Sensitivity, Hazard, and Vulnerability of Farmlands to Saltwater Intrusion in Low-Lying Coastal Areas of Venice, Italy

Saltwater intrusion is a growing threat for coastal aquifers and agricultural practices in low-lying plains. Most of the farmlands located between the margin of the Southern Venice lagoon and the Northern Po delta, Italy, lie a few meters below mean sea level and are drained by a large network of artificial channels and hydraulic infrastructures to avoid frequent flooding and allow agricultural practices. This work proposes an assessment of the vulnerability to saltwater intrusion, following a new concept of the hazard status, resulting in combining the depth of the freshwater/saltwater interface and the electrical resistivity of the shallow subsoil. The sensitivity of the farmland system was assessed by using ground elevation, distance from freshwater and saltwater sources, permeability, potential runoff, land subsidence, and sea-level rise indicators. Relative weights were assigned by a pairwise comparison following the Analytic Hierarchy Process approach. The computed vulnerability map highlights that about 30% of the farmlands is under strong and extreme conditions, 28% between marginal and moderate, and 40% under negligible conditions. Results from previous vulnerability assessments are discussed in order to explain their differences in terms of hazard status conceptualization and sensitivity characterization of farmland system.

Trends of Nitrogen and Phosphorus in Surface Sediments of the Lagoons of the Northern Adriatic Sea as a Study Case

The analysis of nutrient concentrations in surface sediments is a reliable tool for assessing the trophic status of a water body. Nitrogen and phosphorus concentrations are strongly related to the sediment characteristics but are mainly driven by anthropogenic impacts. The results of the determination of total nitrogen and total inorganic and organic phosphorus in surface sediments of the lagoons and ponds of the northwestern Adriatic Sea (Marano-Grado, Venice, Po Delta, Comacchio Valleys, Pialassa della Baiona) show the merit of this approach. Indeed, when previous data are available, the ratio between the actual and background values can provide useful information on the trophic changes that have occurred in the most recent times, and the results can also explain the conditions present in less studied environments. In this context, numerous studies performed in the Venice lagoon since the second half of the 20th century during different environmental scenarios provide mean concentration ranges and propose the main causes of changes. The results of single datasets available for the other lagoons fall into scenarios that occurred in the Venice lagoon. At present, the most eutrophic basins are Pialassa della Baiona, the Po Delta lagoons and ponds and the Comacchio valleys due to industrial effluents, fish farming and clam harvesting, respectively, whereas the Venice lagoon is now experiencing environmental recovery.

Assessment of Seismic Bedrock in Deep Alluvial Plains. Case Studies from the Emilia-Romagna Plain

The estimation of seismic shaking is essential for a realistic assessment of the local seismic hazard and the implementation of effective strategies for prevention and mitigation of the seismic risk. One of the most important aspects in the analysis of the site seismic assessment is the recognition of the seismic bedrock and its depth. Unfortunately, these data are not always easy to evaluate, especially in areas where the thickness of loose or poorly consolidated sediments is high. This article illustrates data and case studies from the Emilia-Romagna sector of the Po Plain, in order to provide examples and suggestions for the recognition of the seismic bedrock in alluvial and coastal areas characterised by significant thicknesses of unconsolidated sediments, using available data and not expensive geophysical surveys. The application of the proposed method indicates that the study area can be divided into four domains characterized by different depths of the seismic bedrock: the marginal or pede-Apennine belt, the high structural zones, the syncline/minor anticline zones, and the Po delta-coast zone.

Evaluating Short-Term Tidal Flat Evolution Through UAV Surveys: A Case Study in the Po Delta (Italy)

The use of Unmanned Aerial Vehicles (UAV) on wetlands is becoming a common survey technique that is extremely useful for understanding tidal flats and salt marshes. However, its implementation is not straightforward because of the complexity of the environment and fieldwork conditions. This paper presents the morphological evolution of the Po della Pila tidal flat in the municipality of Porto Tolle (Italy) and discusses the reliability of UAV-derived Digital Surface Models (DSMs) for such environments. Four UAV surveys were performed between October 2018 and February 2020 on an 8 ha young tidal flat that was generated, amongst others, as a consequence of the massive sediment injection into the Po Delta system due to the floods of the 1950s and 1960s. The DSM accuracy was tested by processing (i.e., photogrammetry) diverse sets of pictures taken at different altitudes during the same survey day. The DSMs and the orthophotos show that the tidal flat is characterised by several crevasse splays and that the sediment provision depends strictly on the river. During the study period, the sediment budget was positive (gaining 800 m3/year and an average rate of vertical changes of 1.3 cm/year). Comparisons of DSMs demonstrated that neither lower flight altitudes (i.e., 20–100 m) nor the combination of more photos from different flights during the same surveys necessarily reduce the error in such environments. However, centimetric errors (i.e., RMSEs) are achievable flying at 80–100 m, as the increase of GCP (Ground Control Point) density is the most effective solution for enhancing the resolution. Guidelines are suggested for implementing high-quality UAV surveys in wetlands.

