Mario A Lenzi | Università degli Studi di Padova (original) (raw)
Papers by Mario A Lenzi
Quantification of bedload transport in high-gradient mountain streams is important, but field dat... more Quantification of bedload transport in high-gradient mountain streams is important, but field data necessary to test transport models are scarce. In the present work, we describe the experimental station for monitoring water and sediment fluxes built in 1985 on the Rio Cordon (Eastern Italian Alps), a small steppool channel. The measuring station consists of an inclined frame that separates (at 20 mm truncation) fine and coarse sediments, which are continuously measured for accumulations by two turbidimeters. The 25year dataset acquired, which comprises high-magnitude/low-recurrence flood events, has allowed a magnitude-frequency analysis of bedload volumes. Results from a combined frequency analysis of peak water discharge and total bedload volumes based on the 25 events are presented, focusing on discrepancies between recurrence intervals of peak discharge and bedload volume for each event. In addition, the integration between the sediment transport dataset and the repeated surveys of sediment sources and of channel changes has permitted to assess the geomorphic effectiveness of different flood events. The Rio Cordon measuring facilities have provided excellent data and valuable insights into the bedload dynamics of steep streams throughout its 25 years of operation, thanks to the close collaboration between the ARPAV-Veneto Region and the Department Land and Agro-forest Environments (University of Padova). However, the maintenance costs of the station are not trivial and may impact its future "vitality". At the same time, improvement of the present instrumentation and installation of novel technology would make the station an ideal location for calibrating surrogate techniques for sediment transport monitoring. 1 10 100 J a n -8 7 J a n -8 9 J a n -9 1 J a n -9 3 J a n -9 5 J a n -9 7 J a n -9 9 J a n -0 1 J a n -0 3 J a n -0 5 J a n -0 7 Time Bedload Volume/Effective Runoff (10 3
Journal of Agricultural Engineering, 2012
Quantification of bed-load transport in high-gradient mountain streams is important, but the fiel... more Quantification of bed-load transport in high-gradient mountain streams is important, but the field data needed to test transport models are scarce and difficult to obtain. In the present study, we describe the experimental station for monitoring water and sediment fluxes built in 1985 on the Rio Cordon, a small step-pool channel in the eastern Italian Alps. The measuring station consists of an inclined frame that separates fine from coarse sediments (D>20 mm), which are continuously measured by a series of ultrasonic sensors fitted above a storage area. The acquired 25-year dataset, which comprises a high-magnitude/low-recurrence flood event, has allowed a magnitude-frequency analysis of bed-load volumes to be performed. Results from a combined frequency analysis of peak water discharge and total bed-load volumes are presented. In addition, the integration between the sediment transport dataset and the repeated surveys of sediment sources and of channel changes allowed us to assess the geomorphological effectiveness of different flood events. Despite the importance of the experimental station for making these bed-load observations possible, its maintenance costs are not low and these may have an impact on its future existence. At the same time, improving current instrumentation and future installations with novel technology would make the station an ideal location for calibrating surrogate techniques for sediment transport monitoring.
Monitoring, Stimulation, Prevention and Remediation of Dense and Debris Flows IV, 2012
ABSTRACT Until very recently, rivers have been considered as the result of the interaction betwee... more ABSTRACT Until very recently, rivers have been considered as the result of the interaction between water and sediments, thus simplifying this very complex system. In doing so, one important component was missed. This is vegetation, namely trees growing on banks, floodplains, and bars/islands. The pattern of riparian vegetation in gravel bed rivers depends on the climate, hydrological regime, floods, sediment transport and the morphological settings of the river. Also, the marked spatial variability of density, height, species diversity, age, and rates of growth reflects the very complex nature of bed colonization, the strong influence of sequences and magnitude of floods, and the feedbacks between morphology, vegetation and hydraulics. Furthermore, a wide array of human impacts acting at either the basin or river network scales can influence substantially the morphodynamics and thus the characteristics, types and distribution of vegetation within the river corridor. The aim of the work is to analyze the relationship between the vegetation structure and the morphological characteristics of two sub-reaches of the Piave river which suffered both floods and intense and multiple human impacts especially due to dam building and inchannel gravel mining. Six cross sections were surveyed and vegetation, soil variables and sediment deposited were measured on 214 plots, (4 x 4 m each one and 10 m spaced). Each vegetation plot were recognized on a recent aerial photo (2009) and its ages were calculated performing both a multi-temporal analysis of older photos (1960, 70, 80, 91, 99, 2006 and 2009) and a dendro-chronological
Journal of Agricultural Engineering, 2013
