The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Umberto Lombardo - One of the best experts on this subject based on the ideXlab platform.
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Alluvial plain dynamics in the southern Amazonian foreland basin
Earth System Dynamics, 2016Co-Authors: Umberto LombardoAbstract:Abstract. Alluvial Plains are formed with sediments that rivers deposit on the adjacent flood-basin, mainly through crevasse splays and avulsions. These result from a combination of processes, some of which push the river towards the crevasse threshold, while others act as triggers. Based on the floodplain sedimentation patterns of large rivers in the southern Amazonian foreland basin, it has been suggested that Alluvial plain sediment accumulation is primarily the result of river crevasse splays and sheet sands triggered by above-normal precipitation events due to La Nina. However, more than 90 % of the Amazonian river network is made of small rivers and it is unknown whether small river floodplain sedimentation is influenced by the ENSO cycle as well. Using Landsat images from 1984 to 2014, here I analyse the behaviour of all 12 tributaries of the Rio Mamore with a catchment in the Andes. I show that these are very active rivers and that the frequency of crevasses is not linked to ENSO activity. The data suggest that most of the sediments eroded from the Andes by the tributaries of the Mamore are deposited in the Alluvial Plains, before reaching the parent river. The mid-to-late Holocene paleo-channels of these rivers are located tens of kilometres further away from the Andes than the modern crevasses. I conclude that the frequency of crevasses is controlled by intrabasinal processes that act on a yearly to decadal timescale, while the average location of the crevasses is controlled by climatic or neo-tectonic events that act on a millennial scale. Finally, I discuss the implications of river dynamics on rural livelihoods and biodiversity in the Llanos de Moxos, a seasonally flooded savannah covering most of the southern Amazonian foreland basin and the world's largest RAMSAR site.
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Alluvial plain dynamics in the southern Amazonian foreland basin
2015Co-Authors: Umberto LombardoAbstract:Abstract. Alluvial Plains are formed with sediments that rivers deposit on the adjacent flood-basin, mainly through crevasse splays and avulsions. These result from a combination of processes, some of which push the river towards the crevasse threshold, while others act as triggers. Based on the floodplain sedimentation patterns of large rivers in the southern Amazonian foreland basin, it has been suggested that Alluvial plain sediment accumulation is primarily the result of river crevasse splays triggered by above normal precipitation events due to La Niña. However, more than 90 % of the Amazonian river network is made of small rivers and it is unknown whether small river floodplain sedimentation is influenced by the ENSO cycle as well. Using Landsat images from 1984 to 2014, here I analyse the behaviour of all the twelve tributaries of the Río Mamoré with a catchment in the Andes. I show that these are very active rivers and that the frequency of crevasses is not linked to ENSO activity. I found that most of the sediments eroded from the Andes by the tributaries of the Mamoré are deposited in the Alluvial Plains, before reaching the parent river. The mid- to late Holocene paleo-channels of these rivers are located tens of kilometres further away from the Andes than the modern crevasses. I conclude that the frequency of crevasses is controlled by intrabasinal processes that act on a year to decade time scale, while the average location of the crevasses is controlled by climatic or neo-tectonic events that act on a millennial scale. Finally, I discuss the implications of river dynamics on rural livelihoods and biodiversity in the Llanos de Moxos, a seasonally flooded savannah covering most of the southern Amazonian foreland basin and the world's largest RAMSAR site.
Asaf Pekdeger - One of the best experts on this subject based on the ideXlab platform.
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origin and dynamics of groundwater salinity in the Alluvial Plains of western delhi and adjacent territories of haryana state india
Hydrological Processes, 2012Co-Authors: G Lorenzen, C Sprenger, Paul Baudron, Dinesh Gupta, Asaf PekdegerAbstract:Groundwater salinity is a widespread problem and a challenge to water resources management. It is an increasing concern in the Alluvial Plains of Delhi and neighbouring Haryana state as well as a risk for agricultural production water supply and sustainable development. This study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer. It combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points. Major ions are analysed to describe the composition and distribution of saline groundwater and dissolution/precipitation dynamics. Density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging. Bromide–chloride ratios hold information on the formation of saline waters, and nitrate is used as an indicator for anthropogenic influences. In addition, stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region. The results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil, sediments and groundwater. Human-induced changes of environmental conditions, especially the implementation of traditional canal and modern groundwater irrigation, have augmented evapotranspiration and led to waterlogging in large areas. In addition, water-level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections. The holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences. Copyright © 2011 John Wiley & Sons, Ltd.
