Tadros Ghobrial - Profile on Academia.edu (original) (raw)
Papers by Tadros Ghobrial
Sustainability, Apr 21, 2024
Droughts have extensive consequences, affecting the natural environment, water quality, public he... more Droughts have extensive consequences, affecting the natural environment, water quality, public health, and exacerbating economic losses. Precise drought forecasting is essential for promoting sustainable development and mitigating risks, especially given the frequent drought occurrences in recent decades. This study introduces the Improved Outlier Robust Extreme Learning Machine (IORELM) for forecasting drought using the Multivariate Standardized Drought Index (MSDI). For this purpose, four observation stations across British Columbia, Canada, were selected. Precipitation and soil moisture data with one up to six lags are utilized as inputs, resulting in 12 variables for the model. An exhaustive analysis of all potential input combinations is conducted using IORELM to identify the best one. The study outcomes emphasize the importance of incorporating precipitation and soil moisture data for accurate drought prediction. IORELM shows promising results in drought classification, and the best input combination was found for each station based on its results. While high Area Under Curve (AUC) values across stations, a Precision/Recall trade-off indicates variable prediction tendencies. Moreover, the F1-score is moderate, meaning the balance between Precision, Recall, and Classification Accuracy (CA) is notably high at specific stations. The results show that stations near the ocean, like Pitt Meadows, have higher predictability up to 10% in AUC and CA compared to inland stations, such as Langley, which exhibit lower values. These highlight geographic influence on model performance.
A Global Analysis of Ice Phenology for 3702 Lakes and 1028 Reservoirs Across the Northern Hemisphere Using Sentinel-2a Imagery
Preface to the special issue on river ice and infrastructure
Canadian Journal of Civil Engineering, Jan 8, 2024
Field monitoring of river ice processes in the vicinity of ice control structures in the province of Quebec, Canada
Canadian Journal of Civil Engineering, Aug 22, 2023
IEEE transactions on geoscience and remote sensing, 2024
Global Navigation Satellite System-Interferometric Reflectometry (GNSS-IR) is an emerging sensor ... more Global Navigation Satellite System-Interferometric Reflectometry (GNSS-IR) is an emerging sensor technique that has become well-established for water level monitoring. While GNSS-IR has previously been employed for monitoring properties of lake ice and sea ice, it has not been applied for monitoring river ice. This paper presents results from monitoring river ice breakup at three sites in Canada. GNSS-IR data was compared to co-located time-lapse camera imagery and it was found that GNSS-IR signal was sensitive to periods where there is rough or broken ice in view of the sensor. Using data from Sentinel-1 and the RADARSAT Constellation Mission (RCM), the first ever comparison of GNSS-IR with Synthetic Aperture Radar (SAR) imagery is presented and a negative correlation of -0.8 is found between the GNSS-IR spectral power and SAR backscatter. Three classification algorithms of varying complexity (K-means clustering, neural network and random forest) are explored for detecting river ice using GNSS-IR. Using a shallow neural network with two hidden layers, an optimal accuracy of up to 94% is achieved over all three sites, or 97% when mixed water-ice conditions are excluded from the analysis. In summary, GNSS-IR has strong potential for ice monitoring applications, including monitoring the formation of ice jams.
Ice accumulation at a water intake: a case study on the Mille-Iles River, Québec
Canadian Journal of Civil Engineering
The blockage of water intakes by ice is recurrent in northern rivers during winter. Previous fiel... more The blockage of water intakes by ice is recurrent in northern rivers during winter. Previous field studies have monitored field conditions leading to ice blockage and provided a review of mitigations methods. However, to improve the efficacy of these measures, the mechanisms that create the blockage need to be locally measured. For this purpose, a field campaign was implemented to monitor a water intake on the Mille-Iles River at Terrebonne, Quebec, during the winter of 2020–2021. Results from this study showed that ice accumulation on the trash rack had an average growth rate of 1.35 cm/h and reached a maximum thickness of 24 cm. The release rate of these trash rack accumulation events was on average 1.8 cm/h, which is 30% faster than the deposition rate. A minimum cumulative degree minutes of supercooling of 4.5 °C.min was required for the start of a trash-rack ice-accumulation event.
