ABSTRACT Prediction requires use of models (e.g. conceptual, physical, analytical or numerical mo... more ABSTRACT Prediction requires use of models (e.g. conceptual, physical, analytical or numerical models). Uncertainty associated with any kind of model and complexity of fluvial systems, specifically of braided rivers, are major issues to be taken into account. This means that we should be aware that prediction of channel morphology has inherent limitations since results of any model are affected by a degree of uncertainty and braided rivers are very complex systems that exhibit self-organized critical behaviour. In this work a long braided reach (33 km in length) of the Tagliamento River (north-eastern Italy) is analysed. This large gravel-bed river (average channel width was 760 m in 2009) underwent notable channel adjustments due to human interventions (i.e. sediment mining and channelization) in the past. Our aim is to explore future channel evolution taking into account different scenarios of flow regime and sediment supply at catchment and reach scale. Two different modelling approaches were combined: (i) a conceptual model based on a historical analysis of channel changes over the last 200 years and controlling factors and (ii) numerical modelling, using a reduced complexity model (CAESAR). According to the conceptual model channel widening will take place in the future, though the evolutionary trajectory will depend on magnitude and frequency of formative discharges. For instance assuming that flow regime in the next years will be similar to that in the period 1993-2009, channel width will increase up to 1020 m in 2080 (in this case an average widening rate of 3.7 m/yr is assumed). From this conceptual model different future trajectories could be derived, for instance more intense channel widening is predicted if an increase in magnitude and frequency of formative discharges is assumed. The numerical modelling, using constant conditions for flow regime and different conditions for sediment supply (i.e. scenarios), showed that channel widening will continue in the next decades, independently from sediment management strategies. As expected, widening turned out to be more intense in the scenario where bank protections were removed (w = 1230 m) compared to the scenario where upstream sediment input was reduced (w = 1130 m). This work should be taken as an attempt to predict channel morphology evolution over long spatial and temporal scales (i.e. tens of km and tens of years) that are rarely considered in river modelling. Such scales are very relevant for river management. Because uncertainty can be very high in modelling long river reaches over several decades, it is worth using different models to reduce uncertainty. The results of the two models used in this study turned to be very coherent, thus increasing reliability of the predictions.
English abstract: This paper deals with the use of landslide records in the analysis of landscape... more English abstract: This paper deals with the use of landslide records in the analysis of landscape sensitivity, with particular reference to climate change as a forcing process. The dating of past landslide events is useful to reconstruct the evolution of the slope-system at a broad temporal scale and to recognize the different formative events it has experienced. If the environmental context can be defined by means of a multidisciplinary approach which comprises geomorphological, sedimentological, palaeobotanical, dendrochronological ...
Journal of Geophysical Research: Earth Surface, 2013
This paper addresses an important question of modeling stream dynamics: How may numerical models ... more This paper addresses an important question of modeling stream dynamics: How may numerical models of braided stream morphodynamics be rigorously and objectively evaluated against a real case study? Using simulations from the Cellular Automaton Evolutionary Slope and River (CAESAR) reduced-complexity model (RCM) of a 33 km reach of a large gravel bed river (the Tagliamento River, Italy), this paper aims to (i) identify a sound strategy for calibration and validation of RCMs, (ii) investigate the effectiveness of multiperformance model assessments, (iii) assess the potential of using CAESAR at mesospatial and mesotemporal scales. The approach used has three main steps: first sensitivity analysis (using a screening method and a variance-based method), then calibration, and finally validation. This approach allowed us to analyze 12 input factors initially and then to focus calibration only on the factors identified as most important. Sensitivity analysis and calibration were performed on a 7.5 km subreach, using a hydrological time series of 20 months, while validation on the whole 33 km study reach over a period of 8 years (2001-2009). CAESAR was able to reproduce the macromorphological changes of the study reach and gave good results as for annual bed load sediment estimates which turned out to be consistent with measurements in other large gravel bed rivers but showed a poorer performance in reproducing the characteristics of the braided channel (e.g., braiding intensity). The approach developed in this study can be effectively applied in other similar RCM contexts, allowing the use of RCMs not only in an explorative manner but also in obtaining quantitative results and scenarios.
