Climate Change Driven Variations in Future Longshore Sediment Transport Rates along the Coast of Vietnam Rev.4 March 2014 Authors : Supott Thammasittirong (AIT) Sutat Weesakul (AIT) Ali Dastgheib (UESCO-IHE) Roshanka Ranasinghe (UESCO-IHE)
Executive Summary Introduction This report presents the results of the study on Climate Change driven variations in longshore sediment transport rates along the coast of Vietnam. The project was funded by Ministry of environment and infrastructure of the etherlands. Vietnam has been identified by the International Panel on Climate Change (IPCC, 2007, 2014) as one of the countries that might be most affected by climate change. In particular the Mekong and the Red River deltas, with their extremely high population density in low lying areas, are severely threatened by sea level rise and anticipated increases in the frequency and intensity of typhoons and storms. The coastline of Vietnam is presently severely eroded and mangrove forests are reduced in area and density by severe storms and sea level rise. The coastline of Vietnam is 3,260 kilometers long and consists of 114 river mouths, 48 Bays, 12 lagoons, and 3000 islands. Impacts of changing climate in the coastal zone are already threatening people s livelihoods as well as the ecological system. Out of the many potential climate change (CC) impacts on coasts, the one impact that has received most attention is coastline recession due to sea level rise (SLR), while little or no attention has been given to other potential coastal CC impacts. Recent sutidies has highlighted that other CC impacts may in fact override the SLR impact on coasts (Stive et al., 2009; Ranasinghe and Stive, 2009; Ranasinghe et al., 2013). One such potentially severe CC impact that has not been sufficiently investigated is the coastal response to CC driven variations in offshore wave characteristics. Since longshore sediment transport is a direct function of breaking wave height and direction, assessment of CC on the longshore sediment is now possible for the Vietnamese coast due to a recent study of "Climate Change driven variations in the wave climate along the coast of Vietnam" funded also by Ministry of environment and infrastructure of the etherlands. Changes in longshore sediment transport rates will determine the coastline evolution in medium to long term time scales (i.e. 1-100 years) and spatial scales (i.e. 1-100 km). Objective The main objective of this study is to evaluate the impact of climate change on the large scale longshore sediment transport rates along the coast of Vietnam. Methodology Wave characteristics are the most important input data for the calculation of longshore sediment transport. The previous study on "Climate Change driven variations in the wave climate along the coast of Vietnam" compared the present (1981-2000) and the future (2081-2100) offshore wave climate at several locations along Vietnam coast using downscaled output from two global climate models (ECHAM and GFDL). i
In the present study, the 1981-2000 and 2081-2100 offshore wave climate derived from the aforementioned study are used to determine the nearshore wave climate for both time slices for 22 different coastline sections along the coast of Vietnam (Figure E-1). This was done by using the spectral wave model SWA model. The nearshore wave climate for the present time slice (1981-2000) is used as the input to the GEESIS model to estimate annual average longshore sediment transport at these 22 coastline sections. These model estimates were verified with reported longshore sediment transport rates as far as possible. The verified GEESIS model was then forced with the nearshore wave climate for 2081-2100 to estimate future climate change modified longshore sediment transport along the Vietnam coast. Figure E-1 Locations of 22 selected coastal sections along the Vietnam coastline. ii
Results The computed results indicate that the volume and direction of longshore sediment transport along the coast of Vietnam is rather variable. For present conditions, the annual average results from ECHAM and GFDL wave climate at 22 costal sections are found to be in the range of 11,000-2,748,000 m 3 /year in total gross transport and 1,400-1,426,000 m 3 /year in net transport in a northerly direction (at coastal section S2, S4 and S18-S21) and 35,000-2,740,000 m 3 /year in net transport in a southerly direction (at coastal section S1, S3, S5-S17 and S22). For future conditions, the annual average results at the 22 costal sections are in the range of 10,000-3,403,000 m 3 /year in total gross transport and 2,000-1,569,000 m 3 /year in net transport in a northerly direction (at coastal section S4, S9, S18-S21) and 500-3,174,000 m 3 /year in net transport in a southerly direction (at coastal section S1-S3, S5-S8, S10-S17 and S22). The estimated results of longshore sediment transport rates for the present (1981-2000) and future (2081-2100) show significant changes in net longshore sediment transport rates along the coast of Vietnam, with upto 0.5 million m 3 /year increase in the net transport rate at some locations. Such large changes in longshore sediment transport rates can lead to significant future variations in the position and orientation of the Vietnamese coastline. The results are summarized in Table E-1. The magnitude of the change and its foreseen effect on the coastline emphasizes the urgent need for detailed coastal morphological studies and quantitative risk assessments at sensitive coastal areas along the coast of Vietnam. This appears to be particularly the case in the vicinity of Danang (coastal sections 17, 18 and 19) due to the large projected future changes in longshore sediment transport direction and magnitude in this area, with an additional 875,000 m 3 of sand being transported away from this area per year. iii
Table E.1 Changes in net sediment longshore sediment transport due to climate change at 22 coastal sections along the Vietnam coastline. Coastal section S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 Description The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 62%, in the order of 30,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the south. The magnitude will decrease with about 7% in order of 1,000 m 3 /year in the southerly direction The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 34%, in the order of 125,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the south. The magnitude will decrease with about 28% in order of 2,000 m 3 /year in the southerly direction The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 50%, in the order of 122,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 37%, in the order of 113,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 40%, in the order of 78,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 30%, in the order of 145,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the north. The magnitude will increase with about 240% in order of 162,000 m 3 /year in the northerly direction The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 7%, in the order of 80,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 22%, in the order of 155,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 30%, in the order of 176,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 16%, in the order of 434,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 23%, in the order of 131,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 9%, in the order of 170,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 15%, in the order of 105,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 23%, in the order of 460,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 45%, in the order of 290,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 10%, in the order of 124,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 15%, in the order of 170,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 20%, in the order of 113,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the north. The magnitude will increase by about 60% in order of 5,000 m 3 /year in the northerly direction iv
Table of Contents Executive Summary.... i Table of Contents. v List of Tables. vi List of Figures... viii 1 Introduction... 1 1.1 Background. 1 1.2 Statement of the Problems......... 1 1.3 Objectives of the Study...... 2 1.4 Scope of the Study... 2 2 Methodology.. 3 2.1 Methods... 3 2.2 GEESIS........ 5 2.3 Computation of Longshore Sediment Transport for the Coast of... Vietnam 6 3 Results and Discussion 15 3.1 Model Calibration... 15 3.2 Modeling Results of Present Longshore Sediment Transport Rates... 20 3.3 Modeling Results of Future Longshore Sediment Transport Rates 28 4 Conclusions....... 40 v
List of Tables Table Page 2.3-1 Summary characteristics of the 22 coastal sections along the Vietnam 7 coastline 3.1-1 Comparison of computed and reported net longshore sediment 18 transport rates at coastal section S1, S19, S20 and S22 3.1-2 Comparison of computed and reported gross longshore sediment 18 transport rates at coastal section S1, S19, S20 and S22 3.2-1 Summary of computed net longshore sediment transport rates for 21 present ECHAM wave climate 3.2-2 Summary of computed gross longshore sediment transport rates for 22 present ECHAM wave climate 3.2-3 Summary of computed net longshore sediment transport rates for 23 present GFDL wave climate 3.2-4 Summary of computed gross longshore sediment transport rates for 24 present GFDL wave climate 3.2-5 Summary of average net and gross longshore sediment transport rate 25 calculated from GEESIS for present period along Vietnam coast 3.3-1 Summary of computed net longshore sediment transport rates for future 30 ECHAM wave climate 3.3-2 Summary of computed gross longshore sediment transport rates for future 31 ECHAM wave climate 3.3-3 Summary of computed net longshore sediment transport rates for future 32 GFDL wave climate 3.3-4 Summary of computed gross longshore sediment transport rates for future 33 GFDL wave climate 3.3-5 Summary of average net and gross longshore sediment transport rate 34 calculated from GEESIS for future period along the Vietnam coast vi
Table (Cont d) Page 3.3-6 Future change in computed average net longshore sediment transport 34 rate from ECHAM and GFDL 3.3-7 Future change in computed average gross longshore sediment transport 35 rate from ECHAM and GFDL 4-1 Changes in net sediment longshore sediment transport at 22 coastal 41 sections along the Vietnam coastline due to climate change. vii
List of Figures Figure Page 2.1-1 Locations at which future CC modified wave climate was obtained 4 2.3-1 Locations of 22 coastal sections along the Vietnam coastline for 8 GEESIS model simulation 2.3-2 Wave rose diagrams from ECHAM climate model for the present period 9 (1981-2000) 2.3-3 Wave rose diagrams from GFDL climate model for the present period 12 (1981-2000) 3.1-1 Locations of the previous research studies area 16 3.1-2 Comparison plots of net longshore sediment transport rates 19 3.1-3 Comparison plots of gross longshore sediment transport rates 19 3.2-1 Computed average net longshore sediment transport rates at 25 22 locations along Vietnam coast for present wave climate (1981-2000) 3.2-2 Computed average gross longshore sediment transport rates at 27 22 locations along Vietnam coast for present wave climate (1981-2000) 3.3-1 Estimates of present and future average net longshore sediment 35 transport rates at 22 costal sections 3.3-2 Estimates of present and future average gross longshore sediment 37 transport rates at 22 costal sections 3.3-3 Future change in average net longshore sediment transport rates at 38 the 22 costal sections along Vietnam Coast 3.3-4 Future change in average gross longshore sediment transport rates at 39 the 22 costal sections along Vietnam Coast viii