River islands are defined as discrete areas of woodland vegetation located in the riverbed and su... more River islands are defined as discrete areas of woodland vegetation located in the riverbed and surrounded by either water-filled channels or exposed gravels, exhibiting some stability and remaining exposed during bank-full flows. Islands are very important from both morphological and ecological points of view, representing the most natural condition of a fluvial system and are strongly influenced by human impacts. This study aims at analyzing the morphological and vegetation characteristics of three different typologies of islands (pioneer, young and stable) in three distinct rivers in the NE of Italy, affected by different intensities of human pressure. The study was conducted on several sub-reaches of the Piave, Brenta and Tagliamento rivers. The first is a gravel-bed river, which suffered intense and multiple human impacts, especially due to dam building and in-channel gravel mining. The same alterations can also be observed in the Brenta river, which also presents bank protections, hydropower schemes and water diversions. On the other hand, the Tagliamento river is a gravel-bed river characterized by a high level of naturality and very low human pressures. The analyses were conducted using aerial photographs and LiDAR data acquired in 2010 in order to define and distinguish the three different island typologies and to obtain a characterization of ground and vegetation features. The results suggest that the fluvial islands lie at different elevations and this fact implies a different resistance capacity during flood events. Pioneer islands and young islands lie at lower elevations than stable islands causing a lower capacity to survive during considerable flood events, in fact in most cases those islands typologies were removed by ordinary floods. Stable islands lie at higher elevations and only intense and infrequent flood events (RI > 10-15 years) are able to determine considerable erosions. Regarding the characteristics of vegetation, we can observe a strong distinction between the three typologies. Stable islands always exhibit the greatest vegetation height and the presence of these plants, sometimes higher than 30 m, contributes to increase the resistance and the stability of these components of fluvial systems.
Journal of Agricultural Engineering, 2013
The evaluation of the morphological quality of rivers is essential to define the level of alterat... more The evaluation of the morphological quality of rivers is essential to define the level of alteration and for implementing future management strategies that consider also hazards related to fluvial processes and channel dynamics. This type of evaluation is particularly significant for the Italian rivers, that, as in many other European countries, have a very high level of human pressure. Recently, in Italy, the National Institute for Environmental Protection and Research has promoted a methodology named IDRAIM for hydromorphological analysis of streams that pursues an integrated approach aimed at a harmonized implementation of both the EU Water Framework Directive (WFD, 2000/60/EC), and the EU Floods Directive (2007/60/EC). In this paper we present the application of the Morphological Quality Index (MQI) protocol, which is part of IDRAIM, to determine the assessment of the morphological quality of the Cordevole River. The water network (only collectors greater than thirdorder were considered), has been divided, through GIS software, into 132 river reaches of homogeneous morphological characteristics, according to the first phase of the method. At this stage the semi-automatic calculation of lateral confinement (defined by "degree of confinement" and a "confinement index") was tried, in order to reduce the implementing time. The application of 28 indicators was made for 42 reaches representing the major river types and human pressures in the site investigation. The results showed that 48% of the analyzed reaches have a very good or good quality status, 38% have a moderate morphological quality, while only 14% have the characteristics of poor or very poor quality. The main causes that lead to a strong alteration of the terms of reference are linked to i) poor connectivity between hillslopes and river corridor, that is very important for the natural supply of sediment and large wood; ii) absence of vegetation in the river corridor, that is functional to a range of geomorphic processes; iii) presence of artificial elements, particularly the bedload interception structures in the catchment, bank protection along the reach, and the removal of sediment, large wood and vegetation.
- Pontificia Universidad Catòlica de Chile, Santiago, Chile (lmao@uc.cl) The bedload transport p... more 2) Pontificia Universidad Catòlica de Chile, Santiago, Chile (lmao@uc.cl) The bedload transport plays a fundamental role in the mountain streams affecting several aspects as morphology and ecological status of the fluvial system, influencing fields as engineering, natural hazard and river management. The monitoring, assessment and quantification of this type of transport is not simple due to impulsive nature that distinguishes it. Moreover, in mountain streams the particle motion is strongly affected by the bed structures as well as by the highly heterogeneous bed material, acting especially through the hiding/exposure, consolidation and embedding effects. Thanks to the assumption that bedload transport may be understood as the result of random individual particle displacements, the sediment tracing method was widely employed in the last years. Such method allow to obtain precious data concerning sediment dynamic in mountain streams, improving the results obtainable by samplers, tra...
Monitoring, Simulation, Prevention and Remediation of Dense Debris Flows II, 2008
Monitoring, Stimulation, Prevention and Remediation of Dense and Debris Flows IV, 2012
... Plan-form changes of river features from 1960 were analyzed using aerial photos, and a LiDAR ... more ... Plan-form changes of river features from 1960 were analyzed using aerial photos, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces and the maximum and mean height of the island vegetation. ...
