Tapas Karmaker | Thapar University, Patiala (original) (raw)
Papers by Tapas Karmaker
Journal of Hydroinformatics
The discharge estimation in rivers is crucial in implementing flood management techniques and ess... more The discharge estimation in rivers is crucial in implementing flood management techniques and essential flood defence and drainage systems. During the normal flood season, water flows solely in the main channel. During a flood, rivers comprise a main channel and floodplains, collectively called a compound channel. Computing the discharge is challenging in non-prismatic compound channels where the floodplains converge or diverge in a longitudinal direction. Various soft computing techniques have nowadays become popular in the field of water resource engineering to solve these complex problems. This paper uses a hybrid soft computing technique – artificial neural network and particle swarm optimization (ANN–PSO) and multivariate adaptive regression splines (MARS) to model the discharge in non-prismatic compound open channels. The analysis considers nine non-dimensional parameters – bed slope, relative flow depth, relative longitudinal distance, hydraulic radius ratio, angle of converg...
Journal of Hydroinformatics, Apr 6, 2023
Composite river bank formation is quite common in large alluvial rivers and very high bank erosio... more Composite river bank formation is quite common in large alluvial rivers and very high bank erosion rate is commonly reported in this type of formation. As of bank composition, cohesive layers of clay or silt formation are sandwiched by sand layers. Bank erosion processes involved are basal erosion at the toe of the bank, cantilever failure of the overhanging soil layers and deposition of the bank failure material. Factor safety of the cantilever failure also depends upon degree of saturation of the bank soil. Integrating all these bank erosion processes with hydrodynamic and morphological processes in a river bend, an analytical river model is proposed here. To demonstrate the model performance, a river bend with active bank erosion rate in the middle reach of Brahmaputra river in India has been considered. The soil erosion parameters such as critical shear stress and erodibility coefficients of cohesive layers were measured by submerged-jet test apparatus and seasonal bank erosion ...
Journal of Hydrology, 2013
In large alluvial river courses where bank failure is prominent, seepage erosion may be a signifi... more In large alluvial river courses where bank failure is prominent, seepage erosion may be a significant contributor that is often overlooked. Seepage erosion typically occurs simultaneously with fluvial erosion and other mass failure processes during the recession period of hydrographs. In this study, a functional relationship between seepage erosion rate and its controlling variables was developed using lysimeter experiments. This experimental relationship was used to formulate a mathematical seepage model that predicts the daily seepage erosion rate for a composite river bank. Soils collected from the Brahmaputra River banks were repacked in lysimeters with horizontal stratification similar to the actual bank stratification. A total of 71 lysimeter experiments were conducted with various combinations of the controlling variables. The results indicate that the seepage gradient has a dominating effect on the time taken in developing undercuts that lead to the bank collapse. Increase in the number of silt layers in the bank profile increased the time to collapse significantly. In situ bank erosion measurements were taken to validate the performance of a bank erosion model for the middle reaches of the Brahmaputra River in India. The model predictions of seepage erosion rate showed a close agreement with the in situ bank retreat measurements.
Lecture Notes in Civil Engineering, 2019
In this study, some of the widely used data for elevation models were compared based on hydrologi... more In this study, some of the widely used data for elevation models were compared based on hydrological parameters such as slope, aspect, flow direction, and slope length and steepness factor (LS factor). The study considers the comparison among ASTER GDEM, SRTM DEM, topographic maps, and aerial photography at 430239 predetermined tests points. Bilinear interpolation technique was used to interpolate the data at these testing points. The result shows the digital elevation model (DEM) from topographic maps has relatively higher vertical accuracy (RMSE = 5.40 m), compared to ASTER GDEM (7.10 m) and SRTM DEM (15.07 m), while comparing with digital surface model (DSM) from stereo pairs. For validation, we used 47 ground control points (GCPs) using GPS. The results show the vertical accuracy are relatively higher for DSM (RMSE = 1.11 m), followed by DEMs from topographic maps (4.10 m), ASTER GDEM (7.36 m), and SRTM DEM (12.22 m). The DSM matches closely with the result of topographic DEM in...
