Intertwined Eco‐Morphodynamic Evolution of Salt Marshes and Emerging Tidal Channel Networks

The formation and development of tidal channels and salt marshes are controlled by complex interactions between hydrodynamics, sediment transport, and vegetation dynamics. Tidal channels affect and, at the same time, are affected by the growth of salt marshes fringing them. The coupled evolution of these morphological units, mediated by vegetation growth, is thus a key ingredient for simulating the behavior of tidal environments. Considering these two factors, we developed a mathematical model to investigate the eco-morphodynamic evolution of intertidal areas fringing a main channel and of the tidal creeks cutting through them. Model results indicate that vegetation promotes the development of channel networks, leading to more complex channel structures and higher drainage efficiency. Vegetation encroachment influences sediment deposition patterns by trapping sediment in the seaward and middle intertidal areas, while reducing the amount of sediment delivered to landward areas. In the presence of sea level rise, this deficit of sediment enhances the landward-decreasing trend of the intertidal platform and leads to more isolated vegetation patches. Overall, sea level rise restricts the extension of salt marshes and consequently reduces the effect of vegetation on channel network form and function

Intertwined eco-morphodynamic evolution of salt marshes and tidal channels cutting through them

The formation and development of tidal channels and salt marshes are controlled by complex interactions between hydrodynamics, sediment transport, and vegetation dynamics. Tidal channels affect and, at the same time, are affected by the growth of salt marshes fringing them. The coupled evolution of these morphological units is thus a key ingredient for simulating the typical behaviour of tidal environments. We developed a mathematical model accounting for vegetation-induced flow resistance and wetting-drying processes typical of tidal environments, to investigate the eco-morphodynamic evolution of intertidal areas fringing a main channel and of the tidal creeks cutting through them. Model results indicate that vegetation promotes the development of channel networks, leading to more complex channel structures and higher drainage efficiency. Vegetation encroachment influences sediment deposition patterns by trapping sediment in the seaward and middle intertidal areas, while reducing the amount of sediment delivered to landward areas. In the presence of sea level rise, this deficit of sediment enhances the landward-decreasing trend of the intertidal platform and leads to more isolated vegetation patches. Overall, sea level rise restricts the extension of salt marshes and consequently reduces the effect of vegetation on channel development

Intertwined eco-morphodynamic evolution of salt marshes and tidal channels cutting through them

The formation and development of tidal channels and salt marshes are controlled by complex interactions between hydrodynamics, sediment transport, and vegetation dynamics. Tidal channels affect and, at the same time, are affected by the growth of salt marshes fringing them. The coupled evolution of these morphological units is thus a key ingredient for simulating the typical behaviour of tidal environments. We developed a mathematical model accounting for vegetation-induced flow resistance and wetting-drying processes typical of tidal environments, to investigate the eco-morphodynamic evolution of intertidal areas fringing a main channel and of the tidal creeks cutting through them. Model results indicate that vegetation promotes the development of channel networks, leading to more complex channel structures and higher drainage efficiency. Vegetation encroachment influences sediment deposition patterns by trapping sediment in the seaward and middle intertidal areas, while reducing the amount of sediment delivered to landward areas. In the presence of sea level rise, this deficit of sediment enhances the landward-decreasing trend of the intertidal platform and leads to more isolated vegetation patches. Overall, sea level rise restricts the extension of salt marshes and consequently reduces the effect of vegetation on channel development

Heparin Induces Apoptosis in Lymphocytes from B-cell Chronic Lymphocytic Leukemia.