Three-dimensional fully-Lagrangian DEM-SPH modeling of river ice interaction with control structures
Cold Regions Science and Technology
Ice processes in culverts with two fish passage designs: a case study in southern Quebec
Canadian Journal of Civil Engineering
According to Department of Fisheries and Oceans Canada, culverts and other stream crossings must ... more According to Department of Fisheries and Oceans Canada, culverts and other stream crossings must be designed to ensure fish passage. The effects of ice processes on these fish passage designs have never been assessed. This study is the first to document ice processes on two different types of fish passage designs (streambed simulation and baffle). The results of a 2 year field monitoring campaign showed that the culvert simulating the streambed retains a natural ice regime, i.e., both freeze-up and break-up occurred concurrently with the rest of the stream, while multiple supercooling events were recorded under a thin ice cover. As for the culvert with baffles, it was observed that the ice cover formed earlier and stayed longer in the culvert, which can create a barrier for fish transiting through them.
Hydrology Research
The Chaudière River in Quebec, Canada, is well known for its frequent ice jam flooding events. As... more The Chaudière River in Quebec, Canada, is well known for its frequent ice jam flooding events. As part of a larger watershed research program, an extensive field campaign has been carried out during the 2018–2019 and 2019–2020 winter seasons to quantify the spatiotemporal characteristics of the break-up processes along the Chaudière River. The results showed that mid-winter ice jams have formed in the Intermediate Chaudière and persisted until spring break-up. Spring break-ups were initiated in the Upper Chaudière, and then, almost simultaneously, in the Intermediate and Lower Chaudière reaches. The break-up in the Intermediate Chaudière usually lasts longer than the rest of the river since the slope is much milder, and the occurrence of mid-winter ice jams has been seen to delay the ice clearing. A reach-by-reach characterization of the cumulative degree day of thawing and discharge thresholds for the onset of break-up has been identified. During the field campaign, 51 ice jams wer...
ECWS-7 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Stratification and its Consequences in Two Constructed Urban Stormwater Wetlands
SSRN Electronic Journal
Analysis of the surface energy budget during supercooling in rivers
Cold Regions Science and Technology
Field Observations of Stratification in Stormwater Wet Ponds
SSRN Electronic Journal, 2022
Continuous In-situ Measurements of Anchor Ice Formation, Growth and Release Mechanisms in Rivers
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of... more Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms.
A study of supercooling in rivers
Cold Regions Science and Technology, 2021
In northern rivers, turbulent water becomes supercooled (i.e. cooled to slightly below the freezi... more In northern rivers, turbulent water becomes supercooled (i.e. cooled to slightly below the freezing point) when exposed to freezing air temperatures. In supercooled turbulent water, frazil (small ice disks) crystals are generated in the water column, and anchor ice starts to form on the bed. Two anchor ice formation mechanisms have been reported in the literature: either by the accumulation of suspended frazil particles, which are adhesive (sticky) in nature, on the riverbed or by in situ growth of ice crystals on the bed material. Once anchor ice has formed on the bed, the accumulation typically continues to grow (due to either further frazil accumulation and/or crystal growth) until release occurs due to mechanical (shear force by the flow or buoyancy of the accumulation) or thermal (warming of the water column which weakens the ice-substrate bond) forcing or a combination of the two. There have been a number of detailed laboratory studies of anchor ice reported in the literature, but very few field measurements of anchor ice processes have been reported. These measurements have relied on either sampling anchor ice accumulations from the riverbed or qualitatively describing the observed formation and release. In this study, a custom-built imaging system (camera and lighting) was developed to capture high-resolution digital images of anchor ice formation and release on the riverbed. A total of six anchor ice events were successfully captured in the time-lapse images, and for the first time, the different initiation, growth, and release mechanisms were measured in the field. Four stages of the anchor ice cycle were identified: Stage 1: initiation by in situ crystal growth; Stage 2: transitional phase; Stage 3: linear growth; and Stage 4: release phase. Anchor ice initiation due to in situ growth was observed in three events, and in the remainder, the accumulation appeared to be initiated by frazil deposition. The Stage 1 growth rates ranged from 1.3 to 2.0 cm/h, and the Stage 2 and 3 growth rates varied from 0.3 to 0.9 cm/h. Anchor ice was observed releasing from the bed in three modes: lifting of the entire accumulation, shearing of layers of the accumulation, and rapid release of the entire accumulation.
