Regimes of human and climate impacts on

Original article Regimes of human and climate impacts on coastal changes in Vietnam Tran Duc Thanh Ỉ Yoshiki Saito Ỉ Dinh Van Huy Ỉ Van Lap Nguyen Thi Kim Oanh Ta Ỉ Masaaki Tateishi Abstract Vietnam is a tropical to subtropical country located on the eastern Asian coast where the Red (Song Hong) and Mekong rivers discharge into the sea The catchments of these two transboundary rivers cover parts of six countries, and their water and sediment discharges greatly influence the coastal seas of Vietnam The impact of human activities include changes in the supply and distribution of water, sediments, and nutrients; changes in the relationships and balance among dynamically interacting factors and processes; and changes in the quality of the coastal and marine environments due to the increased use and accumulation of pollutants and the loss of habitats These impacts have resulted in increasing unpredictability and severity of coastal problems such as floods, erosion, sedimentation, and saltwater intrusion; environmental pollution; and the degradation of ecosystems, with accompanying decrease in biodiversity and fishery productivity Keywords River catchment-based drivers Ỉ Climate change Ỉ Land-use change Ỉ Coastal impact Ỉ Vietnam Received: 18 July 2001 / Accepted: September 2002 Published online: 19 November 2003 ê Springer-Verlag 2003 T.D Thanh (&) ặ D.V Huy Haiphong Institute of Oceanology, 246 Danang Street, Haiphong City, Vietnam E-mail: tdthanh@hio.ac.vn Fax: +84-31-761521 Y Saito MRE, Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan V.L Nguyen Ỉ T.K.O Ta Sub-Institute of Geography, 01 Mac Dinh Chi St., District 1, Ho Chi Minh City, Vietnam M Tateishi Department of Geology, Niigata University, Niigata, 950-2181, Japan Introduction The Vietnamese shoreline stretches across more than 3,200 km The area of coastal waters 50 m deep or less is about 206·103 km2, including 1,600 km2 occupied by more than 3,000 islands (Fig 1) The Vietnamese coastal zone can be divided into four natural parts: the Gulf of Tonkin, the central coast, the southeast coast, and the Gulf of Thailand Along the coastline where 114 small and large rivers flow in, the largest is the Mekong River and the second largest is the Red River (Song Hong) Water and suspended sediments from these two rivers greatly influence the coastal waters of many countries in Southeast Asia In addition to estuaries associated with these rivers, there are also many bays and lagoons that have resulted from the natural interaction between the sea and the land Because of the high productivity of ecosystems such as estuaries, lagoons, mangrove forests, coral reefs, and seagrass beds, the Vietnamese coastal zone is high in biodiversity About 11·103 aquatic and more than 1,300 island species inhabit the coastal zone, including many rare and precious endemic species Because of the presence of rich natural resources and other favorable natural conditions, the coast is a zone of active development Recently, there have been dramatic changes in the terrestrial ecosystems of the coastal environment because the natural interactions between the land and the sea have been modified by human activities taking place both in the coastal zone and in the catchments of the rivers In this paper, we review the present environmental status of the Vietnamese rivers and coast and related problems, and discuss the protection of the Vietnamese coastal environment Materials and methods This paper mainly integrates data from existing publications Almost all of them are synthetic works on river hydrology and water resources (Pho 1984; World Bank 1996; Hau et al 2002), marine hydrology (Ninh et al 1992; Thuy and Khuoc 1994), upstream forest and land use (World Bank 1996; Cuong 1997), mangrove forests (Hong and San 1993), coastal living resources (Ministry of Fishery 1996; Thuoc 2001), and the state of riverine and coastal environments (Ninh et al 1995; Thanh 1995; Hoi et al DOI 10.1007/s10113-003-0062-7 Reg Environ Change (2004) 4:49–62 49 Original article Fig Sketch map of some natural factors and resources in Vietnamese coastal zone 1997; Nguyen et al 1999; Dieu and Hoi 1999; Thanh and Huy 2000; Dieu et al 2000) Some data used in this paper were collected and analyzed by us The data are not as yet synchronized with respect to time and location, and they are still limited in those many coastal areas affected by the catchments of small rivers