It has been shown that glycosaminoglycans play a role in the regulation of immune response. In particular, heparin exerts an antiproliferative and apoptotic action in different cellular systems. In this study we evaluate whether heparin can also induce a naturally occurring programmed cell death in lymphocytes from B-chronic lymphocytic leukemia (B-CLL), a neoplastic lineage where apoptosis is blocked by the expression of the proto-oncogene bc1-2. Peripheral blood lymphocytes (PBL) from 7 cases of B-CLL patients in different stages were cultured with three different heparin sodium concentrations for 4 days. Apoptosis was evaluated by agarose gel electrophoresis and by cytofluorimetric analysis. Bcl-2 expression was tested by flow cytometric analysis and immunohistochemistry on cytospin preparations. Agarose gel electrophoresis showed the characteristic DNA fragmentation pattern of apoptosis in all the cases of B-CLL stage III and IV after heparin incubation. DNA from normal and neoplastic lymphocytes cultured without heparin did not undergo spontaneous apoptosis. Cytofluorimetric analysis confirmed the agarose gel pattern and found a level of apoptosis over 50% after culture of neoplastic PBL with heparin. In these cases bcl-2 expression was found to be significantly reduced after heparin incubation when comparing to bcl-2 level before incubation. Our data adds further evidence regarding the potential role of heparin in oncogene inhibition and in apoptosis induction. In particular, the induction of apoptosis in neoplastic lymphocytes by heparin may have a role in the complicated field of interactions between the immune system and the blood vessels by glycosaminoglycans

Evaluating the use of smart sensors in ground-based monitoring of landslide movement with laboratory experiments

Boulders and cobbles embedded on the body of landslides are carried downstream under the action of gravity, and the study of their transport can give important insight on their dynamics and hence the related hazard. The study examines the reliability of smart sensors to track movements of a cobble and discern between intensity and mode of movement in laboratory experiments. A tag equipped with accelerometer, gyroscope, and magnetometer sensors was installed inside a cobble. The experiments consisted of letting the cobble fall on an inclined plane. By tilting the inclined plane at different angles, different modes of movement such as rolling, bouncing, or sliding were generated. Sliding was generated by embedding the cobble within a thin layer of sand. The position of the cobble travelling down the slope was derived from camera videos. Raw sensor data allowed detection of movement and separation of two modes of movement, namely rolling, and sliding. Additionally, reliable values for the position, velocity, and acceleration were determined by feeding a Kalman filter with smart sensor measurements and camera-based positions. Furthermore, by testing LoRaWAN wireless transmission through sand, the study showed that the signal strength tended to decrease for thicker sand layers. These findings confirm the potential to use these sensors to improve early warning systems and further studies are in progress to assess practicalities of their use in field settings

Smart sensors to detect movements of cobbles and large woody debris dams. Insights from lab experiments.

An increase in population pressure and severe storms under climate change have greatly impacted landslide and flood hazards globally. At the same time, recent advances in Wireless Sensor Network (WSN) and Internet of Things (IoT) technologies, microelectronics and machine learning offer new opportunities to effectively monitor stability of boulder and woody debris on landslides and in flood-prone rivers. In this framework, smart sensors embedded in elements within the landslide body and the river catchment can be potentially used for monitoring purposes and for developing early warning systems. This is because they are small, light-weight, and able to collect different environmental data with low battery consumption and communicate to a server through a wireless connection. However, their reliability still needs to be evaluated. As data from field sites could be fragmented, laboratory experiments are essential to validate sensor data and see their potential in a controlled environment. In the present study, dedicated laboratory experiments were designed to assess the ability of a tag equipped with an accelerometer, a gyroscope, and a magnetometer to detect movements in two different settings. In the first experimental campaign, the tag was installed inside a cobble of 10.0 cm diameter within a borehole of 4.0 cm diameter. The experiments consisted in letting the cobble fall on an experimental table composed of an inclined plane of 1.5 m, followed by a horizontal one of 2.0 m. The inclined plane can be tilted at different angles (18˚- 55˚) and different types of movement have been generated by letting the cobble roll, bounce, or slide. Sliding was generated by embedding the cobble within a layer of sand. The position of the cobble travelling down the slope was derived from camera videos by a tracking algorithm developed within the study. In the second experimental campaign, a simplified analogue model of a woody debris dam was built from a single hollowed dowel with a length of 40 cm and a diameter of 3.8 cm. The sensor tag is installed in the woody dowel within a 2.5 cm longitudinal borehole. Two metal rigs are mounted at both sides of the woody dowel to allow different modes of movement. Specifically, the woody dowel is allowed to move either horizontally or vertically within a range of 20-30 mm, whereas it is always free to complete full rotations. The woody dowel is mounted on a frame within a 20 m long and 0.6 m wide flume. In these two experimental settings, combining data from the accelerometer, gyroscope and magnetometer it was possible to detect movements and differentiate between different type of motions both in a woody dowel and in the cobble under different initial conditions. Data were analysed to understand which type of information could be retrieved. This gives important insights for the assessment of the feasibility and effectiveness of the use of smart sensors in the detection of movements in woody logs within dams and boulders embedded in landslides, thus providing indications for the development of early warning systems using this innovative technology