European Journal of Agronomy, 1997
A modern approach to problems of non-point source water pollution and erosion in a watershed cons... more A modern approach to problems of non-point source water pollution and erosion in a watershed consists in linking distributed models to Geographic Information Systems (GIS). Water quality and quantity are affected by the inherent spatial and time variability of the hydrological attributes within a watershed. Spatially distributed models and data are more suitable than conventional lumped ones. They act directly
Ingeniería del agua, 1999
Abrahams y otros (1995) han demostrado que la morfología de tramos de cauce en escalones se aprox... more Abrahams y otros (1995) han demostrado que la morfología de tramos de cauce en escalones se aproxima a una condición de maximización de la resistencia al flujo y de elevada estabilidad. Para verificar esta teoría ha sido realizado un levantamiento de campo en 5 torrentes con estructuras escalón-remanso, obteniéndose una muestra de 49 secuencias a las cuales corresponden más de 250 escalones. Los resultados muestran que la validez de la inecuación de máxima resistencia : S<(H/Ls)<2S, es sólo parcial. La mencionada teoría se ajusta a los torrentes caracterizados por una alimentación de material sólido limitada y en donde no se ha producido -al menos en los últimos 15-20 años-una crecida excepcional. En los torrentes afectados recientemente por crecidas con Tr> 30-50 años la relación entre (H/Ls) y S puede ser menor de uno, alejándose de la condición de máxima resistencia. En una de las 5 cuencas estudiadas (Rio Cordon) funciona, desde el año 1986, una estación experimental para la medición continua de los caudales líquidos y sólidos. En este torrente ha sido analizada la analogía entre la longitud de onda de las antidunas y la distancia entre los escalones, y evaluada la transformación que han experimentado las secuencias después del pasaje de una crecida con Tr> 30-50 años. El mecanismo evolutivo predominante es el de la migración aguas abajo de las estructuras y la modificación de los escalones se produce por socavación y desestabilización de la base de apoyo.
Riparian vegetation pattern in gravel bed rivers depends on the hydrological regime and the morph... more Riparian vegetation pattern in gravel bed rivers depends on the hydrological regime and the morphological settings of the river. However, the marked spatial variability of density, height, species diversity, age, and rates of growth reflects the very complex nature of bed colonization, the strong influence of sequences and magnitude of floods, and the feedbacks between morphology,
Suspended sediment transport in high mountain streams display a grater time-space variability and... more Suspended sediment transport in high mountain streams display a grater time-space variability and a shorter duration (normally concentrated during the snowmelt period and the duration time of single floods) than in larger lowland rivers. Suspended sedi- ment load and sediment yield were analysed in a small, high-gradient stream of East- ern Italian Alps which was instrumented to measure in continuous water discharge and sediment transport. The research was conducted in the Rio Cordon, a 5 Km2 small catchment of the Dolomites. The ratio of suspended to total sediment yield and the re- lations between sediment concentration and water discharge were analysed for eleven floods which occurred from 1991 to 2001. Different patterns of hysteresis in the re- lation between suspended sediment and discharge were related to types and locations of active sediment sources. The within-storm variation of particle size of suspended sediment during a mayor flood (September 1994, 30 years<Tr<50 years) indicates a coarsening of transported material for increasing discharge. An analysis of grain size has shown that erosion areas on hill-slopes were the main source of suspended load. The relation between water discharge and S.S.C. for both floods and snowmelt runoff shows larger scatter for both series of data, with snowmelt data less scattered than rain- fall induced floods. This is accounted for by the variable effectiveness of erosion pro- cesses and sediment supply mechanisms during snowmelt and rainfall-induced floods. During snowmelt, erosion processes essentially consist in the removal of loose, fine- grained sediment from slopes by surface runoff; as a consequence, suspended sedi- ment transport takes place also with rather low discharges. Abundant suspended sedi- ment transport was recorded during the snowmelt period of May 2001, that followed a winter characterized by a huge snow cover and late snowfalls. Different sources of sed- iment contribute to suspended load during the May11, 2001, snowmelt induced-small- flood. Therefore, the most important erosion processes was a landslide that originates a debris-mud-flow, occur only as a consequence of infiltration-saturation processes and hypodermic runoff (without associated rainfall and/or snow fall). This situation caused the instability of a large part of a sub-catchment hill-slope, the movement and the transport of a big quantity of fine-medium sediment (4176 m3) as mud flow, part of which deposited on the fan tributary (4100 m3) and afterwards reached the main 1 collector and subsequent the instrumented station (400 m3). Total sediment yield of this snowmelt flood measured at the Rio Cordon station is three orders of magnitude greater than previous one. The main processes by which sediments are transferred from hillslope to the channel outlet is also shown. 2
