CONTRIBUTION OF LARGE RIVER SYSTEM ON WATER LEVEL DUE TO A STORM

Bangladesh is a riverine country in South Asia, which contain about 700 big or small rivers. The major Ganges- Brahmaputra-Meghna river system makes the coast of Bangladesh more complex and disaster vulnerable area. This river system may or may not have its impact on the height of the water level due to a storm. This area is a suitable place for research, but there is no such mention of suitable research conducted in this area. Worth mentioning works done by some scholars are Dube et al. (2004), Agnihotri et al. (2006). All the works are important to the Bay-River interaction for the storm surge simulation, but these studies were also limited by the lack of a representation of proper geometry of the river system. Some of them considered idealized river system with constant water depth and some of them did not consider the proper tidal resume. The present study is a step towards the development of an operational surge forecasting nonlinear Bay-River interaction model that incorporates the major river system with realistic geometry. Both the bay and river model equations are discretized by finite difference method with central in space and forward in time and are solved by a conditionally stable, semi-implicit manner on a staggered Arakawa C-grid system. A stable tidal condition was made by forcing the sea level with the most energetic tidal constituent, M2 , along the southern open boundary of the parent model (Bay model). The developed model was applied to foresee sea-surface elevation associated with the catastrophic cyclone 1991 and a recent cyclone MORA 2017 along the coast of Bangladesh. We also investigated how the river influences the sea surface elevation with and without fresh water discharge. We also intend to investigate the effect of river discharge with sediment. It is observed that the water levels are found to be influenced by the river system.

Download Full-text

Feedback Mechanism in Bifurcating River Systems: the Effect on Water-Level Sensitivity

Water ◽

10.3390/w12071915 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1915

Author(s):

Matthijs R.A. Gensen ◽

Jord J. Warmink ◽

Fredrik Huthoff ◽

Suzanne J.M.H. Hulscher

Keyword(s):

Water Level ◽

Flood Risk ◽

River System ◽

Feedback Mechanism ◽

Water Levels ◽

River Systems ◽

Water Level Variations ◽

System Water ◽

Discharge Distribution ◽

Single Branch

Accurate and reliable estimates of water levels are essential to assess flood risk in river systems. In current practice, uncertainties involved and the sensitivity of water levels to these uncertainties are studied in single-branch rivers, while many rivers in deltas consist of multiple distributaries. In a bifurcating river, a feedback mechanism exists between the downstream water levels and the discharge distribution at the bifurcation. This paper aims to quantify the sensitivity of water levels to main channel roughness in a bifurcating river system. Water levels are modelled for various roughness scenarios under a wide range of discharge conditions using a one-dimensional hydraulic model. The results show that the feedback mechanism reduces the sensitivity of water levels to local changes of roughness in comparison to the single-branch river. However, in the smaller branches of the system, water-level variations induced by the changes in discharge distribution can exceed the water-level variations of the single-branch river. Therefore, water levels throughout the entire system are dominated by the conditions in the largest branch. As the feedback mechanism is important, the river system should be considered as one interconnected system in river maintenance of rivers, flood-risk analyses, and future planning of river engineering works.

Download Full-text

The hydrologic regime of Mackenzie River and connection of "no-closure" lakes to distributary channels in the Mackenzie Delta, Northwest Territories

Canadian Journal of Earth Sciences ◽

10.1139/e95-078 ◽

1995 ◽

Vol 32 (7) ◽

pp. 926-937 ◽

Cited By ~ 19

Author(s):

C. R. Burn

Keyword(s):