Seismic evidence of the Messinian events in the Adriatic basin

<p>The Adriatic basin represents one of several restricted basins located in the Mediterranean Area. It consists of the foreland of three different orogenic belts: the Dinarides to the East, active during the Eocene, the Southern Alps to the North, active since the Cretaceous time, and the Apennines to the West, active since the Paleogene. The Apennines had a primary role during the Messinian Salinity Crisis (MSC), conditioning the connection between the Adriatic basin, the Ionian basin, and the proto-Tyrrhenian basin. During the Messinian, the present Adriatic Sea was characterized by shallow water domains, where gypsum evaporites initially deposited and often successively incised or outcropped. </p><p>In the past 50 years, a massive dataset, composed of 2D multichannel seismic data and boreholes, was collected, covering almost the whole Adriatic basin in the Italian offshore. In this work, we interpreted the Plio-Quaternary base (PQb), based on available public datasets and on seismic profiles present in literature, which provided regional information from the northernmost Trieste Gulf (Northern Adriatic Sea) to the Otranto Channel (Southern Adriatic Sea). Here, we propose the PQb time-structural map, obtained by analyzing more than 600 seismic profiles. The PQb represents both the Messinian erosion and/or the top of the Messinian evaporites. It is characterized by a high-amplitude reflector, commonly called “horizon M” in the old literature. Principal findings concerning the Messinian event are summarized as below: </p><p>-The Northern Adriatic (Gulf of Trieste, Gulf of Venice, Po delta, Kvarner Area) reveals widespread channelized systems produced by the initial decrease of the sea level, followed by subaerial erosion, related to further sea level decrease. High-grade erosion involved the nearby Adriatic carbonate platform in the Croatian offshore, where deep valleys, filled with Last Messinian or post- Messinian sediments, cut through the limestones.</p><p>-The Central Adriatic (from the Po delta to the Gargano Promontory) displays a higher evaporites accumulation than the northern sector. Meanwhile, the Mid-Adriatic Ridge was already developing, along with the Apennine Chain, which was in a westernmost position. Erosional features in the deeper area are related to channelized systems, which followed the evaporites deposition. Meanwhile, also the Mid-Adriatic Ridge was affected by erosion.</p><p>-The Southern Adriatic (from the Gargano Promontory to the Otranto Channel) is characterized by the Mesozoic Apulia carbonate platform, covered by a thin Cenozoic sequence affected by subaerial erosion or non-deposition. The platform margin and the slope leading to the deepest South Adriatic basin, where a Messinian gypsum layer, also recorded in the Albanian and Croatian offshore, shows a lower level of upper erosion.</p><p>In general, we notice strongly variable thicknesses of the horizon M, which is related to submarine erosion (channels), subaerial erosion (discontinuous surfaces), non-deposition (possible unconformity), and tilting toward the surrounding chains (deepening horizons). In this work, we evaluate these different components from a regional point of view.  </p>

Relation among geochemical elements in soil and red chicory as a tool for geographical origin identification.

<p>The identification of the geographical origin of food products is important for both consumers and producers to ensure quality and avoid label falsifications. Determination and authentication of the geographical origin of food products throughout scientific research have become recently relevant in investigations against frauds for consumer protection. Advances in methods and analytical techniques led to an increase in the application of fingerprinting analysis of foods for identification of geographical origin. Since in organic material the inorganic component is more stable than the organic one, several studies examined trace elements, suggesting the potential application for determination of geographical origin. Moreover, the studies on territoriality are based on the hypothesis that chemical elements detected in plants and in their products reflect those contained in the soil and, within these studies, the geographical features of the production area, such as the soil type and the climate, are considered relevant factors affecting the specific designation, so an accurate determination of geographical origin would be necessary to guarantee the quality and territoriality of the products.</p><p>In this light, two varieties of red chicory from the southern Po Delta area have been characterized together with the soil. The two inspected red chicory varieties (long-leaves and round-leaves) are cultivated in a well-defined area in the southern part of Po Delta, in an area sited around Massenzatica (Municipality of Mesola, Province of Ferrara, NE of Italy). Sampling was undertaken between October and December 2020 and samples were collected from a randomized field. Together with the red chicory also roots and soils have been collected in order to analyze each part and correlate the geochemical data obtained using ICP-MS and XRF techniques.</p><p>Purpose of this study is to establish a method to identify the geographical origin and the results confirm that some major and trace elements could be used as geochemical markers according to the geological areas. These elements, therefore, could be useful to establish geochemical fingerprints for testing the origin of this product and create a protected designation of origin label.</p>

