The necessity of study
Vietnam boasts a coastline stretching approximately 3,260 km, highlighting the critical importance of protecting and harnessing its marine economic potential for the nation's growth The achievement of these goals necessitates the development of a diverse range of marine structures, including coastal protection systems, storm shelters, harbors, breakwaters, and facilities on remote islands These structures have been extensively studied and constructed worldwide, underscoring their significance in enhancing Vietnam's maritime infrastructure.
Vietnam is experiencing a surge in the construction of seaports and storm shelters, leading to an increased focus on developing sea dikes However, underwater construction in seawater presents unique challenges, including the need for dikes to withstand waves, winds, currents, and erosion, while also being cost-effective and durable As a result, the project titled “Designing Structures to Protect Embankment at the New Economic Zone of Nam Dinh Vu – Haiphong” is crucial for advancing the maritime economy This initiative aims to establish a key multi-sector economic zone that prioritizes the development of maritime infrastructure.
Study objectives
Dinh Vu - Haiphong economic zone is place where it is exploited about the maximum advantage of natural conditions, geographic location, socio-economic potentiality
According to the master plan approved by the Prime Minister with the heart of
Haiphong international gateway harbor, it is determined to attract investments and receive advanced technology and to create a new driving force for Haiphong and
The North Coast is experiencing rapid development, particularly in the field of hydraulic engineering This growth is largely driven by advancements at the University of Water Resources, which is becoming a key institution for education and research in this area The focus on hydraulic studies at the university is essential for addressing the region's infrastructure needs and environmental challenges As the North Coast continues to evolve, the contributions of the University of Water Resources will play a vital role in shaping its future.
The Government has mandated the development of the Dinh Vu - Cat Hai economic zone as an integrated marine economic center, focusing on multiple sectors such as maritime services, industry, finance, banking, tourism, and trade This initiative aligns with the development planning of Haiphong city and the Northern major economic zone, as well as two economic corridors connecting Con Minh, Lao Cai, Hanoi, and Haiphong.
Quang Ninh and Nam Ninh (China) are strategically linked to Lang Son, Hanoi, and Haiphong, forming a cohesive network with the Van Don - Quang Ninh economic zone In the near future, the Dinh Vu - Cat Hai economic zone will prioritize the development of high-quality resort facilities.
(Cat Ba eco-tourist resort, Nam Trang Cat tourist resort, green parks – entertainment…), a modern seaport system with a total natural land area of 1,046ha
(Tan Dinh Vu, Nam Dinh Vu, and Cat Hai harbor, International harbor Gate of
Haiphong, ) tariff zone 12,532ha, non-tariff area 1,258ha, treasure system about
209ha, industrial parks with total natural land area 4,550ha (319haindustrial zone of
The article highlights the extensive land allocations for various industrial and urban developments in the region, including the Ben Rung industrial zone (698 ha), VSIP industrial zone, Trang Cat industrial zone (138 ha), Nam Dinh Vu industrial zone (681 ha), and the Cat Hai and Lach Huyen districts (4,444 ha) Additionally, it mentions the Trang Duc industrial park (400 ha), public service centers (761 ha), specialized centers (2,105 ha), urban areas and populations (2,062 ha), and land designated for national defense and security (103 ha).
Vietnam's sea-oriented economic strategy has led to the development of the Dinh Vu Economic Zone, which is designed to be a modern deep-water hub in the North This economic zone plays a crucial role as a trading gateway for the northern region, highlighting the significant progress of Vietnam's maritime economic landscape.
The Nam Dinh Vu dike is being constructed to expand the industrial zone and enhance the protection of marine economic areas against storm waves This infrastructure aims to provide safe refuge for ships and boats during severe storms, ensuring compliance with design standards for wave protection.
Objects and scope of the study
The study is limited in scope of Nam Dinh Vu dike, which focuses on specific circumstances in Dong Hai and Trang Cat areas
The study focuses on designing and analyzing deep dike protection structures capable of enduring various environmental challenges such as waves, winds, undercurrents, and landslides These structures are engineered to resist corrosion and erosion while ensuring anti-slip and anti-fracture properties Additionally, they aim to achieve low investment costs, reduced construction volume, and a long lifespan, specifically for the new economic zone of Nam Dinh Vu in Haiphong.
Study approaches and methodology
- Collected documents, geological and hydrographical data to determine hydrological border of Nam Dinh Vu new economic zone
- Based on shoreline developments to design sea dike protection structures
- To calculate the stability of the building which was designed.
Expected results
The limit in the framework of Master thesis, the expected results include:
+ To have overview of the design dikes;
+ To propose some design options which can be applied by a new economic Nam
Dinh Vu zone and analyses and select structural solutions for the selected plan
+ To calculate the stability of the design.