Water Level ◽

Drainage Basin ◽

Late Summer ◽

River System ◽

Water Levels ◽

Ice Thickness ◽

Mackenzie Delta ◽

Lake Ice ◽

Discharge System ◽

Mackenzie River

Mackenzie Delta lakes have been classified by the seasonal duration of their connection to Mackenzie River. "No-closure" lakes are determined on the basis of minimum summer water level. Such lakes may become disconnected from the Mackenzie in autumn or winter, as water level falls or if the sills between lakes and distributary channels are frozen through and so sealed. Water level in the central delta rises continuously after late November–early December, at first because discharge into the delta increases once the Mackenzie drainage basin has frozen over, and then as sea and channel ice thickens in the outer delta, impounding discharge. Since 1973 this seasonal increase in stage from its minimum in early December to the level on 1 April has been between 29 and 95 cm. Between 1987 and 1994, the rise in stage near Inuvik has been slightly greater than increases in lake-ice thickness (30–68 cm). Channels and lakes that are connected to the Mackenzie discharge system in December may remain connected throughout winter. A critical sill elevation for connection of such lakes to the river system is the minimum stage minus mid-December ice thickness. Recently, these elevations have been from 1.0 to 1.6 m lower than late summer water levels. Lakes with sill elevations still lower may remain connected to the Mackenzie throughout the year. In 1993-1994, only 3 of 16 "no-closure" lakes surveyed near Inuvik remained open to the Mackenzie discharge throughout winter, representing 2% of the lakes in this portion of the delta.

Download Full-text

The potential of small mountain river systems for paleoenvironmental reconstructions in drylands - An example from the Binaloud Mountains in northeastern Iran

10.5194/egusphere-egu21-3438 ◽

2021 ◽

Author(s):

Azra Khosravichenar ◽

Morteza Fattahi ◽

Hamideh Amini ◽

Hans von Suchodoletz

Keyword(s):

River System ◽

Large River ◽

Alluvial Fan ◽

Small Rivers ◽

River Systems ◽

Mountain Ranges ◽

Geomorphological Mapping ◽

Fluvial Dynamics ◽

Local Tectonics ◽

Numerical Dating

Fluvial sediments are valuable paleoenvironmental archives of the Quaternary. Since besides environmental factors they are also affected by local tectonics or intrinsic processes, large instead of small catchments should be studied. In drylands covering ca. 45% of the global terrestrial surface large river systems are generally missing, and most river systems are small rivers originating from mountain ranges. Their sediments are potentially interesting paleoenvironmental archives, but are often affected by intensive tectonics. During this study, to obtain a robust regional paleoenvironmental signal a small river system in the southwestern Binaloud Mountains in semi-arid NE Iran was exemplarily studied with a combined approach that encompassed both alluvial fan and catchment. By using geomorphological mapping and numerical dating, fluvial aggradation followed by incision was independently identified in larger areas or in different parts of the river system ca. 95&#8211;88 ka, 40 ka, 20 ka, around/after the Pleistocene/Holocene transition and possibly ca. 2.6 ka. These could be linked with regional and over-regional paleoenvironmental data. Furthermore, large boulders on the alluvial fan suggest anthropogenic destabilisation of the catchment during the last decades. Despite strong local tectonics the fluvial dynamics was mostly controlled by paleoenvironmental changes and human activity. This indicates that despite their small size, such river systems form valuable paleoenvironmental archives in drylands where other archive types are largely missing.&#160;

Download Full-text

Relationships between pacific and atlantic ocean sea surface temperatures and water levels from satellite altimetry data in the Amazon rivers

RBRH ◽

10.1590/2318-0331.231820170148 ◽

2018 ◽

Vol 23 (0) ◽

Author(s):

Mylena Vieira Silva ◽

Adrien Paris ◽

Stéphane Calmant ◽

Luiz Antonio Cândido ◽

Joecila Santos da Silva

Keyword(s):

