Modelling coastline evolution using one line model for hoi an quang nam

THUY LOI UNIVERSITY UNIVERSITY OF LIEGE CAO DUC HAI MASTER THESIS MODELING COASTLINE EVOLUTION USING ONE-LINE MODEL FOR HOI AN, QUANG NAM Major: Sustainable Hydraulic Structures Coastal Engineering and Management Supervisor: Ass Prof Dr.NghiemTien Lam Prof Rigo Philippe Hanoi, 2016 ACKNOWLEDGEMENT This master course has been supported by the cooperation project between University of Liege and ThuyLoi University First and foremost, I would like to thank to all members in my big family, specially my father, my mother, grandfather, grandmother and my brother, which they help and promote me a lot when I had got trouble in the master course Next I really world like to show my gratitude to my professor in Vietnam, Assoc Prof Nghiem Tien Lam; also professor at University of Leige, Prof Rigo Philippe during master research, who gives me the direction in study In research, special thanks to Dr Nguyen Quang Chien for supporting to fix mistakes in programming open source code, and Assoc Prof Dr Vu Minh Cat for sharing data and material about Hoi An I am deeply grateful to him about his enthusiasm Last but not least, I want to send my thanks to my site manager, Duong Minh Tinh, and all leaders in Phuc Hung Holdings Construction Joint Stock Company that they give opportunities to complete my master thesis on time Hanoi, August 2016 Author Cao Duc Hai i CHAPTER : INTRODUCTION 1.1 Study area 1.2 Problem definition 1.3 Literature review 1.4 Study objectives 1.5 Approach and methodology 1.6 Thesis structure CHAPTER : PHYSICAL CHARACTERISTICS 2.1 Introduction 2.2 Geographic conditions 2.2.1 Mountain topography 2.2.2 Hilly topography 2.2.3 Delta topography 2.2.4 Sandy coastal topography 2.3 Topographic conditions 2.4 Climatic conditions 10 2.4.1 Wind 10 2.4.2 Temperature 11 2.4.3 Humidity 11 2.4.4 Evaporation 11 2.4.5 Rainfall 12 2.5 River basin and river network 13 2.5.1 River basin 13 2.5.2 River network 14 2.6 Observation stations and hydrologic conditions 16 ii 2.6.1 Observation stations 16 2.6.2 Hydrologic conditions 17 2.7 Oceanographic conditions 19 2.7.1 Tides 19 2.7.2 Wind waves 20 2.7.3 Currents 22 2.8 Sediment 23 2.8.1 River sediment transport 23 2.8.2 Coastal sediment transport 23 2.9 Historical evolution of the coastline 25 2.10 Conclusions 27 CHAPTER : APPLICATION OF GENERIC COASTLINE MODEL 28 3.1 Introduction 28 3.2 Theoretical background 28 3.2.1 One-line theory 28 3.2.2 Fundamental equations 30 3.2.3 Limitations 32 3.2.4 Sediment transport formulae 32 3.3 Model setup 34 3.3.1 Input data 34 3.3.2 Model settings 36 3.3.3 Computation of coastline evolution 38 3.4 Model calibration 40 3.4.1 Bed roughness 40 3.4.2 Grain diameter 46 iii 3.4.3 3.5 Wave breaking parameters 53 Conclusions 55 CHAPTER : PREDICTION OF EVOLUTION FOR HOI AN COASTLINE 56 4.1 Introduction 56 4.2 Zero-option 56 4.2.1 Scenario 56 4.2.2 Scenario 57 4.3 Coastal evolution in other coastal protection solutions 59 4.3.1 Submerge breakwaters 59 4.3.2 Immersed breakwaters 60 4.3.3 Groins 61 4.3.4 Conclusions 63 CHAPTER : CONCLUSIONS AND RECOMMENDATIONS 64 5.1 Conclusions 64 5.1.2 Recommendations 65 References 66 List of figure 68 List of table 70 Appendix A 71 Appendix B 85 iv CHAPTER : INTRODUCTION 1.1 Study area The Cua Dai beach and the ancient town of Hoi An are located in Quang Nam province in the middle of Vietnam They play great important roles in economic development of Quang Nam province, Vietnam Hoi An city is located in the Thu Bon River Basin with 10035 km2 of total area and approximately 120,000 inhabitants Its ancient town is recognized as a UNESCO World Heritage site in Vietnam Quang Nam province shares the border with Thua Thien-Hue province in the north, Quang Ngai province in the south, Kon Tum province and the Laos in the west It is a strategic important position that can cover and monitor almost of the marine