlled by ice melt contributions. At the daily scale, we generally observed that highest discharges in the afternoon temporally coincided with highest bedload rates. A change of one order of magnitude of discharge increased the bedload rates by one or two orders of magnitude.However, in the case of the Eastern Sulden proglacial stream, sudden cloud overcast had an immediate effect on the sediment activation while discharges remained unaffected. Longer-period trends in bedload rate are also likely correlated with air temperature and radiation, suggesting a complex climatic control of sediment transport.These results will help to better understand the important drivers and sensitivities of sediment dynamics in proglacial streams, thus supporting water and sediment management in glacierized catchments.

The map is aimed at illustrating the relationships between landscape evolution and human occupation in the Isernia basin since the Middle Pleistocene. We carried out a detail scale geological–geomorphological investigation integrated with archaeological data. Overall data suggest enhanced landscape modification related to the long-term evolution of the Isernia basin. Moreover, during the Middle Pleistocene an alluvial plain environment was present, as testified also by the famous Lower Palaeolithic site of Isernia La Pineta dated to ca. 600 ky. From 600 ky onwards, extensional tectonics and related valley incision reshaped the Isernia basin, with the formation of terraced surfaces and the deposition of a travertine plateau. Archaeological findings from the Lower Palaeolithic up to the Chalcolithic Age testify to pre- and protohistoric settlements on these surfaces. In historical times, Romans settled on the Isernia terrace ridge taking advantage of the outcropping travertines to support wall foundations and to extract construction material.

River morphology is dynamic in nature, in that it is dictated by unsteady driving variables (water, sediment, and wood fluxes). Focusing on centennial to decadal changes, these driving variables are subject both to naturally and anthropically induced variations and may occur both at the basin and the channel scales. Indeed, the traditional “river equilibrium concept” in fluvial geomorphology is challenged by the more recent concept of “evolutionary trajectory,” which emphasizes how channel characteristics (width, bed elevation, morphological pattern, habitats) undergo variations over time in response to changing driving variables. In Europe, geomorphologists have long identified how rivers responded to major climatic variations (e.g., Pleistocene glaciations). In contrast, climate-induced morphological changes that occurred in historical times (e.g., associated with the Little Ice Age [LIA], 15th–19th centuries), have received far less attention, surely also because they were less dramatic compared to the former ones. Direct human pressures both on basins and channels have instead greatly affected the vast majority of river systems of Europe. Localized morphological alterations and floodplain deforestation, aimed to protect villages and towns from flooding and to increase pastures, can be traced back to ancient times. In order to augment agricultural productivity for a growing population, extensive channel rectifications coupled with floodplain drainage and basin-scale deforestation took place from the late Middle Ages onward, peaking in the 19th century. Several European rivers in these centuries widened and aggraded, as well as during the concurrent “flood-rich” LIA period. However, the trajectory soon reversed, since from the middle of the 20th century onward, natural afforestation, erosion control works, and hydropower dam construction led to a general reduced sediment supply to the downstream river reaches, causing channel narrowing and bed degradation. Nonetheless, in-channel gravel mining—very pronounced from the 1960s to the 1980s—was the most important cause of stream degradation in several rivers. Most of the European rivers are still sediment and wood starved, are subject to flow regulation, and feature impaired longitudinal and lateral connectivity. Since the end of the 20th century, restoration actions have started to be implemented, though, also to comply with the goals of the European Union (EU) Water Framework Directive. Finally, ongoing global warming, increasing in severity since the late 20th century, could determine channel variations in those (few) rivers that are still free to adjust, and the most-relevant changes are expected at the higher elevations and latitudes, where glacial and periglacial processes still exert strong controls on river dynamics.