Supplementi di Geografia Fisica e Dinamica Quaternaria
Most Italian rivers have experienced widespread channel adjust- ments over the last 100 years, ma... more Most Italian rivers have experienced widespread channel adjust- ments over the last 100 years, mainly in response to a range of human activities. The aim of this paper is to show how knowledge of channel ad- justment and reconstruction of evolutionary trajectory are or can be used in river management and restoration. The first part of the paper deals with channel adjustments and summarizes the results of recent studies carried out on twelve rivers in northern and central Italy. The second part illustrates three examples of application. The selected rivers have undergone almost the same processes in terms of temporal trends. Initially, river channels underwent a long phase of narrowing (up to 80%) and incision (up to 8-10 m), which started at the end of the 19th century and was very intense from the 1950s to the 1980s. Then, over the last 15-20 years, channel widening and sedimenta- tion, or bed-level stabilization, have become the dominant processes in most of the rivers, though cha...
Das Ziel dieser Arbeit war es herauszufinden ob es prinzipiell möglich ist die Zusammenhänge, Reg... more Das Ziel dieser Arbeit war es herauszufinden ob es prinzipiell möglich ist die Zusammenhänge, Regeln und Strukturen welche für die (teil)automatisierte Erstellung von validen (d.h. konstruktiv und logistisch möglichen) Bauteilkonstruktion notwendig sind, (i) zu finden und (ii) derart zu formulieren, dass dieses Wissen zur raschen, computergenerierten Erstellung solcher Konstruktionen genutzt werden kann. Eine manuelle Erstellung von Konstruktionen wird in der allgemeinen Planungspraxis ständig durchgeführt, hier werden oftmals Schritte, die gut geeignet für eine Automation erscheinen, wieder und wieder manuell durchgeführt. Diese Beobachtung, wie auch die Arbeit an dem Forschungsprojekt SEMERGY diente als Ausgangspunkt, bei welchem die Idee zu einer solchen Anwendung entstand. Eine Schwierigkeit an der Erstellung eines solchen Tools ist es, das erforderliche Fachwissen (Domain-Knowledge) über die Zusammenstellung der Bauteilaufbauten zusammenzutragen und der Zielsetzung entsprechend aufzubereiten. Um all die komplexen Zusammenhänge und Abhängigkeiten zu erfassen wurde eine große Anzahl von Aufbauten analysiert und daraus Systematiken und Regeln abgeleitet. Es wurden Templates erstellt die als Grundgerüst für eine solche Anwendung dienen können, und eine große Zahl von möglichen Varianten eines Aufbaues enthalten (Es wurde angestrebt Regeln zu definieren, welche jeweils taxativ sind, d.h. alle möglichen Kombinationen berücksichtigen). Das konzentrierte und um Regeln angereicherte Wissen aus diesem Prozess wurde in eine allgemein verständliche Form gebracht: Damit eine programmiertechnische Umsetzung weitestgehend unabhängig von proprietären Programmiersprachen oder Applikationen gemacht werden kann, wurden Abläufe für den Genese-Prozess als "Pseudocode" ausgedrückt. Diese Ausdrucksform besitzt den Vorteil, dass (i) eine spätere Umsetzung auch von Nicht-Baufachleuten relativ einfach (ohne Domänenwissen) durchgeführt werden kann, (ii) potentielle Fehler oder Abweichungen rasch identifiziert werden können, sowie (iii) eine große Flexibilität, Erweiterbarkeit und Editierbarkeit gewährleistet ist. Es wurde auch der gesamte mögliche Arbeitsablauf innerhalb eines solchen Tools modelliert, um die möglichen Konstruktionen genauestens evaluieren zu können und entsprechend des geforderten Anwendungsfalles bestmöglich abzustimmen zu können. Dazu wurden eine Berechnung des Wärmedurchgangskoeffizienten, des etwaig anfallenden (Bauteil-)Kondensats gemäß normativer Methoden, des OI3 Koeffizienten (Environmental Footprints) und der Speichermasse als mögliche Kontrollinstanzen zu einer Qualitätssicherung bzw. Überprüfung abgebildet. Weitere Methoden können nach Maßgabe vorhandener Eingabedaten jederzeit hinzugefügt werden. Beispiele hierfür könnten Kosten und Investition-bzw. Instandhaltung-Kostenberechnung oder bauakustische Eigenschaften und zugehörige Berechnungen sein. Die Ergebnisse dieser Arbeit sollen zur Anwendung in anderen Projekten wie zum Beispiel in einem laufenden Projekt zur Fassung von Bauteileigenschaften in zeitgemäßen Datenstrukturen (Forschungsprojekt BAU_WEB, TU Wien) vorbereitet werden. Eine generische und auf viele Anwendungsfälle übertragbare Methode ist explizites Ziel dieser Arbeit.
