MIKE21 FM Research Articles

Analysis of diversion ratio and study of sediment transport in the first canal station of an irrigation area based on Mike21 hydrodynamic model

Abstract Based on MIKE21 hydrodynamic model, the change of diversion ratio and sediment transport at the first canal station in an irrigation area are analyzed. Two-dimensional numerical simulation is carried out by using MIKE21 FM hydrodynamic module, and the split ratio is studied. In the aspect of sediment transport, the transport path and deposition distribution of different sediment particle sizes are simulated by simulating sediment transport. The results show that under the lowest daily average water level, the diversion canal flow can meet the irrigation demand; The particle size of sediment has a great influence on the deposition distribution and thickness of the approach channel at the first station of the canal, and then affects the water diversion capacity of the pumping station.

Assessing water quality of the Saigon River under the impact of industrial wastewater incidents

The Saigon River, as its economic potential and clusters and industrial parks evolve, is threatened by a high potential for water pollution. The objective is to evaluate the water quality (BOD5 and COD) under the influence of industrial wastewater incidents in the Saigon River using MIKE 21FM model. The results of model calibration and validation have high reliability with NSE values larger than 0.65 for the flow simulation and percentage error values less than 25% for the water quality simulation. Subsequently, the study proceeds to develop hypothetical scenarios in case untreated wastewater from industrial parks is charged directly into the Saigon River with actual discharge volumes of 15,811 m3/day and 30,000 m3/day. The results indicated that when an incident occurs at a location 1.3 km upstream from the Hoa Phu pumping station with a discharge volume of 15,811 m3/day, that has the most consequential impact, in terms of time and concentration of water pollutants on the pumping station. Specifically, the water quality at the pumping station area experiences a remarkable decrease after one and three hours of incidents in the dry and rainy seasons, respectively. In general, the impacts of industrial wastewater incidents vary depending on their location. An incident beneath the Hoa Phu pumping station on the Saigon River is expected to have a faster impact on the raw water source during the dry season compared to the rainy season.

Study on Critical Factors Affecting Tidal Current Energy Exploitation in the Guishan Channel Area of Zhoushan

As a new type of clean and renewable energy, tidal current energy has attracted more and more attention from scholars. The Zhoushan Guishan Channel area (GCA) is an important part of the East China Sea port area, with strong currents due to its special terrain. In order to more comprehensively evaluate the characteristics of tidal energy development near the GCA, this paper uses the MIKE21 FM hydrodynamic model to simulate the tidal hydrodynamic process in the Zhoushan sea area and verifies the reliability of the model through the measured data. Based on the results of numerical simulations, the energy flow density, frequency of flow rate occurrence, flow asymmetry, flow rotation, and effective flow time that can be exploited are considered as the key factors affecting the development of tidal current energy. The distribution characteristics of each influencing factor in the region and the different influences on tidal current energy development are analyzed. Numerical simulations show that the average high-tide velocity in the GCA is lower than the ebb-tide velocity, and the duration of the high tide is also shorter than that of the ebb tide, which has a higher flow velocity than the surrounding area. The annual average energy flow density in the GCA is the highest at 4520 W/m2, and the spatial distribution is uneven. The resource level in the central part is much higher than that at both ends of the waterway. Three sections, i.e., A-A′, B-B′, and C-C′, with different key influence factors are selected for specific analysis, and it is concluded that the tidal energy development conditions are relatively superior near the B-B’ section in the middle of the GCA, and the exploitable power calculated using the Flux method is about 24.19 MW. The discussion of the results provides a certain reference for the development of local tidal current energy. These key factors affecting tidal current energy development can also be applied to assess the suitability of tidal current energy resource development in other regions.

Risk assessment of offshore oil spill in the northern South China Sea: A stochastic scenario modeling approach