Evolutionary trajectories and related control factors of the Fortore River (southern Italy) are analyzed over a 150-year period as to assess channel modifications. A multitemporal GIS analysis of topographic maps and aerial photographs together with topographic and geomorphological field surveys were performed. Attention was focused on the impact caused by human disturbance, above all the presence of the Occhito dam at only 40 km upstream of the Fortore mouth (central Adriatic coast). Results show that channel adjustments occurred in three distinct phases and were primarily driven by human disturbance that diversely affected reaches located upstream and downstream of the dam. From the last decades of the nineteenth century to the 1950s (phase 1), channel widening prevailed along upstream reaches whilst narrowing along downstream reaches. Major channel adjustments occurred from the 1950s until the end of the 1990s (phase 2), especially channel narrowing of up to 81% in upstream reaches and 98% in downstream reaches. Narrowing was accompanied by channel-bed lowering of 1 to 5 m and by pattern changes in prevalence from multithread to largely prevailing single-thread channel configurations. In-channel mining, channel works, and hydraulic interventions are considered key driving factors of observed channel adjustments. The closure of the Occhito dam in 1966 had significant and permanent effects on downstream reaches through overall discharge regulation and permanent sediment trapping as also proved by the progressive retreat of the Fortore river mouth area. From 2000 to 2015 (phase 3), a substantial trend inversion was observed with overall channel widening and partial aggradation of upstream reaches and total stabilization of downstream reaches. As highlighted by an integrated multitemporal analysis of recent channel changes and flood events, the latter have played an important role in channel recovery of upstream reaches. Comparison between the Fortore River and other rivers in southern Italy has allowed us to ascertain that the reconstructed evolutionary trajectories are quite similar and that control factors are essentially the same. In particular, it confirms the role of major hydraulic structures as to the amount of channel adjustments of downstream reaches and the ensuing scarce to nil potential to channel recovery of regulated reaches.

This paper presents the results of the geological and geomorphological investigation carried out during the first level seismic microzonation project in the Isernia Province territory. The study area falls in one of the most seismically active areas of the Apennine chain and it has been struck, in historical times, by destructive earthquakes that caused several causalities and diffuse damages to the buildings. The analysis points out the occurrence of geological features that can determine possible site amplification phenomena related to areas with extensive outcrops of thick continental deposits or to unstable areas (both covering about 48% of the investigated areas). The latter are sometimes combined with geomorphological features such as scarps, isolated peaks, and ridges that are also responsible for possible site amplification. In addition, a susceptibility to local seismic amplification index has been introduced which highlights that more than 64% of the investigated area, along with a significant percentage of buildings, fall within the highest categories of susceptibility to local seismic amplification.

Flash floods represent a major natural hazard whose characterization is usually challenging due to their rapid temporal evolution and severe but localized spatial dynamics. Post-event monitoring of flash floods, in fact, represents still at present a key step in order to improve the assessment of both hazard and vulnerability. In this study, we integrate a chain of tools for an improved characterization of flash flood dynamics and related slope instability phenomena, focusing on a flash flood occurred on Aug 5-6 2017 over a 100 km2 alpine catchment of northeastern Italy. The analyzed dataset encompasses the availability of calibrated radar rainfall, systematic post-event survey of cross sections, ad hoc post-event LiDAR terrain data and satellite/aerial imagery. The methodological framework of the hydrological analysis embraces the calibration of a rainfall-runoff model, its downscaling to ungauged catchments and its cross-validation with field surveys for an estimate of peak discharge and related geomorphic effects. The application of a morphometric index of sediment connectivity has allowed investigating the topographic potential for sediment to be routed downstream and to analyze spatial connectivity patterns at high resolution for all the sub-catchments. The analysis of available (pre and post) satellite and aerial imagery and, above all, the precious availability of pre and post event high-resolution LiDAR DTMs has permitted the assessment of erosion and deposition patterns in the study area together with the estimation volume uncertainty. Preliminary results portray the inner dynamic of the event as characterized by severe spatial and temporal variability and show consistency between simulated discharge and field surveys. The flood response of analyzed sub-catchments shows as well important correlation with the spatial patterns of the triggering thunderstorm. Sediment connectivity pattern has proved to be an important factor controlling the severity of the response at the analyzed catchments. The integration of geomorphic change detection framework for such event has permitted the volumetric quantification of the erosional processes phenomena thus enabling the analysis of the relation between both the triggering and the response quantitative magnitudes.