CHAPTER 1 ITRODUCTIO 1.1 Background Vietnam has been identified by the International Panel on Climate Change (IPCC, 2007, 2014) as one of the countries to be most affected by climate change. In particular the Mekong and the Red River deltas with their extremely high population density in low lying areas are severely threatened by sea level rise and anticipated increases in the frequency and intensity of typhoons and storms. The coastline of Vietnam is 3,260 kilometres long and consists of 114 river mouths, 48 Bays, 12 lagoons, and 3000 islands. About 18 million people, almost a quarter of the total population, live in the coastal districts of Vietnam. Impacts of changing climate in the coastal zone are already threatening people s livelihoods as well as the ecological system. Coastlines are severely eroded and mangrove forests are reduced in area and density by stronger storms and sea level rise. During the last 50 years, the sea level along Vietnam's coastline has risen by approximately 20 cm, while the tropical cyclone frequency has increased by 2.15 events per 50 years. Over the last 50 years, consistent coastal erosion has been observed at 397 sites, covering a total coastline length of 1,000 km, at an average rate of 5-10 m/yr, although at some locations long term erosion rates as large as 30-50 m/yr have been reported. Most of the coastline in the south has been eroded continuously at a rate of approximately 50 m/year since the early twentieth century (Cat et al., 2006, Mazda, Y. et al., 2002). This massive erosion is mostly due to wave and current action and the vanishing mangrove vegetation. Significant erosion also occurs in the central coastal zone of Vietnam and preventive measures such as sea dykes, revetments, and tree plantations have been implemented in many coastal areas. Of the many potential climate change (CC) impacts on coasts, the one impact that has received most attention is coastline recession due to sea level rise (SLR), while little or no attention has been given to other potential coastal CC impacts. Recent literature has highlighted that other CC impacts may in fact override the SLR impact on coasts (Stive et al., 2009; Ranasinghe and Stive, 2009; Ranasinghe et al., 2013). One such potentially severe CC impact that has not been sufficiently investigated is the coastal response to CC driven variations in offshore wave characteristics. Assessment of this phenomenon is now possible for the Vietnamese coast due to a recent study of "Climate Change driven variations in the wave climate along the coast of Vietnam CCWaves Vietnam" funded via the I&M-IHE MoU. Using state-of-the-art Global climate model output, dynamic downscaling and wave modelling, CCWaves-Vietnam has provided future projections for CC modified average wave conditions along the entire Vietnam coast. 1.2 Statement of the Problems As longshore sediment transport is a direct function of breaking wave height and direction, any future CC driven changes in these wave characteristics will have a profound impact on longshore sediment transport rates, and therefore on coastlines, particularly at medium to long term time scales (i.e. 1-100 years) and medium to large spatial scales (i.e. 1-100 1
km). For example, persistent alongshore gradients in longshore sediment transport (even small gradients) could result in chronic impacts such as coastline recession (Cowell et al., 2003a, 2003b; Komar, 1998), inlet migration (FitzGerald, 1988), ebb/flood delta depletion/accretion (Oertel, 1972) etc. Most, if not all, of these impacts are generally considered as negative impacts by coastal managers/planners, and thus, over the last 50 years or so, there has been an enormous amount of research effort expended on developing robust methods and tools to accurately predict longshore sediment transport rates for given wave conditions. The one-line longshore transport model (GEESIS) will be used in this study to calculate the present and future longshore sediment transport rates along the entire coast of Vietnam by using the offshore wave conditions determined in the previous CCWaves-Vietnam study. 1.3 Objectives of the Study The main objective of this study is to investigate the broad scale longshore sediment transport rates for the coast of Vietnam and evaluate the effect of climate change on future longshore sediment transport rates using projected average offshore wave conditions determined in the previous CCWaves-Vietnam study. 1.4 Scope of the Study In order to achieve the objectives, the scope of study can be defined as follows: 1) The present (1981-2000) and future (2081-2100) of ECHAM and GFDL wave climate determined in the previous CCWaves-Vietnam study will be used as wave input data in the GEESIS model. 2) The longshore sediment transport rates will be calculated by the GEESIS model at the 22 selected coastal locations along the Vietnam coastline. 2
CHAPTER 2 METHODOLOGY 2.1 Methods Wave characteristics are the most important input data for the calculation of longshore sediment transport. The CCWaves-Vietnam study derived the future (2081-2100) CC modified wave climate at 10 more or less equally spaced locations along Vietnam coast (Figure 2.1-1). To achieve this, CCWaves-Vietnam adopted the spectral wave model, MIKE21 SW, which was forced with climate model (ECHAM and GFDL) derived winds for the A2 greenhouse gas (GHG) scenario, dynamically downscaled using CSIRO s (Australia) CCAM stretched grid model for three time slices; 1981-2000, 2041-2060 and 2081-2100. The A2 scenario is a high end GHG scenario and thus represents a worst case situation. The output consisted of 6 hourly significant wave height, wave period and wave direction for the present (1981 to 2000) and the future (2041 to 2060 and 2060 to 2100). In this study we will first use the above described 1981-2000 wave conditions to calculate contemporary longshore sediment transport rates using a process based longshore transport model (GEESIS model) at the nearshore coastal locations corresponding to the above mention 10 offshore wave locations, and verify model results with reported longshore sediment transport rates at these locations (i.e. model validation). Subsequently, projected wave conditions for the 2081-2100 time slice will be used in the validated model to derive estimates of future CC modified longshore sediment transport rates at the selected coastal locations along the Vietnam coastline. The main steps of the methodological procedure that will be adopted are summarized below: Step 1: Offshore wave characteristics (~ 50km offshore) will be obtained from the previous CCWaves-Vietnam study for the present (1981-2000) and future (2081-2100) time slices at 10 more or less equally spaced locations along the coast of Vietnam (see Figure 2.1-1). Step 2: The SWA model, which is based on the deep water third generation wave model (WAM model), will be used to transform the offshore wave data to the nearshore wave data which can be used in GEESIS. Step 3: The wave characteristics for the present time slice will be used in GEESIS to obtain annual average longshore sediment transport estimates at 22 selected nearshore locations. These model estimates will then be verified with reported longshore sediment transport rates at or near the selected locations as far as possible. The model will be iteratively calibrated until the best possible match between modelled and reported longshore sediment transport rates is achieved. This will result in a validated GEESIS Model which can then be used confidently to obtain forecasts. 3
Step 4: The validated GEESIS model will be forced with nearshore wave characteristics for the future time slice to obtain the rates of potential sediment transport for 2081-2100. Step 5: Longshore sediment transport rates predicted for the two time slices will be subjected to a sophisticated statistical analysis to determine areas along the Vietnam coast where CC may result in significant changes in longshore sediment transport rates and subsequent changes in the coastline Figure 2.1-1 Locations at which future CC modified wave climate was obtained 4
2.2 GEESIS GEESIS, developed by Coastal Engineering Research Center (CERC), US Army Corps of Engineers, is designed to simulate long-term shoreline change on an open coast, as produced by spatial and temporal differences in longshore sand transport (Hanson 1987, 1989; Hanson and Kraus 1989). The name GEESIS is an acronym that stands for GEEralized model for Simulating Shoreline Change. The modeling system is founded on considerable research and applications of shoreline change numerical models. Wave action is the mechanism producing the longshore sand transport, and, in GEESIS, spatial and temporal differences in the transport rate may be caused by such diverse factors as irregular bottom bathymetry, wave diffraction, boundary conditions, line sources and sinks of sand. There are also constraints on transport (such as seawalls and groins). These factors are interrelated and may work in different combinations at different times. The GEESIS model is generalized in that it allows simulation of a wide variety of userspecified offshore wave inputs, initial beach plan shape configurations, coastal structures, and beach fills. Input to the model is the shoreline position, beach profiles and a time series of significant wave height, significant wave period, and the direction. Based on these data, the model calculates wave breaking properties, longshore sediment transport rates, and shoreline positions. The empirical predictive formula for the long-shore sand transport rate used in this model is: Q = (H 2 C g ) b [a 1 sin θ bs a 2 cos θ bs H x ] b (2.1) where H is the wave height (m), C g is the wave group speed given by linear wave theory, b subscript denoting wave breaking condition and θ bs is the angle of breaking waves to the local shoreline and the non-dimensional parameters a 1 and a 2 are given by: k 1 a 1 = 16 ( ρ s ρ 1)(1 p) (1.416 5 2) and (2.2) a 2 = k 2 8 ( ρ s ρ 1)(1 p) tan β (1.416 7 2) where k 1 and k 2 are the empirical coefficient which treated as the calibration parameters, ρ s is the density of sand (taken to be 2.65x10 3 kg/m 3 for quartz sand), ρ is the density of water (1.03x10 3 kg/m 3 for sea water), p is the porosity of sand on the bed (taken to be 0.4) and tan β is the average bottom slope from the shoreline to the depth of active longshore sand transport. 5
2.3 Computation of Longshore Sediment Transport for the Coast of Vietnam The GEESIS model is applied to compute the longshore sediment transport rates for the coast of Vietnam. The study area covers 22 selected sandy coastal sections starting from the south to the north of Vietnam s coast (S1 to S22) as shown in Figure 2.3-1. This model is a one-dimensional model grid system where to the north, south and east of the study domain is the sea, while to the west is the land. In order to employ GEESIS for sediment transport computations, the initial data of coastline position, offshore/nearshore wave and other parameters must be obtained. - Coastline Position The actual coastline shape (position) of each of the 22 coastal sections considered is simplified to a straight coastline (with coastline orientation obtained from Google Earth) with the assumption that there are no changes in coastline position or effects of structures such as groins, offshore breakwaters and revetments within each section. - Wave Data Offshore wave data obtained from the previous CCWaves-Vietnam study at 10 more or less equally spaced locations along the coast of Vietnam (see Figure 2.1-1), were transformed through wave propagation modelling (SWA model). The nearshore positions are located outside the region of breaking waves such that the wave parameters extracted can be applied to calculate longshore sediment transport. The significant wave height, significant wave period and wave direction from two climate models (GFDL and ECHAM) for the present (1981-2000) and future (2081-2100) time slices at the nearest grid points to the 22 coastal sections of the study area provided by SWA model, were be used as input data for GEESIS model. The wave rose diagrams of the significant wave height at each coastline sections for present period during 1981-2000 are shown in Figure 2.3-2 and 2.3-3, while the results for the future period during 2081-2100 are shown in Appendix A. The wave rose diagrams show that along the coast of Vietnam the wave direction is very dominantly from northeast to east corresponding to the northeast monsoon. The wave height and frequency of waves due to the northeast monsoon are also the strongest. - Other input parameters Other input parameters such as mean sediment grin size d50, beach profiles, berm height and depth of closure were obtained from available projects. The summary characteristics of the 22 coastal sections (S1 to S22) are presented in Table 2.3-1. 6