This circumstance, that data are not systematic and detailed, reflects the current situation of Vietnamese coastal environment research; there are many gaps in coastal environmental information, and 50 Reg Environ Change (2004) 4:49–62 publication and exchange of data is still suffering from limitations Nevertheless, we have attempted to estimate Vietnamese coastal changes reflecting the impact of human activities taking place in both the coastal zone and the river catchments in relation to the ‘‘Land–Ocean Interactions in the Coastal Zone’’ (LOICZ) program Some important coastal changes, for example, coastal erosion and saltwater intrusion, appear to be the consequence of both climate Original article changes and human activities For this reason, the following ‘‘setting’’ section is included focusing primarily on the climatic forces so that ultimately the combined impact of these two main forces on the coastal environment can be evaluated Results and Vietnam) and has an area of 795,000 km2, 9% of which is in Vietnam Its annual discharge is 520.6·109 m3 of water and 98·106 t of suspended sediments The Red River catchment includes parts of two countries (China and Vietnam) and has an area of 169,000 km2, 51% of which is in Vietnam Its annual discharge is 137·106 m3 of water and 116·106 t of suspended sediments (Pho 1984; World Bank 1996) Monthly water discharge shows clear seasonality, with the period of high discharge being from June to September (Table 5) Physical setting and indication of changing climatic forces The Vietnamese coast is located in a tropical monsoon zone that experiences two seasons The season from October to April is characterized by a prevailing northeast (NE) wind (the NE monsoon), and the season from May to September by a southwest (SW) wind (the SW monsoon) The mean wind velocity is 2.5–5 m/s, and the maximum velocity is 30 m/s during the NE monsoon and 50 m/s during the SW monsoon The mean temperature ranges from 22.6–27.2 °C, increasing southward The mean annual rainfall ranges between 1,000 and 2,400 mm, with the least precipitation occurring along the central coast During the period from 1975 to 1995, the coastal zone was struck directly by an annual average of 2.52 typhoons and 2.2 tropical lows The number of typhoons increased during the latter part of that period; for example, an average of 2.8 typhoons/year was recorded from 1991 to 1995 The irregularity of the typhoons also increased recently A mean wave height ranging between 0.5 and 2.0 m was measured at different sites Maximum wave heights of 4.5 m during the NE monsoon and 7.5 m during the SW monsoon were recorded The coastal tides include diurnal, semidiurnal, and mixed types, with a range of 0.5 to 4.0 m The tidal range is high (meso-tide) in the Mekong and Red river deltas facing the South China Sea The coastal current varies in velocity and direction according to season and location Three areas of upwelling exist in the Vietnamese coastal zone The largest is along the central coast, and the second largest is offshore of the Mekong deltas In the Gulf of Tonkin, the site of the upwelling changes according to the season; it lies near the SW gulf coast during the SW monsoon season and in the center of the gulf during the NE monsoon (Ministry of Fishery 1996) Storm surges, which pose a danger to the coastal inhabitants, have amplitudes ranging from 0.5 m to a maximum of m along the coast to the west of the Gulf of Tonkin The average amplitude is 1.4 m along the central and south coasts (Ninh et al 1992) Sea-level rise has been recorded at some coastal sites For example, at Hon Dau station (Red River Delta), a rise averaging 2.24 mm/year was recorded from 1957 to 1989 (Thuy and Khuoc 1994) Pressure from human forces In both the coastal zone and the catchments, human activities have influenced land–sea interactions and have had great impact on the environment and ecosystems of the coastal zone and adjacent areas (Key economic drivers are mapped in Fig 3) The coastal lands have a high population density; of VietnamÕs 77 million people, 24% live in coastal districts Along the coast, there are 12 cities with a population of over 100·103 and 37 smaller ports and harbors Seventeen million people live on only 17·103 km2 in the Red River Delta (RRD), an area which also accounts for 20% of the rice production of Vietnam Fifteen million people live on 39·103 km2 in the Mekong River Delta (MRD), where 50% of the nationÕs rice