A Numerical Approach to Predict Water Levels in Ungauged Regions—Case Study of the Meghna River Estuary, Bangladesh

Abstract

Abstract:Quantitative flood frequency investigation in a large estuary is somewhat challenging by numerical modelling, because the model optimization depends on the appropriate physical and hydrodynamic properties of the estuarine river. This study attempts to solve the bathymetry configurations of the Meghna River estuary and the assimilation of flow data, which exposed an important role in water level prediction. Upstream flow rates and nonlinear semidiurnal tides have an impact on the instability of the flow in this estuarine river. A large amount of flow accumulates in the upstream confluence against or in favor of tides during the rainy season from the adjacent river basins and significantly moves in the Bay of Bengal. The aim of this study is to predict water levels in the un-gauged regions of the Meghna River estuary. A numerical technique was developed using Mike21 flexible mesh, comprising shallow water hydrodynamic components in the estuary. Subsequently, log-normal distribution was employed to analyze the flood magnitudes among the ungauged stations of the estuary. The calibration results comprised with the observed water levels adequately. In conclusion, these water level prediction results can be applied to alleviate the coastal land from extreme flooding and to design hydraulic structures in the narrow streams.

Future Impact of Land Use/Land Cover Changes on Ecosystem Services in the Lower Meghna River Estuary, Bangladesh

“…The Meghna River estuary is one of the widest (2.5-22.4 km) estuarine rivers in the world. The LMRE has 22,156 km 2 of the coastal land surface where semidiurnal tide directly controls streams and estuarine flows [27]. The region has a yearly average temperature of 26.2 • C, and the yearly average precipitation is 2100-3500 mm [26].…”

“…The region has a yearly average temperature of 26.2 • C, and the yearly average precipitation is 2100-3500 mm [26]. The lower Meghna River carries a combined flow of water, typically at 120,000 m 3 /s, which causes a high level of hydro-dynamic activity and leads to a high rate of erosion and sediment deposition [27]. The average elevation of the study area is approximately 5 m above sea level (Figure 1).…”

“…Secondly, the CA-Markov model administered in simulating LULC prediction might not have considered all potential driving factors during the creation of a suitability map or simulations of land use patterns [5]. Although the geomorphology of the study area is very dynamic because of continuous erosion and accretion processes [21,22,27], appropriate indicators to control these factors were not considered. Future studies should consider these driving factors while creating suitability maps and simulations of land use.…”

Phytoplankton ecology in different coastal habitats along the northern Bay of Bengal

“…The study included the Meghna River estuary, mangroves habitat at the Naf River basin (Teknaf) and coral habitat at Saint Martin's Island. The Meghna River estuary is one of the largest estuarine ecosystems in terms of sediment and water discharge, and characterized by high levels of hydro‐dynamics activity (Syed et al., 2018). The estuary has the highest sediment discharge and ranked third for water discharge in the world (Elahi et al., 2020).…”

An Unstructured-Grid Based Morphodynamic Model for Sandbar Simulation in the Modaomen Estuary, China

“…An estuary sandbar, which provides natural protection for coastal beaches by reducing inshore wave energy through depth-induced wave breaking [2], is one of the most important morphological units for deltas and estuaries. It can considerably reduce the potential extreme wave run-up during major storms, which would induce severe flood disaster in tidal zones [3]. Moreover, estuary sandbar would play important role in flood releasing during the wet season, as well as salinity intrusion during the dry season.…”