Bedload yield may have large seasonal or interannual variations as a result of changes in sedimen... more Bedload yield may have large seasonal or interannual variations as a result of changes in sediment supply or sediment storage. Sediment supply along mountain rivers is strongly influenced by both drainage basin and channel processes. Drainage basin sediment inputs include hillslope, valley bottom and tributary channel sources that may be gradual (e.g. slope wash, average tributary inflows, soil creep) or abrupt (e.g. debris flow, rockfalls, tributary flash floods). These inputs may be seasonally driven (e.g. Wetzel, 1994) or aperiodic. The paper illustrates the results of 16 years research conducted on the Rio Cordon catchment (5 km2), where an experimental sta- tion has been operating for the integral and continuous automatic recording of water discharge and sediment transport (Lenzi et al., 1999). The device operates by separat- ing bedload from water discharge and fine sediment and subsequently measuring the two solid components. The 15 recorded floods (1986-2001) are grouped in two dis- tinct categories according to the bedload transport rates: SordinaryT and exceptionalT & cedil;floods (with return times exceeding 30-50 years). Supply-limited conditions of sed- iment transport prevail in the period 1986-1994, before the exceptional flash flood of September 14, 1994. During this cycle, bed armouring is the dominant sediment transport response: the amount of material of a given size range in transport is lim- ited by its availability and not by the competence of the flow. During the subsequent cycle 1995-2001, conditions of bedload transport change a lot given an increases of the sediment budget. An abrupt and aperiodic input of fine-medium grain size material occured to the main Rio Cordon stream during the snowmelt-induced flood of May 11, 2001, by means of a tributary mud flow contribution. This input influenced the bed- load transport by altering the proportion of the bed material which can be moved by the competent flow. The injection of these relatively fine-medium material increased that proportion, thereby enabling the bed load transport to increase. The main processes by which this input of sediments are transferred from the hillslope (landslide) to the Rio Cordon channel and to the outlet (recording station situated 1100 m. downstream) is also shown. References Wetzel, K., 1994. The significance of fluvial erosion, channel storage and gravitational processes in sediment production in a small mountainous catchment area. In: Dynamics and geomorphology of mountain rivers, edited by P. Ergenzinger and 1 K.H. Schmidt, pp. 141-160, Springer-Verlag, Berlin. Lenzi, M.A., D'Agostino, V., Billi, P., 1999. Bedload transport in the instrumented catchment of the Rio Cordon, Part I: Analysis of bedload records, conditions and threshold of bedload entrainment. Catena 36, 171-190. 2
Sediment transport occurring in small, high-gradient streams is one of the most important aspects... more Sediment transport occurring in small, high-gradient streams is one of the most important aspects to be evaluated for land use planning in mountain areas. The research was conducted in two experimental catchments, comparable for dimensions. The Rio Cordon is a small basin in the Dolomites (Italian Alps). Since 1986 an instrumented site has been operating to measure flow discharge, bedload and suspended sediment transport. In September 1994, an extraordinary (T R >50 years) flood produced 900 m 3 of coarse sediment and clearly affected the successive sediment transport: 1996, 1998 and 2000 ordinary floods showed higher sediment loads compared to similar pre-1994 floods. The Tres Arroyos is a 5.93 km 2 Andean catchment (Chile). Water discharge, suspended and coarse sediment load have been monitored since 1997. The paper presents a comparison between the two basins of data regarding suspended sediment and bedload related to flood characteristics and sediment sources. Sediment transport characteristics, relationship between total load, bedload and suspended sediment load in the two catchments, reflect the differences in precipitation patterns, flow regimes and vegetation cover.
In the Erlenbach Torrent (Swiss Alps, 0.70 km 2 ), the intensity of bed-load transport is recorde... more In the Erlenbach Torrent (Swiss Alps, 0.70 km 2 ), the intensity of bed-load transport is recorded indirectly and continuously by special sensors installed in the bottom of the channel. At the observation station in the Rio Cordon Torrent (eastern Italian Alps, 5 km 2 ) coarse bed load is separated from water and fine sediment, and the volume of both deposits is recorded. The Erlenbach shows a much more pronounced response to similar rainfall conditions. The geological conditions lead to a lower slope and channel stability in the Erlenbach than in the Rio Cordon. In both streams a relationship exists between the sediment load of a flood event and the corresponding runoff volume. A trend towards "equal mobility" is observed for higher discharges. Peak bed-load transport may occur before or after the flood peak.
The main purpose of the research is to emphasize the connection between channel processes and sed... more The main purpose of the research is to emphasize the connection between channel processes and sediment sources in mountain basins. The study area is the Rio Cordon basin (northeastern Italian Alps, Belluno, Veneto Region, Italy). This catchment has been instrumented in 1985 to monitor major hydrologic, hydraulic, and morphological parameters. Bed load is measured at a special facility with an inclined grid on which particles larger than 20 mm slide into a storage area. Twenty flood events are analyzed statistically and their relations to channel processes are investigated. Cycles of bed armouring due to "ordinary" events are present along with the occurrence of an high-magnitude, low-frequency event. Limited and unlimited sediment supply conditions and flood hydrograph characteristics are considered, in order to account for large variations of the ratio between bed load volume and effective runoff volume. The analysis demonstrates both the control exerted by sediment availability on bed load transport rates and the persisting long-term impact of major floods on mountain streams.