Structure of thesis
The study is structured into three main chapters, along with an introduction, conclusion, recommendations, and annexes Each chapter focuses on key aspects related to the subject matter, providing a comprehensive analysis and insights This organization ensures clarity and coherence throughout the research, facilitating a better understanding of the topics discussed.
OVERVIEW ABOUT PROTECTED SEADIKE AND
Concept about sea dike and embankment
A sea-dike is a crucial structure designed to protect coastal areas by preventing tidal flooding, reducing wave run-up, and stabilizing shorelines These dikes play a vital role in safeguarding economic zones and livelihoods along the coast, particularly in areas designated for land reclamation or aquaculture Sea-dikes can be categorized based on their construction materials, the protective belt they provide, the water depth in front of the dam, and their cross-sectional shape.
Marine embankments are engineered structures that safeguard riverbanks and coastlines from erosion caused by currents and waves These dikes are specifically designed to withstand the impacts of wave action and water flow, utilizing anti-erosion materials to ensure durability and protection.
The Cat Hai – Haiphong zone is safeguarded by a robust sea dike system, ensuring protection against coastal erosion and flooding This strategic infrastructure plays a crucial role in preserving the area's ecological balance and enhancing its resilience to climate change impacts The implementation of such protective measures is vital for the sustainable development of the region, promoting both environmental conservation and economic growth.
Coastal Vietnam boasts significant potential for the development of agriculture, forestry, and fisheries, enriched by valuable tropical ecosystems like mangroves, seagrass beds, coral reefs, and estuarine areas This region's diverse natural resources, coupled with urban and tourism infrastructure, provide crucial coastal services that drive socio-economic growth at both provincial and national levels.
The government recognizes the expansion of coastal areas as a vital opportunity for economic growth, focusing on land development for tourism and seaport facilities.
The Red River Delta, characterized by vital inland waterways, boasts 20 major ports and cargo handling facilities that significantly enhance the region's socio-economic development Additionally, the area features deep water zones ideal for the establishment of deep water wharves, further supporting maritime trade and economic growth.
Lach Huyen Port in Haiphong is strategically positioned to leverage the benefits of submerged land and estuarine wetlands, making it ideal for seaport development To maximize its potential, it is essential to prioritize the upgrading and expansion of existing seaports, including Cai Lan in Cam Pha, Cua Ong in Bai Tu Long Bay, and Hai.
Phong port, etc Invest in constructing general ports at Nha Mac lake, Bach Dang river port and Chanh river port (Hai Phong)
There are many important seaports such as Da Nang, Tien Sa, Lien Chieu (Da Nang),
Ky Ha in Quang Nam, along with the coastal ports of the South Central region, plays a vital role in establishing seaport systems that drive economic growth This area serves as a crucial maritime artery on a global scale.
The coastal areas of the Mekong Delta also have seaport systems such as My Hoa, Tra
Vinh, Hon Chong, and Ham Ninh are key locations that highlight the marine economic advantages of the area, particularly through the exploitation of seaports and shipping These regions play a significant role in enhancing maritime trade and economic development.
Research on dike structure in the world and in Vietnam
1.2.1 Researches of sea-dike in the world
Sea-dikes have been established in marine countries to protect inland areas from floods and natural disasters, with their development varying based on local conditions and economic factors These systems include structures such as revetments, seawalls, breakwaters, and groins, designed to prevent erosion and manage sediment transport in high-risk areas Erosion often affects the integrity of dikes, making it crucial to use materials that are suitable for the specific natural conditions of each zone This focus on appropriate materials is essential for the effective protection of both the dikes and the land they safeguard Researchers are actively studying innovative structures that can withstand wind, waves, and currents while ensuring long-term durability and cost-effectiveness.
Historically, coastal protection relied on prefabricated stone and concrete dikes, but rising sea levels and severe natural disasters due to global warming have necessitated advancements in these structures Recent research by scientists J Chu, Yan, and Li emphasizes the need to rehabilitate existing coastal defenses and construct new, more resilient structures Coastal protection systems can be categorized into three modern types based on their materials and applications: geological buffer structures, precast concrete structures, and straw structures, each with its own advantages and disadvantages.
Geologically-cushioned construction is essential for dikes and breakwaters in shallow waters This innovative structure consists of multiple layers of thin, geologically arranged cascades that overlap, utilizing materials such as sandbags or clay This design enhances stability and resilience against water forces, making it a vital component in coastal engineering and flood protection strategies.
Fig 1.2 A picture showing the formation of a dike using clay slurry filled geotextile
Concrete structures suitable for breakwater in uneven areas that was prefabricated If the weak ground can be reinforced by rubber cushions
Fig 1.3 Illustration of the prefabricated caisson supported by a rubble mound and source protection cover
The tubular structure represents an innovative and promising solution for deep water applications Its design is particularly well-suited for challenging underwater environments, making it a significant advancement in structural engineering.