Modelling the plano-altimetric equilibrium of a tidal channel

Tidal channels are ubiquitous features of the tidal landscape which play a critical role in the morphodynamic evolution of these landscapes. In addition, tidal channels represent a substantial ecological and economic value, being however vulnerable to climate changes and increasing anthropogenic pressures. Improving current knowledge on tidal channel form and function is therefore key step to model and predict the evolution of tidal systems. A number of studies have analyzed the evolution and equilibrium configuration of tidal channels, focusing on the equilibrium profile of the channel bed for a given channel-width distribution as well as on channel equilibrium cross-sectional shape. However, the role that vegetation growth on the marsh platform plays on the equilibrium morphology of salt-marsh channels has received less attention. Here we developed a model which analyzes the equilibrium configuration of a channel and the adjacent salt-marsh platform and provides a useful tool for quantitative analyses of long-term eco-morphodynamic studies in tidal landscapes. The open channel flow is studied by a 1D hydrodynamic model developed to describe the flow field within the channel and, if present, on the lateral shoals. The 1D hydrodynamics was “validated” considering some test cases comparing the results obtained with a full-fledged 2D model as a reference. The tidal channel evolution can be sought using three different setups which single out landforming effects: purely erosional model, in which the erosion is the only effect shaping the channel; depositional model, in which erosion, sea level rise and settling deposition scour and promote the vertical accretion of the basin; depositional model with vegetation, in which vegetation effects are included in the previous setup. Model results reproduce several observed channel characteristics which are deemed to be relevant from a geomorphological point of view. Model results also show that vegetation encroachment on the marsh surface produces two competing effects. Enhanced marsh accretion associated with the increased particle trapping and with the organic production by halophytic plants, increases marsh elevation in the tidal frame, thus reducing the landscape forming tidal prism and the channel cross-sectional area. However, the increased flow resistance on the canopy promotes flow concentration within the channel, leading to more incised cross sections characterized by smaller width-to-depth ratios. Our simulations indicate that the second process is more important in marshes which are lower in the tidal frame, whereas the first process is more important in marshes higher in the tidal frame when most of the tidal fluxes are already confined within the channel.I canali a marea innervano gli ambienti a marea costituendo dei percorsi preferenziali per il trasporto di acqua, sedimenti e nutrimenti. Inoltre, i canali a marea rappresentano un sostanziale valore ecologico ed economico, essendo tuttavia vulnerabili ai cambiamenti climatici e alle crescenti pressioni antropiche. La comprensione dei meccanismi che regolano la forma ed il funzionamento dei canali a marea è cruciale per migliorare la previsione delle tendenze evolutive degli ambienti a marea. Numerosi studi hanno analizzato l'evoluzione e la configurazione dell'equilibrio dei canali di marea, concentrandosi sul profilo di equilibrio del letto di canale per una data distribuzione della larghezza del canale e sulla forma della sezione trasversale di equilibrio del canale. Tuttavia, il ruolo che la crescita della vegetazione sulla piattaforma di barena svolge sulla morfologia di equilibrio dei canali a marea ha ricevuto meno attenzione. In questa tesi è stato sviluppato un modello che analizza la configurazione di equilibrio di un canale e l'adiacente barena e fornisce uno strumento utile per analisi quantitative di tipo eco-morfodinamico a lungo termine in ambienti a marea. L'idrodinamica è studiata attraverso un modello idrodinamico 1D sviluppato per descrivere il campo di moto all'interno di un canale e, dove presenti, sui bassofondali laterali. L'idrodinamica 1D è stata validata considerando alcuni casi test e confrontando i risultati ottenuti con un modello 2D scelto come riferimento. L'evoluzione del canale a marea può essere analizzata utilizzando tre diverse impostazioni che consentono di considerare separatamente o congiuntamente gli effetti responsabili della formazione del canale: modello puramente erosivo, l'erosione è l'unico effetto che modella il canale; modello deposizionale, in cui gli effetti considerati sono erosione, innalzamento del livello del mare e deposito per sedimentazione; modello con vegetazione, in cui si aggiungono alla precedente configurazione gli effetti di vegetazione. I risultati del modello riproducono diverse caratteristiche osservate del canale ritenute rilevanti dal punto di vista geomorfologico. I risultati del modello mostrano anche che la presenza della vegetazione sulla superficie di barena produce due effetti contrastanti. La crescita della vegetazione associata ad un incremento dell'effetto di intrappolamento di particelle di sedimento e della produzione organica da parte di piante alofite, aumenta la quota della superficie di barena rispetto all'escursione di marea, riducendo così il prisma di marea e l'area della sezione trasversale del canale. Tuttavia, la maggiore resistenza al flusso sulle piattaforme laterali promuove la concentrazione del flusso all'interno del canale, portando a sezioni trasversali più incise caratterizzate da rapporti larghezza-profondità più piccoli. Le nostre simulazioni indicano che il secondo processo è più importante sulle superfici di barena a quote più basse rispetto all'escursione di marea, mentre il primo processo è più importante sulle superfici di barena a quote più alte rispetto all'escursione di marea quando la maggior parte dei flussi di marea sono già confinati all'interno del canale