Journal of Hydroinformatics
Wadi Shueib catchment in Jordan is a water stress area and climate change is creating a further d... more Wadi Shueib catchment in Jordan is a water stress area and climate change is creating a further deficiency in precipitation, streamflow, and soil moisture; which are a deterrent to agriculture production in the area. In order to analyze the drought-like situation in the area, a hybrid drought index (HDI) has been developed considering the combined effect of these three variables. Fuzzy analytical hierarchy process (F-AHP) and entropy weight methods were carried out to develop a hybrid drought index (HDI) which combines meteorological, hydrological, and agricultural drought indices based on precipitation, streamflow, and soil moisture data in the area. The wavelet transform (WT) with cross wavelet (XCT) and wavelet coherence (WTC) were applied to investigate the interaction and the relations between the HDI index, drought indices, and large-scale sunspot activity Niño3.4 index. The results show that HDI can easily capture the trend of the drought-like conditions in the area based on ...
Journal of the Indian Society of Remote Sensing
Arabian Journal of Geosciences
Journal of Hydraulic Engineering
Journal of Hydrology, Feb 1, 2010
ABSTRACT This paper describes a methodology for the generation of synthetic seasonal stage hydrog... more ABSTRACT This paper describes a methodology for the generation of synthetic seasonal stage hydrographs with a number of flood waves for a large braided river basin based on statistical analysis of the historical stage records. The synthetic seasonal hydrographs in a river is required for different purposes such as assessing the hydraulic performances of various river training structures, morphological predictions, environmental impact analysis. The typical stage hydrograph of such a river has two components: flood waves and seasonal (monsoonal) response. Using historical stage records, flood waves in a seasonal stage record were identified and their characteristics were approximated using Maxwell distribution. The extracted characteristics of flood waves such as time of occurrence and successive flood lifts were analysed with various probability distribution function to find out their best distribution. The frequency analysis of the annual maximum flood lift was carried out. Beside this, seasonal responses were also approximated using Maxwell distribution. A relationship between the seasonal lift and total monsoonal rainfall was established. For a given total seasonal rainfall and return period of annual maximum flood wave lift, synthetic seasonal hydrograph is generated by superimposing both seasonal response and flood waves. The generated hydrographs are evaluated by comparing the cumulative frequency function of river stage and relative frequency of daily stage changes (rise/fall) for three seasons with different flood wave return periods, at two river gauging stations for the river Brahmaputra, India.
Sādhanā
Determination of the erodibility parameters, such as critical shear stress and erodibility coeffi... more Determination of the erodibility parameters, such as critical shear stress and erodibility coefficient, are necessary before estimating the annual bank erosion (or bank retreat) at river reaches. However, in many cases, the river site is inaccessible making it difficult to assess the soil parameters either by in situ tests or by laboratory experiments. In this study, Genetic Algorithm (GA)-based optimisation technique was used to estimate the erodibility parameters of middle reaches of the Brahmaputra River in India. Two approaches were followed. At first, erodibility parameters were estimated using daily stage records at a selected site. Secondly, based on the annual observed bank erosions (bank retreat) from satellite images, erodibility parameters were estimated in three different river reaches. All these results were compared with that from a previous study using in situ jet tests. Annual bank erosions (bank retreat) were estimated using the median values of the erodibility parameters. The results agree well with the average observed annual bank erosion of these river reaches. In addition, the effects of measurement errors and optimisation algorithms on the parameter estimation were analysed. Sensitivity analysis of the parameters in GA was evaluated and it was found that GA can be utilised in the data-scarce regions to estimate the average erodibility parameters.
Current Science
In the present study, instability of the river reach of Brahmaputra was analysed for braided belt... more In the present study, instability of the river reach of Brahmaputra was analysed for braided belt width changes, braiding index and bar area. The river reach of the Brahmaputra from its confluence of Lohit, Dibang and Dihang to its confluence with the Tista river was studied from 1973 to 2009. The study was carried out using remotely sensed data from Landsat satellites at different dates. Discharge data synchronized with satellite data was collected by maintaining near-similar water level or discharge. Wavelet of the braided belt change was analysed to get the wavelet power and spatial extent of the changes. Finally, stream power was analysed from the average discharge data during the monsoon period to determine its effect on the instability of parameters considered. Results indicate that stream power does not directly relate to local changes in the braided belt or braiding index. However, with decrease in stream power, an increasing trend of bar area was found. Maximum wavelet power within a period showed a threshold behaviour at stream power of 5 W/km, beyond which the wavelet power raised sharply to a high value with increase in stream power. River response to the stream power was found at a global level rather than local level. Finally, a gradual decrease in stream power over time indicates the stable river reach. However, changes due to local bank erosion cannot be predicted using this analysis.