Fig 1.4 Installation of upper cylinders to form breakwater
In addition to concrete materials, grasses are also a very good material to protect the dike if they were combined with the use of synthetic geotextiles Stefan Cantré and
Fokke Saathoff has discovered dike protection materials derived from the sedimentation process in estuary zones, utilizing synthetic techniques to combine buffer layers, with the dike roof being covered by grasses This model has been validated through laboratory testing and experimental evidence.
In a study conducted in Germany and Poland, researchers demonstrated that sediment and materials from river delta dredging were utilized to construct embankments Additionally, the findings revealed that synthetic materials enhance drainage at the toe of the dike, minimize infiltration within the dike, and ensure impermeability at the dike's roof.
The homogenous dredged material dike, illustrated in Fig 1.5, incorporates a geosynthetic drainage composite to enhance stability and manage seepage effectively Sensor data from a seepage test, depicted in Fig 1.6, provides critical insights into the performance of the dike structure This research, conducted by Dai Hoc Thuy Loi, emphasizes the importance of advanced materials and testing methods in ensuring the integrity and safety of hydraulic structures.
Therefore, If we use the material from the dredging process, sediment from the estuarine zones combined with synthetic material cover with grass layers, dike will be more durable [4]
1.2.2 Researches of sea-dike in Vietnam
Vietnam's extensive coastline of over 3,200 km is significantly affected by climate change, facing challenges such as seawater intrusion, coastal erosion, and forest degradation Protecting banks, rivers, lakes, and coastal areas is a complex task that requires substantial investment, yet these regions are crucial for the national economy and security Advances in science and technology have strengthened sea dikes, which serve as vital protective structures against rising sea levels The design of these dikes aims for cost-effectiveness while ensuring high efficiency, with a focus on creating green wave-breaking walls The stability of these protective structures is essential, and various innovative dike protection methods, including grass plantings, stone carpets, and prefabricated concrete components, have been explored by researchers.
There is based on the phenomenon of breaking waves and created waves over the dike
The “wave overtopping simulator, a device to test the grassed dike slopes in situ” Le
The test aims to simulate wave conditions during specific storms affecting dikes, focusing on the average discharge overtopping per unit length This study investigates the stability and failure mechanisms of the dike's top and roof under the influence of wave overtopping The volume of wave overtopping is influenced by the boundary conditions of the waves, which are calculated using the TAW (2202) method, specifically the 2% wave run-up.
11 to determine the percentage of wave overtopping at a certain height according to the
Velocity and thickness maximum flows are determined by Schuttrumpf and Vagent
(1.2) According to coefficient C a,u * =1,37 and 1,3 ; c a,h * =0,33 and 0,15
Theoretically, the average discharge overtopping is 10; 20; and 40 l/s/m at the sea edge of the crest dike with the same volume of a wave overtopping as similar velocity
Experiments conducted on the discharge machine revealed varying average wave overtopping rates at similar velocities, corresponding to wave overtopping flows of 10, 20, and 40 l/s/m at the sea edge of the dike crest.
The maximum velocity at the sea edge of the crest dike is influenced by the overtopping volumes of waves, specifically in cases where the significant wave height (Hs) is 1.5 meters and the wave period (Tp) is 6 seconds, with a slope angle (tanα) of 0.25 Additionally, a wave overtopping simulator has been tested at the Tien Hai – Thai Binh dike, providing valuable insights into the dynamics of wave overtopping and its impact on coastal structures.
There are many studies on stability of the dike that are applied in the fact Today, PhD
Hoang Duc Thao –Ba Ria – Vung Tau – Urban Sewerage and Development Company
In 2015, Busadco was recognized as one of the top ten significant events in science and technology This innovative event was created by authors and implemented in various provinces, including Thai Binh, Ho Chi Minh City, and Ba Ria – Vung Tau.
Tau province under the accrediting Technical Center for 3 Quality Measurement standard [6]
Fig 1.9 Prefabricated structure protects rivers and sea dike
Fig 1.10 Prefabricated structures protect river and sea dike
The technical design of the Nam Thinh dike in Tien Hai, Thai Binh, includes detailed specifications on structural dimensions, reinforced concrete piles, load capacities, and overall stability The structural integrity has been assessed according to sea dike technical standards and has received accreditation from the Technical Center for Quality Measurement.
The construction of protective structures for shorelines and sea dikes plays a crucial role in preventing landslides, erosion, and wave impacts These measures include the development of breakwaters and embankments, which are essential for land fund development and addressing the challenges posed by rising sea levels Implementing these strategies is vital for safeguarding coastal areas and ensuring sustainable development in the face of environmental changes.
