HQi thao khoa hoc - Hgp tac Qu6c t^ trong digu tra, nghien cihi tAi nguySti va mfli tmong bi5n
THE FIELD SURVEYS AND RESEARCH OF THE COAST LINE AND RIVER MOUTH EVOLUTION IN VIETNAM
Nguyen Manh Hung. Nguyen Thi Viet Lien Institute of Mechanics, VAST, Hanoi, Vietnam Abstract:
In the paper, the results of the cooperation in field survey and research concerning the evolution of the coast line and river mouth of Vietnam in the frame of the Project "The evolution and sustainable management of the coastal areas of Vietnam " code VS/RDE-03 for the periods of 2004 - 2007 and 2007 - 2011, funded by Sida/SAREC have been presented. The Project involved the Center for Marine Environment Survey, Research and Consultation (CMESRC) and The Department of Water Resources and Engineering (DWRE) Lund University as implementing and collaborating institutions.
During the first phase (2004-2007) the Red River Delta coastal zone was chosen as the case study of the coastline evolution (with the emphasis of the erosion in Nam Dinh province's coast line. Four synthesis field surveys of each 3 cross shore profiles with 3 stations equipped by the modem apparatus and many periodic beach bathymetry surveys were carry out The second phase (2008-2011) is focused on the beach changes in the RRD coast zone and Thuan An, Tu Hien (Thua Thien Hue province) inlets migration and the effects of the structures on the of topographic change in the vicinity of its.
The main results of the project are: Enhancing the research infrastructure of CMESRC by high-level sophisticated equipment for field measurements: Field surveys: Collection, compilation, and analysis of data related to beach and shoreline changes in the coastal zone of Vietnam;
Mathematical modeling of coast line change in RRD and inlets migration;
Research on the mechanism of the coast change; Providing of scientific workshops and seminar relating issues and exchange experiences and knowledge between Vietnamese-Sweden an foreign scientist and other as Nelherlands, Poland, Russian and Japanese researches; Master and Doctoral education; Publication in the Vietnamese and foreign journals the Project's outcomes.
I. INTRODUCTION
Vietnam has a coastline that is approximately 3200 km long (excluding islands) and much of it is located below an elevation of 1 m [11]. Since the economic activity in Vietnam is mostly concentrated in the coastal areas, it is of a vital importance that the physical and environmental conditions in these areas are well
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understood and may be assessed for a wide range of situations. For example, the Red River Delta (RRD) in northern Vietnam, which supports nearly one third of the country's rice production, is under a constant threat from high water levels in the sea causing flooding and intrusion of saline water. Such high water levels are typically associated with typhoons or strong wave action during the monsoon periods, although long-term sea level rise due to climate change is a concern as well [11]. Furthermore, deposition of river sediment along the coastline in combination with sediment transport by near shore waves and currents induce variability in the shoreline position at many scales in time and space that must be estimated in order to manage the delta and associated coastal areas in a rational manner. Almost all of the agricultural, industrial, and urban areas of northern Vietnam are concentrated in the RRD. Along the coastline of the RRD there are about 25 segments which are experiencing erosion corresponding to a length of 30 km. In contrast, accumulation is typically occurring at the river mouths of the delta.
In tlie delta the erosion and accumulation processes are very active. The' most severe erosion can be found in Xuan Thuy and Hai Hau district (Nam Dinh Province), where since 1960 a segment of 4000 m length and 500 m width and 3500 m length and 1000 m width, respectively, have been eroded. In contrast, the area at the Ba Lat river mouth moves in the seaward direction at a rate of 80-100 m/year [10] and the siltation in Hai Phong port needs dredging at regular intervals.