crop is grown Annually, 0.8·106 t of fish are caught in the coastal waters and oil production is about 10·106 t/year In 1943, there was 400·103 of mangrove forests, including 250·103 in the MRD alone, but by 1993 only about 170·103 of mangrove forests remained in the whole country (Hong and San 1993) Almost 200·103 of brackish aquaculture ponds have replaced the mangroves A large part of the tidal floodplain, including the mangrove marshes, has been reclaimed for agriculture as well From 1958 to 1995, 24·103 of the tidal flood plain in the RRD was reclaimed During this period, 985 ha/year of tidal flood plain, mainly mangrove marshes, was reclaimed for agriculture or converted to brackish aquaculture ponds During the same period, the land area expanded at a rate of only 361 ha/year by seaward accretion During the last 1,000 years, a great system of dikes has been built to protect the plain and its inhabitants from river and ocean floods In all of Vietnam, there are 5,700 km of river dikes and 2,100 km of sea dikes There are 3,000 km of the river dikes and 1,500 km of sea dikes in the RRD, dividing it into compartments that are lower than the rising sea level Pressures also originate in coastal mining The exploitation of coal deposits, sand and gravel use for construction, and exploitation of heavy minerals, are important activities that deform the landscape, produce solid and liquid wastes, and increase coastal erosion Furthermore, coastal Catchment influence mining operations in Quang Ninh Province annually Every year, rivers discharge about 880·109 m3 of water dump 10·106 t of solid waste and 7·106 m3 of liquid waste and between 200 and 250·10 t of suspended sediments into the coastal zone into the Vietnamese coastal zone, which are concentrated Upstream, forests have been destroyed by war, cultivation, in the Mekong and Red river deltas (Fig 2; Tables 1, 2, logging, and fire Forest coverage decreased from 67% to and 4) The Mekong River catchment includes parts of six 29% during the period between 1943 and 1993 (see Table 6; World Bank 1996; Cuong 1997) countries (China, Myanmar, Laos, Thailand, Cambodia, Reg Environ Change (2004) 4:49–62 51 Original article Fig River system in Vietnam Vietnam has a cultivated land area of more than 7·106 ha, 60% of which is paddy lands (Table 7) A great volume of river water is needed for irrigation every year (Table 8) For example, in 1990, 47·109 m3 of water was used for irrigation: 7.4·109 m3 in the RRD and 18.4·109 m3 in the MRD (World Bank 1996) The demand for irrigation water is most pressing in the dry season In the RRD during the dry season, the demand ranges from 25 to 50% of the riverÕs water discharge, leading to a large decrease in water discharge to the coastal zone In 1993, 2.1·106 t of 52 Reg Environ Change (2004) 4:49–62 chemical fertilizers were used in the cultivated lands, including 1.2·106 t urea, 793·103 t phosphate, and 22·103 t potash In 1988, 20·103 t of pesticides was used, including DDT, lindane, methamidophos, and methyl parathion; by 1994 pesticide use had increased to 30·103 t Pesticide residues have been transported by rivers to the coastal zone, where they may accumulate in the bottom sediments to high concentrations such as has occurred in the RRD Average water quality in selected small rivers of the RRD is shown in Table Original article Table Characteristics of Vietnamese river catchments (after Pho 1984, World Bank 1996) River basins in Vietnam (from north to south) River basin Catchment area (km2) within Vietnam Mean annual discharge in Vietnam (109 m3) Bang-Ky Cung Red Red River delta Ma Ca Gianh-Tri-Huong Thu Bon Tra Khuc Ba Dong Nai Mekong Mekong River delta 10,500 86,660 17,000 17,810 17,730 20,084 10,496 14,705 13,900 36,261 72,000 39,000 8.9 137.0 20.1 24.2 17.0 19.3 6.6 10.4 30.6 520.6 Table Catchment areas (km2) of major Vietnamese river basins River basin Outside Vietnam In Vietnam Percentage in Vietnam Total All basins Red River Mekong River 832,614 82,340 723,000 323,920 86,660 72,000 28 51 1,156,534 169,000 795,000 Table Mean annual water discharge in Vietnam (109 m3) River basins Total Generated in Vietnam All basins Red River Mekong River 880.0 137.0 520.6 353.5 92.9 50.5 The rivers have been dammed to create many reservoirs in the catchments and coastal plains for irrigation and hydroelectric power Nine large reservoirs for hydroelectric power cover an area of 1,267 km2 The largest, Hoa Binh, was built in 1987 on