Hydrological Processes
The erosion of composite river banks is a complex process involving a number of factors including... more The erosion of composite river banks is a complex process involving a number of factors including fluvial erosion, seepage erosion, and cantilever mass failure. To predict the rate of bank erosion with these complexities, a stochastic bank erosion model is suitable to define the probability distribution of the controlling variables. In this study, a bank erosion model in a river bend is developed by coupling several bank erosion processes with an existing hydrodynamic and morphological model. The soil erodibility of cohesive bank layers was measured using a submerged-jet test apparatus. Seasonal bank erosion rates for four consecutive years at a bend in the Brahmaputra River, India were measured by repeated bank-line surveys. The ability of the model to predict erosion was evaluated in the river bend that displayed active bank erosion. In this study, different monsoon conditions and the distribution functions of two variables were considered in estimating the stochastic bank erosion...
Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood... more Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood with its influencing factors such as bank erosion, secondary current formation, land spur and bed-material characteristics. In this study, detailed hydrographic surveys with Acoustic Doppler Current Profiler (ADCP) were conducted at an active erodible river bend to measure suspended load, velocity, bathymetric profile and characteristics of the bed material. Study indicates the presence of multi-thread flow in the channel bend. Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar formation. Vertical distribution of suspended sediment concentration follows a power function with normalized depth. Average bed-material concentration at the reach level is computed from observed sediment profiles, and is compared against various sediment transport functions. Results show that the sediment transport function suggested by Yang gives better predictions for this reach. Transverse bed slopes at critical survey transects were computed from the bathymetric data and evaluated with analytical approaches. Out of three analytical approaches used, Odgaard's approach estimates the bed slopes fairly close to the observed one. These two functions are suitable in the Brahmaputra river for further morphological studies.
Journal of Hydroinformatics
The discharge estimation in rivers is crucial in implementing flood management techniques and ess... more The discharge estimation in rivers is crucial in implementing flood management techniques and essential flood defence and drainage systems. During the normal flood season, water flows solely in the main channel. During a flood, rivers comprise a main channel and floodplains, collectively called a compound channel. Computing the discharge is challenging in non-prismatic compound channels where the floodplains converge or diverge in a longitudinal direction. Various soft computing techniques have nowadays become popular in the field of water resource engineering to solve these complex problems. This paper uses a hybrid soft computing technique – artificial neural network and particle swarm optimization (ANN–PSO) and multivariate adaptive regression splines (MARS) to model the discharge in non-prismatic compound open channels. The analysis considers nine non-dimensional parameters – bed slope, relative flow depth, relative longitudinal distance, hydraulic radius ratio, angle of converg...
Journal of Hydroinformatics, Apr 6, 2023
Composite river bank formation is quite common in large alluvial rivers and very high bank erosio... more Composite river bank formation is quite common in large alluvial rivers and very high bank erosion rate is commonly reported in this type of formation. As of bank composition, cohesive layers of clay or silt formation are sandwiched by sand layers. Bank erosion processes involved are basal erosion at the toe of the bank, cantilever failure of the overhanging soil layers and deposition of the bank failure material. Factor safety of the cantilever failure also depends upon degree of saturation of the bank soil. Integrating all these bank erosion processes with hydrodynamic and morphological processes in a river bend, an analytical river model is proposed here. To demonstrate the model performance, a river bend with active bank erosion rate in the middle reach of Brahmaputra river in India has been considered. The soil erosion parameters such as critical shear stress and erodibility coefficients of cohesive layers were measured by submerged-jet test apparatus and seasonal bank erosion ...