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Origin and dynamics of groundwater salinity in the Alluvial Plains of the western Dehli and adjacent territories of Haryana State, India
Hydrological Processes, 2012Co-Authors: G Lorenzen, C Sprenger, Paul Baudron, Dinesh Gupta, Asaf PekdegerAbstract:Groundwater salinity is a widespread problem and a challenge to water resources management. It is an increasing concern in the Alluvial Plains of Delhi and neighbouring Haryana state as well as a risk for agricultural production water supply and sustainable development. This study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer. It combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points. Major ions are analysed to describe the composition and distribution of saline groundwater and dissolution/precipitation dynamics. Density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging. Bromide-chloride ratios hold information on the formation of saline waters, and nitrate is used as an indicator for anthropogenic influences. In addition, stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region. The results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil, sediments and groundwater. Human-induced changes of environmental conditions, especially the implementation of traditional canal and modern groundwater irrigation, have augmented evapotranspiration and led to waterlogging in large areas. In addition, water-level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections. The holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences. Copyright (c) 2011 John Wiley & Sons, Ltd.
L. S. Chamyal - One of the best experts on this subject based on the ideXlab platform.
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lacustrine record of high magnitude flood events and climate variability during mid to late holocene in the semiarid Alluvial Plains western india
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Alpa Sridhar, Biswajeet Thakur, N Basavaiah, Priyanka Seth, Pooja Tiwari, L. S. ChamyalAbstract:Abstract Long-term data on flooding events are necessary for understanding the flood frequency and magnitude variations, but the available instrumental records span only a few decades. Recently, lake sediment sequences have emerged as a relatively untapped archive for high-magnitude floods over longer timescales. In the present study, multi-proxy data from a lacustrine sequence at Timbi in the Dhadhar river basin were analysed to determine high magnitude floods in this semi-arid region of western India in response to southwest monsoon variability. The results indicate the occurrence of discreet high magnitude flood events and depositional phases corresponding to different climatic conditions during the mid to late Holocene. Three large flash floods between 4830 and 2730 cal yr B.P. (Phase-I) have been identified as coeval with flood events from fluvial archives and correlated to the widespread period of aridity and weak monsoon recorded in the lakes of north western India. A shift in the depositional environment from fluvial to lacustrine occurred around 2730 cal yr B.P. as inferred from an abrupt change in the sediment character and palynofacies caused by high intensity flash floods and high sediment influx. Phase II (2730–1730 cal yr B.P.) was marked by periodic erosion and deposition in the catchment and sediment influx during pulses of higher precipitation as evident in the dominance of Glomus sp. and Alternaria sp., and relatively low values in concentration-related magnetic parameters and S-Ratio. A high magnitude flood event occurred at 1770 cal yr B.P. towards the end of phase II. During phase III (1730–880 cal yr B.P.) the monsoon was enhanced and climate was warmer as suggested by low χfd%, SIRM/χ, S-Ratio, higher Ba/Sr ratio and presence of aquatic palynomorphs. A high percentage of structured Organic Matter (OM), low fungal remains and increased Ba/Sr ratios between 880 and 360 cal yr B.P. indicate higher lake waters and better monsoon condition during phase IV. The phase V (360–0 cal yr B.P.) corresponds to lake level lowering, soil formation and eutrophication. The Timbi lake sediments demonstrate the potential for lakes in semi-arid Alluvial Plains of western India to preserve proxy flood records providing additional archives for generating long-term datasets. The flood record generated substantiates palaeoflood data from the fluvial archive suggestive of regional-scale southwest monsoon variability. Low frequency-high magnitude floods occurred during arid periods and low magnitude-high frequency events during relatively strengthened monsoon and thus have implication for linking the palaeoflood events to the southwest monsoon intensity in the semi-arid continental regions.