In order to combat erosion, dikes have been built along the delta but many of these have been destroyed by continued wave action during the monsoon or extreme typhoons. In southern Vietnam the Mekong Delta plays a similar prominent role for the socio-economic development as the Red River Delta for northern Vietnam Coastal erosion has often been observed along the Vietnamese coastline, and at present there are more than 300 segments of coastline subject to erosion [10].
ir^JJvlJ^T^'. ^u' "^"""^ Environment Survey, Research, and .Consultation (CMbbKC) and the Department of Water Resources Engineering (DWRE) Lund University initiated collaborative research in coastal processes already at the'end of the 1990s, but only from 2004 the project "The evolution and sustainable management of the coastal areas in Vietnam" Coded VS/RDE-03 undertaken between the two institutions has been approved by the Vietnam Sweden Cooperation Program. At present we have completely carry out the first period 2004 - 2007 and coming to the end of the second period (facing out phase) 2008 - 2011.
1, 7^^ '^"K^;^^''!?^?''-'^'^''''^ ° ^ * ^ P"'^^^"' P™j«« and of the ongoing cooperation between CMESRC and DWRE is to develop an integrated and sustainable strategy sn..rf!!"^f'"fi, t ' " " " " T " ' '" ^ ' " ' " ' ™ ' " * e framework of the [1]. More fnllnw ^ ' r n ^ short-term objectives in VS/RDE-03 strives towards arriving at the D m h T ^ ' r ^ l ! , f " ' [ ' ' "^"".'P*'"" of * e coastal evolution in Vietnam and d sc oTion J H ,-r''' '"'''r^^' management of the coastal areas; (2) a the RRD * 1"^" !fi<^«'on of physical processes governing coastal evolution in, 31 an ev'n ,! • •" f L'"l' ' " " ^ " g g " ' i ° " f"-- "-easures to manage the coastal area;
aciieve snl,^ hi . 7 ' " ' ™ ' ' * " ' ™ ' " " ° " =^^™"°^ '" '^e RRD and how to Tnow how ,n V ' """^'"P"'^"' ""''^^ *ese scenarios; (4) a general transfer of know-how to Vietnamese researchers, engineers, and managers providing methods
Nguyen Manh Hung
Hoi thAo khoa hoc - Hgp tac Ou6c t§ trong diiu tta, nghign cilu t^i nguygn vi mfli tnjfmg bifin
and tools for understanding and managing the evolution of the coastal areas; and (5) coordination with other national and intemational research programs for maximum use of available resources and transfer of knowledge between scientific disciplines.
The present project provided the means for a thorough investigation of physical processes in the coastal areas of Vietnam and their implications for managing these areas in a sustainable manner. The VS/RDE-03 project has included specific research tasks as well as capacity building, research education, and general strengthening of the research infrastructure. The project links the coastal evolution with different sustainable management strategies for the whole country of Vietnam by utilizing the experience gained through the focused study of the RRD.
Theoretically, this linkage relies to a large degree on mathematical modeling of coastal evolution, which is based on a clear understanding of the governing physical processes including wave generation, propagation, and transformation, sea-level variations (e.g., tide, sea level rise), coastal circulation, sediment transport, morphological evolution, and long-term coastal response. This modeling is integrated into coastal zone management procedures, where socio-economic, environmental, and rural development aspects are considered. Mathematical modeling in turn depends on the availability of different types of data and analysis of those data to understand the governing processes. Data are also required for model calibration, verification, and validation. After the mathematical models have been calibrated against data and their physical relevance for the description of the governing processes been validated, a variety of scenarios are simulated both with regard to changes in the forcing and the impact of different measures and activities.
The output from such simulations will provide an important input to the development of management strategies for coastal areas. The main results obtained by the project focused dn field surveys and research outcomes have been presented below.
II. FIELD SURVEY CAMPAIGNS
In order to do the field survey, some equipment have been bought by the project budget including two directional wave recorder (Sontek) two sediment concentration recorder OBS-3A and many minor equipment (wind, atmospheric, humidity meters, water quality checkers, current floating buoys etc). In the frame of the project two types of the field survey have been organized as main synthesis field survey campaign and periodic field surveys (water level, bathymetry, beach elevation, cross shore profile, wave induced current...) _^-
II.1. Major field survey campaigns: Four major, synthesis field survey campaigns were carried out within the framework of RIDE03 during NE and SW monsoon seasons of 2005 and 2006 in which extensive measurements of waves, currents, sediment transport, and profile change were made [6]. The field campaigns lasted one to two weeks involving 20-30 Vietnamese researchers aiid technical staff as well as representatives from DWRE. Two field experiments were done during the winter monsoon (January 2005, 2006) and two during the summer
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monsoon (August 2005, 2006). The field survey area extended from the water line . . . _ _ . „ _. to a depth of 20m in the offshore
direction (that is, approximately 15 km offshore) and from the soufli bank of the Ba Lat to the north bank of flie Ninh Co river mouths covering approximately 40km in the alongshore direction. In total there were four measurement stations in the sea and three instrumented cross-shore profiles mainly covering the surf zone. The locations of these stations and profiles are shown in figure 1. The measurement parameters were as follows:
Fig. 1: The map of measurement stations in the sea and instrumented cross-shore
profiles.