The Cryosphere Discussions, 2019
Measurements of the size and shape of frazil ice particles and flocs in saline water and of frazi... more Measurements of the size and shape of frazil ice particles and flocs in saline water and of frazil ice flocs in freshwater are limited. This study consisted of a series of laboratory experiments producing frazil ice at salinities of 0 ‰, 15 ‰, 25 ‰, and 35 ‰ to address this lack of data. The experiments were conducted in a large tank in a cold room with bottom mounted propellers to create turbulence. A high-resolution camera system was used to capture images of frazil ice particles and flocs passing through cross polarizing lenses. The high-resolution images of the frazil ice were processed using a computer algorithm to differentiate particles from flocs and determine key properties including size, shape, and volume. The size and volume distributions of particles and flocs at all four salinities were found to fit lognormal distributions closely. The concentration, mean size, and standard deviation of flocs and particles were assessed at different times during the supercooling process to determine how these properties evolve with time. Comparisons were made to determine the effect of salinity on the properties of frazil ice particles and flocs. The overall mean size of frazil ice particles in saline water and freshwater was found to range between 0.52 and 0.45 mm with particles sizes in freshwater ~ 13% larger than in saline water. However qualitative observations showed that frazil ice particles in saline water tend to be more irregularly shaped. The overall mean size of frazil ice flocs in freshwater was 2.57 mm compared to a mean size of 1.47 mm for flocs in saline water. Estimates for the porosity of frazil ice flocs were made by equating the estimated volume of ice produced based on thermodynamic conditions to the estimated volume of ice determined from the digital images. The estimated porosities of frazil ice flocs were determined to be 0.
Monitoring Frazil Ice Evolution during Freeze-up using the Shallow Water Ice Profiling Sonar
Freeze-up processes in the North Saskatchewan River, Edmonton, AB, Canada were monitored during t... more Freeze-up processes in the North Saskatchewan River, Edmonton, AB, Canada were monitored during the 2009/10 freeze-up season. Instrumentation used for monitoring included the following: a high (545 kHz) and low (235 kHz) frequency Shallow Water Ice Profiling Sonars (SWIPS), 2 MHz AquaDopp current profiler, underwater video camera, and a real-time monitoring station that recorded and transmitted digital images of river ice conditions and air and water temperatures. Different river ice phenomena were distinguished and recorded using the SWIPS acoustic signal. Preliminary linkages between meteorological and hydraulic factors affecting river ice processes are presented and discussed for some selected events of interest. The SWIPS proved to be a very effective instrument for studying the properties of suspended frazil ice and frazil pans.
Laboratory Measurement of Ice Sheet Creep and Recovery Under Varying Loads
Experiments were conducted in a laboratory cold room to investigate the effects of varying loads ... more Experiments were conducted in a laboratory cold room to investigate the effects of varying loads on ice sheet creep and recovery. These types of varying loads occur when ice sheets are used as construction platforms or for geotechnical investigations. When a load is placed on an ice sheet, the ice defects elastically; but, if the load remains on the ice for any length of time, additional plastic deformation or creep also occurs. The objective of the experiments was to gain an understanding of the creep recovery process after a load is removed from the ice and the effect of this recovery on the ultimate load capacity of the ice sheet under creep conditions. In the experiments, a load was first left on an ice sheet until failure occurred and after a new ice sheet of the same thickness was formed, the same load was applied and removed repeatedly over time until the ice sheet failed. The differences in load duration between the tests were then evaluated to determine the amount of additi...