Journal of Hydrology, 2013
In large alluvial river courses where bank failure is prominent, seepage erosion may be a signifi... more In large alluvial river courses where bank failure is prominent, seepage erosion may be a significant contributor that is often overlooked. Seepage erosion typically occurs simultaneously with fluvial erosion and other mass failure processes during the recession period of hydrographs. In this study, a functional relationship between seepage erosion rate and its controlling variables was developed using lysimeter experiments. This experimental relationship was used to formulate a mathematical seepage model that predicts the daily seepage erosion rate for a composite river bank. Soils collected from the Brahmaputra River banks were repacked in lysimeters with horizontal stratification similar to the actual bank stratification. A total of 71 lysimeter experiments were conducted with various combinations of the controlling variables. The results indicate that the seepage gradient has a dominating effect on the time taken in developing undercuts that lead to the bank collapse. Increase in the number of silt layers in the bank profile increased the time to collapse significantly. In situ bank erosion measurements were taken to validate the performance of a bank erosion model for the middle reaches of the Brahmaputra River in India. The model predictions of seepage erosion rate showed a close agreement with the in situ bank retreat measurements.
Lecture Notes in Civil Engineering, 2019
In this study, some of the widely used data for elevation models were compared based on hydrologi... more In this study, some of the widely used data for elevation models were compared based on hydrological parameters such as slope, aspect, flow direction, and slope length and steepness factor (LS factor). The study considers the comparison among ASTER GDEM, SRTM DEM, topographic maps, and aerial photography at 430239 predetermined tests points. Bilinear interpolation technique was used to interpolate the data at these testing points. The result shows the digital elevation model (DEM) from topographic maps has relatively higher vertical accuracy (RMSE = 5.40 m), compared to ASTER GDEM (7.10 m) and SRTM DEM (15.07 m), while comparing with digital surface model (DSM) from stereo pairs. For validation, we used 47 ground control points (GCPs) using GPS. The results show the vertical accuracy are relatively higher for DSM (RMSE = 1.11 m), followed by DEMs from topographic maps (4.10 m), ASTER GDEM (7.36 m), and SRTM DEM (12.22 m). The DSM matches closely with the result of topographic DEM in...
Journal of Hydroinformatics
Wadi Shueib catchment in Jordan is a water stress area and climate change is creating a further d... more Wadi Shueib catchment in Jordan is a water stress area and climate change is creating a further deficiency in precipitation, streamflow, and soil moisture; which are a deterrent to agriculture production in the area. In order to analyze the drought-like situation in the area, a hybrid drought index (HDI) has been developed considering the combined effect of these three variables. Fuzzy analytical hierarchy process (F-AHP) and entropy weight methods were carried out to develop a hybrid drought index (HDI) which combines meteorological, hydrological, and agricultural drought indices based on precipitation, streamflow, and soil moisture data in the area. The wavelet transform (WT) with cross wavelet (XCT) and wavelet coherence (WTC) were applied to investigate the interaction and the relations between the HDI index, drought indices, and large-scale sunspot activity Niño3.4 index. The results show that HDI can easily capture the trend of the drought-like conditions in the area based on ...
Journal of the Indian Society of Remote Sensing
Arabian Journal of Geosciences
Journal of Hydraulic Engineering
Journal of Hydrology, Feb 1, 2010
ABSTRACT This paper describes a methodology for the generation of synthetic seasonal stage hydrog... more ABSTRACT This paper describes a methodology for the generation of synthetic seasonal stage hydrographs with a number of flood waves for a large braided river basin based on statistical analysis of the historical stage records. The synthetic seasonal hydrographs in a river is required for different purposes such as assessing the hydraulic performances of various river training structures, morphological predictions, environmental impact analysis. The typical stage hydrograph of such a river has two components: flood waves and seasonal (monsoonal) response. Using historical stage records, flood waves in a seasonal stage record were identified and their characteristics were approximated using Maxwell distribution. The extracted characteristics of flood waves such as time of occurrence and successive flood lifts were analysed with various probability distribution function to find out their best distribution. The frequency analysis of the annual maximum flood lift was carried out. Beside this, seasonal responses were also approximated using Maxwell distribution. A relationship between the seasonal lift and total monsoonal rainfall was established. For a given total seasonal rainfall and return period of annual maximum flood wave lift, synthetic seasonal hydrograph is generated by superimposing both seasonal response and flood waves. The generated hydrographs are evaluated by comparing the cumulative frequency function of river stage and relative frequency of daily stage changes (rise/fall) for three seasons with different flood wave return periods, at two river gauging stations for the river Brahmaputra, India.