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holocene climatic fluctuations in the gujarat Alluvial Plains based on a multiproxy study of the pariyaj lake archive western india
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Rachna Raj, L. S. Chamyal, Vandana Prasad, Anupam Sharma, Jayant K Tripathi, Poonam VermaAbstract:Abstract A sediment core from Pariyaj Lake, from the Vatrak River basin, located at the desert margin in the Gujarat Alluvial Plains of western India, was investigated in a multidisciplinary aspect. The goal was to reconstruct the palaeoclimate, palaeoenvironment and tectonic history and to understand the role these factors played in the geomorphological evolution of the area during the Holocene. Palaeoclimatic interpretations also shed light on the factors responsible for the rise and fall of the Harappan civilisation. The results obtained based on multiproxy studies show five climatic phases during the last 11,000 yr BP. Phase 1 (~ 11,000 cal yr BP) represents a very humid climate and high precipitation/discharge leading to high lake stand as attested by the high pollen concentration of semi-evergreen tree taxa, phytoliths belonging to cool and moist grasses, and large proportion of algae, marking the onset of Holocene. In phase 2 (~ 8000 to 9000 cal yr BP) a significantly reduced yield of pollen, phytoliths and aquatic algae indicates shrinkage of the lake. Phase 3 (~ 7630 cal yr BP) shows moderate yield of pollen and phytolith pointing towards fluctuating precipitation conditions. Phase 4 (~ 5864 to 4680 cal yr BP) shows very low pollen and phytolith counts, indicating a very dry spell. Finally, phase 5 (~ 4680 to 3500 cal yr BP) shows a good density and diversity of flora. The wet climate and high lake stand ~ 11,000 cal yr BP, 7630 cal yr BP and after ~ 4680 cal yr BP are synchronous with the lacustrine, marine and aeolian records of western India. The contribution of winter precipitation at 7630 cal yr BP and after ~ 4680 cal yr BP can be correlated with similar records from Rajasthan Lake. Decrease in the precipitation activity, the low lake stand and the onset of dry climatic condition between 8000 and 9000 cal yr BP corresponds to a near global anomaly of this period. Another dry event between ~ 5864 and 4680 cal yr BP documented in Pariyaj Lake record is synchronous with various proxy records of the mid–late Holocene Afro-Asiatic monsoonal belt.
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History of Tectonic Evolution of Gujarat Alluvial Plains, Western India during Quaternary: A Review
Journal of The Geological Society of India, 2000Co-Authors: D. M. Maurya, Rachna Raj, L. S. ChamyalAbstract:The lineaments recognised in the Gujarat Alluvial Plains correspond to major structural and basement fault trends. The geomorphic and drainage anomalies in the Plains are in conformity with the subsurface structural features. The variable thickness of the Quaternary sediment cover suggests sedimentation in fault-bounded sub-basins within a larger basin. The exposed sediment column of 40-50 m dates back to ∼125 ka. The Quaternary evolutionary history of the Gujarat Alluvial Plains has been divided into three stages marked by distinct tectonic changes. Four phases of tectonic activity during the Quaternary have played a significant role in the evolution of these Plains. The first two are associated with the deposition of a large volume of sediments. The last two comprise tectonic uplifts which have shaped the present landscape of Gujarat Alluvial Plains. Extensive ravines, valley fill terraces, asymmetric drainage, deeply incised fluvial valleys and entknched meanders are manifestations of tectonic uplift during the Holocene. The seismic record of the last few hundred years suggests continued tectonic instability of the area in and around Gujarat Alluvial Plains.
G Lorenzen - One of the best experts on this subject based on the ideXlab platform.
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origin and dynamics of groundwater salinity in the Alluvial Plains of western delhi and adjacent territories of haryana state india
Hydrological Processes, 2012Co-Authors: G Lorenzen, C Sprenger, Paul Baudron, Dinesh Gupta, Asaf PekdegerAbstract:Groundwater salinity is a widespread problem and a challenge to water resources management. It is an increasing concern in the Alluvial Plains of Delhi and neighbouring Haryana state as well as a risk for agricultural production water supply and sustainable development. This study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer. It combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points. Major ions are analysed to describe the composition and distribution of saline groundwater and dissolution/precipitation dynamics. Density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging. Bromide–chloride ratios hold information on the formation of saline waters, and nitrate is used as an indicator for anthropogenic influences. In addition, stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region. The results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil, sediments and groundwater. Human-induced changes of environmental conditions, especially the implementation of traditional canal and modern groundwater irrigation, have augmented evapotranspiration and led to waterlogging in large areas. In addition, water-level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections. The holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences. Copyright © 2011 John Wiley & Sons, Ltd.