ABSTRACT This work addresses the temporal dynamics of riparian vegetation in large braided rivers... more ABSTRACT This work addresses the temporal dynamics of riparian vegetation in large braided rivers, exploring the relationship between vegetation erosion and flood magnitude. In particular, it investigates the existence of a threshold discharge, or a range of discharges, above which erosion of vegetated patches within the channel occurs. The research was conducted on a 14 km long reach of the Tagliamento River, a braided river in northeastern Italy. Ten sets of aerial photos were used to investigate vegetation dynamics in the period 1954-2011. By using different GIS procedures, three aspects of geomorphic-vegetation dynamics and interactions were addressed: (i) long-term (1954-2011) channel evolution and vegetation dynamics; (ii) the relationship between vegetation erosion/establishment and flow regime and (iii) vegetation turnover, in the period 1986-2011. Results show that vegetation turnover is remarkably rapid in the study reach with 50 % of in-channel vegetation persisting for less than 5-6 years and only 10 % of vegetation persisting for more than 18-19 years. The analysis shows that significant vegetation erosion is determined by relatively frequent floods, i.e. floods with a recurrence interval of ca. 1-2.5 years, although some differences exist between subreaches with different densities of vegetation cover. These findings suggest that the erosion of riparian vegetation in braided rivers may be not controlled solely by very large floods, as is the case for lower energy gravel-bed rivers. Besides flow regime, other factors seem to play a significant role for in-channel vegetation cover over long time spans. In particular, erosion of marginal vegetation, which supplies large wood elements to the channel, increased notably over the study period and was an important factor for in-channel vegetation trends. This article is protected by copyright. All rights reserved.
The aim of this paper is to explore possibilities and limitations of restoring physical processes... more The aim of this paper is to explore possibilities and limitations of restoring physical processes in five gravel-bed rivers (Brenta, Piave, Cellina, Tagliamento and Torre Rivers) in northeastern Italy. The selected rivers were analysed through a range of techniques, specifically analysis of historical maps and aerial photographs with geographical information systems (GIS), comparison of topographic surveys and geomorphological surveys. After illustrating channel adjustments and sediment fluxes, we discuss how the understanding of physical processes can be used for channel restoration. The studied river channels have undergone notable adjustments in the last 100 years, specifically narrowing by up to 76%, incision by up to 8.5 m, and changes in channel configuration. Alteration of sediment fluxes, mainly due to in-channel mining, has been the main factor driving such channel adjustments. Evolutionary trends show that channel recovery is ongoing in several of the selected reaches, since widening and aggradation have occurred over the last 15-20 years. This channel recovery has been possible because sediment mining has significantly decreased or ceased along the study reaches. However, several constraints still exist on sediment fluxes (e.g. dams). Four categories of river channel were defined, taking into account the recent evolution of the studied channels (from 'A', high channel recovery, to 'D', no channel recovery). The impact of different sediment management strategies on channel dynamics over the next 40-50 years was then analysed. Without any intervention, channel recovery would only be possible in those reaches that have a relatively high degree of connectivity with upstream sediment sources or tributaries, while further incision and narrowing would be expected in those reaches where connectivity is low. A more substantial channel recovery could be obtained through interventions at reach (e.g. removal of bank protection) and basin (e.g. sediment transfer downstream of dams) scales. Notwithstanding such actions, it is likely that channels will not recover in the next few decades to the morphology they exhibited in the first half of the 20th century, when bed-load yield and connectivity were higher.