Table 2.3-1 Summary characteristics of the 22 coastal sections along the Vietnam coastline. Length of coastal Water depth at input Mean sediment Section Coastline orientation section waves grin size d 50 o. (km) (degree) (m) (mm) S1 83.5 151.8 26 0.25 S2 16.1 184.2 29 0.25 S3 26.2 116.7 29 0.25 S4 10.6 184.7 29 0.25 S5 76.4 144.7 27 0.25 S6 25.4 97.9 29 0.25 S7 19.1 118.3 26 0.25 S8 34.6 55.5 38 0.25 S9 9.2 53.9 47 0.25 S10 11.7 62.0 39 0.25 S11 10.3 64.4 27 0.25 S12 11.3 58.6 22 0.25 S13 6.2 91.9 22 0.25 S14 15.6 65.9 20 0.25 S15 9.4 82.3 20 0.25 S16 46.5 65.0 27 0.25 S17 6.5 110.4 21 0.25 S18 117.6 48.3 29 0.25 S19 139.5 37.6 25 0.25 S20 111.8 46.1 26 0.25 S21 120.0 48.1 28 0.25 S22 114.0 97.7 25 0.25 7
Figure 2.3-1 Locations of 22 coastal sections along the Vietnam coastline for GEESIS model simulation 8
68.61 % Coastal Section S1 65.48 % Coastal Section S2 61.33 % Coastal Section S3 61.33 % Coastal Section S4 56.79 % Coastal Section S5 64.1 Coastal Section S6 72.19 % Coastal Section S7 53.18 % Coastal Section S8 Figure 2.3-2 Wave rose diagrams from ECHAM climate model for the present period (1981-2000) 9
51.1 Coastal Section S9 50.90 % Coastal Section S10 50.60 % Coastal Section S11 51.84 % Coastal Section S12 51.84 % 50.72 % Coastal Section S13 Coastal Section S14 Figure 2.3-2 (cont d) Wave rose diagrams from ECHAM climate model for the present period (1981-2000) 10
50.72 % Coastal Section S15 50.33 % Coastal Section S16 50.37 % 51.44 % Coastal Section S17 Coastal Section S18 51.52 % Coastal Section S19 51.59 % Coastal Section S20 64.81 % 56.17 % Coastal Section S21 Coastal Section S22 Figure 2.3-2 (cont d) Wave rose diagrams from ECHAM climate model for the present period (1981-2000) 11
71.72 % 68.34 % Coastal Section S1 Coastal Section S2 63.14 % Coastal Section S3 63.14 % Coastal Section S4 57.78 % 67.57 % Coastal Section S5 Coastal Section S6 77.02 % Coastal Section S7 53.46 % Coastal Section S8 Figure 2.3-3 Wave rose diagrams from GFDL climate model for the present period (1981-2000) 12
50.77 % Coastal Section S9 50.70 % Coastal Section S10 50.48 % Coastal Section S11 51.89 % Coastal Section S12 51.89 % 50.89 % Coastal Section S13 Coastal Section S14 Figure 2.3-3 (cont d) Wave rose diagrams from GFDL climate model for the present period (1981-2000) 13
50.89 % 50.37 % Coastal Section S15 Coastal Section S16 50.40 % 51.57 % Coastal Section S17 Coastal Section S18 51.64 % 52.08 % Coastal Section S19 Coastal Section S20 58.73 % 69.67 % Coastal Section S21 Coastal Section S22 Figure 2.3-3 (cont d) Wave rose diagrams from GFDL climate model for the present period (1981-2000) 14
CHAPTER 3 RESULTS AD DISCUSSIO 3.1 Model Calibration The computed longshore sediment transport rates from this study will be compared with longshore sediment transport rates reported in literature at or near the selected locations for the present time slice (1980-2000). There are various research studies of longshore sediment transport for the coast of Vietnam, but most of them are focused on the central coast of Vietnam, especially at the coast of Thua Thien-Hue province. Estimations of longshore sediment transport rates at some areas along the coast of Vietnam from previous research studies are selected for model calibration and comparison as shown in Figure 3.1-1. The results of these previous research studies can be summarized as follows: (1) orthern coast of Vietnam at Hai Hau Beach (am Dinh province) Hung et al. (2006) computes the longshore sediment transport at Hai Hau beach using the program SEDTRA with input wave conditions during 2001-2005. The estimated net sediment transport is 63,000 m 3 /year in a southwest direction (which agrees with the enlargement of the sand spit toward the southwest and the southwest overlapping of the bypass bar in the inh Co mouth), while the gross transport is 490,000 m 3 /year. In the present study, the GEESIS model was used for shoreline change simulation at Hai Hau beach with calibration parameters k 1 = 0.80 and k 2 = 0.40. The best fit between calculated and measured coastline positions for the period from 1912 to 1965 and 2001 to 2005 was determined for model calibration and verification, respectively. (2) Central coast of Vietnam at Thua Thien Hue province and Quang Binh province Tran Quang Tien (2004) calculates the longshore sediment transport in littoral zone of Vietnam Central using the Bijker method, CERC method and the improved method based on the Meyer-Peter formula with 2002 hindcasted waves. The computed results at Thuan An area (Thua Thien Hue province) was found to be in the range of 600,000-1,100,000 m 3 /year in total gross transport and 400,000-700,000 m 3 /year in net transport in a northwest direction while the net transport at Hai Duong (Thua Thien Hue province) and gu Thuy (Quang Binh province) is about 1,500,000 m 3 /year and 900,000 m 3 /year in a northwest direction, respectively. In the present study, the GEESIS model was used for shoreline change simulation at Thuan An beach with calibration parameters k 1 = 0.75 and k 2 = 0.50. The result of GEESIS agreed well with recent observed trend along this shoreline. 15
Hai Hau Beach gu Thuy Hai Duong Thuan An Beach Tat Channel LEGED Coastal sections of this study area Previous research study area Figure 3.1-1 Locations of the previous research studies area 16
Lam (2009) evaluates different measurements and calculations of the longshore sediment transport for the coast of Thua Thien Hue done by different authors through the years 1970-2004. The most reasonable results (with an agreement with the development of the sand spit and dredge records) is found to be in the range of 600,000-1,600,000 m 3 /year in total gross transport and 300,000-700,000 m 3 /year in net transport in a northwest direction. (3) Southern coast of Vietnam at Tat channel, near Mekong delta Q.T.Doan et al. (2013) presents the calculation results of littoral sediment transport at Tat channel (Phu Long province) using the LITDRIFT model with input wave condition during 9 years from 1999 to 2008. The estimated net sediment transport was found to be in the range of 150,000-170,000 m 3 /year in a southwest direction. The sediment transports in the present time slice (1980-2000) at or near the above selected locations, which are coastal section S1, S19, S20 and S22, were computed by the GEESIS model. First, the calibration parameters k 1 and k 2 were set equal to the values of previous studies and has finally been adjusted after comparing the computed results of net and gross longshore sediment transport rates between this study and the previous studies. The selected values of the calibration parameters k 1 and k 2 are shown in the following table: Coastal Section k 1 k 2 S1 0.95 0.50 S19 0.65 0.50 S20 0.75 0.50 S22 0.80 0.40 The computed results of net and gross longshore sediment transport rates from the GEESIS model at these coastal sections and corresponding reliable estimated values reported in literature are summarized in Table 3.1-1 and Table 3.1-2. The comparison plots of longshore sediment transport rates between the computed results and the reported values are shown in Figure 3.1-2 and 3.1-3. The computed results of longshore sediment transport rates seem to vary annually and depend on the wave climate condition (ECHAM or GFDL) and coastline orientation as well. However, there is reasonable quantitative agreement between the computed results and the reported values. Difference in methods and period of computation, coastline orientation and wave climate condition are the main reasons that cause the difference of longshore sediment transport rates between this study and previous studies. For example, at Thuan An beach (located in coastal section S19), the previous study of Tran Quang Tien in 2004 were used hindcast wave in 2002 as input data for the calculation of longshore sediment transport by CERC, Bijker, and Meyer-Peter improved method. While in this 17
study, the 1981-2000 of ECHAM and GFDL wave climate data were used as input data in GEESIS model to compute longshore sediment transport rate. Thus, the above k 1 and k 2 values were used as calibration coefficients in GEESIS with input ECHAM and GFDL wave climate to calculate annual longshore sediment transport at other coastal sections for the present (1981-2000) and future (2081-2100) time slices. Table 3.1-1 Comparison of computed and reported net longshore sediment transport rates at coastal section S1, S19, S20 and S22. Study Area Estimates of Q net (m 3 /yr)* Coastal This study earby area section ECHAM wave GFDL wave Previous study S1 Tat channel 33,000 to 102,000 9,000 to 77,000 150,000 to 170,000 S19 Thuan An -786,000 to -1,772,000-721,000 to -1,703,000-300,000 to -700,000 beach S19 Hai Duong -786,000 to -1,772,000-721,000 to -1,703,000-1,500,000 S20 qu Thuy -768,000 to -1,725,000-684,000 to -1,579,000-900,000 S22 Hai Hau beach -21,000 to 71,000 5,000 to 111,000 63,000 ote: (*) the positive transport direction is southward Table 3.1-2 Comparison of computed and reported gross longshore sediment transport rates at coastal section S1, S19, S20 and S22. Study Area Estimates of Q gross (m 3 /yr) Coastal This study earby area Previous study Section ECHAM wave GFDL wave S1 Tat channel 96,380 to 168,000 73,892 to 151,000 /A S19 Thuan An beach 787,000 to 1,772,000 721,000 to 1,705,000 600,000 to 1,600,000 S19 Hai Duong 787,000 to 1,772,000 721,000 to 1,705,000 /A S20 qu Thuy 769,000 to 1,727,000 686,000 to 1,580,000 /A S22 Hai Hau beach 77,000 to 136,000 53,000 to 152,000 490,000 18
Figure 3.1-2 Comparison plots of net longshore sediment transport rates Figure 3.1-3 Comparison plots of gross longshore sediment transport rates 19
3.2 Modeling Results of Present Longshore Sediment Transport Rates Modeling work of GEESIS was conducted at 22 coastal sections along the coast of Vietnam as shown in Figure 3.1-1. The computed annual net and gross longshore sediment transport rates for the present time slice (1981-2000) at the 22 locations are summarized in Table 3.2-1 to 3.2-4, while the average annual net and gross longshore sediment transport rates are summarized in Table 3.2-5 and shown in Figure 3.2-1 to 3.2-2. The plots of computed average annual net and gross longshore sediment transport rates at 22 locations are shown in Appendix B. The computed results indicate that the magnitude and direction of longshore sediment transport along the coast of Vietnam is rather variable. The annual average results at 22 costal sections from ECHAM wave climate input data are found to be in the range of 12,000-2,780,000 m 3 /year in total gross transport and 900-1,457,000 m 3 /year in net transport in a northerly direction (at coastal section S2, S4, S9 and S18-S21) and 26,000-2,750,000 m 3 /year in net transport in a southerly direction (at coastal section S1, S3, S5-S8, S10-S17 and S22). While, the results from GFDL wave climate input data are found to be in the range of 11,000-2,748,000 m 3 /year in total gross transport and 1,900-1,390,000 m 3 /year in net transport in a northerly direction (at coastal section S2, S4, S18- S21) and 32,000-2,720,000 m 3 /year in net transport in a southerly direction (at coastal section S1, S3, S5-S17 and S22). Comparison of average computed results of annual longshore sediment transport rates from ECHAM and GFDL at each coastal section for 1981-2000 in Figure 3.2-1 and 3.2-2 show that all of them have similar magnitude and direction, except at S9. There are significant temporal variations in the computed annual longshore sediment transport rates from both ECHAM and GFDL wave climates during 1981-2000 as shown in Appendix B. The results from ECHAM wave climate seem to have less fluctuation than the results from GFDL wave climate except during the period 1994-1997. 20