Water Level ◽

Satellite Altimetry ◽

Amazon Basin ◽

Strong Relationship ◽

Water Levels ◽

Sea Surface ◽

Altimetry Data ◽

Negro River ◽

Hydrological Extremes ◽

Satellite Altimetry Data

ABSTRACT The influence of SST (Sea Surface Temperature) of adjacent oceans on the variability of water levels in the Amazon basin was investigated by using radar altimetry from the ENVISAT and Jason-2 missions. Data from the in situ network was used to compare the correlations of water level and SST anomalies in the sub-basins of the Amazonas-Peru, Solimões, Negro and Madeira Rivers. The analysis was made on the monthly and annual scales between 2003 and 2015. The correlations with anomalies of levels from altimetry presented higher accuracy indices than those from the conventional network. In general, ATN and PAC are better correlated with the entire basin. During the flood months, most of the sub-basins presented negative associations with ATN. In the months of ebb, the response to the indexes varies according to the region. The satellite altimetry data permitted to reach regions non-monitored by the conventional network. We also analyzed the impacts of hydrological extremes in all these sub-regions in the last 13 years. In Western Amazon, the drought of 2010 stands out, associated with the warming of the Tropical Atlantic and the El Niño. In the Negro River, the water level anomalies were the lowest in the basin during the 2005 drought. In the Purus River, the effects of the 2010 drought that affected the entire Amazon, were higher in 2011 due to its strong relationship with the Atlântic and Pacific oceans. In general, hydrological extremes are stronger or highlighted when SST increases simultaneously in both oceans.

Download Full-text

Impact Assessment of a Major River Basin in Bangladesh on Storm Surge Simulation

Journal of Marine Science and Engineering ◽

10.3390/jmse6030099 ◽

2018 ◽

Vol 6 (3) ◽

pp. 99

Author(s):

Md. Abdul Al Mohit ◽

Masaru Yamashiro ◽

Noriaki Hashimoto ◽

Md. Bodruddoza Mia ◽

Yoshihiko Ide ◽

...

Keyword(s):

River System ◽

Water Levels ◽

Open Boundary ◽

Sea Levels ◽

Junction Area ◽

Coupled Numerical Model ◽

Tidal Condition ◽

Major River ◽

The Impact ◽

Surge Height

A two-dimensional bay and river coupled numerical model in Cartesian coordinates was developed to find the impact of the river on the simulated water levels associated with a storm along the coast of Bangladesh. The shallow water models developed for both the bay and river were discretized by the finite difference method with forward in time and central in space. The boundaries for the coast and islands were approximated through proper stair steps representation and solved by a conditionally stable semi-implicit manner on a staggered Arakawa C-grid. A one-way nested scheme technique was used in the bay model to include coastal complexities as well as to save computational costs. A stable tidal condition was made by forcing the sea levels with the most energetic tidal constituent, M2, along with the southern open boundary of the bay model omitting wind stress. The developed model was then applied to foresee the sea-surface elevation associated with the catastrophic cyclone of 1991 and cyclone MORA. A comparative study of the water levels associated with a storm was made through model simulations with and without the inclusion of the river system. We found that the surge height in the bay-river junction area decreased by 20% and the surge height reduced by about 3–8% outside the junction area from this study. The obtained results were found to have a satisfactory similarity with some of the observed data.

Download Full-text

The Potential of Small Mountain River Systems for Paleoenvironmental Reconstructions in Drylands—An Example from the Binaloud Mountains in Northeastern Iran

Geosciences ◽

10.3390/geosciences10110448 ◽

2020 ◽

Vol 10 (11) ◽

pp. 448

Author(s):

Azra Khosravichenar ◽

Morteza Fattahi ◽

Hamideh Amini ◽

Hans von Suchodoletz

Keyword(s):