the Da River, which is the largest tributary of the Red River The Hoa Binh reservoir occupies an area of 208 km2 and holds 9.5·109 m3 of water Annually, 48·106 t of sediments, equal to 83% of the suspended-sediment load, is transported into the reservoir and deposited Consequently the building of Hoa Binh Dam has made a substantial change to the sediment and water discharge of the Red River (Tables 10 and 11) An even larger reservoir to be named Son La (Lake Son La), which will have an area of 440 km2, is planned for the upper Da River above the Hoa Binh reservoir Annual domestic and industrial water demand is over 4·109 m3 A great volume of wastewater, most of which is left untreated, is dumped into the rivers and discharged into the coastal zone From 657·103 to 820·103 m3/day of wastewater is produced by the industrial area of Hanoi– Viet Tri–Haiphong in the north and 550·103 m3/day by the industries of Ho Chi Minh City in the south The 34·106 m3 wastewater/year dumped into the Red River from the Viet Tri industrial site includes 100 t H2SO4, 40 t HCl, 300 t benzene, and 25 t pesticide (Hoi et al 1997) An initial estimate shows that every year 24,747 t PO4) and 35,068 t NO3) are transported into the coastal zone by the currents of the Red River (Ninh et al 1995) Impact of coastal changes Recently, changes in the Vietnamese coastal environment and ecosystems have become obvious However, quantitative analyses of these changes are few The changes have been caused by both natural processes and human activities Changes due to human activities can be global, as in the case of sea-level rise, unusual typhoons, and meteorological disturbances related to human-induced global warming; or regional such as from upstream deforestation and the construction of dams, or they can be localized to the coastal zone In terms of land–sea interactions, human activities have had the following impacts on the Vietnamese coastal zone: – Changed supply and distribution of water, sediments, nutrients, and other materials The present status of nutrient concentrations in the RRD and MRD are shown in Tables 12 and 13 – Changed quality of coastal and marine environments by pollution, eutrophication, and reduction of biodiversity resulting from the increased loading and accumulation of pollutants The change of some pollutants such as oil, Cu and Zn in the Vietnamese coastal zone are shown in Reg Environ Change (2004) 4:49–62 53 Original article Table Characteristics of the Mekong and Red River basins (after Pho 1984, World Bank 1996) Mekong River basin Number of river mouths Measurements of river details Catchment area Delta area in general and in Vietnam Maximum elevation Length Gradient within Indochina Sediment discharge in Laos Sediment discharge in Vietnam Flood season discharge Has nine great river mouths on the 320-km-long deltaic coastline Date of flood season Date of date season Water discharge measured at Crache, Cambodia Average annual discharge Average discharge during wet season and dry season Maximum in September, minimum in April Sediment concentration in dry season and flood season Salt intrusion landward Dates of wet period Date of dry period Red River Basin Measurements of river details Catchment area Delta area Coastline Length Mean basin elevation Maximum elevation River gradient Details of flood season Details of dry season Sediment concentration Salt intrusion landward Wet period Dry period Table Monthly water discharge of the Red River (m3/s) at Son Tay Station near upper Hanoi (1961–1980; after Pho (1984) Month m3/s % 795 ·103 km2 $50·103 km2, $36·103 km2 $5,000 m 4,500 km of which 200 km is in Vietnam 16 cm/km 132 ·106 t/year 98·106 t/year 60·109 m3held by Tonle Sap Lake in Cambodia, which is part of the Mekong River system June to November December to May 13.56·103 m3/s 23.87·103 m3/s, 3.27·103 m3/s 38.81·103 m3/s, 1.91·103 m3/s 50–100 g/m3, 250–300 g/m3 60–70 km 1937–1953 1954–1977 169 ·103 km2 (including 14 ·103 km2 in the catchment area of the Thai Binh River, entirely in Vietnam) 17 ·103 km2 entirely in Vietnam $150 km length 1,126 km of which 556 km is in Vietnam 1,090 m $3,000 m 230 cm/km June to October with 74.4% of total annual discharge and a maximum of 21.2% in August November to May with 25.6% of total annual discharge and a minimum of 2.05% in March Very high, annual mean value 1,000 g/m3at Son Tay near Hanoi 30–50 km 1932–1951 1952–1967 These impacts have led to various negative consequences