Table 3.2-1 Summary of computed net longshore sediment transport rates for present ECHAM wave climate. Year et Longshore Sediment Transport Rates for Present ECHAM Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 1981 78,000-753 474,000-5,263 314,000 385,000 253,000 367,000-7,000 977,000 585,000 1982 40,128-3,205 267,000-7,348 178,000 216,000 150,000 248,000 31,000 625,000 394,000 1983 54,270 620 349,000-1,790 240,000 287,000 190,000 400,000 40,000 926,000 569,000 1984 38,000 6,301 393,000 5,671 267,000 323,000 196,000 417,000 37,000 1,019,000 604,000 1985 102,000-3,558 568,000-6,793 377,000 462,000 308,000 342,000-87,000 997,000 568,000 1986 86,000-346 509,000-3,268 408,000 430,000 287,000 410,000 33,000 1,195,000 703,000 1987 74,000 1,860 442,000 189 300,000 366,000 241,000 271,000-176,000 841,000 447,000 1988 64,000 381 422,000-2,145 286,000 349,000 229,000 289,000-139,000 839,000 450,000 1989 33,000-1,545 358,000-5,013 206,000 295,000 191,000 231,000-152,000 648,000 343,000 1990 45,000-736 321,000-4,601 191,000 259,000 175,000 189,000-155,000 523,000 265,000 1991 69,000 260 395,000-3,632 321,000 330,000 223,000 392,000 44,000 1,022,000 619,000 1992 63,000-513 468,000-4,443 310,000 386,000 248,000 581,000 88,000 1,292,000 790,000 1993 47,000-6,843 360,000-11,967 237,000 299,000 202,000 290,000-74,000 775,000 434,000 1994 93,000 4,358 295,000 865 215,000 214,000 158,000 329,000 105,000 797,000 512,000 1995 87,000 1,094 542,000-1,276 413,000 457,000 290,000 539,000 100,000 1,397,000 885,000 1996 58,000-7,602 567,000-12,599 392,000 471,000 292,000 835,000 524,000 1,834,000 1,294,000 1997 66,000-674 400,000-5,673 234,000 316,000 211,000 310,000-87,000 819,000 479,000 1998 43,000-1,680 361,000-5,607 245,000 298,000 192,000 368,000 41,000 924,000 557,000 1999 77,000-1,215 451,000-3,688 297,000 368,000 243,000 273,000-125,000 807,000 440,000 2000 75,000-3,539 481,000-6,662 313,000 391,000 261,000 202,000-191,000 706,000 358,000 Average 64,620-867 421,150-4,252 287,200 345,100 227,000 364,150-7,500 948,150 564,800 ote: the positive transport direction is southward Table 3.2-1 (cont d) Summary of computed net longshore sediment transport rates for present ECHAM wave climate. Year et Longshore Sediment Transport Rates for Present ECHAM Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 1981 436,000 2,767,000 484,000 1,799,000 620,000 2,176,000-861,000-1,156,000-1,135,000-624,000 16,590 1982 297,000 1,738,000 312,000 1,123,000 392,000 1,339,000-537,000-786,000-768,000-438,000 16,093 1983 441,000 2,537,000 464,000 1,651,000 590,000 1,970,000-830,000-1,300,000-1,262,000-678,000 36,275 1984 477,000 2,874,000 467,000 1,818,000 618,000 2,208,000-906,000-1,288,000-1,267,000-727,000 41,000 1985 430,000 3,013,000 488,000 1,945,000 642,000 2,420,000-1,007,000-1,392,000-1,366,000-730,000 15,585 1986 530,000 3,406,000 534,000 2,139,000 713,000 2,615,000-1,000,000-1,343,000-1,307,000-690,000 21,385 1987 305,000 2,730,000 392,000 1,742,000 536,000 2,237,000-988,000-1,291,000-1,271,000-696,000 15,890 1988 314,000 2,673,000 378,000 1,692,000 520,000 2,165,000-951,000-1,256,000-1,242,000-682,000 14,051 1989 241,000 2,146,000 307,000 1,374,000 416,000 1,772,000-807,000-1,099,000-1,086,000-611,000 20,078 1990 179,000 1,804,000 239,000 1,146,000 325,000 1,496,000-706,000-934,000-938,000-520,000-21,250 1991 466,000 3,011,000 448,000 1,854,000 613,000 2,288,000-875,000-1,294,000-1,252,000-674,000 41,000 1992 628,000 3,513,000 639,000 2,283,000 818,000 2,716,000-1,122,000-1,772,000-1,725,000-931,000 58,000 1993 313,000 2,490,000 331,000 1,536,000 459,000 1,968,000-842,000-1,179,000-1,158,000-612,000 8,851 1994 400,000 2,056,000 398,000 1,335,000 496,000 1,544,000-619,000-987,000-951,000-529,000 45,505 1995 666,000 3,867,000 684,000 2,469,000 889,000 2,934,000-1,127,000-1,682,000-1,623,000-841,000 58,000 1996 1,054,000 4,292,000 973,000 2,826,000 1,177,000 3,043,000-974,000-1,621,000-1,544,000-777,000 71,000 1997 336,000 2,644,000 375,000 1,656,000 507,000 2,097,000-935,000-1,295,000-1,284,000-710,000 24,259 1998 424,000 2,579,000 433,000 1,641,000 563,000 1,984,000-830,000-1,236,000-1,202,000-653,000 49,234 1999 311,000 2,559,000 376,000 1,630,000 504,000 2,071,000-900,000-1,251,000-1,253,000-666,000 7,867 2000 244,000 2,383,000 321,000 1,514,000 437,000 1,969,000-864,000-1,088,000-1,105,000-600,000-11,974 Average 424,600 2,754,100 452,150 1,758,650 591,750 2,150,600-884,050-1,262,500-1,236,950-669,450 26,372 ote: the positive transport direction is southward 21
Table 3.2-2 Summary of computed gross longshore sediment transport rates for present ECHAM wave climate. Year Gross Longshore Sediment Transport Rates for Present ECHAM Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 1981 139,000 11,539 493,000 13,162 364,000 389,000 263,000 524,000 531,000 1,107,000 767,000 1982 96,380 11,176 281,000 14,408 226,000 222,000 160,000 367,000 354,000 757,000 538,000 1983 98,549 10,026 365,000 12,361 273,000 292,000 200,000 545,000 518,000 1,046,000 752,000 1984 138,000 21,982 452,000 28,597 362,000 367,000 254,000 594,000 649,000 1,216,000 885,000 1985 148,000 8,331 582,000 11,571 420,000 467,000 319,000 593,000 755,000 1,116,000 821,000 1986 146,000 15,382 524,000 19,644 449,000 434,000 295,000 574,000 587,000 1,308,000 856,000 1987 128,000 10,863 467,000 13,724 343,000 375,000 257,000 414,000 482,000 924,000 608,000 1988 112,000 9,377 440,000 11,144 323,000 356,000 241,000 409,000 476,000 937,000 611,000 1989 115,000 10,309 389,000 13,374 272,000 306,000 214,000 401,000 490,000 764,000 546,000 1990 100,000 13,064 335,000 16,165 233,000 265,000 185,000 334,000 480,000 638,000 478,000 1991 125,000 11,589 413,000 13,527 367,000 336,000 236,000 542,000 545,000 1,143,000 784,000 1992 134,000 11,521 490,000 13,201 368,000 393,000 263,000 702,000 829,000 1,371,000 975,000 1993 105,000 10,200 372,000 14,243 294,000 301,000 212,000 476,000 538,000 923,000 667,000 1994 116,000 12,420 305,000 13,604 237,000 227,000 166,000 500,000 403,000 941,000 678,000 1995 134,000 10,228 562,000 12,496 454,000 466,000 305,000 617,000 563,000 1,441,000 956,000 1996 168,000 12,512 594,000 16,862 473,000 475,000 309,000 939,000 936,000 1,871,000 1,357,000 1997 131,000 13,488 419,000 15,795 290,000 322,000 225,000 506,000 580,000 929,000 672,000 1998 116,000 16,484 390,000 22,259 311,000 314,000 215,000 483,000 454,000 1,038,000 711,000 1999 108,000 7,068 459,000 8,564 320,000 371,000 249,000 431,000 532,000 881,000 580,000 2000 129,000 11,907 494,000 16,073 353,000 394,000 267,000 417,000 494,000 829,000 569,000 Average 124,346 11,973 441,300 15,039 336,600 353,600 241,750 518,400 559,800 1,059,000 740,550 Table 3.2-2 (cont d) Summary of computed gross longshore sediment transport rates for present ECHAM wave climate. Year Gross Longshore Sediment Transport Rates for Present ECHAM Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 1981 629,000 2,786,000 621,000 1,835,000 743,000 2,192,000 863,000 1,157,000 1,135,000 624,000 92,396 1982 440,000 1,771,000 431,000 1,187,000 513,000 1,366,000 551,000 787,000 769,000 438,000 77,638 1983 630,000 2,551,000 600,000 1,678,000 705,000 1,984,000 847,000 1,301,000 1,263,000 678,000 92,439 1984 731,000 2,925,000 711,000 1,951,000 827,000 2,267,000 914,000 1,288,000 1,268,000 727,000 105,000 1985 697,000 3,025,000 663,000 1,967,000 769,000 2,435,000 1,039,000 1,393,000 1,368,000 730,000 91,949 1986 689,000 3,438,000 658,000 2,197,000 824,000 2,645,000 1,005,000 1,344,000 1,308,000 690,000 91,647 1987 493,000 2,743,000 504,000 1,765,000 617,000 2,251,000 989,000 1,291,000 1,271,000 696,000 84,172 1988 495,000 2,690,000 498,000 1,722,000 612,000 2,181,000 959,000 1,256,000 1,242,000 682,000 79,602 1989 461,000 2,160,000 454,000 1,409,000 524,000 1,787,000 830,000 1,100,000 1,087,000 611,000 85,469 1990 408,000 1,842,000 394,000 1,205,000 453,000 1,545,000 712,000 935,000 938,000 520,000 80,090 1991 637,000 3,043,000 589,000 1,915,000 739,000 2,317,000 889,000 1,295,000 1,253,000 674,000 106,000 1992 839,000 3,526,000 768,000 2,304,000 908,000 2,729,000 1,205,000 1,772,000 1,727,000 931,000 136,000 1993 555,000 2,510,000 521,000 1,576,000 612,000 1,987,000 848,000 1,179,000 1,159,000 612,000 87,319 1994 557,000 2,094,000 536,000 1,406,000 635,000 1,579,000 626,000 988,000 952,000 529,000 99,518 1995 751,000 3,876,000 729,000 2,482,000 927,000 2,946,000 1,131,000 1,682,000 1,624,000 841,000 107,000 1996 1,143,000 4,307,000 1,022,000 2,848,000 1,214,000 3,062,000 1,001,000 1,621,000 1,544,000 777,000 115,000 1997 558,000 2,667,000 513,000 1,694,000 616,000 2,120,000 938,000 1,296,000 1,286,000 710,000 96,889 1998 582,000 2,608,000 562,000 1,702,000 675,000 2,005,000 837,000 1,236,000 1,202,000 653,000 96,106 1999 477,000 2,568,000 474,000 1,644,000 576,000 2,080,000 951,000 1,253,000 1,253,000 666,000 78,677 2000 463,000 2,399,000 472,000 1,548,000 554,000 1,982,000 877,000 1,089,000 1,106,000 600,000 79,444 Average 611,750 2,776,450 586,000 1,801,750 702,150 2,173,000 900,600 1,263,150 1,237,750 669,450 94,118 22
Table 3.2-3 Summary of computed net longshore sediment transport rates for present GFDL wave climate. Year et Longshore Sediment Transport Rates for Present GFDL Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 1981 28,000-1,850 310,000-5,578 185,000 260,000 157,000 427,000 157,000 913,000 603,000 1982 46,000-2,536 475,000-7,692 400,000 416,000 259,000 975,000 756,000 1,978,000 1,452,000 1983 35,000-8,334 414,000-13,912 248,000 337,000 201,000 867,000 612,000 1,695,000 1,238,000 1984 66,007 4,275 308,000 2,622 273,000 254,000 172,000 622,000 392,000 1,325,000 910,000 1985 43,000-4,741 462,000-7,581 327,000 385,000 233,000 971,000 680,000 1,950,000 1,418,000 1986 13,000-5,995 300,000-10,879 151,000 244,000 155,000 218,000-14,000 580,000 370,000 1987 14,000-3,435 253,000-8,009 152,000 204,000 134,000 428,000 208,000 915,000 618,000 1988 71,941 7,556 406,000 6,641 287,000 334,000 212,000 588,000 173,000 1,280,000 808,000 1989 9,000-3,924 315,000-9,965 160,000 261,000 162,000 454,000 188,000 937,000 652,000 1990 60,000-4,953 329,000-8,950 187,000 257,000 174,000 212,000-18,000 581,000 356,000 1991 43,845 5,160 211,000 3,537 134,000 161,000 109,000 530,000 372,000 934,000 691,000 1992 74,497 922 460,000-1,090 318,000 376,000 237,000 636,000 285,000 1,418,000 954,000 1993 11,000-6,404 364,000-11,662 175,000 291,000 169,000 867,000 656,000 1,490,000 1,129,000 1994 17,528 217 251,000-5,407 129,000 202,000 127,000 395,000 187,000 785,000 558,000 1995 32,000-3,809 275,000-8,548 140,000 210,000 133,000 547,000 360,000 1,034,000 764,000 1996 20,000-4,293 330,000-8,177 163,000 265,000 162,000 383,000 143,000 795,000 543,000 1997 42,000-1,375 443,000-4,582 302,000 367,000 214,000 905,000 648,000 1,773,000 1,290,000 1998 77,000-4,105 526,000-8,766 376,000 436,000 269,000 779,000 532,000 1,626,000 1,172,000 1999 41,125-7,037 321,000-11,219 154,000 254,000 165,000 246,000 59,000 590,000 413,000 2000 69,210 6,336 343,000 3,569 280,000 279,000 175,000 899,000 754,000 1,728,000 1,296,000 Average 40,708-1,916 354,800-5,782 227,050 289,650 180,950 597,450 356,500 1,216,350 861,750 ote: the positive transport direction is southward Table 3.2-3 (cont d) Summary of computed net longshore sediment transport rates for present GFDL