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| Comparison between modelled and observed flow depth evolution over the floodplains at the gauges (a) P1, (b) P3, (c) P5, (d) P6, (e) P7, (f) P9, (g) P11, (h) P12, (i) P14, (j) P15, and (k) P16 for the hydrographs Q1, Q2, and Q3.
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Flood simulations demand mathematical models, which are rigorously calibrated and validated against benchmarking datasets. For this purpose, experiments are conducted in a river-network-floodplain set-up. Hypothetical stepped hydrographs are passed through the channel-network, and fluvial flooding situations are created. Flood depths are recorded a...
Citations
... 3. The dynamic noise covariance can be denoted as 4. The observation noise covariance can be denoted as: 5. predicted error variance matrix using Eqs. (17) to (20), can be obtained as: 6. Gain matrix is obtained as: ...
The accuracy and reliability of hydrodynamic models are sensitive to both hydraulic state variables and model parameters, particularly the bed roughness, while their simultaneous real-time corrections and corresponding effects still need to be well-established and understood. This paper presents a real-time data assimilation model that corrects channel-bed roughness and water level in a river network hydrodynamic model, ensuring its accuracy and reliability. Experiments and parameter analysis evaluated the effect of initial roughness and observation noise level on model performance. Correcting both roughness and water level improved filtering time and forecasting accuracy by up to 63% and 80%, respectively, compared to methods only correcting water level. The filtering time was reduced by 44–63%, and the water level forecasting RMSE decreased by up to 80%. Both models experienced increased filtering time and forecasting error as observation noise increased, but the proposed model had a lower increase. With accurate hydraulic state measurement (e.g., 0.005 m error), the model achieved negligible water level forecasting error after 7 h of data assimilation. The model's accuracy depended on the initial channel-bed roughness, and the algorithm enables real-time roughness correction, making it useful for flood forecasting.
... TELEMAC2D's open-source limited element system has been used to simulate a wide range of hydrodynamic and morphodynamical situations such as waterways, curved channels, recirculation flows, and wave-induced littoral transportation. This 2D shallow water flow model is chosen based on its strengths such as geometric flexibility, availability of different solution schemes and turbulence closure models and being an open-source code (Mali et al. 2020). The open boundary in the South China Sea using the astronomical tides, TPXO binary data (TPXO data is provided by Egbert & Erofeeva, CEOAS, Oregon State University, USA). ...
Estuaries are transition zones between the sea and inland rivers, where oceanic tidal waves and fluvial flows control hydrodynamic processes. However, these natural changes and implications are not thoroughly understood, particularly in tropical estuaries. The interactions between tidal and riverine flows in the Kuala Pahang Estuary were examined using numerical modelling techniques applying TELEMAC2D. Our results model demonstrate that prolonged heavy rainfall significantly impacted water levels in the estuary system during the neap tide cycle. Moreover, the results show that the tidal range and current speed significantly influenced estuary morphological changes. The flood-ebb current can affect sediment transport near the river bank, leading to erosion. Meanwhile, the ebb-flood current significantly affected the bed sediment and suspension in the estuary mouth area while deposition happens during the slack water, either flood or ebb. Our results have a major impact on estuary morphology and sediment transport in the estuary water column, which will lead to a reduction in estuary water quality and the local economy, particularly fisheries.
... In this study, numerical simulation was performed using the software TELEMAC 2D, a hydrodynamic computing environment within the open-source platform TELEMAC-MASCARET, which solves shallow-water equations in two dimensions (Hervouet 2007) using the finite-element technique on an unstructured grid. Details about the equations and numerical schemes can be obtained from Fernandes et al. (2001) and Mali et al. (2020). Frictional resistance was quantified using Manning's coefficient. ...
The study establishes, with the aid of field measurements and numerical modeling, that
the upper reach of the Hooghly estuary (India), though damped, registers an intense
tidal bore. The lower estuary is amplified but does not show signs of bore formation.