The project involves the reinforcement, repair, renovation, and upgrading of 13 damaged coastal protection works, alongside investments in new constructions Notably, the construction progress is achieved in just one-third of the time compared to traditional methods, effectively addressing weather, climate, and hydrological challenges This innovative approach not only simplifies operations and maintenance but also reduces investment costs by at least 20% compared to conventional solutions With a high life expectancy and enhanced durability, these constructions minimize the need for repeated investments, earning appreciation across various localities.
Basic types of dike cross sections, structures and materials to form sea dikes 13
According to the TCVN 9001-2014 design standard for sea dikes, the cross-section and structure of sea dikes are determined by the geometric characteristics of the dike roofing The design categorizes dike sections into three primary types: embankment, standing wall, and mixed dike, which can be oriented either upside down or downside.
Fig 1.11 The section shapes of the sea-dike
Embankments constructed with homogeneous soil typically feature a trapezoidal shape, with side slopes (m) ranging from 3.0 to 5.0 for seaside dikes and 2.0 to 3.0 for inland dikes These structures are primarily composed of compacted soils, which serve as the foundational material for the embankment In instances where the dike height is less than 2 meters, specific cross-sectional designs can be employed to ensure stability and effectiveness.
In areas with poor geological conditions, tall dikes can be vulnerable to wave impact To mitigate this risk, a berm can be constructed at the downstream side of the dike, effectively reducing wave energy and enhancing stability.
When local soil reserves are insufficient for constructing a dike using homogeneous materials, alternative mixed materials can be utilized These local materials often exhibit high permeability and significant diversity, making them suitable for effective embankment construction By leveraging the unique properties of these materials, engineers can enhance the structural integrity and functionality of the dike.
The dike structure features a core of 15 permeability layers, surrounded by a low-permeability cover, as illustrated in Fig 1.11c Additionally, rocks are strategically placed at the upstream side to protect against wave erosion, while soil is utilized on the downstream side, as depicted in Fig 1.11d.
The seawall and combined slope dike are essential structures built to protect coastal areas from flooding, particularly during high tide Due to insufficient soil reserves for dike coverage, alternative designs are necessary While reinforced concrete walls offer stability, they can be complex and costly Therefore, an effective design incorporates a combination of stone walls and soil dikes, as illustrated in various figures This approach not only prevents flooding but also accommodates residential boats and goods transportation, ensuring that the top of the dike serves as a functional traffic road.
Slope dikes utilizing geotextiles are essential in areas with weak soil conditions, characterized by low adhesive forces, minimal corner friction, and a high permeability coefficient Traditional dike construction often requires large sections and extensive materials, leading to prolonged construction times and increased costs due to subsidence issues However, employing geotextile reinforcement effectively addresses these challenges by reducing construction costs, minimizing the dike's footprint, and expediting the building process Figure 1.11h illustrates the layout of geotechnical fabric within the dike structure.
The analysis of dike sections and sea-dike protection structures reveals various advantages and disadvantages Selecting the appropriate cross-section type depends on geological topographies, hydrographical conditions, construction materials, construction conditions, and the intended purposes of the study area This careful consideration ensures the optimal design and functionality of the dike form proposed by the author.
Proposing of cross-section selection
Nam Dinh Vu dike project was started since 2012 and was approved by the investment managements from the plans as following:
- PA1: Using a traditional protector method as rocks, very gentle slope and combining sheet piles to prevent sliding formation
Fig 1.12 Rock on seaside slope, sheet piles under embankment
- PA2: Using fill stones with double layers by CMC
Fig 1.13 The gentle slope, protection of the roof with two layers of stone, the use of geotextile on ground Đất đắp k=0.9
BT lãt M150; 10cm Tấm lót vải bạt Vải địa kỹ thuật Đất đắp k=0.9
Cấu kiện P.Đ.TAC-CM5874 D16 M300 Đá dăm 1x2 dày 20cm
Cát hạt trung Cát hạt trung
Vải ĐKT cường độ cao Vải ĐKT cường độ cao
Vải địa kỹ thuật Đất đắp k=0.9
Cấu kiện P.Đ.TAC-CM5874 D16 M300 Đá dăm 1x2 dày 20cm
Cấu kiện P.Đ.TAC-CM5874 D24 M300 Đá dăm 1x2 dày 20cm Vải địa kỹ thuật Đá hỗn hợp dày 50cm Cát đắp
Cấu kiện P.Đ.TAC-CM5874 D24 M300 Đá dăm 1x2 dày 20cm Vải địa kỹ thuật Đá hỗn hợp dày 50cm Bao tải cát
Cấu kiện P.Đ.TAC-CM5874 D24 M300 bao gồm đá dăm 1x2 dày 20cm và đá hỗn hợp dày 50cm, được sử dụng trong các công trình xây dựng Sản phẩm này được thiết kế để đáp ứng các tiêu chuẩn chất lượng cao, phù hợp cho các dự án tại trường Đại học Thủy Lợi Với tính năng bền bỉ và khả năng chịu lực tốt, cấu kiện này là lựa chọn lý tưởng cho các ứng dụng trong ngành xây dựng.