wave climate. Year et Longshore Sediment Transport Rates for Present GFDL Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 1981 499,000 2,292,000 486,000 1,510,000 614,000 1,719,000-602,000-1,100,000-1,045,000-526,000 43,606 1982 1,221,000 4,412,000 1,052,000 2,899,000 1,285,000 3,035,000-724,000-1,691,000-1,562,000-752,000 96,000 1983 1,047,000 3,538,000 968,000 2,433,000 1,143,000 2,456,000-659,000-1,380,000-1,283,000-581,000 45,935 1984 757,000 3,165,000 656,000 2,023,000 848,000 2,242,000-663,000-1,415,000-1,291,000-630,000 85,000 1985 1,186,000 4,177,000 1,095,000 2,836,000 1,319,000 2,909,000-801,000-1,703,000-1,579,000-717,000 69,527 1986 289,000 1,621,000 331,000 1,089,000 414,000 1,282,000-518,000-805,000-775,000-394,000 6,780 1987 510,000 2,177,000 484,000 1,442,000 598,000 1,594,000-563,000-1,075,000-1,010,000-502,000 31,858 1988 654,000 3,281,000 650,000 2,143,000 843,000 2,492,000-920,000-1,617,000-1,526,000-739,000 53,218 1989 530,000 2,179,000 555,000 1,517,000 655,000 1,638,000-607,000-1,088,000-1,035,000-501,000 17,248 1990 266,000 1,637,000 316,000 1,093,000 402,000 1,313,000-520,000-788,000-751,000-408,000 24,143 1991 612,000 1,877,000 553,000 1,316,000 647,000 1,295,000-358,000-1,018,000-953,000-490,000 59,000 1992 770,000 3,394,000 768,000 2,268,000 957,000 2,519,000-853,000-1,509,000-1,417,000-669,000 45,870 1993 987,000 2,738,000 916,000 1,998,000 1,017,000 1,859,000-486,000-1,252,000-1,189,000-545,000 42,610 1994 453,000 1,781,000 466,000 1,243,000 544,000 1,321,000-465,000-844,000-802,000-393,000 11,345 1995 636,000 2,171,000 604,000 1,507,000 691,000 1,513,000-496,000-945,000-894,000-421,000 5,446 1996 446,000 1,877,000 468,000 1,302,000 559,000 1,419,000-502,000-931,000-888,000-434,000 17,532 1997 1,092,000 3,677,000 1,006,000 2,525,000 1,190,000 2,538,000-677,000-1,536,000-1,425,000-654,000 70,000 1998 968,000 3,509,000 917,000 2,402,000 1,079,000 2,479,000-689,000-1,307,000-1,233,000-565,000 39,226 1999 315,000 1,496,000 367,000 1,045,000 433,000 1,163,000-414,000-721,000-684,000-350,000 9,872 2000 1,113,000 3,499,000 967,000 2,371,000 1,157,000 2,329,000-506,000-1,443,000-1,309,000-615,000 111,000 Average 717,550 2,724,900 681,250 1,848,100 819,750 1,955,750-601,150-1,208,400-1,132,550-544,300 44,261 ote: the positive transport direction is southward 23
Table 3.2-4 Summary of computed gross longshore sediment transport rates for present ECHAM wave climate. Year Gross Longshore Sediment Transport Rates for Present GFDL Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 1981 105,000 13,057 348,000 17,129 271,000 276,000 191,000 514,000 481,000 1,054,000 753,000 1982 151,000 17,497 509,000 21,963 479,000 426,000 281,000 1,079,000 1,048,000 2,097,000 1,589,000 1983 108,000 12,460 429,000 17,575 316,000 340,000 214,000 917,000 822,000 1,741,000 1,294,000 1984 92,522 8,839 321,000 9,425 290,000 264,000 179,000 710,000 609,000 1,429,000 1,024,000 1985 119,000 8,693 480,000 11,345 380,000 389,000 244,000 999,000 863,000 1,975,000 1,458,000 1986 121,000 13,689 332,000 18,814 236,000 255,000 175,000 337,000 384,000 672,000 489,000 1987 150,000 12,842 307,000 18,269 262,000 217,000 168,000 585,000 490,000 1,063,000 789,000 1988 91,430 10,138 421,000 10,817 301,000 346,000 223,000 628,000 642,000 1,315,000 875,000 1989 123,000 17,108 349,000 21,722 250,000 266,000 180,000 540,000 521,000 1,002,000 739,000 1990 100,000 8,226 336,000 11,314 225,000 259,000 181,000 313,000 321,000 676,000 470,000 1991 73,892 10,297 228,000 11,527 153,000 172,000 118,000 617,000 603,000 1,038,000 810,000 1992 99,937 7,155 469,000 8,172 338,000 381,000 244,000 694,000 581,000 1,455,000 1,031,000 1993 111,000 13,405 391,000 17,478 254,000 297,000 187,000 914,000 873,000 1,538,000 1,187,000 1994 97,783 16,942 275,000 20,031 193,000 206,000 141,000 483,000 467,000 878,000 666,000 1995 103,000 11,257 296,000 14,343 204,000 216,000 147,000 634,000 573,000 1,121,000 862,000 1996 115,000 10,005 361,000 13,220 238,000 272,000 183,000 444,000 462,000 859,000 618,000 1997 112,000 9,920 468,000 12,312 355,000 374,000 231,000 940,000 812,000 1,806,000 1,334,000 1998 121,000 9,096 536,000 11,922 423,000 438,000 277,000 851,000 830,000 1,678,000 1,246,000 1999 97,582 8,449 332,000 12,813 208,000 256,000 175,000 331,000 339,000 662,000 497,000 2000 96,062 12,297 357,000 12,873 299,000 290,000 185,000 958,000 880,000 1,793,000 1,368,000 Average 109,410 11,569 377,250 14,653 283,750 297,000 196,200 674,400 630,050 1,292,600 954,950 Table 3.2-4 (cont d) Summary of computed gross longshore sediment transport rates for present GFDL wave climate. Year Gross Longshore Sediment Transport Rates for Present GFDL Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 1981 632,000 2,324,000 615,000 1,592,000 741,000 1,747,000 704,000 1,101,000 1,045,000 526,000 83,214 1982 1,360,000 4,435,000 1,158,000 2,941,000 1,391,000 3,059,000 916,000 1,697,000 1,563,000 752,000 148,000 1983 1,108,000 3,557,000 1,011,000 2,464,000 1,186,000 2,479,000 721,000 1,380,000 1,283,000 581,000 85,582 1984 863,000 3,207,000 761,000 2,093,000 956,000 2,276,000 733,000 1,415,000 1,293,000 630,000 136,000 1985 1,230,000 4,188,000 1,125,000 2,853,000 1,345,000 2,923,000 856,000 1,705,000 1,580,000 717,000 95,523 1986 405,000 1,641,000 414,000 1,123,000 483,000 1,306,000 530,000 807,000 778,000 394,000 59,123 1987 668,000 2,222,000 630,000 1,528,000 744,000 1,643,000 606,000 1,076,000 1,011,000 502,000 92,071 1988 744,000 3,299,000 709,000 2,170,000 883,000 2,515,000 975,000 1,618,000 1,527,000 739,000 98,630 1989 631,000 2,187,000 612,000 1,530,000 703,000 1,649,000 645,000 1,089,000 1,037,000 501,000 53,405 1990 386,000 1,663,000 410,000 1,140,000 496,000 1,338,000 551,000 791,000 755,000 408,000 74,147 1991 728,000 1,915,000 653,000 1,381,000 750,000 1,333,000 519,000 1,021,000 958,000 490,000 111,000 1992 860,000 3,405,000 819,000 2,287,000 998,000 2,533,000 880,000 1,509,000 1,419,000 669,000 85,414 1993 1,049,000 2,747,000 963,000 2,024,000 1,063,000 1,872,000 672,000 1,255,000 1,191,000 545,000 75,875 1994 570,000 1,799,000 546,000 1,272,000 622,000 1,340,000 480,000 844,000 803,000 393,000 57,873 1995 733,000 2,210,000 689,000 1,571,000 781,000 1,546,000 505,000 945,000 894,000 421,000 64,152 1996 531,000 1,896,000 526,000 1,337,000 617,000 1,436,000 548,000 931,000 890,000 434,000 66,405 1997 1,139,000 3,694,000 1,040,000 2,551,000 1,223,000 2,562,000 744,000 1,537,000 1,426,000 654,000 106,000 1998 1,062,000 3,517,000 964,000 2,415,000 1,121,000 2,489,000 728,000 1,308,000 1,233,000 565,000 79,077 1999 416,000 1,515,000 432,000 1,081,000 499,000 1,188,000 447,000 721,000 686,000 350,000 67,322 2000 1,186,000 3,534,000 1,032,000 2,426,000 1,227,000 2,371,000 604,000 1,444,000 1,311,000 615,000 152,000 Average 815,050 2,747,750 755,450 1,888,950 891,450 1,980,250 668,200 1,209,700 1,134,150 544,300 89,541 24
Table 3.2-5 Summary of average net and gross longshore sediment transport rate calculated from GEESIS for present period along Vietnam coast. Area Average et Sediment Transport Rate * Average Gross Sediment Transport Rate ECHAM (1981-2000) GFDL (1981-2000) ECHAM (1981-2000) GFDL (1981-2000) Section1 64,620 40,708 124,346 109,410 Section2-867 -1,916 11,973 11,569 Section3 421,150 354,800 441,300 377,250 Section4-4,252-5,782 15,039 14,653 Section5 287,200 227,050 336,600 283,750 Section6 345,100 289,650 353,600 297,000 Section7 227,000 180,950 241,750 196,200 Section8 364,150 597,450 518,400 674,400 Section9-7,500 356,500 559,800 630,050 Section10 948,150 1,216,350 1,059,000 1,292,600 Section11 564,800 861,750 740,550 954,950 Section12 424,600 717,550 611,750 815,050 Section13 2,754,100 2,724,900 2,776,450 2,747,750 Section14 452,150 681,250 586,000 755,450 Section15 1,758,650 1,848,100 1,801,750 1,888,950 Section16 591,750 819,750 702,150 891,450 Section17 2,150,600 1,955,750 2,173,000 1,980,250 Section18-884,050-601,150 900,600 668,200 Section19-1,262,500-1,208,400 1,263,150 1,209,700 Section20-1,236,950-1,132,550 1,237,750 1,134,150 Section21-669,450-544,300 669,450 544,300 Section22 26,372 44,261 94,118 89,541 ote: (*) the positive transport direction is southward Figure 3.2-1 Computed average net longshore sediment transport rates at 22 locations along Vietnam coast for present wave climate (1981-2000) 25
Figure 3.2-1 (cont d) Computed average net longshore sediment transport rates at 22 locations along Vietnam coast for present wave climate (1981-2000) Figure 3.2-1 (cont d) Computed average net longshore sediment transport rates at 22 locations along Vietnam coast for present wave climate (1981-2000) 26
Figure 3.2-2 Computed average gross longshore sediment transport rates at 22 locations along Vietnam coast for present wave climate (1981-2000) Figure 3.2-2 (cont d) Computed average gross longshore sediment transport rates at 22 locations along Vietnam coast for present wave climate (1981-2000) 27
Figure 3.2-2 (cont d) Computed average gross longshore sediment transport rates at 22 locations along Vietnam coast for present wave climate (1981-2000) 3.3 Modeling Results of Future Longshore Sediment Transport Rates The computed annual net and gross longshore sediment transport rates from ECHAM and GFDL wave climate for the future time slice (2081-2100) at the 22 costal sections along Vietnam coast are summarized in Table 3.3-1 to 3.3-4, while the average net and gross longshore sediment transport rates are summarized in Table 3.3-5. The estimates of future average net and gross longshore sediment transport rates at these coastal locations compared with the results from present wave climate (1981-2000) are shown in Figure 3.3-1 and 3.3-2, respectively. The corresponding plots of computed annual net and gross longshore sediment transport rates are also shown in Appendix C. From Table 3.3-1 to 3.3-4, the annual average results at 22 costal sections from future ECHAM wave climate are in the range of 11,000-2,989,000 m 3 /year in total gross transport and 400-1,493,000 m 3 /year in net transport in a northerly direction (at coastal section S4, S9 and S18-S21) and 2,000-2,964,000 m 3 /year in net transport in a southerly direction (at coastal section S1-S3, S5-S8, S10-S17 and S22). While, the results from future GFDL wave climate are found to be in the range of 10,000-3,403,000 m 3 /year in total gross transport and 1,400-1,645,000 m 3 /year in net transport in a northerly direction (at coastal section S2, S4, S9, S18- S21) and 14,000-3,380,000 m 3 /year in net transport in a southerly direction (at coastal section S1, S3, S5-S8, S10-S17 and S22). Future change in net and gross longshore sediment transport rates at the 22 costal sections are summarized in Table 3.3-6 to 3.3-7 and shown in Figure 3.3-3 to 3.3-4. Analysis and comparison of simulated results of changes in longshore sediment transport rates due to the present wave climate (1981 to 2000) and future (2081 to 2100) conditions along the coast of Vietnam can be summarized as follows: 28
- Direction of computed net longshore sediment transport from ECHAM and GFDL climate wave at most coastal section are mainly from north to south, except coastal section S2, S4, S9, S18, S19, S20 and S21 where the net longshore sediment transport from south to north. - Changes of longshore sediment transport rates between present and future period have both increasing and decreasing trends. For example, there are expected to increase in net and gross longshore sediment transport rate at coastal section S1, S3, S5-S7, S13, S15 and S17-S21; and decrease at coastal section S4, S8, S10-S12, S14 and S16. - The results from ECHAM and GFDL future wave climate provide the same trend (increasing or decreasing) of longshore sediment transport changes for almost all coastal sections (except coastal section S9 in net transport rate and coastal section S22 in gross transport rate). - At coastal section S2, S4, S9 and S22, there are large percentage differences of net longshore sediment transport rates between the two different climate models (GFDL and ECHAM). The large percentage changes between 1981-2000 and 2081-2100 can also be found at these coastal sections in ECHAM, and at S1 and S9 in GFDL. This is because their coastline orientations are almost perpendicular to the present day (1981-2000) wave direction and therefore present net longshore sediment transport rates are very small (at costal section S2, S4, S9 and S22). 29