River System ◽

Large River ◽

Alluvial Fan ◽

Small Rivers ◽

River Systems ◽

Mountain Ranges ◽

Geomorphological Mapping ◽

Fluvial Dynamics ◽

Local Tectonics ◽

Numerical Dating

Fluvial sediments are valuable paleoenvironmental archives of the Quaternary. Since besides environmental factors they are also affected by local tectonics or intrinsic processes, large instead of small catchments should be studied. In drylands covering ca. 45% of the global terrestrial surface large river systems are generally missing, and most river systems are small rivers originating from mountain ranges. Their sediments are potentially interesting paleoenvironmental archives, but are often affected by intensive tectonics. During this study, to obtain a robust regional paleoenvironmental signal a small river system in the southwestern Binaloud Mountains in semi-arid NE Iran was exemplarily studied with a combined approach that encompassed both alluvial fan and catchment. By using geomorphological mapping and numerical dating, fluvial aggradation followed by incision was independently identified in larger areas or in different parts of the river system ca. 95–88 ka, 40 ka, 20 ka, around/after the Pleistocene/Holocene transition and possibly ca. 2.6 ka. These could be linked with regional and over-regional paleoenvironmental data. Furthermore, large boulders on the alluvial fan suggest anthropogenic destabilisation of the catchment during the last decades. Despite strong local tectonics the fluvial dynamics was mostly controlled by paleoenvironmental changes and human activity. This indicates that despite their small size, such river systems form valuable paleoenvironmental archives in drylands where other archive types are largely missing.

Download Full-text

Grey box modelling for river control

Journal of Hydroinformatics ◽

10.2166/hydro.2002.0026 ◽

2002 ◽

Vol 4 (4) ◽

pp. 265-280 ◽

Cited By ~ 11

Author(s):

Björn Sohlberg ◽

Mats Sernfält

Keyword(s):

Water Level ◽

Water Flow ◽

Energy Demand ◽

Power Plants ◽

Energy Requirement ◽

River System ◽

Measured Data ◽

Water Levels ◽

Unknown Parameters ◽

Power Stations

This paper deals with modelling and identification of a river system using physical insights about the process, experience of operating the system and information about the system dynamics shown by measured data. These components together form a linear model structure in the state space form. The inputs of the prospective model are physical variables, which are not directly measured. However, the model inputs can be found by a nonlinear transformation of measured variables. Unknown parameters of the model are estimated from measured data. The modelling work focuses on the principle of parsimony, which means the best model approach is the simplest one that fit the purpose of the application. The goal of the model is to control the water level of the river, where the water flow is mainly determined by the demand for energy generation produced by the hydropower stations along the river. The energy requirement increases in the morning and decreases in the evening. These flow variations, caused by the energy demand, have to be compensated by controlling the power plants downstream, in such a way that the water level between the power stations is guaranteed. Simulation of the control system by using an adaptive model predictive controller shows that the water levels vary less and can be maintained at a higher level than during manual control. This means that more electric power can be produced with the same amount of water flow.

Download Full-text

Analytical approach for determining the mean water level profile in an estuary with substantial fresh water discharge

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-8381-2015 ◽

2015 ◽

Vol 12 (8) ◽

pp. 8381-8417 ◽

Cited By ~ 3

Author(s):

H. Cai ◽

H. H. G. Savenije ◽

C. Jiang ◽

L. Zhao ◽

Q. Yang

Keyword(s):

Water Level ◽

Fresh Water ◽

Flood Control ◽

Analytical Approach ◽

Water Discharge ◽

Water Levels ◽

Wide Range ◽

Mean Water Level ◽

The Mean ◽

Fresh Water Discharge

Abstract. Although modestly, the mean water level in estuaries rises in landward direction induced by a combination of the salinity gradient, the tidal asymmetry, and the backwater effect. The water level slope is increased by the fresh water discharge. However, the interactions between tide and river flow and their individual contributions to the rise of the mean water level along the estuary are not yet completely understood. In this study, we adopt an analytical approach to describe the tidal wave propagation under the influence of fresh water discharge, in which the friction term is approximated by a Chebyshev polynomials approach. The analytical model is used to quantify the contributions made by tide, river, and tide–river interaction to the water level slope along the estuary. Subsequently, the method is applied to the Yangtze estuary under a wide range of river discharge conditions and the influence of tidal amplitude and fresh water discharge on the longitudinal variation of mean water level is explored. The proposed method is particularly useful for accurately predicting water levels and the frequency of extreme high water, relevant for water management and flood control.