Sustainability, Apr 21, 2024
Droughts have extensive consequences, affecting the natural environment, water quality, public he... more Droughts have extensive consequences, affecting the natural environment, water quality, public health, and exacerbating economic losses. Precise drought forecasting is essential for promoting sustainable development and mitigating risks, especially given the frequent drought occurrences in recent decades. This study introduces the Improved Outlier Robust Extreme Learning Machine (IORELM) for forecasting drought using the Multivariate Standardized Drought Index (MSDI). For this purpose, four observation stations across British Columbia, Canada, were selected. Precipitation and soil moisture data with one up to six lags are utilized as inputs, resulting in 12 variables for the model. An exhaustive analysis of all potential input combinations is conducted using IORELM to identify the best one. The study outcomes emphasize the importance of incorporating precipitation and soil moisture data for accurate drought prediction. IORELM shows promising results in drought classification, and the best input combination was found for each station based on its results. While high Area Under Curve (AUC) values across stations, a Precision/Recall trade-off indicates variable prediction tendencies. Moreover, the F1-score is moderate, meaning the balance between Precision, Recall, and Classification Accuracy (CA) is notably high at specific stations. The results show that stations near the ocean, like Pitt Meadows, have higher predictability up to 10% in AUC and CA compared to inland stations, such as Langley, which exhibit lower values. These highlight geographic influence on model performance.
A Global Analysis of Ice Phenology for 3702 Lakes and 1028 Reservoirs Across the Northern Hemisphere Using Sentinel-2a Imagery
Preface to the special issue on river ice and infrastructure
Canadian Journal of Civil Engineering, Jan 8, 2024
Field monitoring of river ice processes in the vicinity of ice control structures in the province of Quebec, Canada
Canadian Journal of Civil Engineering, Aug 22, 2023
IEEE transactions on geoscience and remote sensing, 2024
Global Navigation Satellite System-Interferometric Reflectometry (GNSS-IR) is an emerging sensor ... more Global Navigation Satellite System-Interferometric Reflectometry (GNSS-IR) is an emerging sensor technique that has become well-established for water level monitoring. While GNSS-IR has previously been employed for monitoring properties of lake ice and sea ice, it has not been applied for monitoring river ice. This paper presents results from monitoring river ice breakup at three sites in Canada. GNSS-IR data was compared to co-located time-lapse camera imagery and it was found that GNSS-IR signal was sensitive to periods where there is rough or broken ice in view of the sensor. Using data from Sentinel-1 and the RADARSAT Constellation Mission (RCM), the first ever comparison of GNSS-IR with Synthetic Aperture Radar (SAR) imagery is presented and a negative correlation of -0.8 is found between the GNSS-IR spectral power and SAR backscatter. Three classification algorithms of varying complexity (K-means clustering, neural network and random forest) are explored for detecting river ice using GNSS-IR. Using a shallow neural network with two hidden layers, an optimal accuracy of up to 94% is achieved over all three sites, or 97% when mixed water-ice conditions are excluded from the analysis. In summary, GNSS-IR has strong potential for ice monitoring applications, including monitoring the formation of ice jams.
Ice accumulation at a water intake: a case study on the Mille-Iles River, Québec
Canadian Journal of Civil Engineering
The blockage of water intakes by ice is recurrent in northern rivers during winter. Previous fiel... more The blockage of water intakes by ice is recurrent in northern rivers during winter. Previous field studies have monitored field conditions leading to ice blockage and provided a review of mitigations methods. However, to improve the efficacy of these measures, the mechanisms that create the blockage need to be locally measured. For this purpose, a field campaign was implemented to monitor a water intake on the Mille-Iles River at Terrebonne, Quebec, during the winter of 2020–2021. Results from this study showed that ice accumulation on the trash rack had an average growth rate of 1.35 cm/h and reached a maximum thickness of 24 cm. The release rate of these trash rack accumulation events was on average 1.8 cm/h, which is 30% faster than the deposition rate. A minimum cumulative degree minutes of supercooling of 4.5 °C.min was required for the start of a trash-rack ice-accumulation event.