The coastal area in the northern South China Sea (nSCS) is one of China’s most economically active regions. The fast-growing industry of marine sector and the shipping has increased the probability of oil spill accidents. An oil spill is a usually unexpected incident that is harmful to the ecological environment and marine organisms of the coastal area. As a result, utilizing a numerical model to simulate the fate and transport trajectory of spilled oil and to assess the potential risk of an oil spill accident to the coastal marine environment is of great necessity. The present study aimed to examine the impact of the risk of oil spills on the coastal environment in the nSCS. We built a hydrodynamic model and an oil spill dispersion model based on MIKE21 FM to study the tidal dynamics and oil spill dispersion in the coastal area in the nSCS. Moreover, the stochastic approach was used to simulate and predict the fastest arrival time and the probability distribution of the pollution of the oil film to the surrounding environment in the coastal regions of the nSCS. We examined the mechanisms for the influences of tides and wind on the fastest arrival time of oil film and the spatial distribution of the pollution probability of oil spill incidents at different locations in the nSCS based on the model. The results showed that the wind direction has a dominating effect on the direction of the oil dispersion. Due to the differences in the tidal dynamics in different regions, the migration and dispersion of the oil are also affected by the tidal current. This research provides guidance on the risk assessment of oil spill accidents for marine environmental management.

Hydrodynamic Modelling of Tidally-Influenced Fluvial Zone, a study case of Palembang, Indonesia

The development planning of a tidally-influenced fluvial zone poses a complex interaction between river discharge and its effect on the tidal patterns, especially in the dense population and high economic activity like Palembang located in South Sumatra Indonesia. Previous studies on numerical modelling in this area have focused on the flood; however, the hydrodynamic modelling described interaction between river discharge and tidal is not described in more detail. The present study aims to better understand the zone by using a combination of numerical modelling and qualitative assessment of in situ measurement data. Hence, the water level condition in the study area is a mix of tidal and river discharge. A 2D-hydrodynamic modeling has been successfully conducted to assess their interaction in this zone properly by using the commercial software, called MIKE21 FM. This study describes setting up the computational model, boundary location, type of forcing (tidal and non-tidal), bedform roughness, turbulent viscosity and extensive calibration and validation. In situ measurement indicates that the site's water level and flow characteristic is complex, a mixture of tidal force from the downstream and river flows from the upstream in which seasons play an important role. It is found that comparing model outputs and the measurement data in the study area for the validation and verification process effectively describes the hydrodynamic condition in the fluvial-estuarine transition area of Palembang. As the model shows good reliability, the long term hydrodynamic in line with transport model should be developed to support the Palembang area rapid development.

Assessment of water quality changes in Saigon and Dong Nai rivers under the influence of domestic wastewater discharges

The study was conducted to evaluate the impact of domestic wastewater discharges on surface water quality (BOD5 and DO) at pumping stations on Sai Gon – Dong Nai river during the dry season and the wet season using the MIKE 21FM model. The results indicated that the water quality in Dong Nai river is rated better than the Sai Gon River. Specifically, the BOD5 concentration was high, and the DO concentration was low at Hoa Phu station in Sai Gon River. However, the surface water quality at pumping stations on Dong Nai river, namely Hoa An and Binh An was up to standard compared to column A2 for domestic water supply purposes according to QCVN 08- MT:2015/BTNMT. Specifically, the wastewater source from Thu Dau Mot city on the Sai Gon river was about 4 km from Hoa Phu pumping station with a discharge volume of 0,66 m3/s, and another source from Bien Hoa city on the Dong Nai river reached a discharge volume of 2,15 m3/s, which was about 4.7 km and 5.5 km from Hoa An and Binh An intakes, respectively. The outcomes proved that Hoa Phu and Hoa An pumping stations were not affected by the wastewater from these cities. Otherwise, there was markedly degraded water quality at Binh An intake in the dry season, which was unsatisfied with QCVN 08- MT:2015/BTNMT (A2 type).

Finding the optimum groin layout for the Konaweha river banks protection via 2D numerical modeling

River bank erosion has become a critical issue, especially for river bends with an alluvial soil type. Mostly, river bank erosions have caused structural failures because many national roads in Indonesia are placed near the river bend areas. Groins can reduce flow velocity, thereby increasing riverbank stability. However, most groins were installed in the river without impacting the river flow due to the improper design. This paper analyzes the use of groins placed at the river bend of the Konaweha River to protect the river bank with a length of 250 m from erosion. The evaluation employs 2D numerical modeling using MIKE21 FM to observe the influence of the groin on the river velocity, flow distribution pattern, and water level. Sixteen model scenarios with four groin configurations were tested for 25-year discharge, 2-year discharge, normal discharge 600 m3/s, and low discharge 197 m3/s to achieve the most effective plan. Based on the simulation results, Scenarios with five groins are recommended to reduce the flow velocity along the outer river bank from 2 to 0.3 m/s, thus minimizing the erosion. In addition, the spacing of groins being twice the groin length is recommended.