Limited quantitative studies are available on bores forming in damped estuaries. This
study attempts to fill such a gap using tidal gauge and velocity observations
supplemented with simulation results obtained using the open-source numerical
shallow-water solver TELEMAC 2D. New estimates of bore intensity in the Hooghly are
presented confirming that the bore Froude number may reach as high as 1.37 in the
upper estuary for higher tidal ranges. The numerical model is used in gaining further
insights on the formation and evolution of the Hooghly bore. The model, despite using
a vertically averaged velocity field, simulates the tidal wave propagation and estimates
the velocity magnitude during bore propagation with significant accuracy. The study
demonstrates that the proposed model is an efficient and inexpensive tool for capturing
the bore phenomenon and may be used in supplementing field observations. Using the
simulation results, key features of the Hooghly bore, such as the distance of bore
inception from the ocean mouth and the threshold tidal range for bore formation are
investigated. The numerical simulations highlight the impact of river bed asymmetry in
bore appearance in natural estuaries. The analysis reveals new information about
bores in the Hooghly estuary, which may be useful for planning shipping and berthing
operations in the port terminals along the river. A comparison with other estuaries
witnessing tidal bores indicates that the Hooghly experiences a strong bore despite the
high dissipative forces owing to the rapid convergence of river width.
... Physical model experiments are required to investigate these phenomena, but they have limitations such as high cost, time-consuming, the uncertainty of scale effect, and limited measuring points (Jing 2002;Tang et al. 2007;Kalita et al. 2014;Gu et al. 2016;Kalita 2020). Due to these constraints, numerically-based river models are used, which are more practical for simulating near-actual field conditions (Molls et al. 1995;Mohapatra 2006;Tang et al. 2007;Kalita et al. 2014;Taormina and Chau 2015;Gu et al. 2016;Karmaker and Dutta 2016;Naik et al. 2018;Das 2018;Mali et al. 2020). They are regarded as effective adaptive management approaches that can be used to test hypotheses that interpret various river processes (Kidova et al. 2021). ...
Riverbank erosion is widespread in alluvial rivers in India and elsewhere. River training works are frequently used to aid in the prevention of these losses by regulating the river and therefore protecting critical human habitats. These structures often become unstable and incapable of performing adequately during periods of heavy flooding. For the first time, the three- dimensional hydrodynamic open-source Open Field Operation and Manipulation (OpenFOAM) model is used to assess the potential of a novel hybrid river training arrangement to reduce downstream flow velocity and divert downstream flow to the opposite bank. The results indicate that for single- phase approximation, algorithms such as the Semi Implicit Method for Pressure- Linked Equations (SIMPLE) with lower computational requirements can satisfactorily reproduce flow patterns discovered in the laboratory (R2>0.74\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R^2 > 0.74$$\end{document}). The hybrid configuration outperforms the porcupine and geobag layouts. When compared to geobag, dual- screen porcupine, and single- screen porcupine, its downstream velocity decreases by 1.33%, 11.62%, and 13.34%, respectively. Similarly, flow diversion to the opposing bank increases by 0.49%, 0.65%, and 0.92%. Thus, the porcupine structure reduces the intensity of the incoming flow prior to it reaching the impermeable geobag in a hybrid layout. It dissipates the flow energy to the point where it can no longer scour the bed, thereby eliminating the disadvantage associated with the formation of scour holes.
... From the flood depth, the water levels are calculated with proper benchmarking. The floodwater level data of the area is analyzed to understand the relation of the internal flood process with the external river stage of the Jamuna River by the coefficient of determination (R 2 ), Nash-Sutcliffe model efficiency coefficient (NSE), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE) analysis (Mali et al. 2020). Secondary data on the water level of the Jamuna River is collected from BWDB. ...
Monsoon flooding inundates a substantial part of Bangladesh, where 80% of the areas are floodplains. Sirajganj, located beside the Jamuna River in northwestern Bangladesh, is home to many communities living in the low-lying unprotected floodplains. The Ranigram village of Sirajganj has a hydraulic connection with the Jamuna River and is flooded almost every year. This study aims to explore how flood propagates in the floodplain, determine the water level variation in the floodplain with respect to the Jamuna River stage, and develop a hydrodynamic model of the flood propagation process in Ranigram. Water level gauges were installed at strategically selected locations in Ranigram, and flood data were collected during the 2018 and 2020 monsoons. In the R2, NSE, MSE, and RMSE analyses, the observed floodwater level in Ranigram shows an excellent dynamic relation with the water level at Sirajganj on the Jamuna River. The statistical relation derived from the 2018 data is validated with the observed data of 2020. A two-dimensional hydrodynamic model is developed with HEC-RAS using a DEM generated with surveyed bathymetry and UAV-based data and is calibrated and validated with the observed water level data and flood images. The maps of flood arrival time, duration, and maximum extent and depth were extracted from the model. The outcomes of this study will be useful in flood risk and damage assessments and forecasting of floods in floodplain areas.