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Origin and dynamics of groundwater salinity in the Alluvial Plains of the western Dehli and adjacent territories of Haryana State, India
Hydrological Processes, 2012Co-Authors: G Lorenzen, C Sprenger, Paul Baudron, Dinesh Gupta, Asaf PekdegerAbstract:Groundwater salinity is a widespread problem and a challenge to water resources management. It is an increasing concern in the Alluvial Plains of Delhi and neighbouring Haryana state as well as a risk for agricultural production water supply and sustainable development. This study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer. It combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points. Major ions are analysed to describe the composition and distribution of saline groundwater and dissolution/precipitation dynamics. Density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging. Bromide-chloride ratios hold information on the formation of saline waters, and nitrate is used as an indicator for anthropogenic influences. In addition, stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region. The results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil, sediments and groundwater. Human-induced changes of environmental conditions, especially the implementation of traditional canal and modern groundwater irrigation, have augmented evapotranspiration and led to waterlogging in large areas. In addition, water-level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections. The holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences. Copyright (c) 2011 John Wiley & Sons, Ltd.
Bart Vandecasteele - One of the best experts on this subject based on the ideXlab platform.
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Assessment of the Pollution Status of Alluvial Plains: A Case Study for the Dredged Sediment-Derived Soils Along the Leie River
Archives of Environmental Contamination and Toxicology, 2004Co-Authors: Bart Vandecasteele, Paul Quataert, Bruno De Vos, Filip M. G. TackAbstract:The concept of an integrated multifunctional river management is gaining importance. For major rivers, restoring the contact between rivers and Alluvial Plains is an important goal, as riparian areas have a specific role for several riverine processes. However, former and current human activities are an obstruction or a limitation for river restoration. We studied the influence of former dredging activities along the river Leie on the Alluvial plain quality. A soil survey and an archive query for reconstructing the history of dredging operations were conducted simultaneously. The geographical impact expressed as topographical changes and covering of the original soil profile and related processes and biota was large. The pollution status of dredged sediment-derived soils was found to be far from negligible: concentrations of Cd, Cr, and Zn were, in 10% of the cases, higher than 20, 480, and 2800 mg kg^−1 DM, respectively. Both agriculture and nature rehabilitation on dredged sediment-derived soils can only be accepted after profound risk assessment, and management should focus on ecological risk reduction. Results indicate the importance of soil quality assessment in Alluvial Plains for an integrated river management, rather than a priori assuming pristine soil conditions. The collected “off-line” sediment data can be used as a reconstruction of past sediment pollution, especially when long-term sediment monitoring programs are not available.
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earthworm biomass as additional information for risk assessment of heavy metal biomagnification a case study for dredged sediment derived soils and polluted floodplain soils
Environmental Pollution, 2004Co-Authors: Bart Vandecasteele, Paul Quataert, Jurgen Samyn, Bart Muys, Filip TackAbstract:The important role of earthworms in the biomagnification of heavy metals in terrestrial ecosystems is widely recognised. Differences in earthworm biomass between sites is mostly not accounted for in ecological risk assessment. These differences may be large depending on soil properties and pollution status. A survey of earthworm biomass and colonisation rate was carried out on dredged sediment-derived soils (DSDS). Results were compared with observations for the surrounding Alluvial Plains. Mainly grain size distribution and time since disposal determined earthworm biomass on DSDS, while soil pollution status of the DSDS was of lesser importance. Highest earthworm biomass was observed on sandy loam DSDS disposed at least 40 years ago.
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identification of dredged sediment derived soils in the Alluvial Plains of the leie and the upper and sea scheldt rivers belgium based on physico chemical soil properties
Journal of Environmental Monitoring, 2002Co-Authors: Bart Vandecasteele, Bruno De Vos, Filip TackAbstract:An approach was developed to identify surface soils affected by historical dredged sediment disposal in the Alluvial Plains of the Upper Scheldt, the Sea Scheldt and the Leie river. Dredged sediment-derived soils were identified based on field observations, comparative granulometric analyses and chemical analyses. Criteria developed were based on a comparison between reference data from 102 aerobic soil samples of areas known to be affected by dredged sediment disposal and 104 samples from undisturbed Alluvial soils along the studied rivers. A comparative grain size analysis with optical laser diffractometry between the A and C horizon proved useful for the identification of levelled-up sites. The chemical soil characteristics that were most useful in identifying dredged sediment-derived soils were CaCO3, sulfur (S), organic carbon (OC) and phosphorus (P) contents, electrical conductivity (EC), and the C/P and C/S ratios. Criteria for concluding the origin of an investigated soil were specific for the studied area, but the approach presented may provide useful guidelines for developing criteria valid for different regions.