Effetto della sedimentazione e della vegetazione sulla forma di equilibrio di un canale a marea

Lo scopo della tesi è quello di analizzare l’evoluzione morfodinamica a lungo termine di un canale a marea, con particolare attenzione alla sua configurazione di equilibrio, tendendo conto dei più rilevanti aspetti idrodinamici, morfologici ed ecologici. L’evoluzione del canale e la sua configurazione di equilibrio sono valutati su un dominio tridimensionale opportunamente discretizzato per un canale rettiline

Modelling the plano-altimetric equilibrium of a tidal channel

Tidal channels are ubiquitous features of the tidal landscape which play a critical role in the morphodynamic evolution of these landscapes. In addition, tidal channels represent a substantial ecological and economic value, being however vulnerable to climate changes and increasing anthropogenic pressures. Improving current knowledge on tidal channel form and function is therefore key step to model and predict the evolution of tidal systems. A number of studies have analyzed the evolution and equilibrium configuration of tidal channels, focusing on the equilibrium profile of the channel bed for a given channel-width distribution as well as on channel equilibrium cross-sectional shape. However, the role that vegetation growth on the marsh platform plays on the equilibrium morphology of salt-marsh channels has received less attention. Here we developed a model which analyzes the equilibrium configuration of a channel and the adjacent salt-marsh platform and provides a useful tool for quantitative analyses of long-term eco-morphodynamic studies in tidal landscapes. The open channel flow is studied by a 1D hydrodynamic model developed to describe the flow field within the channel and, if present, on the lateral shoals. The 1D hydrodynamics was “validated” considering some test cases comparing the results obtained with a full-fledged 2D model as a reference. The tidal channel evolution can be sought using three different setups which single out landforming effects: purely erosional model, in which the erosion is the only effect shaping the channel; depositional model, in which erosion, sea level rise and settling deposition scour and promote the vertical accretion of the basin; depositional model with vegetation, in which vegetation effects are included in the previous setup. Model results reproduce several observed channel characteristics which are deemed to be relevant from a geomorphological point of view. Model results also show that vegetation encroachment on the marsh surface produces two competing effects. Enhanced marsh accretion associated with the increased particle trapping and with the organic production by halophytic plants, increases marsh elevation in the tidal frame, thus reducing the landscape forming tidal prism and the channel cross-sectional area. However, the increased flow resistance on the canopy promotes flow concentration within the channel, leading to more incised cross sections characterized by smaller width-to-depth ratios. Our simulations indicate that the second process is more important in marshes which are lower in the tidal frame, whereas the first process is more important in marshes higher in the tidal frame when most of the tidal fluxes are already confined within the channel

Effects of vegetation, sediment supply and sea level rise on the morphodynamic evolution of tidal channels

Data computed by a numerical model developed to give insight about the long-term evolution of a straight channel cutting through a rectangular basin and data about real tidal channels (Venice lagoon, Western Scheldt