- PA 3: Consultant recommends lightweight hollow structural components
Fig 1.14 Steep slope, using hollow box to reduce load
The advantages and disadvantages of the three options are effectively summarized in the following table This concise overview allows for a quick comparison, highlighting the strengths and weaknesses of each choice Understanding these pros and cons is essential for making informed decisions regarding educational pathways By analyzing the information presented, students can better evaluate which option aligns with their academic and career goals.
Table 1.1 The projects are arranged by the structure for Nam Dinh Vu dike
Project Advantages Disadvantages Cost prices
PA1 + Using locally available materials
+Ability to reduce wave height
+ Reduced erosion in front of the structure
+ Distributed energy through breaking waves
+Suitable for weak geology (soft soils)
+ High Cost + Use normal construction equipment + Construction is dominated by weather, it takes a lot of time
+ Difficult to maintenance + Difficult to control the quality of earth works
PA2 + Using locally available materials
+ Ability to reduce wave height by raft
+ Reduced erosion in front of the structure
+ Suitable for weak soil geology
+ Complex construction is affected by the weather
+The progress of construction takes much time
+ Difficult to control the quality and size of stone
The University of Water Resources, known as "Dai Hoc Thuy Loi," is a prominent institution in Vietnam, specializing in water resource management and engineering With a focus on sustainable development, the university offers various programs aimed at addressing the challenges of water management in the region Students benefit from a comprehensive curriculum that combines theoretical knowledge with practical applications, preparing them for careers in environmental protection and infrastructure development The university is committed to research and innovation, contributing significantly to advancements in water resource technologies.
+ Surface roughness, wave height will be reduced
PA3 + Structures to withstand the impact of waves, wind, underground flow
+ To ensure anti-corrosion and anti-invasion marine environment (use fiber reinforced concrete)
+ Structure of synchronous system: blocks, pillars, gravity to stabilize
+ Convenient in produce, installation according to the specific requirements of each region,
+ To control the quality of products before sending out;
+ Cost of construction investment is lower than traditional solutions;
+ American work compact, clean beautiful;
+ Convenient for maintenance and management;
+ Suitable for soft soil foundations
+ This technology solution is suitable only for shallow water, soft soil and mudflats
The University of Water Resources (Dai Hoc Thuy Loi) is a prominent institution specializing in water resource management and engineering With a strong emphasis on research and innovation, it prepares students to address critical challenges in water sustainability and environmental protection The university offers various programs aimed at equipping graduates with the skills necessary for careers in hydrology, civil engineering, and environmental science Through a blend of theoretical knowledge and practical experience, students are well-prepared to contribute to the field and tackle global water issues.
From analysis above the dissertation to choose option 3 by the following reasons:
Coastal Vietnam is increasingly facing landslides and erosion, significantly impacting its economy, environment, and social welfare Traditional dikes and coastal protection structures have been crucial in flood prevention and safeguarding large residential areas along rivers and lakes However, these older designs often fail to meet technical standards and suffer from severe damage To address these challenges, there is a pressing need to innovate and implement new technologies for shoreline reinforcement Modern solutions, such as stone carpets and concrete slabs, are replacing outdated methods, ensuring compliance with technical requirements and enhancing protection against natural disasters The innovative dike cross-section proposed by Busadco Company exemplifies this shift, offering efficient protection against landslides and erosion while promoting land development and responding to rising sea levels This advanced construction technology reduces project timelines to one-third of traditional methods and cuts investment costs by at least 20%, while also being easier to manage and maintain Overall, these new structures promise improved durability and operational efficiency, making them a vital component of coastal resilience strategies in Vietnam.
21 expectancies to make a long-term durability, not have to invest many times about a construction item and by highly appreciated in many localities.
Conclusion of chapter
Reclamation and sea encroachment have long been essential practices for our people, aimed at expanding land for economic development in coastal regions while safeguarding residential, economic, and cultural areas Since ancient times, our ancestors recognized the importance of these efforts, particularly focusing on the construction of sea dikes to protect and enhance their communities.
The construction of sea dikes faces significant challenges due to weak geological conditions, tidal waves, and frequent tides Traditionally, these dikes, made from local materials, were designed to withstand storms up to level 9, but they are now inadequate for modern weather patterns As a result, there is an urgent need for innovative dike structures that can meet contemporary demands Globally, many modern and sustainable dike designs have been researched and implemented Analyzing and assessing both local and international sea dike constructions is crucial for developing effective structural solutions for the sea dike project in Nam Dinh Vu.