. We adopt a multidisciplinary approach toward the quantitative assessment of juvenile fish habi... more . We adopt a multidisciplinary approach toward the quantitative assessment of juvenile fish habitats in Alpine rivers using analytical modeling. The study focuses on braided and single-thread channel configurations together with their associated hydrodynamic patterns. A distinct difference between flows in these channels is the number and spatial arrangement of recirculation zones. These are due to the separation of flow from
ABSTRACT Prediction requires use of models (e.g. conceptual, physical, analytical or numerical mo... more ABSTRACT Prediction requires use of models (e.g. conceptual, physical, analytical or numerical models). Uncertainty associated with any kind of model and complexity of fluvial systems, specifically of braided rivers, are major issues to be taken into account. This means that we should be aware that prediction of channel morphology has inherent limitations since results of any model are affected by a degree of uncertainty and braided rivers are very complex systems that exhibit self-organized critical behaviour. In this work a long braided reach (33 km in length) of the Tagliamento River (north-eastern Italy) is analysed. This large gravel-bed river (average channel width was 760 m in 2009) underwent notable channel adjustments due to human interventions (i.e. sediment mining and channelization) in the past. Our aim is to explore future channel evolution taking into account different scenarios of flow regime and sediment supply at catchment and reach scale. Two different modelling approaches were combined: (i) a conceptual model based on a historical analysis of channel changes over the last 200 years and controlling factors and (ii) numerical modelling, using a reduced complexity model (CAESAR). According to the conceptual model channel widening will take place in the future, though the evolutionary trajectory will depend on magnitude and frequency of formative discharges. For instance assuming that flow regime in the next years will be similar to that in the period 1993-2009, channel width will increase up to 1020 m in 2080 (in this case an average widening rate of 3.7 m/yr is assumed). From this conceptual model different future trajectories could be derived, for instance more intense channel widening is predicted if an increase in magnitude and frequency of formative discharges is assumed. The numerical modelling, using constant conditions for flow regime and different conditions for sediment supply (i.e. scenarios), showed that channel widening will continue in the next decades, independently from sediment management strategies. As expected, widening turned out to be more intense in the scenario where bank protections were removed (w = 1230 m) compared to the scenario where upstream sediment input was reduced (w = 1130 m). This work should be taken as an attempt to predict channel morphology evolution over long spatial and temporal scales (i.e. tens of km and tens of years) that are rarely considered in river modelling. Such scales are very relevant for river management. Because uncertainty can be very high in modelling long river reaches over several decades, it is worth using different models to reduce uncertainty. The results of the two models used in this study turned to be very coherent, thus increasing reliability of the predictions.
English abstract: This paper deals with the use of landslide records in the analysis of landscape... more English abstract: This paper deals with the use of landslide records in the analysis of landscape sensitivity, with particular reference to climate change as a forcing process. The dating of past landslide events is useful to reconstruct the evolution of the slope-system at a broad temporal scale and to recognize the different formative events it has experienced. If the environmental context can be defined by means of a multidisciplinary approach which comprises geomorphological, sedimentological, palaeobotanical, dendrochronological ...
Journal of Geophysical Research: Earth Surface, 2013
This paper addresses an important question of modeling stream dynamics: How may numerical models ... more This paper addresses an important question of modeling stream dynamics: How may numerical models of braided stream morphodynamics be rigorously and objectively evaluated against a real case study? Using simulations from the Cellular Automaton Evolutionary Slope and River (CAESAR) reduced-complexity model (RCM) of a 33 km reach of a large gravel bed river (the Tagliamento River, Italy), this paper aims to (i) identify a sound strategy for calibration and validation of RCMs, (ii) investigate the effectiveness of multiperformance model assessments, (iii) assess the potential of using CAESAR at mesospatial and mesotemporal scales. The approach used has three main steps: first sensitivity analysis (using a screening method and a variance-based method), then calibration, and finally validation. This approach allowed us to analyze 12 input factors initially and then to focus calibration only on the factors identified as most important. Sensitivity analysis and calibration were performed on a 7.5 km subreach, using a hydrological time series of 20 months, while validation on the whole 33 km study reach over a period of 8 years (2001-2009). CAESAR was able to reproduce the macromorphological changes of the study reach and gave good results as for annual bed load sediment estimates which turned out to be consistent with measurements in other large gravel bed rivers but showed a poorer performance in reproducing the characteristics of the braided channel (e.g., braiding intensity). The approach developed in this study can be effectively applied in other similar RCM contexts, allowing the use of RCMs not only in an explorative manner but also in obtaining quantitative results and scenarios.