Large floods may produce remarkable channel changes, which determine damages and casualties in inhabited areas. However, our knowledge of such processes remains poor, as is our capability to predict them. This study analyses the geomorphic response of the Nure River (northern Italy) and nine tributaries to a high-magnitude flood that occurred in September 2015. The adopted multi-disciplinary approach encompassed: (i) hydrological and hydraulic analysis; (ii) analysis of sediment delivery to the stream network by means of landslides mapping; (iii) assessment of morphological modifications of the channels, including both channel width and bed elevation changes. The spatial distribution of rainfall showed that the largest rainfall amounts occur in the upper portions of the catchment, with cumulative rainfall reaching 300 mm in 12 h, and recurrence intervals exceeding 100–150 years. The unit peak discharge ranged between 5.2 and 25 m3 s−1 km−2. Channel widening was the most evident effect. In the tributaries, the ratio between post-flood and pre-flood channel width averaged 3.3, with a maximum approaching 20. Widening was associated with channel aggradation up to 1.5 m and removal of riparian vegetation. New islands formed due to the fragmentation of the former floodplain. In the Nure River, the average width ratio was 1.7, and here widening occurred mainly at the expenses of islands. Bed level dynamics in the Nure were varied, including aggradation, incision, and overall stability. The flood geomorphic effectiveness was more pronounced in the middle-higher portions of the basin. Planimetric and elevation changes were well correlated. Regression analysis of the relationship between widening and morphological/ hydraulic controlling factors indicated that unit stream power and confinement index were the most relevant variables. The study provides useful insights for river management, especially with regard to the proportion of the valley floor subject to erosion and/or deposition during large events.

Some major rivers in southern Italy (Trigno, Biferno, Fortore and Volturno), as most of Italy's rivers, have suffered significant channel changes during the last 60 years. Channel adjustments mainly consisted in channel narrowing and bed lowering coupled with pattern changes. Over the last 10-15 years, these rivers have undergone some important modifications in their evolutionary trends. More specifically, the Trigno River and the reaches of the Fortore River located upstream the Occhito dam are interested by moderate channel recovery, while the Volturno and Biferno rivers and the Fortore reaches located downstream the dam are affected by slight channel recovery or no significant changes in morphology. Key driving factors of these recent evolutionary trends seem to be the occurrence of major flood events and the degree of channel mobility that is conditioned by channel works and riparian woody vegetation.

This paper proposes a new methodological approach to silted reservoir management and defence, which combines the reservoir rehabilitation process and the utilization of the recovered water volumes and sediments. This approach, strategic from both the economical and environmental points of view, is here defined as Economic Environmental Defence (EED) of a reservoir. The EED approach is applied to the case study of Guardialfiera reservoir, where the available experimental data allowed the estimation of siltation up to date, the analysis of the distribution of sediment particle size along the reservoir bottom and the possibility to propose a feasible utilization of water and sediments resulting from the reservoir rehabilitation.

The need for a multidisciplinary approach for characterizing water bodies in terms of morphological, chemical and ecological quality has hastened the growth of hydromorphology as a cross-disciplinary topic at the interface of hydrology, geomorphology and ecology. Many authors have analysed how hydroecology may affect freshwater biodiversity, although little is known about how this biodiversity might be affected by river morphological quality. We examined how well the presence of the semi-aquatic Eurasian otter can be predicted by the rivers' morphological quality and its adjustments over the last decades. We tested the morphological quality index (MQI) methodology in 38 reaches of five rivers in southern Italy, 23 of which were positive to otter presence. In each reach, we examined 28 indicators contributing to the MQI and its 11 sub-indices. The results showed a significant relationship between the probability of the presence of otters, MQI, and some sub-indices. The best performing sub-indices were related to channel adjustments and the continuity of river processes. A more detailed analysis of channel adjustments showed a detrimental effect of channel incision (>3 m) and a positive effect of narrowing, particularly where it occurred simultaneously with the development of forest in the new floodplain. The continuity of river processes has driven the migration of river banks and the development of ponds and secondary channels, likely increasing the availability of dens and resting sites and the hunting capabilities of otters. Our results stressed the importance of fluvial dynamics and sustainable adaptive river management for the habitat quality of semi-aquatic species. Copyright © 2014 John Wiley & Sons, Ltd.

This paper deals with the risk assessment to alluvial fan flooding at the piedmont zone of carbonate massifs of the southern Apennines chain (southern Italy). These areas are prime spots for urban development and are generally considered to be safer than the valley floors. As a result, villages and towns have been built on alluvial fans which, during intense storms, may be affected by flooding and/or debris flow processes. The study area is located at the foothills of the Maddalena mountains, an elongated NW-SE trending ridge which bounds to the east the wide intermontane basin of Vallo di Diano. The area comprises a wide detrital talus (bajada) made up by coalescent alluvial fans, ranging in age from the Middle Pleistocene to the Holocene. Historical analysis was carried out to ascertain the state of activity of the fans and to identify and map the zones most hit by past flooding. According to the information gathered, the Sala Consilina fans would appear prone to debris flows; in the past these processes have produced extensive damage and loss of life in the urban area. The watershed basins feeding the fans have very low response times and may produce debris flow events with high magnitudes. Taking into account the historical damage, the fan surface morphology, and the present urban development (street orientation and hydraulic network), the piedmont area was zoned and various susceptibility classes were detected. These results may represent a useful tool for studies aiming at territorial hazard mapping and civil protection interventions.