Quantification of bedload transport in high-gradient mountain streams is important, but field dat... more Quantification of bedload transport in high-gradient mountain streams is important, but field data necessary to test transport models are scarce. In the present work, we describe the experimental station for monitoring water and sediment fluxes built in 1985 on the Rio Cordon (Eastern Italian Alps), a small steppool channel. The measuring station consists of an inclined frame that separates (at 20 mm truncation) fine and coarse sediments, which are continuously measured for accumulations by two turbidimeters. The 25year dataset acquired, which comprises high-magnitude/low-recurrence flood events, has allowed a magnitude-frequency analysis of bedload volumes. Results from a combined frequency analysis of peak water discharge and total bedload volumes based on the 25 events are presented, focusing on discrepancies between recurrence intervals of peak discharge and bedload volume for each event. In addition, the integration between the sediment transport dataset and the repeated surveys of sediment sources and of channel changes has permitted to assess the geomorphic effectiveness of different flood events. The Rio Cordon measuring facilities have provided excellent data and valuable insights into the bedload dynamics of steep streams throughout its 25 years of operation, thanks to the close collaboration between the ARPAV-Veneto Region and the Department Land and Agro-forest Environments (University of Padova). However, the maintenance costs of the station are not trivial and may impact its future "vitality". At the same time, improvement of the present instrumentation and installation of novel technology would make the station an ideal location for calibrating surrogate techniques for sediment transport monitoring. 1 10 100 J a n -8 7 J a n -8 9 J a n -9 1 J a n -9 3 J a n -9 5 J a n -9 7 J a n -9 9 J a n -0 1 J a n -0 3 J a n -0 5 J a n -0 7 Time Bedload Volume/Effective Runoff (10 3
Journal of Agricultural Engineering, 2012
Quantification of bed-load transport in high-gradient mountain streams is important, but the fiel... more Quantification of bed-load transport in high-gradient mountain streams is important, but the field data needed to test transport models are scarce and difficult to obtain. In the present study, we describe the experimental station for monitoring water and sediment fluxes built in 1985 on the Rio Cordon, a small step-pool channel in the eastern Italian Alps. The measuring station consists of an inclined frame that separates fine from coarse sediments (D>20 mm), which are continuously measured by a series of ultrasonic sensors fitted above a storage area. The acquired 25-year dataset, which comprises a high-magnitude/low-recurrence flood event, has allowed a magnitude-frequency analysis of bed-load volumes to be performed. Results from a combined frequency analysis of peak water discharge and total bed-load volumes are presented. In addition, the integration between the sediment transport dataset and the repeated surveys of sediment sources and of channel changes allowed us to assess the geomorphological effectiveness of different flood events. Despite the importance of the experimental station for making these bed-load observations possible, its maintenance costs are not low and these may have an impact on its future existence. At the same time, improving current instrumentation and future installations with novel technology would make the station an ideal location for calibrating surrogate techniques for sediment transport monitoring.
Monitoring, Stimulation, Prevention and Remediation of Dense and Debris Flows IV, 2012
ABSTRACT Until very recently, rivers have been considered as the result of the interaction betwee... more ABSTRACT Until very recently, rivers have been considered as the result of the interaction between water and sediments, thus simplifying this very complex system. In doing so, one important component was missed. This is vegetation, namely trees growing on banks, floodplains, and bars/islands. The pattern of riparian vegetation in gravel bed rivers depends on the climate, hydrological regime, floods, sediment transport and the morphological settings of the river. Also, the marked spatial variability of density, height, species diversity, age, and rates of growth reflects the very complex nature of bed colonization, the strong influence of sequences and magnitude of floods, and the feedbacks between morphology, vegetation and hydraulics. Furthermore, a wide array of human impacts acting at either the basin or river network scales can influence substantially the morphodynamics and thus the characteristics, types and distribution of vegetation within the river corridor. The aim of the work is to analyze the relationship between the vegetation structure and the morphological characteristics of two sub-reaches of the Piave river which suffered both floods and intense and multiple human impacts especially due to dam building and inchannel gravel mining. Six cross sections were surveyed and vegetation, soil variables and sediment deposited were measured on 214 plots, (4 x 4 m each one and 10 m spaced). Each vegetation plot were recognized on a recent aerial photo (2009) and its ages were calculated performing both a multi-temporal analysis of older photos (1960, 70, 80, 91, 99, 2006 and 2009) and a dendro-chronological
Journal of Agricultural Engineering, 2013
River islands are defined as discrete areas of woodland vegetation located in the riverbed and su... more River islands are defined as discrete areas of woodland vegetation located in the riverbed and surrounded by either water-filled channels or exposed gravels, exhibiting some stability and remaining exposed during bank-full flows. Islands are very important from both morphological and ecological points of view, representing the most natural condition of a fluvial system and are strongly influenced by human impacts. This study aims at analyzing the morphological and vegetation characteristics of three different typologies of islands (pioneer, young and stable) in three distinct rivers in the NE of Italy, affected by different intensities of human pressure. The study was conducted on several sub-reaches of the Piave, Brenta and Tagliamento rivers. The first is a gravel-bed river, which suffered intense and multiple human impacts, especially due to dam building and in-channel gravel mining. The same alterations can also be observed in the Brenta river, which also presents bank protections, hydropower schemes and water diversions. On the other hand, the Tagliamento river is a gravel-bed river characterized by a high level of naturality and very low human pressures. The analyses were conducted using aerial photographs and LiDAR data acquired in 2010 in order to define and distinguish the three different island typologies and to obtain a characterization of ground and vegetation features. The results suggest that the fluvial islands lie at different elevations and this fact implies a different resistance capacity during flood events. Pioneer islands and young islands lie at lower elevations than stable islands causing a lower capacity to survive during considerable flood events, in fact in most cases those islands typologies were removed by ordinary floods. Stable islands lie at higher elevations and only intense and infrequent flood events (RI > 10-15 years) are able to determine considerable erosions. Regarding the characteristics of vegetation, we can observe a strong distinction between the three typologies. Stable islands always exhibit the greatest vegetation height and the presence of these plants, sometimes higher than 30 m, contributes to increase the resistance and the stability of these components of fluvial systems.