Download Full-text

River Discharge and Water Level Changes in the Mekong River: Droughts in an Era of Mega-Dams

10.22541/au.161189206.60684509/v1 ◽

2021 ◽

Author(s):

XiXi Lu ◽

Samuel Chua

Keyword(s):

Water Level ◽

Water Discharge ◽

Dry Season ◽

Water Levels ◽

Mekong River ◽

Wet Season ◽

Discharge Data ◽

Mekong Basin ◽

Lower Mekong Basin ◽

Dry Conditions

While 1992 marked the first major dam – Manwan – on the main stem of the Mekong River, the post-2010 era has seen the construction and operationalisation of mega dams such as Xiaowan (started operations in 2010) and Nuozhadu (started operations in 2014) that were much larger than any dams built before. The scale of these projects implies that their operations will likely have significant ecological and hydrological impacts from the Upper Mekong Basin to the Vietnamese Delta and beyond. Historical water level and water discharge data from 1960 to 2020 were analysed to examine the changes to streamflow conditions across three time periods: 1960-1991 (pre-dam), 1992-2009 (growth) and 2010-2020 (mega-dam). At Chiang Saen, the nearest station to the China border, monthly water discharge in the mega-dam period has increased by up to 98% during the dry season and decreased up as much as -35% during the wet season when compared to pre-dam records. Similarly, monthly water levels also rose by up to +1.16m during the dry season and dropped by up to -1.55m during the wet season. This pattern of hydrological alterations is observed further downstream to at least Stung Treng (Cambodia) in our study, showing that Mekong streamflow characteristics have shifted substantially in the post-2010 era. In light of such changes, the 2019-2020 drought – the most severe one in the recent history in the Lower Mekong Basin – was a consequent of constructed dams reducing the amount of water during the wet season. This reduction of water was exacerbated by the decreased monsoon precipitation in 2019. Concurrently, the untimely operationalisation of the newly opened Xayaburi dam in Laos coincided with the peak of the 2019-2020 drought and could have aggravated the dry conditions downstream. Thus, the mega-dam era (post-2010) may signal the start of a new normal of wet-season droughts.

Download Full-text

Hydrodynamic modelling of compound flood drivers in estuaries

10.5194/egusphere-egu2020-14885 ◽

2020 ◽

Author(s):

Anais Couasnon ◽

Dirk Eilander ◽

Paul Bates ◽

Hessel C. Winsemius ◽

Philip J. Ward

Keyword(s):

Time Series ◽

Water Level ◽

Transition Zone ◽

River System ◽

Water Levels ◽

Flood Events ◽

Sea Levels ◽

Coastal Flood ◽

Highly Nonlinear ◽

Maximum Water

Compound flooding in deltas and estuaries can be defined as the combination of various flood drivers leading to a significant flood impact (Zscheischler et al., 2018). For example, elevated sea-levels can impede flood drainage and create backwater effects that worsen flood damages. This was observed recently in March 2019 during cyclone Idai, where devastating floods from a high storm surge and discharge destroyed the port city of Beira. Even though the importance of accounting for compound flooding in flood risk assessments has been heavily underlined in recent literature, little research has been done on the impacts of compound flood events globally.In this study, we investigate how compound flood hazard in estuaries is influenced by their various geophysical characteristics and the nature of their upstream river basins. The influence of riverine and coastal flood drivers on the water level varies along the estuary.&#160; The water level at the river mouth is dependent on sea-levels, whereas one can expect this influence to reduce moving upstream in the river system and to become negligible completely upstream in large river systems. The location within a river system where both riverine and coastal flood drivers significantly contribute to the water level is referred to as the transition zone (Bilskie and Hagen, 2018).We set up a model experiment to compare maximum water levels across realistic estuary types and boundary conditions. We use the 1-D unsteady hydrodynamic model LISFLOOD-FP to simulate water level time series for average and anomalous compound flood events of sea-levels and discharge. For each estuary type, resulting water level time series are analyzed to quantify the contribution of each flood driver in the maximum water level obtained along the complete coastal river profile and on the extent of the transition zone. We find that the interaction between the extreme sea level and extreme discharge is highly nonlinear and that this effect strongly varies depending on the estuary shape and length. We foresee this extensive overview of estuarine compound flood behavior to globally identify areas particularly vulnerable for interactions between extreme discharge and sea levels.

Download Full-text