Current including wave-induced current.
Sediment concentiation.
Main meteorological parameters such
Fig. 2. Detail apparatas set-up in tiie cross shoreprofileP2-Sl
Wave and water level,
as wind velocity and direction, pressure, air temperature, and records of atmospheric phenomena.
Water temperature, salinity and some environmental parameters (e.g., pH, turbidity) measured from collected samples.
Grain-size analysis of samples from tiie sea bottom at the sea stations.
The detail measurement apparatus and set-up is depicted
in the figure 2.
The figures 3a, b shown flie preparation for providing the measurement at the cross shore profiles and sea stations.
Fig. 3. P ' W - ^ f ' t e equipment in tiie cross shore station with specialists from WRDE (a) and one ship wifl, survey staff going to one sea station (b) "
166
Nguyen Manh Hung
HQi thao khoa hoc - Hgp tic Qu5c tfi ttpng digu tra, hRhifin c6u tii nguyfin va mfli trupng biln
The information for four major field survey campaigns is tabulated in the table 1 and detail recorded data for the first survey is shown in the table 2.
Tab. 1: The information of four major field survey of the VS/RDE-03 project N.of field
surveys 1 2 3 4
Duration
17/01/2005-27/01/2005 04/08/2005-13/08/2005 07/01/2006-18/01/2006 06/08/2006 - 14/08/2006
N.of participants
30 25 32 28
Note
NE monsoon SW monsoon NE monsoon SW monsoon Tab. 2: Infoi^mation on the data recorded during the first field survey 17/01/2005 -
27/01/2005 [6].
station
iix
Sl I9"59'987 106°17'582 Sl 19°59'987 106°17'582 Sl 19"59'987 106°17'582 S2 20"09'300 106°24'500 S2 20"09'3D0
106°24'500 S3 20"05'548 106°20'794 S3 20"05'548 I06°20'794 S4 20"10'57.66
106°23'11.59 S4 20"00'000
106°I5'200 PI Quat Lam PI Quat Lam P2 Hai Ly P2 Hai Ly
P3Thitih Long Dept
h/
Layer 18m 3m 18m 10m 18m 10m 3m 10m
10m 3m 10m 10m 3m 10m 3.0m 3.0m 3.5m 3.0m
3.5m
Date Start
13h00' 17/1/05 13h00' 17/1/05 13h00 17/1/05 IShOO' 17/1/05 17h00 17/1/05 13h45' 17/1/05 17h00 17/1/05 13h30' 17/1/05 IhOO 17/1/05 08h00' 19/1/05 08h00' 19/1/05 15hl3' 18/1/05 15hl3' 18/1/05 9h50' 18/1/05
End
04h00' 27/1/05 04h00' 27/1/05 03h00 27/1/05 06h30' 23/1/05 03h00 27/1/05 03hl5' 27/1/05 03hOO 27/1/05 04hl5' 27/1/05 04h00 27/1/05 llhOO' 26/1 12hO0' 26/1 09h2r 26/1/05 09h21' 26/1/05 06h50' 26/2/05
Rec.
periof]
Rec.