Table 3.3-1 Summary of computed net longshore sediment transport rates for future ECHAM wave climate. Year et Longshore Sediment Transport Rates for Future ECHAM Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 2081 72,000 1,438 527,000-2,947 384,000 449,000 289,000 344,000-144,000 1,046,000 563,000 2082 75,000 7,215 415,000 4,821 322,000 344,000 227,000 231,000-86,000 748,000 429,000 2083 112,000-1,709 633,000-4,820 481,000 532,000 354,000 225,000-405,000 955,000 394,000 2084 125,000-3,891 598,000-7,724 463,000 499,000 336,000 176,000-259,000 848,000 423,000 2085 140,000 12,504 542,000 10,132 511,000 451,000 309,000 475,000 165,000 1,329,000 835,000 2086 126,000 4,543 676,000 1,597 566,000 581,000 391,000 251,000-409,000 1,085,000 465,000 2087 54,000-567 459,000-2,999 284,000 385,000 246,000 176,000-310,000 632,000 276,000 2088 82,000 3,830 394,000 282 285,000 320,000 219,000 116,000-187,000 550,000 257,000 2089 142,000 5,566 780,000 3,561 666,000 675,000 446,000 277,000-457,000 1,299,000 560,000 2090 77,000 349 519,000-2,464 368,000 441,000 295,000 88,000-410,000 591,000 192,000 2091 67,000 7,328 364,000 4,520 241,000 291,000 202,000 152,000-166,000 544,000 272,000 2092 48,000 48 331,000-2,620 184,000 267,000 175,000 183,000-123,000 552,000 303,000 2093 109,000 3,967 491,000 1,967 406,000 403,000 277,000 434,000 32,000 1,178,000 691,000 2094 98,000-1,758 570,000-3,907 377,000 468,000 305,000 260,000-206,000 875,000 454,000 2095 73,000 2,095 441,000-471 284,000 359,000 233,000 341,000-72,000 900,000 518,000 2096 44,619 3,015 341,000 1,207 192,000 276,000 176,000 240,000-153,000 634,000 343,000 2097 120,000-1,835 697,000-5,648 542,000 590,000 380,000 483,000-38,000 1,490,000 886,000 2098 78,000 1,725 412,000-694 298,000 337,000 230,000 271,000-86,000 799,000 430,000 2099 129,000 1,553 653,000-707 465,000 537,000 363,000 117,000-375,000 763,000 317,000 2100 55,000 2,258 404,000-1,540 261,000 336,000 227,000 154,000-240,000 559,000 246,000 Average 91,331 2,384 512,350-423 379,000 427,050 284,000 249,700-196,450 868,850 442,700 ote: the positive transport direction is southward Table 3.3-1 (cont d) Summary of computed net longshore sediment transport rates for future ECHAM wave climate. Year et Longshore Sediment Transport Rates for Future ECHAM Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 2081 390,000 3,429,000 433,000 2,103,000 617,000 2,722,000-1,139,000-1,529,000-1,521,000-805,000 19,000 2082 296,000 2,403,000 335,000 1,493,000 460,000 1,891,000-759,000-953,000-942,000-516,000-1,545 2083 234,000 3,648,000 328,000 2,200,000 534,000 3,047,000-1,403,000-1,697,000-1,728,000-923,000-21,232 2084 264,000 3,070,000 346,000 1,884,000 515,000 2,522,000-1,094,000-1,381,000-1,374,000-750,000 18,598 2085 636,000 3,706,000 587,000 2,289,000 785,000 2,757,000-909,000-1,277,000-1,224,000-646,000 54,000 2086 278,000 4,122,000 362,000 2,460,000 596,000 3,407,000-1,458,000-1,696,000-1,719,000-908,000-16,870 2087 157,000 2,408,000 270,000 1,515,000 391,000 2,056,000-944,000-1,118,000-1,155,000-623,000-35,631 2088 160,000 1,988,000 214,000 1,218,000 320,000 1,640,000-755,000-957,000-950,000-537,000 7,424 2089 335,000 4,941,000 409,000 2,908,000 703,000 4,042,000-1,696,000-1,965,000-1,973,000-1,042,000-3,242 2090 79,000 2,618,000 176,000 1,564,000 319,000 2,262,000-1,008,000-1,091,000-1,127,000-627,000-26,410 2091 178,000 1,911,000 237,000 1,198,000 327,000 1,578,000-725,000-913,000-923,000-521,000-12,899 2092 201,000 1,788,000 272,000 1,158,000 356,000 1,473,000-671,000-891,000-892,000-497,000-7,078 2093 520,000 3,498,000 497,000 2,149,000 677,000 2,673,000-1,064,000-1,520,000-1,493,000-802,000 39,000 2094 312,000 2,872,000 408,000 1,837,000 553,000 2,368,000-1,012,000-1,246,000-1,259,000-686,000-1,555 2095 374,000 2,705,000 430,000 1,736,000 564,000 2,153,000-910,000-1,267,000-1,255,000-679,000 15,000 2096 225,000 2,093,000 307,000 1,349,000 403,000 1,724,000-795,000-1,055,000-1,071,000-582,000-19,130 2097 636,000 4,520,000 673,000 2,817,000 920,000 3,503,000-1,333,000-1,773,000-1,734,000-918,000 50,000 2098 317,000 2,482,000 349,000 1,562,000 474,000 1,988,000-842,000-1,122,000-1,115,000-613,000 14,937 2099 189,000 2,946,000 303,000 1,829,000 459,000 2,515,000-1,127,000-1,280,000-1,308,000-731,000-14,479 2100 154,000 2,130,000 219,000 1,314,000 323,000 1,798,000-874,000-1,140,000-1,165,000-631,000-23,820 Average 296,750 2,963,900 357,750 1,829,150 514,800 2,405,950-1,025,900-1,293,550-1,296,400-701,850 1,703 ote: the positive transport direction is southward 30
Table 3.3-2 Summary of computed gross longshore sediment transport rates for future ECHAM wave climate. Year Gross Longshore Sediment Transport Rates for Future ECHAM Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 2081 134,000 9,034 551,000 9,065 435,000 455,000 307,000 520,000 657,000 1,097,000 756,000 2082 131,000 16,962 442,000 19,200 363,000 364,000 246,000 352,000 386,000 837,000 545,000 2083 155,000 9,334 643,000 11,433 511,000 537,000 361,000 452,000 680,000 1,055,000 660,000 2084 162,000 7,189 605,000 9,588 499,000 501,000 343,000 414,000 537,000 925,000 572,000 2085 158,000 17,373 555,000 17,914 525,000 471,000 321,000 653,000 659,000 1,442,000 968,000 2086 158,000 10,843 688,000 11,331 594,000 588,000 401,000 588,000 797,000 1,179,000 784,000 2087 117,000 9,040 484,000 11,293 334,000 390,000 261,000 320,000 494,000 693,000 440,000 2088 141,000 13,920 418,000 15,961 333,000 337,000 238,000 295,000 357,000 666,000 411,000 2089 212,000 10,610 820,000 11,419 725,000 689,000 474,000 622,000 847,000 1,367,000 848,000 2090 134,000 9,071 543,000 11,179 418,000 450,000 313,000 346,000 619,000 722,000 478,000 2091 135,000 14,364 394,000 15,369 291,000 305,000 221,000 371,000 485,000 687,000 507,000 2092 108,000 8,441 360,000 10,729 242,000 276,000 196,000 298,000 329,000 644,000 423,000 2093 143,000 11,511 507,000 12,901 430,000 414,000 289,000 666,000 725,000 1,304,000 920,000 2094 120,000 4,529 577,000 6,436 402,000 471,000 311,000 465,000 606,000 938,000 657,000 2095 108,000 8,393 457,000 9,374 316,000 367,000 247,000 495,000 568,000 990,000 692,000 2096 93,938 9,505 366,000 10,881 230,000 287,000 195,000 367,000 390,000 718,000 508,000 2097 181,000 10,842 722,000 13,979 600,000 599,000 399,000 603,000 639,000 1,552,000 992,000 2098 126,000 9,678 432,000 11,119 336,000 347,000 245,000 475,000 601,000 919,000 626,000 2099 185,000 10,117 677,000 11,849 508,000 546,000 381,000 498,000 754,000 876,000 645,000 2100 137,000 11,911 440,000 13,349 325,000 347,000 252,000 434,000 612,000 723,000 558,000 Average 141,947 10,633 534,050 12,218 420,850 437,050 300,050 461,700 587,100 966,700 649,500 Table 3.3-2 (cont d) Summary of computed gross longshore sediment transport rates for future ECHAM wave climate. Year Gross Longshore Sediment Transport Rates for Future ECHAM Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 2081 620,000 3,444,000 590,000 2,125,000 696,000 2,743,000 1,143,000 1,529,000 1,521,000 805,000 100,000 2082 415,000 2,462,000 440,000 1,585,000 561,000 1,965,000 765,000 954,000 944,000 516,000 79,713 2083 533,000 3,661,000 523,000 2,226,000 648,000 3,058,000 1,406,000 1,698,000 1,728,000 923,000 84,221 2084 461,000 3,083,000 468,000 1,905,000 589,000 2,534,000 1,096,000 1,381,000 1,375,000 750,000 90,619 2085 778,000 3,746,000 714,000 2,362,000 900,000 2,794,000 947,000 1,277,000 1,224,000 646,000 108,000 2086 647,000 4,131,000 626,000 2,474,000 725,000 3,419,000 1,459,000 1,696,000 1,720,000 908,000 85,166 2087 366,000 2,418,000 367,000 1,530,000 452,000 2,069,000 945,000 1,118,000 1,155,000 623,000 69,598 2088 324,000 2,040,000 338,000 1,301,000 441,000 1,695,000 759,000 957,000 950,000 537,000 90,143 2089 684,000 4,957,000 662,000 2,935,000 818,000 4,060,000 1,697,000 1,965,000 1,974,000 1,042,000 88,444 2090 411,000 2,637,000 381,000 1,596,000 450,000 2,284,000 1,009,000 1,092,000 1,127,000 627,000 78,463 2091 424,000 1,958,000 415,000 1,276,000 477,000 1,633,000 727,000 914,000 924,000 521,000 84,814 2092 338,000 1,814,000 364,000 1,201,000 447,000 1,500,000 678,000 891,000 892,000 497,000 69,437 2093 771,000 3,534,000 687,000 2,212,000 813,000 2,701,000 1,080,000 1,520,000 1,493,000 802,000 112,000 2094 545,000 2,882,000 539,000 1,852,000 627,000 2,380,000 1,018,000 1,246,000 1,260,000 686,000 80,624 2095 579,000 2,730,000 548,000 1,781,000 658,000 2,182,000 917,000 1,267,000 1,257,000 679,000 100,000 2096 415,000 2,110,000 421,000 1,376,000 492,000 1,747,000 795,000 1,055,000 1,071,000 582,000 72,892 2097 773,000 4,536,000 755,000 2,843,000 978,000 3,524,000 1,339,000 1,773,000 1,735,000 918,000 115,000 2098 534,000 2,513,000 493,000 1,616,000 593,000 2,021,000 848,000 1,122,000 1,116,000 613,000 83,600 2099 552,000 2,967,000 527,000 1,864,000 592,000 2,543,000 1,132,000 1,280,000 1,308,000 731,000 90,036 2100 482,000 2,150,000 453,000 1,350,000 499,000 1,820,000 877,000 1,140,000 1,165,000 631,000 79,155 Average 532,600 2,988,650 515,550 1,870,500 622,800 2,433,600 1,031,850 1,293,750 1,296,950 701,850 88,096 31
Table 3.3-3 Summary of computed net longshore sediment transport rates for future GFDL wave climate. Year et Longshore Sediment Transport Rates for Future GFDL Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 2081 53,000 2,075 456,000 69 301,000 370,000 224,000 984,000 696,000 1,897,000 1,398,000 2082 54,000-4,933 384,000-8,508 224,000 307,000 199,000 312,000 65,000 739,000 485,000 2083 32,000-8,016 357,000-13,427 224,000 293,000 186,000 456,000 159,000 1,038,000 667,000 2084 110,000 1,314 695,000-1,181 542,000 594,000 387,000 277,000-443,000 1,107,000 444,000 2085 60,000 577 558,000-5,029 419,000 482,000 303,000 474,000-180,000 1,316,000 703,000 2086 76,000 499 562,000-3,225 451,000 485,000 315,000 354,000-97,000 1,129,000 631,000 2087 81,000-577 561,000-3,834 432,000 481,000 317,000 229,000-271,000 911,000 435,000 2088 42,000-4,437 333,000-8,494 196,000 274,000 181,000 217,000-62,000 602,000 352,000 2089 70,000 6,240 436,000 4,164 341,000 363,000 229,000 630,000 238,000 1,455,000 939,000 2090 137,000 1,170 812,000-844 697,000 701,000 453,000 755,000 85,000 2,034,000 1,192,000 2091 76,000-5,579 572,000-8,873 438,000 487,000 310,000 567,000 119,000 1,452,000 909,000 2092 36,000 1,357 427,000 594 291,000 362,000 225,000 418,000 114,000 1,019,000 654,000 2093 36,000-2,667 373,000-6,055 224,000 307,000 192,000 514,000 218,000 1,094,000 742,000 2094 103,000 2,049 659,000 368 520,000 565,000 361,000 364,000-153,000 1,223,000 682,000 2095 72,000-3,898 510,000-7,459 352,000 426,000 277,000 284,000-86,000 858,000 485,000 2096 77,000-6,201 435,000-10,816 252,000 349,000 228,000 117,000-126,000 495,000 271,000 2097 107,000 3,449 522,000 1,191 453,000 432,000 278,000 746,000 420,000 1,704,000 1,204,000 2098 151,000-263 841,000-1,748 731,000 732,000 488,000 291,000-616,000 1,362,000 540,000 2099 58,000-3,658 518,000-6,539 326,000 426,000 266,000 426,000 43,000 1,086,000 677,000 2100 52,098-5,523 322,000-8,908 170,000 258,000 179,000 3,000-270,000 207,000 51,000 Average 74,155-1,351 516,650-4,428 379,200 434,700 279,900 420,900-7,350 1,136,400 673,050 ote: the positive transport direction is southward Table 3.3-3 (cont d) Summary of computed net longshore sediment transport rates for future GFDL wave climate. Year et Longshore Sediment Transport Rates for Future GFDL Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 2081 1,162,000 4,068,000 1,053,000 2,753,000 1,215,000 2,794,000-908,000-1,688,000-1,611,000-796,000 64,000 2082 366,000 1,946,000 401,000 