Three-dimensional fully-Lagrangian DEM-SPH modeling of river ice interaction with control structures
Cold Regions Science and Technology
Ice processes in culverts with two fish passage designs: a case study in southern Quebec
Canadian Journal of Civil Engineering
According to Department of Fisheries and Oceans Canada, culverts and other stream crossings must ... more According to Department of Fisheries and Oceans Canada, culverts and other stream crossings must be designed to ensure fish passage. The effects of ice processes on these fish passage designs have never been assessed. This study is the first to document ice processes on two different types of fish passage designs (streambed simulation and baffle). The results of a 2 year field monitoring campaign showed that the culvert simulating the streambed retains a natural ice regime, i.e., both freeze-up and break-up occurred concurrently with the rest of the stream, while multiple supercooling events were recorded under a thin ice cover. As for the culvert with baffles, it was observed that the ice cover formed earlier and stayed longer in the culvert, which can create a barrier for fish transiting through them.
Hydrology Research
The Chaudière River in Quebec, Canada, is well known for its frequent ice jam flooding events. As... more The Chaudière River in Quebec, Canada, is well known for its frequent ice jam flooding events. As part of a larger watershed research program, an extensive field campaign has been carried out during the 2018–2019 and 2019–2020 winter seasons to quantify the spatiotemporal characteristics of the break-up processes along the Chaudière River. The results showed that mid-winter ice jams have formed in the Intermediate Chaudière and persisted until spring break-up. Spring break-ups were initiated in the Upper Chaudière, and then, almost simultaneously, in the Intermediate and Lower Chaudière reaches. The break-up in the Intermediate Chaudière usually lasts longer than the rest of the river since the slope is much milder, and the occurrence of mid-winter ice jams has been seen to delay the ice clearing. A reach-by-reach characterization of the cumulative degree day of thawing and discharge thresholds for the onset of break-up has been identified. During the field campaign, 51 ice jams wer...
ECWS-7 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Stratification and its Consequences in Two Constructed Urban Stormwater Wetlands
SSRN Electronic Journal
Analysis of the surface energy budget during supercooling in rivers
Cold Regions Science and Technology
Field Observations of Stratification in Stormwater Wet Ponds
SSRN Electronic Journal, 2022
Continuous In-situ Measurements of Anchor Ice Formation, Growth and Release Mechanisms in Rivers
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of... more Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms.
A study of supercooling in rivers
Cold Regions Science and Technology, 2021
In northern rivers, turbulent water becomes supercooled (i.e. cooled to slightly below the freezi... more In northern rivers, turbulent water becomes supercooled (i.e. cooled to slightly below the freezing point) when exposed to freezing air temperatures. In supercooled turbulent water, frazil (small ice disks) crystals are generated in the water column, and anchor ice starts to form on the bed. Two anchor ice formation mechanisms have been reported in the literature: either by the accumulation of suspended frazil particles, which are adhesive (sticky) in nature, on the riverbed or by in situ growth of ice crystals on the bed material. Once anchor ice has formed on the bed, the accumulation typically continues to grow (due to either further frazil accumulation and/or crystal growth) until release occurs due to mechanical (shear force by the flow or buoyancy of the accumulation) or thermal (warming of the water column which weakens the ice-substrate bond) forcing or a combination of the two. There have been a number of detailed laboratory studies of anchor ice reported in the literature, but very few field measurements of anchor ice processes have been reported. These measurements have relied on either sampling anchor ice accumulations from the riverbed or qualitatively describing the observed formation and release. In this study, a custom-built imaging system (camera and lighting) was developed to capture high-resolution digital images of anchor ice formation and release on the riverbed. A total of six anchor ice events were successfully captured in the time-lapse images, and for the first time, the different initiation, growth, and release mechanisms were measured in the field. Four stages of the anchor ice cycle were identified: Stage 1: initiation by in situ crystal growth; Stage 2: transitional phase; Stage 3: linear growth; and Stage 4: release phase. Anchor ice initiation due to in situ growth was observed in three events, and in the remainder, the accumulation appeared to be initiated by frazil deposition. The Stage 1 growth rates ranged from 1.3 to 2.0 cm/h, and the Stage 2 and 3 growth rates varied from 0.3 to 0.9 cm/h. Anchor ice was observed releasing from the bed in three modes: lifting of the entire accumulation, shearing of layers of the accumulation, and rapid release of the entire accumulation.