time 15' 15' 60' 05' 15' 60' OS- IS' 6 0 ' OS- IS' 6 0 ' 0 5 - 60- 60- 2- 2'
60'
E q u i p . I D
D N C 2 M ID-233 D N C 2 M ID-248 D N W 5 M ID-072 D N C 2 M ID-207 D N W 5 M ID-073 D N C 2 M ID-250 D N W S M ID-077 D N C 2 M ID-251 D N W S M l D - 0 7 6 S O N T E K 145 0 B S - 3 A 177 STAR- 2000 V A L 7 30 D 3 D A C M
F i l e ' s n a m e
S 1 - C 3 - J A N 0 5 S l - C l O - JANOS S l - W - JANOS S 2 - C 3 - J A N 0 5 S 2 - W - J A N 0 5 S 3 - C 3 - J A N 0 5 S 3 - W - JANOS S 4 - C 3 - J A N 0 5 S 4 - W - JANOS P l - W - J A N 0 5 P l - S S - lANOS S T A R - 2000 P2-T1DE- JANOS wavean_P3
N o t e
13h30- 24/1 the buoy were taken t o the vessel for repair
0 7 h - 0 7 h 3 0 ' 24/1 the buoy were taken to t h e vessel for repair
2 0 " 1 0 ' 5 7 . 6 6 "
1 0 6 ° 2 3 ' 1 1 . 5 9 "
W.buist o f 7 3 0 D n o t installed
2 0 ° 0 7 ' 0 4 . 3 2 "
1 0 6 ° 1 9 ' 1 S . 4 0 "
2 0 " 0 0 ' 5 S . 6 3 "
106°13'12.24-'
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Station iii.
PSThinh Long FSThinh Long P3Thmh Long P3Thinh Long
Dept b/
Layer 3.5m 3.Sm 3.0m 3.0m
Date Start
9h20' 18/1/OS 9h38' 18/1/05 lOhOO' 18/1/05 lOhOO' 18/1/OS
End
06h20' 26/2/05 06h38- 26/1/OS O6I1OO- 26/1 06h00- 26/1
R e c . p e r i o d
R e c . time 30- 60- 60- 60'
Equip.
ID
3DACM 3DACM SONTEK 174 0BS-3A 178
FUe's name
Cur P3 dig_P3 P3-W- JAN05 P3-SS- JANOS
Note s
From the bottom n . 2 . Periodic field surveys
Periodic field surveys and surveys on the cross-shore profile changes and storm surged caused by storms during the 2005 storm season were executed.
The main objective of these surveys is stiidding the changes of the cross- shore profiles caused by storms, monsoons and to determine the average rate of the lowering of beach elevation. In order to execute the periodic field surveys, three daturas (at Thinh Long, Van Ly and Quat Lam villages) have been made and all the beach elevations from the dyke foot to 250 - 300 m off shore with 20m equal spacing were referred to these datums. Two snapshots of the beach elevation and storm surge surveys are shown in tiie figures 4a, b. Cross-shore profiles before and after storm action were measured at several locations and based on these data some analyzing of flie effects of storm induced changes of beach especially sea dyke foots change are published [3]. The figure 5 depicts the change of beach elevation at Thinh Long town caused by the passage of storm.
Fig.4. Periodic beach elevation measurement (a) and storm surge measurement (b) caused by the storm
N7/2005 DAMREY.
Fig. 5: The cross-shore profile changes during the period of August and September 2005
special focused on the change caused by the DAMREY storm (from 20* to 29 September
2005) [3].
168 Nguyen Manh Hung
HQI thao khoa hgc - HIJT) tac Quflc tg trong dieu tra, nghien ciru xki nguy5n v^ m6i tru&ng bifin
III. MATHEMATICAL MODELING OF COASTAL EVOLUTION IN THE RED RIVER DELTA
The collected data during the field campaigns have been presented in different reports, where the data are summarized and the initial data processing discussed.
Some statistical analysis was also performed to provide the main seasonal regime of tides, waves, and near shore currents in the surveyed area as well as along the RRD costal zone in general.