Multi-temporal GIS analysis of topographic maps and aerial photographs along with topographic and geomorphological surveys are used to assess evolutionary trends and key control factors of channel adjustments for five major rivers in southern Italy (the Trigno, Biferno, Volturno, Sinni and Crati rivers) to support assessment of channel recovery and river restoration. Three distinct phases of channel adjustment are identified over the past 150 years primarily driven by human disturbances. Firstly, slight channel widening dominated from the last decades of the nineteenth century to the 1950s. Secondly, from the 1950s to the end of the 1990s, altered sediment fluxes induced by in-channel mining and channel works brought about moderate to very intense incision (up to 6–7 m) accompanied by strong channel narrowing (up to 96%) and changes in channel configuration from multi-threaded to single-threaded patterns. Thirdly, the period from around 2000 to 2015 has been characterized by channel stabilization and local widening. Evolutionary trajectories of the rivers studied are quite similar to those reconstructed for other Italian rivers, particularly regarding the second phase of channel adjustments and ongoing transitions towards channel recovery in some reaches. Analyses of river dynamics, recovery potential and connectivity with sediment sources of the study reaches, framed in their catchment context, can be used as part of a wider interdisciplinary approach that views effective river restoration alongside sustainable and risk-reduced river management.

Several case studies of geomorphological mapping at various scales in order to identify areas prone to alluvial fan flooding are presented in this paper. The selected areas are located in southern Italy and are representative of a geomorphic unit (foothills consisting of coalescent alluvial fans) found throughout the southern Apennines. The medium-scale approach represents the best tool to identify areas susceptible to flooding, using detailed geomorphological mapping of fan systems. It can be considered a preliminary analysis, which provides important information for large areas and identifies zones which need further investigation. Large-scale map analysis may be applied to a single fan and used to distinguish fan portions prone to different degrees of hazard exposure, thus providing accurate information for decision-makers who are called upon to plan hazard management. In both cases, analysis based on detailed geological and geomorphological field surveys is often coupled with remotely sensed data.

This study presents the analysis of flash floods triggered by an extreme rainfall event that occurred on 7 October, 2011, over the Marzano carbonate massif (Southern Apennines). The rainfall event reactivated alluvial fans built up at the outlet of two mountain basins. Detailed geological surveys carried out immediately after the event allowed the reconstruction of the main erosion and depositional processes that occurred both in the drainage basin and in the fan areas. The volume of materials eroded in the basin and deposited in the fan was evaluated by means of accurate topographic surveying and GPS measurements. Morphological and morphometric properties of the basin/fan system as well as the presence of human interventions and structures along the main channel and in the fan area influenced flow propagation. The transported materials came mainly from debris and gravels previously accumulated along the stream beds and mobilised by the flow during the event. No significant evidence of landslide contribution to transported bed load was detected. Extensive damage was done to buildings, river bank structures and agricultural crops. Despite the existence of hundreds of similar alluvial/fan systems in the Southern Apennines, few studies have been conducted to support adequate risk mitigation action in these areas. Indeed, to our knowledge, this is the first study focusing on assessing the magnitude of alluvial fan flooding in the context of the Southern Apennines. Studies like the present one may help determine the volumes involved during flash floods whilst providing support for detailed flood hazard zoning and for risk mitigation planning.

A 1:20,000-scale geomorphologic map of the valley floor system of the Biferno River (Molise Region, Italy) is presented in this paper. Map analysis and aerial photography interpretation, in addition to field surveys, have allowed digital mapping of fluvial landforms and associated coastal, slope and anthropogenic forms which have characterised the valley floor in different periods. Comparative multi-temporal analysis performed in a GIS for the time-period 1869–2010 allowed the reconstruction of spatial-temporal relationships between most of the mapped landforms and acquisition of quantitative data on channel adjustments. The geomorphologic map provides an overall large-scale view of major channel adjustments over the past 150 years as well as the current morphological setting and dynamics of the Biferno valley floor. It provides a basic map for land planning policy with the observed distribution of active geomorphic processes to be used for landslide and erosion susceptibility assessment and the data obta...