The Haiphong Economic Zone is a pivotal area for economic development in Vietnam, offering a range of opportunities for investment and growth It is strategically located, facilitating trade and commerce, and is home to various industries The zone is supported by educational institutions, including the University of Water Resources, which contributes to the skilled workforce needed for the region's development With its focus on sustainable practices and innovation, the Haiphong Economic Zone is poised to become a leading hub for economic activities in the region.
Natural features of the study area
The study area is located in about 20.5 -20.9 the North latitude and 106.5 -107.1 the
East longitude, the West coast of the Gulf of Tonkin, the Northeastern margin of the
Red River delta of Haiphong city about 102 km the East of Hanoi (Fig 2.1)
Fig 2.1 Haiphong coastal estuary and Bach Dang estuary
(Source: Imagery from Google earth)
The study area features a complex interplay of river, marine, and mixed river dynamics, characterized by a diurnal tidal system and significant tidal amplitudes typical of tropical monsoonal climates These tidal and saltwater dynamics are crucial for the formation and evolution of the terrain Additionally, human activities such as waterway traffic, sea dike construction, and natural resource exploitation in the estuaries further complicate the area's development The Haiphong coastline, with its concave curvature along the western Gulf of Tonkin, exemplifies these dynamic interactions and their impact on the coastal environment.
23 fairly flat, mainly composed of sediments from five estuaries The landscape of the estuary of Haiphong coastal area is not very large, with small slope
The coastal estuary of Haiphong experiences the influence of two primary monsoon systems: the Northeast monsoon and the Southeast monsoon During winter, the region is significantly impacted by the interplay between these monsoon systems and the Xibiri high pressure, alongside the monsoon tide from the East China Sea This dynamic results in fluctuating weather conditions throughout the season The monsoon systems are particularly dominant from October to March, leading to intense weather patterns, while the early winter months see a different atmospheric behavior.
During the winter months of November and February to March, the polar system is significantly influenced by the credit system This season is marked by alternating cold and warm days, typical of the monsoon period, particularly when the Northeast monsoon sets in The prevailing winds during this time predominantly come from the North and Northeast, with average speeds ranging from 3.2 to 3.7 m/s The winter monsoons occur 3 to 4 times a month, lasting between 5 to 7 days and often accompanied by light rainfall On days with stronger winds, speeds can reach levels of 5 to 6 (approximately 8-13 m/s), while maximum wind speeds in the islands may soar to 25-30 m/s before gradually tapering off.
Table 2.1 Frequency of wind velocity and annual directions at Hon Dau (1960 - 2011)
The frequency of calm wind is recorded at 16.56% This data is significant for studies conducted at Dai Hoc Thuy Loi, a prominent institution in the field of hydraulic engineering Understanding wind patterns is essential for various applications, including environmental assessments and engineering projects.
The water content of the Red River delta is influenced by the Southwest monsoon
During the summer months, tropical cyclones and hurricanes significantly impact various regions, particularly from June to July The Red River experiences its highest flow in August, while the lowest flow occurs in March.
Each year, the Hong and Thai Binh river systems deliver approximately 120 billion cubic meters of water and 114 million tons of alluvial deposits to coastal areas, primarily through nine major estuaries: Bach Dang, Cam, Lach Tray, Van Uc, Thai Binh, Tra Ly, Ba Lat, and Ninh.
Co and Day rivers According to Haiphong coastal area, there are direct impacts of
The Bach Dang, Cam, Lach Tray, Van Uc, and Thai Binh rivers, part of the Hong – Thai Binh river system, exhibit significant seasonal fluctuations in their flow regime An analysis of multi-annual data indicates that the majority of annual water flow occurs during the rainy months, primarily from June to November.
During the rainy season, river discharge to the sea ranges from 300 to 2,200 m³/s, while in the dry season, it significantly decreases to an average of 50 to 300 m³/s.
Water level fluctuations in the Haiphong coastal estuary are primarily influenced by tidal patterns, with tidal and semi-diurnal tides occurring only 2-3 days each month during periods of low water Each tide phase includes one high tide and one ebb tide, while the lunar cycle features two intense water periods lasting 11-13 days, with average amplitude fluctuations of 2.6-3.6 meters Additionally, there are two periods of low water lasting 3-4 days, characterized by amplitude fluctuations of 0.5-1.0 meters The tidal wave exhibits a standing wave characteristic, dominated by the O1 and K1 tides, which have amplitudes of 70-90 cm, while the M2 and S2 semi-diurnal tides play a secondary role with smaller amplitudes.
Tidal oscillations experience their peak values during drought periods, coinciding with maximum solar flux in June and December Conversely, the lowest tidal fluctuations occur in March and September when solar flux reaches zero Understanding these patterns is essential for analyzing the relationship between solar energy and tidal movements throughout the year.