Journal of Agricultural Engineering, 2013
The evaluation of the morphological quality of rivers is essential to define the level of alterat... more The evaluation of the morphological quality of rivers is essential to define the level of alteration and for implementing future management strategies that consider also hazards related to fluvial processes and channel dynamics. This type of evaluation is particularly significant for the Italian rivers, that, as in many other European countries, have a very high level of human pressure. Recently, in Italy, the National Institute for Environmental Protection and Research has promoted a methodology named IDRAIM for hydromorphological analysis of streams that pursues an integrated approach aimed at a harmonized implementation of both the EU Water Framework Directive (WFD, 2000/60/EC), and the EU Floods Directive (2007/60/EC). In this paper we present the application of the Morphological Quality Index (MQI) protocol, which is part of IDRAIM, to determine the assessment of the morphological quality of the Cordevole River. The water network (only collectors greater than thirdorder were considered), has been divided, through GIS software, into 132 river reaches of homogeneous morphological characteristics, according to the first phase of the method. At this stage the semi-automatic calculation of lateral confinement (defined by "degree of confinement" and a "confinement index") was tried, in order to reduce the implementing time. The application of 28 indicators was made for 42 reaches representing the major river types and human pressures in the site investigation. The results showed that 48% of the analyzed reaches have a very good or good quality status, 38% have a moderate morphological quality, while only 14% have the characteristics of poor or very poor quality. The main causes that lead to a strong alteration of the terms of reference are linked to i) poor connectivity between hillslopes and river corridor, that is very important for the natural supply of sediment and large wood; ii) absence of vegetation in the river corridor, that is functional to a range of geomorphic processes; iii) presence of artificial elements, particularly the bedload interception structures in the catchment, bank protection along the reach, and the removal of sediment, large wood and vegetation.
- Pontificia Universidad Catòlica de Chile, Santiago, Chile (lmao@uc.cl) The bedload transport p... more 2) Pontificia Universidad Catòlica de Chile, Santiago, Chile (lmao@uc.cl) The bedload transport plays a fundamental role in the mountain streams affecting several aspects as morphology and ecological status of the fluvial system, influencing fields as engineering, natural hazard and river management. The monitoring, assessment and quantification of this type of transport is not simple due to impulsive nature that distinguishes it. Moreover, in mountain streams the particle motion is strongly affected by the bed structures as well as by the highly heterogeneous bed material, acting especially through the hiding/exposure, consolidation and embedding effects. Thanks to the assumption that bedload transport may be understood as the result of random individual particle displacements, the sediment tracing method was widely employed in the last years. Such method allow to obtain precious data concerning sediment dynamic in mountain streams, improving the results obtainable by samplers, tra...
Monitoring, Simulation, Prevention and Remediation of Dense Debris Flows II, 2008
Monitoring, Stimulation, Prevention and Remediation of Dense and Debris Flows IV, 2012
... Plan-form changes of river features from 1960 were analyzed using aerial photos, and a LiDAR ... more ... Plan-form changes of river features from 1960 were analyzed using aerial photos, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces and the maximum and mean height of the island vegetation. ...