1,300,000 476,000 1,498,000-585,000-848,000-845,000-450,000-2,967 2083 525,000 2,602,000 524,000 1,702,000 649,000 1,945,000-747,000-1,166,000-1,141,000-586,000 24,371 2084 274,000 4,208,000 354,000 2,505,000 603,000 3,486,000-1,553,000-1,877,000-1,900,000-1,012,000-7,057 2085 476,000 4,398,000 509,000 2,651,000 752,000 3,464,000-1,443,000-1,872,000-1,872,000-954,000-6,337 2086 434,000 3,681,000 446,000 2,219,000 644,000 2,862,000-1,146,000-1,498,000-1,489,000-785,000 8,420 2087 275,000 3,283,000 343,000 1,990,000 525,000 2,685,000-1,170,000-1,450,000-1,464,000-769,000-14,878 2088 250,000 1,829,000 302,000 1,187,000 382,000 1,469,000-671,000-969,000-973,000-516,000-12,788 2089 727,000 3,853,000 677,000 2,420,000 871,000 2,824,000-1,063,000-1,649,000-1,600,000-816,000 44,000 2090 898,000 5,961,000 856,000 3,662,000 1,169,000 4,536,000-1,703,000-2,303,000-2,277,000-1,162,000 34,000 2091 687,000 4,080,000 680,000 2,569,000 890,000 3,080,000-1,156,000-1,679,000-1,645,000-851,000 40,000 2092 502,000 2,602,000 529,000 1,718,000 649,000 1,970,000-755,000-1,123,000-1,106,000-570,000 19,347 2093 594,000 2,673,000 586,000 1,778,000 703,000 1,970,000-767,000-1,305,000-1,269,000-658,000 41,000 2094 470,000 3,909,000 541,000 2,438,000 755,000 3,105,000-1,203,000-1,472,000-1,464,000-802,000 34,000 2095 349,000 2,643,000 402,000 1,682,000 529,000 2,114,000-876,000-1,184,000-1,194,000-629,000 917 2096 176,000 1,642,000 250,000 1,068,000 323,000 1,364,000-593,000-720,000-729,000-408,000-14,872 2097 929,000 4,435,000 835,000 2,782,000 1,060,000 3,146,000-1,024,000-1,611,000-1,531,000-795,000 74,000 2098 287,000 5,684,000 360,000 3,264,000 708,000 4,671,000-1,971,000-2,240,000-2,266,000-1,201,000-7,000 2099 505,000 3,015,000 545,000 1,958,000 679,000 2,326,000-929,000-1,283,000-1,284,000-659,000-2,147 2100-14,000 1,174,000 74,000 724,000 120,000 1,071,000-536,000-577,000-609,000-350,000-43,655 Average 493,600 3,384,300 513,350 2,118,500 685,100 2,619,000-1,039,950-1,425,700-1,413,450-738,450 13,618 ote: the positive transport direction is southward 32
Table 3.3-4 Summary of computed gross longshore sediment transport rates for future GFDL wave climate. Year Gross Longshore Sediment Transport Rates for Future GFDL Wave Climate (m 3 /year) Section1 Section2 Section3 Section4 Section5 Section6 Section7 Section8 Section9 Section10 Section11 2081 119,000 11,312 484,000 13,527 348,000 381,000 243,000 1,096,000 1,110,000 1,956,000 1,514,000 2082 114,000 9,047 398,000 12,184 273,000 311,000 209,000 447,000 466,000 851,000 631,000 2083 120,000 11,558 379,000 16,419 301,000 299,000 202,000 530,000 475,000 1,112,000 751,000 2084 156,000 8,219 713,000 9,211 576,000 600,000 399,000 528,000 814,000 1,162,000 724,000 2085 139,000 13,450 586,000 15,091 482,000 489,000 321,000 579,000 668,000 1,365,000 856,000 2086 159,000 13,867 593,000 16,618 507,000 496,000 335,000 518,000 561,000 1,226,000 795,000 2087 139,000 10,302 582,000 12,787 482,000 489,000 332,000 435,000 607,000 1,001,000 634,000 2088 105,000 9,667 353,000 13,545 258,000 278,000 195,000 377,000 399,000 697,000 494,000 2089 113,000 12,796 459,000 13,784 372,000 377,000 247,000 725,000 645,000 1,543,000 1,065,000 2090 188,000 7,658 835,000 9,221 738,000 710,000 470,000 1,079,000 1,200,000 2,107,000 1,526,000 2091 144,000 8,485 588,000 11,440 488,000 491,000 322,000 704,000 704,000 1,507,000 1,053,000 2092 136,000 15,499 463,000 21,374 352,000 368,000 241,000 481,000 401,000 1,084,000 730,000 2093 110,000 9,050 401,000 12,084 289,000 314,000 213,000 654,000 653,000 1,168,000 879,000 2094 155,000 9,733 685,000 12,037 562,000 576,000 379,000 469,000 494,000 1,288,000 791,000 2095 137,000 8,812 531,000 12,148 407,000 432,000 293,000 515,000 582,000 981,000 697,000 2096 116,000 8,485 443,000 12,638 302,000 352,000 238,000 279,000 375,000 588,000 433,000 2097 144,000 10,370 538,000 11,649 482,000 445,000 291,000 844,000 678,000 1,813,000 1,330,000 2098 174,000 5,470 847,000 6,747 746,000 736,000 493,000 570,000 1,003,000 1,436,000 843,000 2099 142,000 8,346 544,000 11,241 386,000 433,000 283,000 529,000 577,000 1,146,000 793,000 2100 89,312 6,467 328,000 9,722 208,000 259,000 185,000 189,000 323,000 350,000 261,000 Average 134,966 9,930 537,500 12,673 427,950 441,800 294,550 577,400 636,750 1,219,050 840,000 Table 3.3-4 (cont d) Summary of computed gross longshore sediment transport rates for future GFDL wave climate. Year Gross Longshore Sediment Transport Rates for Future GFDL Wave Climate (m 3 /year) Section12 Section13 Section14 Section15 Section16 Section17 Section18 Section19 Section20 Section21 Section22 2081 1,298,000 4,082,000 1,133,000 2,773,000 1,278,000 2,808,000 940,000 1,690,000 1,613,000 796,000 121,000 2082 535,000 1,966,000 514,000 1,334,000 580,000 1,520,000 596,000 848,000 845,000 450,000 77,933 2083 615,000 2,627,000 597,000 1,744,000 721,000 1,970,000 775,000 1,167,000 1,143,000 586,000 77,290 2084 593,000 4,227,000 572,000 2,535,000 707,000 3,512,000 1,558,000 1,878,000 1,900,000 1,012,000 99,065 2085 663,000 4,409,000 615,000 2,668,000 809,000 3,479,000 1,459,000 1,873,000 1,873,000 954,000 90,282 2086 619,000 3,706,000 568,000 2,260,000 747,000 2,889,000 1,154,000 1,498,000 1,489,000 785,000 96,633 2087 508,000 3,295,000 509,000 2,016,000 623,000 2,700,000 1,175,000 1,451,000 1,464,000 769,000 79,867 2088 413,000 1,843,000 412,000 1,215,000 473,000 1,484,000 672,000 970,000 973,000 516,000 68,065 2089 858,000 3,877,000 785,000 2,460,000 964,000 2,846,000 1,069,000 1,649,000 1,600,000 816,000 105,000 2090 1,275,000 5,973,000 1,126,000 3,678,000 1,302,000 4,553,000 1,725,000 2,303,000 2,278,000 1,162,000 133,000 2091 860,000 4,086,000 783,000 2,581,000 953,000 3,089,000 1,188,000 1,681,000 1,647,000 851,000 115,000 2092 590,000 2,620,000 588,000 1,749,000 710,000 1,985,000 769,000 1,123,000 1,106,000 570,000 70,434 2093 751,000 2,689,000 679,000 1,804,000 778,000 1,990,000 789,000 1,305,000 1,272,000 658,000 101,000 2094 603,000 3,924,000 615,000 2,463,000 819,000 3,126,000 1,210,000 1,473,000 1,466,000 802,000 103,000 2095 587,000 2,651,000 562,000 1,696,000 647,000 2,123,000 884,000 1,184,000 1,195,000 629,000 73,326 2096 359,000 1,670,000 373,000 1,115,000 424,000 1,396,000 595,000 721,000 730,000 408,000 69,887 2097 1,047,000 4,485,000 947,000 2,866,000 1,176,000 3,199,000 1,033,000 1,612,000 1,531,000 795,000 144,000 2098 673,000 5,694,000 635,000 3,279,000 809,000 4,684,000 1,977,000 2,240,000 2,266,000 1,201,000 101,000 2099 647,000 3,024,000 622,000 1,974,000 738,000 2,335,000 954,000 1,284,000 1,284,000 659,000 71,653 2100 221,000 1,202,000 226,000 769,000 257,000 1,103,000 536,000 577,000 610,000 350,000 58,757 Average 685,750 3,402,500 643,050 2,148,950 775,750 2,639,550 1,052,900 1,426,350 1,414,250 738,450 92,810 33
Table 3.3-5 Summary of average net and gross longshore sediment transport rate calculated from GEESIS for future period along the Vietnam coast. Area Average et Sediment Transport Rate * Average Gross Sediment Transport Rate ECHAM (2081-2100) GFDL (2081-2100) Difference ECHAM (2081-2100) GFDL (2081-2100) Difference (m 3 /yr) (m 3 /yr) (m 3 /yr) (%) (m 3 /yr) (m 3 /yr) (m 3 /yr) (%) Section1 91,331 74,155-17,176-20.8 141,947 134,966-6,981-5.0 Section2 2,384-1,351-3,735-723.4 10,633 9,930-704 -6.8 Section3 512,350 516,650 4,300 0.8 534,050 537,500 3,450 0.6 Section4-423 -4,428-4,005 165.1 12,218 12,673 455 3.7 Section5 379,000 379,200 200 0.1 420,850 427,950 7,100 1.7 Section6 427,050 434,700 7,650 1.8 437,050 441,800 4,750 1.1 Section7 284,000 279,900-4,100-1.5 300,050 294,550-5,500-1.8 Section8 249,700 420,900 171,200 51.1 461,700 577,400 115,700 22.3 Section9-196,450-7,350 189,100-185.6 587,100 636,750 49,650 8.1 Section10 868,850 1,136,400 267,550 26.7 966,700 1,219,050 252,350 23.1 Section11 442,700 673,050 230,350 41.3 649,500 840,000 190,500 25.6 Section12 296,750 493,600 196,850 49.8 532,600 685,750 153,150 25.1 Section13 2,963,900 3,384,300 420,400 13.2 2,988,650 3,402,500 413,850 13.0 Section14 357,750 513,350 155,600 35.7 515,550 643,050 127,500 22.0 Section15 1,829,150 2,118,500 289,350 14.7 1,870,500 2,148,950 278,450 13.9 Section16 514,800 685,100 170,300 28.4 622,800 775,750 152,950 21.9 Section17 2,405,950 2,619,000 213,050 8.5 2,433,600 2,639,550 205,950 8.1 Section18-1,025,900-1,039,950-14,050 1.4 1,031,850 1,052,900 21,050 2.0 Section19-1,293,550-1,425,700-132,150 9.7 1,293,750 1,426,350 132,600 9.7 Section20-1,296,400-1,413,450-117,050 8.6 1,296,950 1,414,250 117,300 8.7 Section21-701,850-738,450-36,600 5.1 701,850 738,450 36,600 5.1 Section22 1,703 13,618 11,914 155.5 88,096 92,810 4,713 5.2 ote: (*) the positive transport direction is southward Table 3.3-6 Future change in computed average net longshore sediment transport rate from ECHAM and GFDL. Area ECHAM Wave Climate GFDL Wave Climate Present (1981-2000) Future (2081-2100) Change Present (1981-2000) Future (2081-2100) (m 3 /yr) (m 3 /yr) (m 3 /yr) (%) (m 3 /yr) (m 3 /yr) (m 3 /yr) (%) Section1 64,620 91,331 26,711 41.3 40,708 74,155 33,447 82.2 Section2-867 2,384 3,250-375.0-1,916-1,351 565-29.5 Section3 421,150 512,350 91,200 21.7 354,800 516,650 161,850 45.6 Section4-4,252-423 3,829-90.1-5,782-4,428 1,355-23.4 Section5 287,200 379,000 91,800 32.0 227,050 379,200 152,150 67.0 Section6 345,100 427,050 81,950 23.7 289,650 434,700 145,050 50.1 Section7 227,000 284,000 57,000 25.1 180,950 279,900 98,950 54.7 Section8 364,150 249,700-114,450-31.4 597,450 420,900-176,550-29.6 Section9-7,500-196,450-188,950 2,519.3 356,500-7,350-363,850-102.1 Section10 948,150 868,850-79,300-8.4 1,216,350 1,136,400-79,950-6.6 Section11 564,800 442,700-122,100-21.6 861,750 673,050-188,700-21.9 Section12 424,600 296,750-127,850-30.1 717,550 493,600-223,950-31.2 Section13 2,754,100 2,963,900 209,800 7.6 2,724,900 3,384,300 659,400 24.2 Section14 452,150 357,750-94,400-20.9 681,250 513,350-167,900-24.6 Section15 1,758,650 1,829,150 70,500 4.0 1,848,100 2,118,500 270,400 14.6 Section16 591,750 514,800-76,950-13.0 819,750 685,100-134,650-16.4 Section17 2,150,600 2,405,950 255,350 11.9 1,955,750 2,619,000 663,250 33.9 Section18-884,050-1,025,900-141,850 16.0-601,150-1,039,950-438,800 73.0 Section19-1,262,500-1,293,550-31,050 2.5-1,208,400-1,425,700-217,300 18.0 Section20-1,236,950-1,296,400-59,450 4.8-1,132,550-1,413,450-280,900 24.8 Section21-669,450-701,850-32,400 4.8-544,300-738,450-194,150 35.7 Section22 26,372 1,703-24,669-93.5 44,261 13,618-30,643-69.2 Change 34
Table 3.3-7 Future change in computed average gross longshore sediment transport rate from ECHAM and GFDL. Area ECHAM Wave Climate GFDL Wave Climate Present (1981-2000) Future (2081-2100) Change Present (1981-2000) Future (2081-2100) Change (m 3 /yr) (m 3 /yr) (m 3 /yr) (%) (m 3 /yr) (m 3 /yr) (m 3 /yr) (%) Section1 124,346 141,947 17,600 14.2 109,410 134,966 25,555 23.4 Section2 11,973 10,633-1,340-11.2 11,569 9,930-1,639-14.2 Section3 441,300 534,050 92,750 21.0 377,250 537,500 160,250 42.5 Section4 15,039 12,218-2,820-18.8 14,653 12,673-1,980-13.5 Section5 336,600 420,850 84,250 25.0 283,750 427,950 144,200 50.8 Section6 353,600 437,050 83,450 23.6 297,000 441,800 144,800 48.8 Section7 241,750 300,050 58,300 24.1 196,200 294,550 98,350 50.1 Section8 518,400 461,700-56,700-10.9 674,400 577,400-97,000-14.4 Section9 559,800 587,100 27,300 4.9 630,050 636,750 6,700 1.1 Section10 1,059,000 966,700-92,300-8.7 1,292,600 1,219,050-73,550-5.7 Section11 740,550 649,500-91,050-12.3 954,950 840,000-114,950-12.0 Section12 611,750 532,600-79,150-12.9 815,050 685,750-129,300-15.9 Section13 2,776,450 2,988,650 212,200 7.6 2,747,750 3,402,500 654,750 23.8 Section14 586,000 515,550-70,450-12.0 755,450 643,050-112,400-14.9 Section15 1,801,750 1,870,500 68,750 3.8 1,888,950 2,148,950 260,000 13.8 Section16 702,150 622,800-79,350-11.3 891,450 775,750-115,700-13.0 Section17 2,173,000 2,433,600 260,600 12.0 1,980,250 2,639,550 659,300 33.3 Section18 900,600 1,031,850 131,250 14.6 668,200 1,052,900 384,700 57.6 Section19 1,263,150 1,293,750 30,600 2.4 1,209,700 1,426,350 216,650 17.9 Section20 1,237,750 1,296,950 59,200 4.8 1,134,150 1,414,250 280,100 24.7 Section21 669,450 701,850 32,400 4.8 544,300 738,450 194,150 35.7 Section22 94,118 88,096-6,022-6.4 89,541 92,810 3,269 3.7 Figure 3.3-1 Estimates of present and future average net longshore sediment transport rates at 22 costal sections 35