April, August and September, the tides are falling with the tidal of 3-4 days a month
The Haiphong coastline's estuary features a shallow bay with intricate bottom topography shaped by river systems and fluctuating channels Due to bottom friction, deep water waves interact with the shore, resulting in variable characteristics such as propagation speed, height, cycle, length, and movement direction Consequently, the wave regime in this area differs significantly from that of deep-water waves in both trends and intensity.
In winter, the NE monsoon exhibits strong frequency and speed, but the presence of Cat Hai and Cat Ba islands significantly mitigates its wind energy impact on the sea The study area experiences shorter wave lengths and shallower depths, resulting in less development compared to offshore regions Nonetheless, during tidal changes, wind waves still have the potential to develop and refract as they propagate into coastal areas.
In the season, the prevailing waves are E and NE and average wave height is 0.5 –
0.6m The maximum wave height about 2.0 -2.5m in the coastal area east of Do Son peninsula wave height can be up to 3.0m
During the summer, the wind patterns differ significantly from those in winter and at high altitudes In this season, the prevailing wind waves primarily come from the southeast and south, which greatly influence the hydrodynamic processes in the study area.
In June and July, the northern wave direction significantly impacts the erosion of the northern banks of Dinh Vu Peninsula and Cat Hai Island, as well as the surrounding channel area The average wave height during this period ranges from 0.6 to 0.8 meters Additionally, this time of year often brings storms and tropical low-pressure systems, resulting in larger waves and stronger winds that exacerbate coastal erosion.
Table 2.2 Frequency of wave heights and directions at Hon Dau (1970 -2011) [8]
The frequency of calm wind is recorded at 28.22% This data is significant for understanding wind patterns, particularly in the context of studies conducted by Dai Hoc Thuy Loi Analyzing wind frequency is crucial for various applications, including environmental assessments and engineering projects Understanding these patterns can aid in optimizing designs and improving sustainability efforts in related fields.
The result of statistical analysis of wave rule data for several years (1970 – 2011) at
Simulating the development of Nam Dinh Vu new economic zone
MIKE 21 is a 2D surface flow model, the Mike 21 model is used to simulate hydraulic processes and environmental phenomena in lakes, estuarine areas, bays, coastal areas and waters In order to design the structure of sea dykes in Nam Dinh Vu - Haiphong new economic zone, the problem is to determine the impact of waves, currents and tidal currents on river mouths in dry and rainy seasons, from which to find the compensation – erosion rules through the application of mathematical models to simulate this process MIKE 21 is widely used in the calculation of estuarine, coastal and marine dynamics MIKE 21 is used to calculate some modules such as tide calculations, grid netting, calculating coastal river mouth flows, calculating wave propagation from offshore to coastal areas, wave in the harbor area, sediment transport calculations, transpiration calculations, oil spill calculations, storm surges calculations, salinity intrusion calculations, etc… Within the scope of the research, the author uses the MIKE 21 model to calculate the simulation of the shoreline to determine the flow velocity, and the wave height in front of the building
This thesis is based on a comprehensive collection and analysis of essential documents synthesized from relevant research findings These documents are integral to the subjects and contents of the thesis, reflecting the academic rigor and insights derived from the studies conducted at Dai Hoc Thuy Loi.
Terrain significantly influences the hydrodynamic conditions of each study area The depth and coastal data of the Haiphong coastal estuaries have been digitized from topographic maps using UTM Geographic Coordinates VN 2000 at a scale of 1:5000.
50000 and 1:25 000 by the Department of Mapping (Ministry of Natural Resources and Environment of Vietnam) published in 2005 These data have been digitized and corrected according to recent depth measurements
The depth and topography of the outer zone and the Gulf of Tonkin are using the
GEBCO -1/8 database of the UK Oceanographic Resource Center This is a terrain data which has 30 seconds about a resolution that is processed from a satellite image combined with in-depth measurements
Meteorological characteristics significantly influence the dynamics of Haiphong's coastal estuaries, playing a crucial role in the seasonal variations of the area's dynamic regime This study involved the collection and analysis of long-term wind data from the Hon Due station, alongside regular monitoring data.
6h /time during February and March and July-September 2009 were also collected for inclusion in the model for the current scenario
Data on water level fluctuations in Haiphong coastal estuaries were gathered to calibrate the model and establish maritime boundary conditions The calibration utilized hourly water level measurements taken at Hon Dau during March and August 2009.
Databases on water level fluctuations at maritime openings have been collected to develop a hydrodynamic model, analyzing tidal regulation constants for four tidal waves: O1, K1, M2, and S2 Near-shore border points have been monitored, with data gathered from organizations such as the Center for Marine Meteorology and Hydrology This information is crucial for understanding tidal dynamics and improving coastal management strategies.