Monitoring land subsidence and element at risk in the Po Delta area (Northern Italy) through MT-InSAR and GNSS surveys

<p>Delta areas are more likely to suffer from land subsidence due to tectonic and geological processes. Po Delta evolution shows a succession and superposition of complex processes caused by both natural and anthropogenic factors. The factors include sediment loading and compaction, post-glacial rebound, coastal flooding and erosion, sea level rise, land use changes, underground resources exploitation, population growth and urbanization. The natural subsidence has been estimated in the order of millimeters per year and the anthropogenic subsidence is greater than 10 mm/year. Several areas are located under the mean sea level and are exposed to flooding. These areas have been protected by embankments which represent a crucial element for flood risk mitigation. Multi-temporal interferometric synthetic aperture radar (MT-InSAR) and global navigation satellite system (GNSS) allow the continuous monitoring of land subsidence and structures and infrastructures deformations. The Po Delta landscape is characterized by large mudflats, farmland, and wetlands, and a low level of urbanization. Interferometry survey is difficult in this area, due to the temporal decorrelation caused by variations of the scattering properties associated with soil moisture and volume scattering, especially in the case of summer acquisitions. Then, MT-InSAR has to be integrated with ground-based measurements techniques which are costly and time consuming. In this study, MT-InSAR and GNSS techniques are combined to monitor the land subsidence and the deformations of the elements at risk, in particular the flood protection infrastructures. C-band Sentinel-1 and X-band COSMO-SkyMed SAR data acquired in 2014-2020 and 2012-2020, respectively, are considered. An MT-InSAR technique is exploited using the interferometric point target analysis (IPTA) method, making a network of targets including both distributed scatterers (DS) and persistent scatterers (PS). GNSS data have been collected by 3 permanent stations and 46 non-permanent stations (NPS) distributed in the Po Delta. The NPS were measured during three survey campaigns in 2016, 2018, and 2020. Results from MT-InSAR applied to Sentinel-1 data and GNSS techniques are compared and integrated to estimate the subsidence rates for most of the area. The monitoring of the embankments is possible using COSMO-SkyMed data due to their high resolution and high backscatter on structures and infrastructures. For future studies, the regression analysis between the natural/anthropogenic processing and the land subsidence of the Po Delta area can be performed to identify the major driving factors of the deformations in the different periods, which can improve the risk mitigation strategies.</p>

Assessing Po River Deltaic Vulnerability Using Earth Observation and a Bayesian Belief Network Model

Deltaic systems are broadly recognized as vulnerable hot spots at the interface between land and sea and are highly exposed to harmful natural and manmade threats. The vulnerability to these threats and the interactions of the biological, physical, and anthropogenic processes in low-lying coastal plains, such as river deltas, requires a better understanding in terms of vulnerable systems and to support sustainable management and spatial planning actions in the context of climate change. This study analyses the potential of Bayesian belief network (BBN) models to represent conditional dependencies in vulnerability assessment for future sea level rise (SLR) scenarios considering ecological, morphological and social factors using Earth observation (EO) time series dataset. The BBN model, applied in the Po Delta region in the northern Adriatic coast of Italy, defines relationships between twelve selected variables classified as driver factors (DF), land cover factors (LCF), and land use factors (LUF) chosen as critical for the definition of vulnerability hot spots, future coastal adaptation, and spatial planning actions to be taken. The key results identify the spatial distribution of the vulnerability along the costal delta and highlight where the probability of vulnerable areas is expected to increase in terms of SLR pressure, which occurs especially in the central and southern delta portion.

Graphic geography: drawing territories at the Po Delta (Italy)

Geography and the graphic image have a long, intertwined history of exchange. In recent scholarship, the graphic image plays an important role in geography’s creative (re)turn and geographers are experimenting with new visual languages and creative practices to carry out research and communicate with wider audiences. This paper explores geography as a ‘graphic’ discipline that represents and produces spatial knowledge by experimenting with scribing, a verbo-visual technique. In the first part of the article, we propose an auto-ethnographic account of a residential seminar with students in Local and Sustainable Territorial Development, held in 2017 at the Po Delta (Italy), where we experimented with scribing as a tool for geographical fieldwork and spatial storytelling, understanding it as a practice for seeing beyond representing territories. The second more theoretical part of the paper presents scribing as a means to respond to the increasing need for more creative visualisation tools in qualitative research and highlights the performative potential of scribing as a practice/product for thinking about space. The graphic product of scribing results from an intersubjective dialogue and is used to develop spatial analyses and disseminate geographical research beyond academic boundaries, engaging non-expert audiences and local communities.