routes in the East Sea Figure 1-1 Map of study area (Viet and Tanaka, 2015) 1.2 Problem definition Over last decade, coastal erosion in Cua Dai Beach has been happening severely and quickly, causing a significant retreat of the coastline The Hoi An beach is lost day by day On average, the Hoi An coastline is eroding 12m per year So a great number of resorts, restaurants and houses are either destroyed or threatened Therefore, the number of tourists visiting Hoi An is significantly decreasing, losing the great amount of money that invested to build infrastructure along coastline In Hoi An, tourism accounts for 64% of the total municipal revenue, and it is also the province’s main source of income In 2013, Quang Nam province’s tourism earned up to 170 million USD, which is approximately 10 per cent of the gross provincial product (Vietnam News, 2013) Hoi An also contributes about 40 million USD (UNESCO, 2008) Almost local inhabitants live on tourism, hence they are affected by coastal erosion on their livelihood In the world, climate change is a global problem This could also influence on the coastal area of Hoi An According to ASEC Consultants (2014), sea level rise around Hoi An will be 5mm per year They predicted that a quarter of the Hoi An area will be regularly flooded in 2020 Beside, typhoon tends to move toward the south along the country’s coastal line The combination between extreme events, such as storm surge, tide and sea level rise leads to more severe coastal erosion According to Marcel Stive (2015), there is a difference in sediment volume between the loss of sediment on the northern beaches and the gain of sediment on the southern beaches He claimed that the newest situationin 2015 is shown in Figure 12 in Hoi An They illustrate part of the morphology situation that happened there Figure 1-2 Erosion on study area (Hoi An Project)1 The Dutch master student group from Tu-Delft University took the pictures on the field site Thus, the study area needs to assess the problem in a careful way to support the decision making process for an effective solution 1.3 Literature review Long-term prediction of coastal erosion can be done based on one-line model theory This research is intended to apply this kind of model to study the coastal erosion in Hoi An and propose the solution to cope with it One of the commonly used one-line model is GENESIS (Hanson and Kraus, 1989) GENESIS can simulate successfully the evolution of coastline being make up a great volume of fine-grained sediment transport Chantal et al (2004) compared equilibrium beach profiles which the processes in surf zone not affect and affect to calculate the deviation of fine material The continuity equation of sediment transport in GENESIS was adjusted represent the volume of these losses Existing dykes in Hai Hau, Nam Dinh province was simulated in GENESIS as seawalls that erosion in the past the dykes were prevent Murray and Ashton (2004) explored coastline evolution under such wave climates using a one-line model require some alterations to avoid discretization artefacts related to high-angle waves, and allow complex shoreline structures to emerge in the model However, it does not imply that these solutions are unique; other approaches to solving these problems are certainly possible Regarding Hoi An coastline, there are some researches have done related to the erosion problem or the surrounding study area In Hoi An, the beach north of Cua Dai estuary has been eroding severely Pre-built coastal structures significantly affect the adjacent beaches Viet and Tanaka (2015) claimed that the main cause of erosion in Cua Dai beach is due to the hydropower reservoirs and dams built upstream which are keeping a great amount of sediment upstream of the dams As a result, lack of sediment supplies to downstream It is considered as the highly possible mechanism of erosion Concerning the three researches