Several different types of mathematical models of near shore processes were developed and applied to reproduce and forecast the physical conditions in the coastal zone of the RRD. These models included wave tiansformation, near shore current circulation, water level change, sediment transport, and topographic evolution. Computations of topographic change (i.e., shoreline evolution, profile response; and 2D bed level response) were carried out by coupling one or several models, since the waves, current, and water level must be known before sediment transport and the evolution of the topography can be determined. Both existing and newly developed models were applied, where the latter included the work done by the Vietnamese doctoral students. The most important modeling efforts included:
1. Comprehensive topographic evolution model. Two sets of models were used to simulate waves, circulation patterns, sediment transport, and morphological change in the RRD [5]. The first set of models consists of the regional wave model SWAN employed for the entire East Sea and the local wave model STWAVE. The circulation simulations started from ADCIRC and proceeded with CMS-M2D for sediment transport.
2. Shoreline change modeling. GENESIS - the GENEralized model for Simulating Shore line change [2] was used in this study to simulate the long-term shoreline evolution caused by gradients in long shore sediment transport [3]. A newly enhanced version of GENESIS was applied to verify the hypothesis postulated that gradients in the long shore sediment transport rates together with offshore losses of fine sediment are the main causes generating the serious erosion at Hai Hau beach.
3. Model for water level and current with patching and welting/drying technique. A model was developed to simulate wetting and drying in coastal areas in response to water level changes. The model was calibrated and verified with prototype data and subsequently applied to the Nam Dinh coastal zone [8].
4. Topographic evolution model based on the advection-diffusion equation. A model was developed based on the advection-diffusion equation and employed to simulate sediment transport, the bed level change, and the shoreline evolution of the coast of Nam Dinh province. The obtained results prove the ability of the model to describe the sediment transport as well as the shoreline evolution of Nam Dinh province.
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5. Model of waves and near shore circulation. A numerical model of near shore currents induced by breaking waves, wind, and tides was developed. The model was applied to simulate tine long shore current as well as more complex near shore circulation patterns. Simulation results will be used as input to a sediment ti-anspoit
and bed evolution model in progress.
As an example of the comprehensive topographic evolution model the figure ( shows the meshing grids of ADCIR, STWAVE and M2D models.
The large-scale regional circulation model included a grid meshing with a semi- circular ocean boundary to get the optimal iiirthest distance from tiie Ba Lat moufli to the boundary, which yielded a value of 100,000m.
The finite-element grid was generated according to the local wavelength at each node. The largest elements were in flie deep sea zone, in the regions with a wavelength of 5,000m, and conversely the smallest elements had a size of 75m in the vicinity of tiie Ba Lat river mouth.
Fig. 6: The Red River Delta coastal zone wifli ADCIRC, M2D
and STWAVE grids [5].
The STWAVE square grid witii a cell
„ f « < : n o • .u . , size spacing of 50m was meshed in a domain direction "^550 u T l " ' '^•'"'=1'™ (1270 cells) and 27,500m in the cross-shore t^dienK • , . } ^'%^P^<='"g «d^q"^tely resolved flie radiation stiess S r r e m t h e r l ' ™ ' " ' ^ ^"^ ' ° ' ' " ^ ' ' " ' ^^'™l^'i™» °f water level and with ^ l ^ ? f''• ^V^Z ' T ? ' ™ ' ' ™"P"tational domain was a rectilinear grid t l l a t t e T w a r'fi ' T i °?n^ " " " ^ ^ ' ' " ^ ^"^ ™"^^'^ ^^" ^'^^ ^='°^» ^^ore, whTre the latter was refined from 50m to 150m with a bias of 1.01 at two points' the first r a d l t i l stie': ' ' V i f "' ^"^ ' " * ^ " ^ ' « - ' ' - * ' o T o r ^ n flie w ve f o t f o n flie river ^ ^ * i : ^ ^ ° ' " ' ""« *" * e access chamiel of tiie Balat mouth to S a ; ; * ^ " " " * - ^ ' ""^ ^ " ' ^ CSTWAVE-and M2D) covered an identical TV. CONCLUSIONS
Main results of the project VS/RDE-03 are:
a c o m S r ^ l f T ' ; ' " ' of CMESRC has been enhanced primarily through zone T I O w a v T '°f'''''^''^ ^ ' ' " ' P ' " ^ ' ^ ^ A^ld measurements in the coastel coTection e s p e c l i w t t h " " ' ^ ' " " ' ^ " ( ' " " ' * > ^ ^ " - ^ - " — " ' ^^ ion, especially in the surf zone, and two sediment concenti-ation recorders
170 "
Nguyen Manh Hung
HQi thao khoa hoc - Hgp tac Quflc li trong dieu tra, nghign cuu tai nguygn va m6i tru&ng bifin
OBS-3A for measuring the sediment transport in the near shore zone of the Red River Delta were bought by the Project. These pieces of equipment have been extensively utilized in the field campaigns.