Figure 3.3-1 (cont d) Estimates of present and future average net longshore sediment transport rates at 22 costal sections Figure 3.3-1 (cont d) Estimates of present and future average net longshore sediment transport rates at 22 costal sections 36
Figure 3.3-2 Estimates of present and future average gross longshore sediment transport rates at 22 costal sections Figure 3.3-2 (cont d) Estimates of present and future average gross longshore sediment transport rates at 22 costal sections 37
Figure 3.3-2 (cont d) Estimates of present and future average gross longshore sediment transport rates at 22 costal sections Figure 3.3-3 Future change in average net longshore sediment transport rates at the 22 costal sections along Vietnam Coast 38
Figure 3.3-4 Future change in average gross longshore sediment transport rates at the 22 costal sections along Vietnam Coast 39
CHAPTER 4 COCLUSIOS 1. The present study has estimated the present and future longshore sediment transport rates at 22 coastal sections along Vietnam coast using a one-line longshore transport model (GEESIS), which has been forced by ECHAM and GFDL wave climates determined in the previous CCWaves-Vietnam study for two time span of 1981-2000 and 2081-2100. 2. GEESIS model calibration was conducted by applying calibration parameters values for k 1 and k 2 from previous research studies. Calibration parameters k 1 and k 2 with values of 0.75-0.80 and 0.40-0.50, give moderate and good quantitative agreement between the computed results and the reported values. 3. The computed results indicate that the volume and direction of longshore sediment transport along the coast of Vietnam is rather variable. For present conditions, the annual average results from ECHAM and GFDL wave climate at 22 costal sections are found to be in the range of 11,000-2,748,000 m 3 /year in total gross transport and 1,400-1,426,000 m 3 /year in net transport in a northerly direction (at coastal section S2, S4 and S18-S21) and 35,000-2,740,000 m 3 /year in net transport in a southerly direction (at coastal section S1, S3, S5-S17 and S22). For future conditions, the annual average results at 22 costal sections are in the range of 10,000-3,403,000 m 3 /year in total gross transport and 2,000-1,569,000 m 3 /year in net transport in a northerly direction (at coastal section S4, S9, S18-S21) and 500-3,174,000 m 3 /year in net transport in a southerly direction (at coastal section S1-S3, S5-S8, S10-S17 and S22). 4. For the two time span of 1981-2000 and 2081-2100, directions of net longshore sediment transport at almost all coastal sections are the same, except at coastal sections S2, S4, S9 and S22. In these sections the net transport in both time spans are variable in different years but net sediment transport due to climate change effect (time span of 2081-2100) at S2 and S4 is turning more toward the south and at S9 and S22 is changing more toward the north. 5. The estimated results of longshore sediment transport rates from present (1981-2000) and future (2081-2100) CC modified wave climate show significant changes in net and gross longshore sediment transport rates along the coast of Vietnam. 40
Table 4.1 Changes in net sediment longshore sediment transport at 22 coastal sections along the Vietnam coastline due to climate change. Coastal section S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 Description The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 62%, in the order of 30,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the south. The magnitude will decreases with about 7% in order of 1,000 m 3 /year in the southerly direction The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 34%, in the order of 125,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the south. The magnitude will decreases with about 28% in order of 2,000 m 3 /year in the southerly direction The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 50%, in the order of 122,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 37%, in the order of 113,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 40%, in the order of 78,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 30%, in the order of 145,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the north. The magnitude will increases with about 240% in order of 162,000 m 3 /year in the northerly direction The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 7%, in the order of 80,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 22%, in the order of 155,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 30%, in the order of 176,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 16%, in the order of 434,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 23%, in the order of 131,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 9%, in the order of 170,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport decreases by 15%, in the order of 105,000 m3/yr The net longshore sediment transport is toward the south at present and will remain towards the south upto 2100. The magnitude of net annual transport increases by 23%, in the order of 460,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 45%, in the order of 290,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 10%, in the order of 124,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 15%, in the order of 170,000 m3/yr The net longshore sediment transport is toward the north at present and will remain towards the north upto 2100. The magnitude of net annual transport increases by 20%, in the order of 113,000 m3/yr There is no dominant direction of net longshore sediment transport in this section it will remain the same upto 2100 but with more tendency toward the north. The magnitude will increases with about 60% in order of 5,000 m 3 /year in the northerly direction 41
REFERECES Cat,.., Tien, P.H., Sam, D.D. &.. Bien., 2006. Status of coastal erosion of Vietam and proposed measures for protection. FAO Asia Pacific. Eva-Lena E. and Madeleine H. P., 2014. Sediment transport and coastal evolution at Thuan An Inlet, Vietnam. Master Thesis, Lund University. Hung,.M., Dien. D.C., 2006. Effects of the storm number 7 (DAMREY) on the sea dyke system of am Dinh Province, J. Mar. Sci. 4 (T6). Lam,.T., 2009. Hydrodynamics and morphodynamics of a seasonally force tidal inlet system. Ph.D. Thesis, Delft University of Technology. Mazda, Y., Magi, M., anao, H., Kogo, M., Miyagi, T., Kanazawa,. and Kobashi, D, 2002. Coastal Erosion due to longterm human impact on mangrove forests. Wetlands Ecology and Management. Vol. 10: 1-9. Hanson,H. and Kraus,.C., 1989. GEESIS: Generalized model for simulating shoreline change. Technical Report CERC 89-19. U.S. Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, Vicksburg, Mississippi, 185p. Q. T. Doan, Y.C. Chen, T.T. Quach and P.K. Mishra., 2013. umerical modeling in shore line evolution prediction: Case study of Tat Dike, Vietnam. International Journal of Earth Sciences and Engineering, Vol.6, pp 1251-1259. Tien, T.Q., 2004. Use of hindcast wave field by WAM model for calculation of sediment transport in littoral zone of Vietnam Central. The 14th OMISAR Workshop on Ocean Models.Taipei, Taiwan. Young, R.S.; Pilkey, D.H.; Bush, D.M.; and Thieler, E.R., 1995. A discussion of the Generalized Model for Simulating Shoreline Change (GEESIS). Journal of Coastal Research, 11(3), 875-886. 42
Appendix A Result of Present Longshore Sediment Transport Rates 43
66.94 % 64.22 % Coastal Section S1 Coastal Section S2 60.29 % Coastal Section S3 60.29 % Coastal Section S4 56.1 62.82 % Coastal Section S5 Coastal Section S6 70.6 Coastal Section S7 52.43 % Coastal Section S8 Figure A-1 Wave rose diagrams from ECHAM climate model for the future period (2081-2100) 44
49.98 % 49.91 % Coastal Section S9 Coastal Section S10 49.62 % Coastal Section S11 51.2 Coastal Section S12 51.2 49.82 % Coastal Section S13 Coastal Section S14 Figure A-1 (cont d) Wave rose diagrams from ECHAM climate model for the future period (2081-2100) 45
49.82 % Coastal Section S15 49.27 % Coastal Section S16 49.24 % Coastal Section S17 50.90 % Coastal Section S18 51.31 % Coastal Section S19 51.58 % Coastal Section S20 55.6 64.24 % Coastal Section S21 Coastal Section S22 Figure A-1 (cont d) Wave rose diagrams from ECHAM climate model for the future period (2081-2100) 46
66.91 % 63.94 % Coastal Section S1 Coastal Section S2 59.91 % Coastal Section S3 59.91 % Coastal Section S4 55.36 % 62.83 % Coastal Section S5 Coastal Section S6 70.80 % Coastal Section S7 52.6 Coastal Section S8 Figure A-2 Wave rose diagrams from GFDL climate model for the future period (2081-2100) 47
47.80 % Coastal Section S9 0 2.00-2.50 1.50-2.00 1.00-1.50 0.50-1.00 0 50.21 % Coastal Section S10 49.91 % Coastal Section S11 51.19 % Coastal Section S12 51.19 % 50.10 % Coastal Section S13 Coastal Section S14 Figure A-2 (cont d) Wave rose diagrams from GFDL climate model for the future period (2081-2100) 48
50.10 % Coastal Section S15 49.86 % Coastal Section S16 49.7 Coastal Section S17 50.80 % Coastal Section S18 50.58 % Coastal Section S19 50.86 % Coastal Section S20 55.22 % 64.91 % Coastal Section S21 Coastal Section S22 Figure A-2 (cont d) Wave rose diagrams from GFDL climate model for the future period (2081-2100) 49
Appendix B Result of Present Longshore Sediment Transport Rates 50
Figure B-1 Computed annual net longshore sediment transport rates for present wave climate (1981-2000) 51
Figure B-1 (cont d) Computed annual net longshore sediment transport rates for present wave climate (1981-2000) 52
Figure B-1 (cont d) Computed annual net longshore sediment transport rates for present wave climate (1981-2000) 53
Figure B-1 (cont d) Computed annual net longshore sediment transport rates for present wave climate (1981-2000) 54
Figure B-1 (cont d) Computed annual net longshore sediment transport rates for present wave climate (1981-2000) Figure B-2 Computed annual gross longshore sediment transport rates for present wave climate (1981-2000) 55
Figure B-2 (cont d) Computed annual gross longshore sediment transport rates for present wave climate (1981-2000) 56
Figure B-2 (cont d) Computed annual gross longshore sediment transport rates for present wave climate (1981-2000) 57
Figure B-2 (cont d) Computed annual gross longshore sediment transport rates for present wave climate (1981-2000) 58
Figure B-2 (cont d) Computed annual gross longshore sediment transport rates for present wave climate (1981-2000) 59
Appendix C Result of Future Longshore Sediment Transport Rates 60
Figure C-1 Computed annual net longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 61
Figure C-1 (cont d) Computed annual net longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 62
Figure C-1 (cont d) Computed annual net longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 63
Figure C-1 (cont d) Computed annual net longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 64
Figure C-1 (cont d) Computed annual net longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) Figure C-2 Computed annual gross longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 65
Figure C-2 (cont d) Computed annual gross longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 66
Figure C-2 (cont d) Computed annual gross longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 67
Figure C-2 (cont d) Computed annual gross longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 68
Figure C-2 (cont d) Computed annual gross longshore sediment transport rates for present (1981-2000) and future wave climate (2081-2100) 69