European Journal of Agronomy, 1997
A modern approach to problems of non-point source water pollution and erosion in a watershed cons... more A modern approach to problems of non-point source water pollution and erosion in a watershed consists in linking distributed models to Geographic Information Systems (GIS). Water quality and quantity are affected by the inherent spatial and time variability of the hydrological attributes within a watershed. Spatially distributed models and data are more suitable than conventional lumped ones. They act directly
Ingeniería del agua, 1999
Abrahams y otros (1995) han demostrado que la morfología de tramos de cauce en escalones se aprox... more Abrahams y otros (1995) han demostrado que la morfología de tramos de cauce en escalones se aproxima a una condición de maximización de la resistencia al flujo y de elevada estabilidad. Para verificar esta teoría ha sido realizado un levantamiento de campo en 5 torrentes con estructuras escalón-remanso, obteniéndose una muestra de 49 secuencias a las cuales corresponden más de 250 escalones. Los resultados muestran que la validez de la inecuación de máxima resistencia : S<(H/Ls)<2S, es sólo parcial. La mencionada teoría se ajusta a los torrentes caracterizados por una alimentación de material sólido limitada y en donde no se ha producido -al menos en los últimos 15-20 años-una crecida excepcional. En los torrentes afectados recientemente por crecidas con Tr> 30-50 años la relación entre (H/Ls) y S puede ser menor de uno, alejándose de la condición de máxima resistencia. En una de las 5 cuencas estudiadas (Rio Cordon) funciona, desde el año 1986, una estación experimental para la medición continua de los caudales líquidos y sólidos. En este torrente ha sido analizada la analogía entre la longitud de onda de las antidunas y la distancia entre los escalones, y evaluada la transformación que han experimentado las secuencias después del pasaje de una crecida con Tr> 30-50 años. El mecanismo evolutivo predominante es el de la migración aguas abajo de las estructuras y la modificación de los escalones se produce por socavación y desestabilización de la base de apoyo.
Riparian vegetation pattern in gravel bed rivers depends on the hydrological regime and the morph... more Riparian vegetation pattern in gravel bed rivers depends on the hydrological regime and the morphological settings of the river. However, the marked spatial variability of density, height, species diversity, age, and rates of growth reflects the very complex nature of bed colonization, the strong influence of sequences and magnitude of floods, and the feedbacks between morphology,
Suspended sediment transport in high mountain streams display a grater time-space variability and... more Suspended sediment transport in high mountain streams display a grater time-space variability and a shorter duration (normally concentrated during the snowmelt period and the duration time of single floods) than in larger lowland rivers. Suspended sedi- ment load and sediment yield were analysed in a small, high-gradient stream of East- ern Italian Alps which was instrumented to measure in continuous water discharge and sediment transport. The research was conducted in the Rio Cordon, a 5 Km2 small catchment of the Dolomites. The ratio of suspended to total sediment yield and the re- lations between sediment concentration and water discharge were analysed for eleven floods which occurred from 1991 to 2001. Different patterns of hysteresis in the re- lation between suspended sediment and discharge were related to types and locations of active sediment sources. The within-storm variation of particle size of suspended sediment during a mayor flood (September 1994, 30 years<Tr<50 years) indicates a coarsening of transported material for increasing discharge. An analysis of grain size has shown that erosion areas on hill-slopes were the main source of suspended load. The relation between water discharge and S.S.C. for both floods and snowmelt runoff shows larger scatter for both series of data, with snowmelt data less scattered than rain- fall induced floods. This is accounted for by the variable effectiveness of erosion pro- cesses and sediment supply mechanisms during snowmelt and rainfall-induced floods. During snowmelt, erosion processes essentially consist in the removal of loose, fine- grained sediment from slopes by surface runoff; as a consequence, suspended sedi- ment transport takes place also with rather low discharges. Abundant suspended sedi- ment transport was recorded during the snowmelt period of May 2001, that followed a winter characterized by a huge snow cover and late snowfalls. Different sources of sed- iment contribute to suspended load during the May11, 2001, snowmelt induced-small- flood. Therefore, the most important erosion processes was a landslide that originates a debris-mud-flow, occur only as a consequence of infiltration-saturation processes and hypodermic runoff (without associated rainfall and/or snow fall). This situation caused the instability of a large part of a sub-catchment hill-slope, the movement and the transport of a big quantity of fine-medium sediment (4176 m3) as mud flow, part of which deposited on the fan tributary (4100 m3) and afterwards reached the main 1 collector and subsequent the instrumented station (400 m3). Total sediment yield of this snowmelt flood measured at the Rio Cordon station is three orders of magnitude greater than previous one. The main processes by which sediments are transferred from hillslope to the channel outlet is also shown. 2