Bottom Morphology In Hau Estuaries Under Influences Of Sediment Reduction And Climate Variation

The study focuses on simulating the bottom morphology under the influence of river currents and tides in Hau Estuary in Soc Trang province during the flood season according to the scenarios in 2017, sea level rise of 73 cm and reducing sediment by using MIKE 21FM. The results show that the erosion and accretion processes are consistent with the velocity distribution of the flow; the accretion trend prevailed over the erosion trend in Hau Estuary. The maximum velocity at the islet upstream was distributed in the river bed with the maximum erosion level of 0.3m. The strong erosion areas were concentrated on the river bed at the banks of the islet with the largest level being 0.13m while the accreation area along the Dinh An estuary was a level of 0.24 m. For the scenario of sea level rise and reducing sediment, the trends of accretion and erosion did not change much compared to the scenario in 2017. With sea level rise scenario, the value of erosion will be decreased, however, deposition value will be recorded a decrease in the estuary. Regarding the reducing sediment scenario, the islet upstream will be eroded more than scenario in 2017, on contrary, the accretion of the river mouth will be reduced.

Simulating Flow of An Urban River Course with Complex Cross Sections Based on the MIKE21 FM Model

In this case study, the method of unsteady flow was used to study the flow characteristics of a planned urban river course, River A, with complex cross sections, based on the MIKE21 FM hydrodynamic module, which is an important tool for analyzing and solving hydrodynamic problems. First, the rationality and feasibility of the planning scheme were verified by building a two-dimensional numerical model, which can provide a scientific basis for the river course planning. Then, the flow characteristic of the river course was analyzed and summarized, to give several suggestions and improvement measures for follow-up river planning. Finally, on the basis of the case study, the general rules of hydraulic factors in river courses with complex cross sections were summarized, which can facilitate the understanding of the genesis and evolution of river courses.

Numerical modeling of abrasion hazard in Senindara River, Bintuni Bay

The Senindara River area, which is part of Bintuni Bay, was influenced by the dynamics of the seawater and widely used to support community and industries activities. Alluvium land conditions and partially cliff were potential to abrasion. The research location was Senindara River with focused in Maga River area. This study aims was to obtain potential abrasion hazard of the study area. Numerical modelling was used to analysed the data. Tidal observations were carried out for 15 days with peilschaal and processed using Admiralty method. Current measurements were conducted for 26 hours using the Eulerian method. Modeling using MIKE21 FM Model with momentum, temperature, and density equations. Spatial discretion of the equation was done using the cell-centered finite volume method. Model calibration was done by comparing the output of the model (current and water level) with the observation results. The study shows the value of the basic shear stress of the average model value was greater than the value of the basic shear stress critical model erosion 0.1 N/m2. This shows that at the observation location has a high risk abrasion, especially in the industrial supporting area. Therefore, prevention of abrasion hazards was indispensable.

Study of high tide level changes in estuary area in response to coastline deformation in Wenzhou Bay

Wenzhou Bay, which is located in the southern coast of China with rich tidal flat resources, is frequently influenced by human activities, leading coastline deformation and high tide level changes in estuary area. A two-dimensional tidal numerical model of high resolution including Wenzhou Bay and East China Sea was established based on the MIKE21 FM model. The model was calibrated with field data and then was employed to predict high tide level changes under the development plan of coastline deformation. According to the simulating results, high tide level and tidal range in the Ou River and the Feiyun River estuary area will decrease about 0.01~0.13 m and 0.01~0.18 m, whether in dry season or flood season. Further analysis from tide wave point illustrates that weaken of the tidal system outside estuary area will occur after the coastline deformation. The direction of tidal propagation will change from vertical to parallel to coastline, causing weaken reflection, leading to the decreases of tidal range and high tidal level.

The simulation of water quality in Chanba Ecological District

In order to investigate the characteristic of migration and transformation of various pollutants in rivers, the river in Chanba Ecological District was selected as the research object. The MIKE21 FM model coupled with Ecolab module was employed to establish the twodimensional water quality model to simulate the distribution characteristic of different water quality parameters, which were Total Nitrogen (TN), Total Phosphorus (TP), Ammonium Nitrogen (NH3-N), Chemical Oxygen Demand (COD), Chlorophyll a (Chla), and Dissolved Oxygen (DO) separately. The results demonstrated that the concentration values of TP, NH3-N, and COD in Chanhe River were greater than them in Bahe River before the water flowed into the junction zone. The TN concentration value in the calculation zone except the region which held poor hydraulic conditions exceeded the standard of Grade V (GB3838-2002). Because the water in Bahe River was disturbed by water in Chanhe River and point sources in Bahe River, COD and NH3-N concentration values increased clearly after the water passed from the NO.4 Dam in Bahe River.