The Cryosphere Discussions, 2019
Measurements of the size and shape of frazil ice particles and flocs in saline water and of frazi... more Measurements of the size and shape of frazil ice particles and flocs in saline water and of frazil ice flocs in freshwater are limited. This study consisted of a series of laboratory experiments producing frazil ice at salinities of 0 ‰, 15 ‰, 25 ‰, and 35 ‰ to address this lack of data. The experiments were conducted in a large tank in a cold room with bottom mounted propellers to create turbulence. A high-resolution camera system was used to capture images of frazil ice particles and flocs passing through cross polarizing lenses. The high-resolution images of the frazil ice were processed using a computer algorithm to differentiate particles from flocs and determine key properties including size, shape, and volume. The size and volume distributions of particles and flocs at all four salinities were found to fit lognormal distributions closely. The concentration, mean size, and standard deviation of flocs and particles were assessed at different times during the supercooling process to determine how these properties evolve with time. Comparisons were made to determine the effect of salinity on the properties of frazil ice particles and flocs. The overall mean size of frazil ice particles in saline water and freshwater was found to range between 0.52 and 0.45 mm with particles sizes in freshwater ~ 13% larger than in saline water. However qualitative observations showed that frazil ice particles in saline water tend to be more irregularly shaped. The overall mean size of frazil ice flocs in freshwater was 2.57 mm compared to a mean size of 1.47 mm for flocs in saline water. Estimates for the porosity of frazil ice flocs were made by equating the estimated volume of ice produced based on thermodynamic conditions to the estimated volume of ice determined from the digital images. The estimated porosities of frazil ice flocs were determined to be 0.
Monitoring Frazil Ice Evolution during Freeze-up using the Shallow Water Ice Profiling Sonar
Freeze-up processes in the North Saskatchewan River, Edmonton, AB, Canada were monitored during t... more Freeze-up processes in the North Saskatchewan River, Edmonton, AB, Canada were monitored during the 2009/10 freeze-up season. Instrumentation used for monitoring included the following: a high (545 kHz) and low (235 kHz) frequency Shallow Water Ice Profiling Sonars (SWIPS), 2 MHz AquaDopp current profiler, underwater video camera, and a real-time monitoring station that recorded and transmitted digital images of river ice conditions and air and water temperatures. Different river ice phenomena were distinguished and recorded using the SWIPS acoustic signal. Preliminary linkages between meteorological and hydraulic factors affecting river ice processes are presented and discussed for some selected events of interest. The SWIPS proved to be a very effective instrument for studying the properties of suspended frazil ice and frazil pans.
Laboratory Measurement of Ice Sheet Creep and Recovery Under Varying Loads
Experiments were conducted in a laboratory cold room to investigate the effects of varying loads ... more Experiments were conducted in a laboratory cold room to investigate the effects of varying loads on ice sheet creep and recovery. These types of varying loads occur when ice sheets are used as construction platforms or for geotechnical investigations. When a load is placed on an ice sheet, the ice defects elastically; but, if the load remains on the ice for any length of time, additional plastic deformation or creep also occurs. The objective of the experiments was to gain an understanding of the creep recovery process after a load is removed from the ice and the effect of this recovery on the ultimate load capacity of the ice sheet under creep conditions. In the experiments, a load was first left on an ice sheet until failure occurred and after a new ice sheet of the same thickness was formed, the same load was applied and removed repeatedly over time until the ice sheet failed. The differences in load duration between the tests were then evaluated to determine the amount of additi...