Institute of Geography, the Institute of Mechanics and Institute of Marine Resources and Environment
Flow databases collected from various survey sites in the Haiphong coastal river estuary were analyzed to verify the reliability of the hydrodynamic model This included flow measurement data relevant to the study, alongside wave databases provided by the National Meteorological and Hydrographic services.
The meteorological stations at Hon Dau and Bach Long Vy have collected and processed data over several years, providing observation databases for daily readings at 7 AM, 1 PM, and 7 PM This data will serve as a crucial reference for developing a wave propagation model in the estuary of the Haiphong coastal river.
2.2.3.1 Simulated domain and computed mesh
To study the dynamic regime of the estuarine area, the domain and grid calculations are chosen as follows:
The calculation range of the model includes the waters of Bach Dang, Cam,
Lach Tray, Van Uc mouth rivers and outside of these estuaries
The model uses flexible triangles (unstructured grid) with varying resolution increasing from deep seas to estuaries and estuaries The grid has a total of
The model consists of 14,046 nodes and 26,535 elements, specifically designed for estuarine and coastal areas The grid features a length of approximately 50 meters, ensuring detailed representation of the geographical features within these regions.
Fig 2.2 Domain topography of zone Fig 2.3 Computed gird
The model has the open and river boundary:
+ The river boundaries include: the average flow at the section of Bach Dang river
(Pha Rung), Cam river (near Cau Binh bridge), Lach Tray (nearly Phan Dung), Van
+ The sea side boundary: Northern 1, Northern 2, river, and Southern boundary
The water level boundary condition is determined using the harmonic constant databases from the MIKE 21 model and toolbox In this model, the tidal oscillator is calculated in GTM world time, and the water level is derived by comparing calculated and measured databases within the same time zone For Vietnam, the calculation accounts for a 7-hour difference, aligning 0 hours in the model with the local time.
The flow river boundary of condition: the average water flow of the month is determined by two seasons
Initial set of flow model:
The time period for calculation spans from 00:00 on July 25, 2008, to 23:00 on August 4, 2008 This timeline is crucial for understanding the events related to Dai Hoc Thuy Loi, a prominent institution in the field of water resources and engineering education.
The horizontal viscosity is calculated by the Smagorinsky formula and is averaged on the domain all equal to: 0,28
Manning number is given the average on the domain all equal to: 35 m 1/3 /s
Carioles force: is taken into account
The result of calculation: region, step output time: 1 hour per 1 value
The flow model was calibrated using real data collected from the Bach Dang station between 4:30 PM on July 29 and 4:00 AM on July 30, 2008, sourced from the estuary dredging project The data was gathered at a depth of 0.6 meters, and the calibration results are illustrated in Figure 2.4.
Fig 2.4 Compared results between actual and computed flow velocities
The flow velocity test results reveal the correlation between calculated and actual flow velocities, highlighting their trends and process paths However, it is noted that the calculated velocity is often lower than the actual velocity measured at a depth of 0.6 m, as the computed velocity represents an average across all depths.
The databases are used to calibrate and the model test is the measured water level at
Hon Dau station This is the only station in the area of the measured water level and monitoring data is 1 hour per value
This comparison can be carried out visually (comparing the two calculated and actual paths on the graph) and combining the Nash – Sutcliffe (1970) index for testing
The period of time is selected to be the model calibration from 01/03/2009 to
On March 32, 2009, calibration results were incorporated into the process lines at Hon Dau station, where the orange line represents the actual water level and the blue line indicates the calculated water level.
Fig 2.5 The water level line between observed water level and computed water level at
The database is established using tidal boundary conditions and harmonic constants, and a numerical model has been employed to validate the measured data The comparison reveals that the measured water level fluctuations yield a Nash coefficient of 0.89, which exceeds the acceptable threshold of 0.8, indicating a reliable correlation Consequently, the calculated service parameter set is confirmed and can be utilized for further calculations.
Hydrodynamic conditions in the coastal estuaries of Haiphong are influenced by factors such as fluctuations in water levels, wind fields, waves and river water bodies
In the above factors, changes in the wind field and river flow have caused changes in the flow field
2.2.4.1 No construction works yet a) Spatial variation
The synthetic flow of dry season in the estuary of Haiphong coastal zone fluctuates sharply in the tidal phase
The chapter conclusion
The Tonkin Gulf exhibits a uniform tidal regime characterized by significant wave amplitudes, with predominant sea wave directions towards the East, Southeast, and South During the dry season, the main current flows southward, while it shifts to an eastward direction in the rainy season Hydrodynamic simulations indicate that wave heights, influenced by wind conditions and water levels, are highest at specific coastal points For the level III project, simulations accounting for storm and wind waves, as well as wave propagation from Bach Long Vi, yield parameters of significant wave height (H s = 2.21m), wave length (L s = 52.4m), and wave period (T = 11.25s) These findings are critical for determining the design specifications of the dyke, as detailed in Chapter 3.