Simulation of Storm Surges in the South Central Coast of Vietnam Under Climate Change

The research was supported by National Research Project Program of Vietnam: science and technology in response to climate change, natural resources and environmental management in the 2016-2020 period (program number: BĐKH/16-20), Developing a sustainable socio-economic model adapting to extreme natural disasters under climate change in the South Central region of Viet Nam. A case study of Ninh Thuan province (grant number: BĐKH.04/16-20). Abstract This paper presents the results of storm surge simulation in the South Central region of Vietnam using the Mike 21-FM HD model. Wind pressure fields of typical storms were first identified in period of 1986-2005 using the parametric wind field model. Storm surge risk was then simulated based on the rare 10, 50 and 100-year frequency corresponding to 2030, 2050, and 2100 scenarios. Storm surge model was finally calibrated and validated using the level of water measured in the November 2009 Typhoon Mirinae and October 2013 Typhoon Nari. The results show that storm surges were consistent with water level variation and amplitude; the maximum and minimum storm surges were 2.34m in the Binh Thuan coastal area and 0.78m in the Khanh Hoa coastal area, respectively. The results of this study demonstrated the use of MIKE 21-FM HD model for the simulation of storm surges in the future plays an important role in damage risk reduction caused by storm surges. Keywords: storm surge simulation, climate change, Mike 21-FM HD model, South Central coast of Vietnam. DOI : 10.7176/JEES/9-6-08 Publication date :June 30 th 2019

OPTIMIZATION OF NEW BEACH NOURISHMENT CONCEPT FOR LANDOWNERS WITH PROPERTIES AT ACUTE RISK

In Denmark it is the landowners responsibility to get a permit for coastal protection and pay for it. On natural coasts without man made structure, a new concept consisting of a sandbuffer with a sleeping defence has been implemented on two locations. The sandbuffer must ensure that the sleeping defence must be covered with sand at all time. The optimization of the sandbuffer is done numerically using Mike21 FM Shoreline Model, and by surveying the performance in Interreg project Building With Nature.

Character of extreme high tide level variations response to coastline deformation in Taizhou Bay

Taizhou Bay, which locates in the southern coast of China, is frequently influenced by human activities, leading coastline changes frequently in coastline changes visible from space. Coastline deformation in this area will obviously affect the character of extreme high tide level variations in Jiaojiang River and Estuary especially during flood and typhoon periods. Statistic data showed that 54.5% of the extreme high tide levels of Jiaojiang River were caused by typhoon and 27.3% by flood in the past twenty-two years. So, a two-dimensional (2-D) hydrodynamic numerical model including Jiaojiang River and East China Sea was established based on the Mike21 FM model. The model was calibrated with field data and then was employed to predict the extreme flood and storm high tide level changes under three different assumption plans of coastline deformation. 100-year return discharge upstream with 2-year return tide level downstream conditions were set in the model to simulate extreme flood level changes, while Typhoon 0414 with actual discharge upstream were considered to simulate extreme storm high tide level variations. According to the flood level changes simulating results, an increase of 0.01∼0.03 m in extreme flood level will happen in river section and estuarine section and a decrease of 0.01∼0.06 m will occur outside estuarine section. Predictions of the typhoon conditions show that an increase of 0.01∼0.15 m in extreme storm high tide level will happen in both river and estuarine sections with a decrease of 0.01∼0.03 m outside of the Jiaojiang Estuary. Further analysis from tide wave point illustrates that propagation direction of nearshore tide wave in Taizhou Bay will be turned by coastline deformation, thus reflection effect of tide wave will be weakened, while distribution of storm tide currents field changes shows that tidal influx of Jiaojiang Estuary increases due to the blocking effect of the seawalls, causing this kind of special extreme high tide level changing formation.