above, they just simulate very well type of smooth coastline, but they can mention rough coastlines that changing strongly angle of coastline, and the coastlines are influenced significantly by river mounts According to Long et al (2013), the annual runoff is quite abundant in the Vu GiaThu Bon river basin, but it unequally distribute in space and time The flow regime in the study area is impacted significantly in both negative and positive ways by the construction of reservoir system upstream in order to exploit water resource efficiently They assessed the cause of erosion from upstream due to building hydropower plants and the loss of a great volume of sediment supply to the coasts adjacent the Thu Bon estuary 1.4 Study objectives The main objective of this research is to increase the fundamental understanding on the physical regime influencing the evolution of the coastline Specifically, the study is aimed to get further insight into the parameters which are the most sensitive to the coastline change in Hoi An in order to propose an effective countermeasure to cope with the coastal erosion problem To achieving the research goal, the following questions have to be answered during research: - What is the main factors influencing the evolution of the Hoi An coastline? - How will the Hoi An coastline tend to change in next 20, 50 years? - What is an effective solution to deal with the erosion of the Hoi An coastline? 1.5 Approach and methodology The research questions can be answered and the objectives can be achieved by means of a numerical coastline evolution model In this research, the Generic 73 74 75 76 77 78 79 80 81 82 83 84 Appendix B Wave windows for groin system scenario 863152.5965 1758793.061 -10 120 854137.2597 1765365.523 -10 120 861454.5804 1760129.441 -10 120 861455.5804 1760128.441 0 862071.2607 1759755.414 0 862072.2607 1759754.414 -10 120 862601.4994 1759402.192 -10 120 862602.4994 1759401.192 0 862822.2134 1759191.944 0 862823.2134 1759190.944 -10 120 863280.4734 1758658.726 -10 120 863281.4734 1758657.726 0 863442.4151 1758425.306 0 863443.4151 1758426.306 -10 120 863447.4151 1758430.306 -10 120 Wave windows for breakwater scenario 85 863152.5965 1758793.061 -10 120 854137.2597 1765365.523 -10 120 861454.5804 1760129.441 -10 120 862486.7116 759480.4653 -10 45 862488.6180 1759479.1616 0 862488.6179 1759479.1615 0 862488.6180 1759477.6940 45 86 862558.8421 1759431.1332 28 74 962645.6033 1759360.2545 37 47 862646.3337 1759359.5589 0 862646.3338 1759359.5588 0 862647.2609 1759358.6759 47 92 862712.4700 1759296.4730 21 77 862807.9084 1759205.6808 44 62807.9132 1759205.6761 -10 44 862807.9133 1759205.6762 0 862807.9134 1759205.6761 0 862807.9142 1759205.6752 44 90 862948.2414 1759147.1719 21 75 862948.2885 1759063.1395 0 862948.3355 1759063.0914 0 862948.2356 1759063.0913 44 88 86 863007.1243 1759002.9734 21 71 863074.2488 1758934.3312 21 46 863074.2500 1758934.3300 0 863074.2501 1758934.3299 0 963074.2520 1758934.3279 46 101 863133.1821 1758855.7117 21 84 863195.0603 1758773.1632 57 863195.1262 1758773.0752 0 863195.1260 1758773.0753 0 863195.2289 1758772.9382 57 101 863250.6305 1758699.0298 33 85 863314.0429 1758612.2744 11 58 863314.0450 1758612.2714 0 863314.0451 1758612.2713 0 863314.0452 1758612.2712 58 120 863447.4151 1758430.306 -10 120 87 ... Model (Roelvink and Reniers, 2011) will be utilized to model the coastline evolution for Hoi An The Generic Coastline Model is an one- line model which allow to predict the coastline change in a long-term... influencing the evolution of the Hoi An coastline? - How will the Hoi An coastline tend to change in next 20, 50 years? - What is an effective solution to deal with the erosion of the Hoi An coastline? ... beach and the ancient town of Hoi An are located in Quang Nam province in the middle of Vietnam They play great important roles in economic development of Quang Nam province, Vietnam Hoi An city