- Collection, compilation, and analysis of data related to beach and shoreline changes in the coastal zone of Vietnam, such as hydro-meteorology (wind, typhoon), marine hydrodynamics (tide, typhoon surges, currents, waves), sea bottom topology and coastline evolution (erosion areas, maps, remote sensing images), especially in the RRD, were carried out [7]. These data were organized as a GIS database that allows for simple updates with new data, performing analysis, creating maps, and generating reports. The obtained data have been used for the model calibration, verification, and validation in the project
- Two courses were held during RDE03 focusing of near shore hydrodynamics and sediment transport. The courses were provided by the World well known scientists from DWRE. The Courses were very attractive and about 30 persons from different institutions in Hanoi and Ho Chi Minh City participated the courses.
- Two doctor students have successfully defended their doctor thesis by the end of 2010 years, 3 master students were supported and have gained their maste'r degree, during the time (2011), two more master students are supporting by the project. Several junior Vietnamese researchers have made great progress in developing their skill to understand and model coastal processes.
- In the frame of the project three international scientific workshops have been organized with more than 50 participant iri each and the beside the Vietnamese and Sweden scientists the specialists from Netherlands, Japan, Poland and Russia were invited to the workshops and present their works on coast line evolution.
- In the present project there has been close interaction with other international researchers carrying out related coastal research to avoid overlaps and to exchange information for maximum benefit in the present project. Contacts and information sharing are going on with Delft University of Technology and Utrecht University in The Netherlands, The Institute of Hydro engineering, Polish Academy of Science, Gdansk, in Poland, Kiel University in Germany, Tohoku University in Japan and the Institute Oceanography Shirshov in Russia.
Many papers concerning the research outcomes of the Project have been published in the Vietnamese and foreign journals among them a monograph "Coast line and river mouths evolution in Vietnam" (in Vietnamese) have been published by the end of 2010 and the second edition (in English) will be publish in the end of this year.
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4(T6), pp 87-99.
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5. Hung N.M., Larson, M., and Dien, D.C. 2007b. "Modeling wave transformation, nearshore currents, and morphology change in the nearshore zone of the Red River Delta," Proceedings of the 1st Scientific Workshop of VS/RDE/03, Thinh Long, Vietnam.
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7. Lien, N.T.V., Moi, N.V., and Nga, N.T.K. 2007. "Compilation and analysis of data collected (hydro-meteorology, bottom and beach change)," Proceedings of the Isl Scientific Workshop of VS/RDE/03, Thinh Long, Vietnam.
8. Manh, V.D., Quynh, D.N., Lien, N.T.V., and Duyet, T.T.N. 2007. "Modeling of sea level and nearshore circulation in the Red River Delta coastal zone," Proceedings of the 1st Scientific Workshop of VS/RDE/03, Thinh Long, Vietnam.
9. MTR 2007. "Report to the mid-term review of the country strategy for development cooperation with Vietnam 2004-2008," Unpublished Report, Embassy of Sweden, Hanoi, VietNam.
10. Ninh, P.V., Hung N.M., Hong L.X., Tan, T.D., and Nga, N.T.K. 2007. "Overview of the coast line evolution in Vietnam and especially in the Red River Delta by maps and historical data," Proceedings of the 1st Scientific Workshop of VS/RDE/03, Thinh Long, Vietnam.
11. VCZVA 1996. "Vietnam coastal zone vulnerability assessment," Final Report, Ministry of Foreign Affairs, Government of The Netherlands, and Hydrometeorological Service, Government of the Socialist Republic of Vietnam, December 1996.
Nguyen Manh Hung
