Multitemporal UAV surveys for landslide mapping and characterization

This paper presents the preliminary results of the IPL project 196 “Development and applications of a multi-sensor drone for geohazards monitoring and mapping.” The objective of the project is to test the applicability of a multi-sensor drone for the mapping and monitoring of different types of geohazards. The Department of Earth Sciences of the University of Florence has developed a new type of drone airframe. Several survey campaigns were performed in the village of Ricasoli, in the Upper Arno river Valley (Tuscany, Italy) with the drone equipped with an optical camera to understand the possibility of this rising technology to map and characterize landslides. The aerial images were combined and analyzed using Structure-from-Motion (SfM) software. The collected data allowed an accurate reconstruction and mapping of the detected landslides. Comparative analysis of the obtained DTMs also permitted the detection of some slope portions being prone to failure and to evaluate the area and volume of the involved mass.     

The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation

After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions.     

Water in the Martian interior—The geodynamical perspective

Petrological analysis of the Martian meteorites suggests that rheologically significant amounts of water are present in the Martian mantle. A bulk mantle water content of at least a few tens of ppm is thus expected to be present despite the potentially efficient degassing during accretion, magma ocean solidification, and subsequent volcanism. We examine the dynamical consequences of different thermochemical evolution scenarios testing whether they can lead to the formation and preservation of mantle reservoirs, and compare model predictions with available data. First, the simplest scenario of a homogenous mantle that emerges when ignoring density changes caused by the extraction of partial melt is found to be inconsistent with the isotopic evidence for distinct reservoirs provided by the analysis of the Martian meteorites. In a second scenario, reservoirs can form as a result of partial melting that induces a density change in the depleted mantle with respect to its primordial composition. However, efficient mantle mixing prevents these reservoirs from being preserved until present unless they are located in the stagnant lid. Finally, reservoirs could be formed during fractional crystallization of a magma ocean. In this case, however, the mantle would likely end up being stably stratified as a result of the global overturn expected to accompany the fractional crystallization. Depending on the assumed density contrast, little secondary crust would be produced and the lithosphere would be extremely cool and dry, in contrast to observations. In summary, it is very challenging to obtain a self‐consistent evolution scenario that satisfies all available constraints.     

Multi-thread river channels: A perspective on changing European alpine river systems

Rivers are natural systems whose planform pattern in alluvial reaches reflects a balance between three fundamental ingredients: flow energy, sediment calibre and supply, and vegetation. Whilst early research on river channel classification emphasised flow (stream power) and sediment controls, the impact of vegetation is now recognised in increasingly detailed classification schemes. Different planform patterns are more or less sensitive to changes in these three fundamental ingredients, which in the absence of human interventions all respond to changes in climate, allowing different morphological configurations to evolve and in some cases shift from one planform style to another. Multi-thread, braided and transitional river channel styles are common in European regions where conditions for the development of these planform styles, notably high bed material supply and steep channel gradients, exist. However, widespread, intense human impacts on European river systems, particularly over recent centuries, have caused major changes in river styles. Human activities impact on all three major controls on channel pattern: flow regime, sediment regime, vegetation (both riparian and catchment-wide). Whilst the mix of human activities may vary greatly between catchments, research from across Europe on the historical evolution of river systems has identified consistent trends in channel pattern change, particularly within rivers draining the Alps. These trends involve periods of narrowing and widening, and also switching between multi-thread and single-thread styles. Although flow regulation is often the key focus of explanations for human-induced channel change, our review suggests that human manipulation of sediment supply is a major, possibly the dominant, causal factor. We also suggest that “engineering” by riparian trees can accelerate transitions in pattern induced by flow and sediment change and can also shift transition thresholds, offering a new perspective for interpretation of channel change in addition to the focus on flow and sediment regime within existing models. Whilst the development of planform classifications of increasing complexity have been crucial in developing terminology and highlighting the main factors that control channel styles, additional approaches are needed to understand, predict and manage European Alpine river systems. A combination of field, laboratory and numerical modeling approaches are needed to advance the process understanding that is necessary to anticipate river landscape, particularly planform, changes and thus to make ecologically sound management choices.     

Managing tourist harbors: Are managers aware of the real environmental risks?

The management of tourist harbors has traditionally been analyzed with little attention to managers’ awareness of the effects of their decisions on the environment. The aims of this paper were to assess managers’ perceptions of the main environmental risks in their regions and to identify common behaviors among the managers involved in eight tourist harbors in southern Italy, where the same tourist harbor is often managed by different managers. A questionnaire was administered and statistical analyses were performed to test differences between managers of big and small harbors. Managers showed a low perception of environmental risks and, surprisingly, in certain harbors, some meaningful cases were highlighted: the most homogeneous case, where all managers showed a reasonable level of environmental awareness, and cases with strong mismatches among managers. In this paper, we propose that an assessment of managers’ perceptions of risk be included as a new form of analysis when environmental risk assessments are carried out.     

Morphological effects of different channel‐forming discharges in a gravel‐bed river

The study analyses the morphological response of a gravel‐bed river to discharges of different magnitude (from moderate events that occur several times a year to a 12‐year flood) and so defines the range of formative discharges for single morphological units (channels, bars, islands) and a range of magnitude of morphological activity from the threshold discharges for gravel transport and minor bar modification up to flows causing major morphological changes. The study was conducted on the Tagliamento River, a large gravel‐bed river in north‐eastern Italy, using two different methods, analysis of aerial photographs and field observation of painted gravel particles. The available photographs (five flights from August 1997 to November 2002) and the two commissioned flights (June 2006 and April 2007) do not define periods with a single flood event, but the intervals are short enough (11 to 22 months) to have a limited number of flood events in each case. The fieldwork, which involved cross‐section survey, grain‐size analysis and observation of painted sediments, complemented the aerial surveys by allowing analysis of channel response to single flood events. Substantial morphological changes (e.g. bank erosion of several tens of metres up to more than 100 m) associated with flood events with a recurrence interval between 1·1 year and 12 years have been documented. Multiple forming discharges were defined based on the activity of different morphological units. Discharges equal to 20–50% of the bankfull discharge are formative for the channels, whereas the bankfull discharge (1·1 year flood in this case of the Tagliamento River) is formative for low bars. Larger floods, but still relatively frequent (with a recurrence interval less than five years), are required for full gravel transport on high bars and significant morphological changes of islands. Copyright © 2009 John Wiley & Sons, Ltd.     

Evaluating the effects of protection on two benthic habitats at Tavolara-Punta Coda Cavallo MPA (North-East Sardinia, Italy)

In this paper, two benthic habitats have been investigated in a fully protected site and two control sites at the Tavolara-Punta Coda Cavallo marine protected area (MPA) (NE Sardinia). Overall, a protection effect on the benthic assemblages was highlighted in the shallow subtidal (5 m deep) rather than at intertidal algal turf habitat. Structure of assemblages at the shallow subtidal habitat is different in the fully protected site vs. controls, while this was not true for the intertidal habitat. At the subtidal, this finding is probably linked to indirect effects due to an increase of consumers in the protected site (e.g., sea urchins), while the lack of direct impacts in the intertidal at control sites is indicative of very similar assemblages. Cover of encrusting algae was significantly higher at the subtidal protected site suggesting a possible higher grazing pressure. Possible causes underlying the inconsistency of results obtained between habitats include the possibility that trophic cascade effects have a different influence at different heights on the shore. The need to estimate the interconnection among benthic habitats through trophic links is also highlighted to provide an estimate of the vulnerability to protection of various habitats.