Hydrodynamic Simulation of an Irregularly Meandering Gravel-Bed River: Comparison of MIKE 21 FM and Delft3D Flow models

This study aims at hydrodynamic modelling of Bow River, which passes through the City of Calgary, Canada. Bow River has a mobile gravel bed. Erosion and deposition processes were exacerbated by a catastrophic flood in 2013. Channel banks were eroded at various locations, and large gravel bars formed, which could lead to water level changes and accordingly more flooding. This study investigates the performance of Delft3D-Flow and MIKE 21 FM to simulate the hydrodynamics of the river during the 2013 flood. MIKE 21FM employs unstructured triangular mesh while Delft3D-Flow model uses curvilinear structured grids. Performance of each model was evaluated by the available historical water levels. The results of this study demonstrated that, with approximately the same averaged grid resolution, MIKE 21 FM resulted in more accurate results with a higher computational cost compared to the Delft3DFlow model. It was shown that Delft3D-Flow model may require higher grid cell resolution to result in comparably same depth-averaged velocities throughout the study area. However, considering the balance between the computational cost and the accuracy of the results, both models were capable to adequately replicate the hydrodynamics of the river during the 2013 flood. Results of statistical KS and ANOVA test analysis showed that the model predictions were sensitive to the horizontal eddy viscosity and the Manning roughness. This confirms the necessity of an appropriate calibration of the generated numerical models. The findings of this study shed light on the Bow River flood modelling, which can guide flood management.

A daily power generation optimized operation method of hydropower stations with the navigation demands considered

Under the influence of hydraulic uncertainty, the various operational safety risks exist in the shortterm hydropower generation scheduling and navigation inevitably. Therefore, it is very crucial to establish a daily power generation optimized method of hydropower stations with the navigation demands considered. The daily power generation optimized operation method was established for generation scheduling and navigation problems of Xiangjiaba hydropower station during the dry seasons. Taking the mutual feedback relationship between the Hydraulic coupling of power generation and navigation as the pointcuts, an improved genetic algorithm was put forward with maximizing daily power generation. A two-dimensional flow model was carried out to validate constraints since the complex flow field was located at the entrance area of the approach channel. With the help of the software MIKE21 FM, the flow field data, such as the water surface lines, flow velocity and direction, was obtained by the numerical simulation. The results showed that the daily power generation optimization and numerical simulation methods could achieve the maximized daily capacity of hydropower station under the premise that ensuring the safety of navigation.

Numerical modeling of storm surge attenuation by mangroves in protected area of mangroves of Qheshm Island

With the experience of storm surges along Persian Gulf of Iran it is needed to simulate storms in coastal areas and study the protection techniques in order to protect communities and industrial facilities in coastal areas. Mangrove forests play a unique role in attenuating storm surge during tropical cyclones. MIKE21 FM is an applicable software for simulating cyclones within coastal environments. A hydrodynamic model is used to analyze the attenuating role of the protected area of mangroves between Gheshm Island and Khamir Port mangroves under a realistic conditions by updating the calibrated Manning's coefficient based on the land cover data to incorporate the mangrove effect with modifying bottom friction and characteristics of cyclone Gonu 2007 which is the strongest cyclone recorded in the Arabian Sea and Persian Gulf. In this research we measured the maximum surge levels in both scenarios (in situ conditions and the condition which mangrove forest is neglected); maximum storm tide reduction by mangroves (MSTRM) by mangroves and maximum storm tide reduction rate by mangroves (MSTRRM). Also inundation maps are presented aiming to measure the areas rescued from inundation and the areas inundated caused by mangroves. The simulations shows that the minimum and maximum storm tide reduction rate by mangroves are 5.32% and 34.88% respectively.

SURF ZONE HYDRODYNAMICS – COMPARISON OF MODELLING AND FIELD DATA

Field data from the NOURTEC project is used for comparison with simulation results by the MIKE21 FM model complex. The study includes generation of boundary data by a regional model and simulations by local models of the water level, waves conditions and current fields in the nearshore area of the island of Terschelling.

温排水排放对长江的水质研究

本文采用数值模拟方法来研究海洋和分析环境问题，并预测在长江口海域潮流场特性。然后运用Mike21 FM对流扩散模型预测温排水排放对海洋水质的影响。研究表明该结果很好的反映了研究海域的物质输运和热量扩散规律。 The article adopts the methods of numerical simulation to research the environmental problem of ocean and analyzes and predicts the characteristics of flow field in the sea areas of Yangtze River Estuary. And then by means of Mike21 FM convection-diffusion model, it predicts the influence of thermal discharge on the marine water quality nearby. Research shows that the results reflected the rules of transportation and diffusion of heat quantity in study water area bitterly.