Sādhanā
Determination of the erodibility parameters, such as critical shear stress and erodibility coeffi... more Determination of the erodibility parameters, such as critical shear stress and erodibility coefficient, are necessary before estimating the annual bank erosion (or bank retreat) at river reaches. However, in many cases, the river site is inaccessible making it difficult to assess the soil parameters either by in situ tests or by laboratory experiments. In this study, Genetic Algorithm (GA)-based optimisation technique was used to estimate the erodibility parameters of middle reaches of the Brahmaputra River in India. Two approaches were followed. At first, erodibility parameters were estimated using daily stage records at a selected site. Secondly, based on the annual observed bank erosions (bank retreat) from satellite images, erodibility parameters were estimated in three different river reaches. All these results were compared with that from a previous study using in situ jet tests. Annual bank erosions (bank retreat) were estimated using the median values of the erodibility parameters. The results agree well with the average observed annual bank erosion of these river reaches. In addition, the effects of measurement errors and optimisation algorithms on the parameter estimation were analysed. Sensitivity analysis of the parameters in GA was evaluated and it was found that GA can be utilised in the data-scarce regions to estimate the average erodibility parameters.
Current Science
In the present study, instability of the river reach of Brahmaputra was analysed for braided belt... more In the present study, instability of the river reach of Brahmaputra was analysed for braided belt width changes, braiding index and bar area. The river reach of the Brahmaputra from its confluence of Lohit, Dibang and Dihang to its confluence with the Tista river was studied from 1973 to 2009. The study was carried out using remotely sensed data from Landsat satellites at different dates. Discharge data synchronized with satellite data was collected by maintaining near-similar water level or discharge. Wavelet of the braided belt change was analysed to get the wavelet power and spatial extent of the changes. Finally, stream power was analysed from the average discharge data during the monsoon period to determine its effect on the instability of parameters considered. Results indicate that stream power does not directly relate to local changes in the braided belt or braiding index. However, with decrease in stream power, an increasing trend of bar area was found. Maximum wavelet power within a period showed a threshold behaviour at stream power of 5 W/km, beyond which the wavelet power raised sharply to a high value with increase in stream power. River response to the stream power was found at a global level rather than local level. Finally, a gradual decrease in stream power over time indicates the stable river reach. However, changes due to local bank erosion cannot be predicted using this analysis.
Hydrological Processes
The erosion of composite river banks is a complex process involving a number of factors including... more The erosion of composite river banks is a complex process involving a number of factors including fluvial erosion, seepage erosion, and cantilever mass failure. To predict the rate of bank erosion with these complexities, a stochastic bank erosion model is suitable to define the probability distribution of the controlling variables. In this study, a bank erosion model in a river bend is developed by coupling several bank erosion processes with an existing hydrodynamic and morphological model. The soil erodibility of cohesive bank layers was measured using a submerged-jet test apparatus. Seasonal bank erosion rates for four consecutive years at a bend in the Brahmaputra River, India were measured by repeated bank-line surveys. The ability of the model to predict erosion was evaluated in the river bend that displayed active bank erosion. In this study, different monsoon conditions and the distribution functions of two variables were considered in estimating the stochastic bank erosion...
Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood... more Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood with its influencing factors such as bank erosion, secondary current formation, land spur and bed-material characteristics. In this study, detailed hydrographic surveys with Acoustic Doppler Current Profiler (ADCP) were conducted at an active erodible river bend to measure suspended load, velocity, bathymetric profile and characteristics of the bed material. Study indicates the presence of multi-thread flow in the channel bend. Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar formation. Vertical distribution of suspended sediment concentration follows a power function with normalized depth. Average bed-material concentration at the reach level is computed from observed sediment profiles, and is compared against various sediment transport functions. Results show that the sediment transport function suggested by Yang gives better predictions for this reach. Transverse bed slopes at critical survey transects were computed from the bathymetric data and evaluated with analytical approaches. Out of three analytical approaches used, Odgaard's approach estimates the bed slopes fairly close to the observed one. These two functions are suitable in the Brahmaputra river for further morphological studies.