Supplementi di Geografia Fisica e Dinamica Quaternaria
Most Italian rivers have experienced widespread channel adjust- ments over the last 100 years, ma... more Most Italian rivers have experienced widespread channel adjust- ments over the last 100 years, mainly in response to a range of human activities. The aim of this paper is to show how knowledge of channel ad- justment and reconstruction of evolutionary trajectory are or can be used in river management and restoration. The first part of the paper deals with channel adjustments and summarizes the results of recent studies carried out on twelve rivers in northern and central Italy. The second part illustrates three examples of application. The selected rivers have undergone almost the same processes in terms of temporal trends. Initially, river channels underwent a long phase of narrowing (up to 80%) and incision (up to 8-10 m), which started at the end of the 19th century and was very intense from the 1950s to the 1980s. Then, over the last 15-20 years, channel widening and sedimenta- tion, or bed-level stabilization, have become the dominant processes in most of the rivers, though cha...
Das Ziel dieser Arbeit war es herauszufinden ob es prinzipiell möglich ist die Zusammenhänge, Reg... more Das Ziel dieser Arbeit war es herauszufinden ob es prinzipiell möglich ist die Zusammenhänge, Regeln und Strukturen welche für die (teil)automatisierte Erstellung von validen (d.h. konstruktiv und logistisch möglichen) Bauteilkonstruktion notwendig sind, (i) zu finden und (ii) derart zu formulieren, dass dieses Wissen zur raschen, computergenerierten Erstellung solcher Konstruktionen genutzt werden kann. Eine manuelle Erstellung von Konstruktionen wird in der allgemeinen Planungspraxis ständig durchgeführt, hier werden oftmals Schritte, die gut geeignet für eine Automation erscheinen, wieder und wieder manuell durchgeführt. Diese Beobachtung, wie auch die Arbeit an dem Forschungsprojekt SEMERGY diente als Ausgangspunkt, bei welchem die Idee zu einer solchen Anwendung entstand. Eine Schwierigkeit an der Erstellung eines solchen Tools ist es, das erforderliche Fachwissen (Domain-Knowledge) über die Zusammenstellung der Bauteilaufbauten zusammenzutragen und der Zielsetzung entsprechend aufzubereiten. Um all die komplexen Zusammenhänge und Abhängigkeiten zu erfassen wurde eine große Anzahl von Aufbauten analysiert und daraus Systematiken und Regeln abgeleitet. Es wurden Templates erstellt die als Grundgerüst für eine solche Anwendung dienen können, und eine große Zahl von möglichen Varianten eines Aufbaues enthalten (Es wurde angestrebt Regeln zu definieren, welche jeweils taxativ sind, d.h. alle möglichen Kombinationen berücksichtigen). Das konzentrierte und um Regeln angereicherte Wissen aus diesem Prozess wurde in eine allgemein verständliche Form gebracht: Damit eine programmiertechnische Umsetzung weitestgehend unabhängig von proprietären Programmiersprachen oder Applikationen gemacht werden kann, wurden Abläufe für den Genese-Prozess als "Pseudocode" ausgedrückt. Diese Ausdrucksform besitzt den Vorteil, dass (i) eine spätere Umsetzung auch von Nicht-Baufachleuten relativ einfach (ohne Domänenwissen) durchgeführt werden kann, (ii) potentielle Fehler oder Abweichungen rasch identifiziert werden können, sowie (iii) eine große Flexibilität, Erweiterbarkeit und Editierbarkeit gewährleistet ist. Es wurde auch der gesamte mögliche Arbeitsablauf innerhalb eines solchen Tools modelliert, um die möglichen Konstruktionen genauestens evaluieren zu können und entsprechend des geforderten Anwendungsfalles bestmöglich abzustimmen zu können. Dazu wurden eine Berechnung des Wärmedurchgangskoeffizienten, des etwaig anfallenden (Bauteil-)Kondensats gemäß normativer Methoden, des OI3 Koeffizienten (Environmental Footprints) und der Speichermasse als mögliche Kontrollinstanzen zu einer Qualitätssicherung bzw. Überprüfung abgebildet. Weitere Methoden können nach Maßgabe vorhandener Eingabedaten jederzeit hinzugefügt werden. Beispiele hierfür könnten Kosten und Investition-bzw. Instandhaltung-Kostenberechnung oder bauakustische Eigenschaften und zugehörige Berechnungen sein. Die Ergebnisse dieser Arbeit sollen zur Anwendung in anderen Projekten wie zum Beispiel in einem laufenden Projekt zur Fassung von Bauteileigenschaften in zeitgemäßen Datenstrukturen (Forschungsprojekt BAU_WEB, TU Wien) vorbereitet werden. Eine generische und auf viele Anwendungsfälle übertragbare Methode ist explizites Ziel dieser Arbeit.