Bedload yield may have large seasonal or interannual variations as a result of changes in sedimen... more Bedload yield may have large seasonal or interannual variations as a result of changes in sediment supply or sediment storage. Sediment supply along mountain rivers is strongly influenced by both drainage basin and channel processes. Drainage basin sediment inputs include hillslope, valley bottom and tributary channel sources that may be gradual (e.g. slope wash, average tributary inflows, soil creep) or abrupt (e.g. debris flow, rockfalls, tributary flash floods). These inputs may be seasonally driven (e.g. Wetzel, 1994) or aperiodic. The paper illustrates the results of 16 years research conducted on the Rio Cordon catchment (5 km2), where an experimental sta- tion has been operating for the integral and continuous automatic recording of water discharge and sediment transport (Lenzi et al., 1999). The device operates by separat- ing bedload from water discharge and fine sediment and subsequently measuring the two solid components. The 15 recorded floods (1986-2001) are grouped in two dis- tinct categories according to the bedload transport rates: SordinaryT and exceptionalT & cedil;floods (with return times exceeding 30-50 years). Supply-limited conditions of sed- iment transport prevail in the period 1986-1994, before the exceptional flash flood of September 14, 1994. During this cycle, bed armouring is the dominant sediment transport response: the amount of material of a given size range in transport is lim- ited by its availability and not by the competence of the flow. During the subsequent cycle 1995-2001, conditions of bedload transport change a lot given an increases of the sediment budget. An abrupt and aperiodic input of fine-medium grain size material occured to the main Rio Cordon stream during the snowmelt-induced flood of May 11, 2001, by means of a tributary mud flow contribution. This input influenced the bed- load transport by altering the proportion of the bed material which can be moved by the competent flow. The injection of these relatively fine-medium material increased that proportion, thereby enabling the bed load transport to increase. The main processes by which this input of sediments are transferred from the hillslope (landslide) to the Rio Cordon channel and to the outlet (recording station situated 1100 m. downstream) is also shown. References Wetzel, K., 1994. The significance of fluvial erosion, channel storage and gravitational processes in sediment production in a small mountainous catchment area. In: Dynamics and geomorphology of mountain rivers, edited by P. Ergenzinger and 1 K.H. Schmidt, pp. 141-160, Springer-Verlag, Berlin. Lenzi, M.A., D'Agostino, V., Billi, P., 1999. Bedload transport in the instrumented catchment of the Rio Cordon, Part I: Analysis of bedload records, conditions and threshold of bedload entrainment. Catena 36, 171-190. 2
Sediment transport occurring in small, high-gradient streams is one of the most important aspects... more Sediment transport occurring in small, high-gradient streams is one of the most important aspects to be evaluated for land use planning in mountain areas. The research was conducted in two experimental catchments, comparable for dimensions. The Rio Cordon is a small basin in the Dolomites (Italian Alps). Since 1986 an instrumented site has been operating to measure flow discharge, bedload and suspended sediment transport. In September 1994, an extraordinary (T R >50 years) flood produced 900 m 3 of coarse sediment and clearly affected the successive sediment transport: 1996, 1998 and 2000 ordinary floods showed higher sediment loads compared to similar pre-1994 floods. The Tres Arroyos is a 5.93 km 2 Andean catchment (Chile). Water discharge, suspended and coarse sediment load have been monitored since 1997. The paper presents a comparison between the two basins of data regarding suspended sediment and bedload related to flood characteristics and sediment sources. Sediment transport characteristics, relationship between total load, bedload and suspended sediment load in the two catchments, reflect the differences in precipitation patterns, flow regimes and vegetation cover.
In the Erlenbach Torrent (Swiss Alps, 0.70 km 2 ), the intensity of bed-load transport is recorde... more In the Erlenbach Torrent (Swiss Alps, 0.70 km 2 ), the intensity of bed-load transport is recorded indirectly and continuously by special sensors installed in the bottom of the channel. At the observation station in the Rio Cordon Torrent (eastern Italian Alps, 5 km 2 ) coarse bed load is separated from water and fine sediment, and the volume of both deposits is recorded. The Erlenbach shows a much more pronounced response to similar rainfall conditions. The geological conditions lead to a lower slope and channel stability in the Erlenbach than in the Rio Cordon. In both streams a relationship exists between the sediment load of a flood event and the corresponding runoff volume. A trend towards "equal mobility" is observed for higher discharges. Peak bed-load transport may occur before or after the flood peak.
The main purpose of the research is to emphasize the connection between channel processes and sed... more The main purpose of the research is to emphasize the connection between channel processes and sediment sources in mountain basins. The study area is the Rio Cordon basin (northeastern Italian Alps, Belluno, Veneto Region, Italy). This catchment has been instrumented in 1985 to monitor major hydrologic, hydraulic, and morphological parameters. Bed load is measured at a special facility with an inclined grid on which particles larger than 20 mm slide into a storage area. Twenty flood events are analyzed statistically and their relations to channel processes are investigated. Cycles of bed armouring due to "ordinary" events are present along with the occurrence of an high-magnitude, low-frequency event. Limited and unlimited sediment supply conditions and flood hydrograph characteristics are considered, in order to account for large variations of the ratio between bed load volume and effective runoff volume. The analysis demonstrates both the control exerted by sediment availability on bed load transport rates and the persisting long-term impact of major floods on mountain streams.