ABSTRACT This work addresses the temporal dynamics of riparian vegetation in large braided rivers... more ABSTRACT This work addresses the temporal dynamics of riparian vegetation in large braided rivers, exploring the relationship between vegetation erosion and flood magnitude. In particular, it investigates the existence of a threshold discharge, or a range of discharges, above which erosion of vegetated patches within the channel occurs. The research was conducted on a 14 km long reach of the Tagliamento River, a braided river in northeastern Italy. Ten sets of aerial photos were used to investigate vegetation dynamics in the period 1954-2011. By using different GIS procedures, three aspects of geomorphic-vegetation dynamics and interactions were addressed: (i) long-term (1954-2011) channel evolution and vegetation dynamics; (ii) the relationship between vegetation erosion/establishment and flow regime and (iii) vegetation turnover, in the period 1986-2011. Results show that vegetation turnover is remarkably rapid in the study reach with 50 % of in-channel vegetation persisting for less than 5-6 years and only 10 % of vegetation persisting for more than 18-19 years. The analysis shows that significant vegetation erosion is determined by relatively frequent floods, i.e. floods with a recurrence interval of ca. 1-2.5 years, although some differences exist between subreaches with different densities of vegetation cover. These findings suggest that the erosion of riparian vegetation in braided rivers may be not controlled solely by very large floods, as is the case for lower energy gravel-bed rivers. Besides flow regime, other factors seem to play a significant role for in-channel vegetation cover over long time spans. In particular, erosion of marginal vegetation, which supplies large wood elements to the channel, increased notably over the study period and was an important factor for in-channel vegetation trends. This article is protected by copyright. All rights reserved.
The aim of this paper is to explore possibilities and limitations of restoring physical processes... more The aim of this paper is to explore possibilities and limitations of restoring physical processes in five gravel-bed rivers (Brenta, Piave, Cellina, Tagliamento and Torre Rivers) in northeastern Italy. The selected rivers were analysed through a range of techniques, specifically analysis of historical maps and aerial photographs with geographical information systems (GIS), comparison of topographic surveys and geomorphological surveys. After illustrating channel adjustments and sediment fluxes, we discuss how the understanding of physical processes can be used for channel restoration. The studied river channels have undergone notable adjustments in the last 100 years, specifically narrowing by up to 76%, incision by up to 8.5 m, and changes in channel configuration. Alteration of sediment fluxes, mainly due to in-channel mining, has been the main factor driving such channel adjustments. Evolutionary trends show that channel recovery is ongoing in several of the selected reaches, since widening and aggradation have occurred over the last 15-20 years. This channel recovery has been possible because sediment mining has significantly decreased or ceased along the study reaches. However, several constraints still exist on sediment fluxes (e.g. dams). Four categories of river channel were defined, taking into account the recent evolution of the studied channels (from 'A', high channel recovery, to 'D', no channel recovery). The impact of different sediment management strategies on channel dynamics over the next 40-50 years was then analysed. Without any intervention, channel recovery would only be possible in those reaches that have a relatively high degree of connectivity with upstream sediment sources or tributaries, while further incision and narrowing would be expected in those reaches where connectivity is low. A more substantial channel recovery could be obtained through interventions at reach (e.g. removal of bank protection) and basin (e.g. sediment transfer downstream of dams) scales. Notwithstanding such actions, it is likely that channels will not recover in the next few decades to the morphology they exhibited in the first half of the 20th century, when bed-load yield and connectivity were higher.
. We adopt a multidisciplinary approach toward the quantitative assessment of juvenile fish habi... more . We adopt a multidisciplinary approach toward the quantitative assessment of juvenile fish habitats in Alpine rivers using analytical modeling. The study focuses on braided and single-thread channel configurations together with their associated hydrodynamic patterns. A distinct difference between flows in these channels is the number and spatial arrangement of recirculation zones. These are due to the separation of flow from
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