as explained below Increase in coastal risks Floods Coastal floods have increased in intensity and in frequency of occurrence They are a consequence of the combined impact of upstream deforestation, heavy rains, sea-level rise, and the blocking of lagoonal inlets or river mouths by sedimentation Coastal floods are especially severe and very dangerous when heavy rains and storm surges coincide with spring tides Annual flooding in the MRD, which lasts from to months mainly between August and October, inundates an area of more than 1.7·106 affecting million people directly From 1926 to 1997, there were 23 heavy floods, of which those in 1991, 1994, and 1996 were particularly noteworthy Floods along the central coast involving the many small Tables 14 and 15 The changes of some nutrient conrivers are particularly heavy because of their sudden centrations and water quality parameters in the coastal onset after heavy rains, a consequence of destroyed upzone of North Vietnam are shown in Table 16 stream forests, steep coastal landforms with longshore sand dunes, and rapid blocking of lagoonal inlets and the – Loss of coastal habitat, e.g., mangroves Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean annual discharge Flood season % Dry season % 54 1,328 1,100 914 1,071 1,893 1,692 7,986 9,246 6,690 4,122 2,813 1,746 3,633 Reg Environ Change (2004) 4:49–62 3.0 2.5 2.1 2.4 4.3 10.8 18.4 21.3 15.3 9.5 6.4 4.0 100 75.3 24.7 Original article Fig Sketch map of economical zones and activities in Vietnamese coastal zone Table Deforested and barren lands in Vietnam After World Bank (1996), Cuong (1997) Region Land area (1,000 ha) Percentage forest cover in 1943 Percentage forest cover in 1991 Percentage barren land area in 1993 Northern mountains Northern midlands Red River delta North central coast South central coast Central highlands NE of Mekong R Total 7,645 3,982 1,030 4,002 4,582 5,557 2,348 33,104 95 55 66 62 93 54 67 17 29 35 32 60 24 29 60–65 27–33 5–14 40–44 42–49 25–32 23–34 35–42 Reg Environ Change (2004) 4:49–62 55 Original article Table Land use in 1993 (ha; after World Bank (1996) Land use Entire Vietnam Red River delta (lowlands only) Mekong River delta Total area Total crop land Total annual crop land Area with rice paddies 33,099,093 6,771,060 5,523,899 4,079,483 1,251,167 668,851 643,021 585,284 3,956,918 2,444,060 2,104,593 1,933,280 Table Agricultural water use (106 m3; after World Bank 1996) Region 1985 1990 2000 Entire country Red River delta Mekong River delta 40,660 6,601 15,617 46,996 7,377 18,398 60,479 8,902 23,775 Table Average water quality in selected small rivers in Hanoi–upper RRD (1992–1994) From the Interim Report of the Institute of Water Resources Planning and Management Please note that these values are high (after World Bank 1996) River BOD5(mg/L) COD (mg/L) NH4 (mg/L) PO4 (mg/L) Set River at Cau Set To Lich River at Thanh Liet Kim Nguu River at Yen So Lu River 31.6 19.6 95.4 47.8 1.1 0.9 2.2 2.2 38.4 31.0 106.3 83.8 1.1 1.3 2.2 3.2 BOD5biochemical oxygen demand; COD chemical oxygen demand Table 10 Suspended sediment in transport in the Red River at Son Tay Station (mg/m3) between period 19592–1985 (before completing Hoa Binh Dam) and period 1986–1997 (after completing Hoa Binh Dam; after Hau et al (2002) Month 10 11 12 Yearly 1959–1985 1986–1997 200 128 172 123 170 137 220 203 556 458 1,070 719 1360 855 1,530 936 1050 847 797 776 581 303 299 143 1,010 677 Table 11 Change of water discharge distribution patterns at Son Tay, Ha Noi and Thuong Cat Stations in the Red River (m3/s) every month between periods 1976–1985 (before completing Hoa Binh Dam) and 1986–1995 (after completing Hoa Binh Dam) Son Tay Station lies above on the main branch of the Red River Ha Noi and Thuong Cat Stations lie below on two sub-branches of the Red River (After Hau et al 2002) Month 10 11 12 56 Son Tay Station Ha Noi Station Thuong Cat Station 1976–1985 1986–1995 1976–1985 1986–1995 1976–1985 1986–1995 1,309 1,133 930 1,053 2,045 4,061 6,570 8,345 6,871 4,099 2,868 1,640 1,222 1,124 1,179 1,294 2,519 5,092 8,768 7,347 4,779 3,910 2,208 1,474 1,098 955 794 926 1,632 3,175 5,105 6,463 5,633 3,362 2,417 1,405 963 895 899 989 1,521 3,402 5,884 5,209 3,501 2,857 1,681 1,163 293 244 213 231 491 1,111 1,808 2,377 2,025 1,192 812 427 272 244 260 289 496 1,304 2,608 2,098 1,252 975 529 340 Reg Environ Change (2004) 4:49–62 Original article Table 12 PO4 and NO3in the coastal zone of the RRD (mg/L) The Vietnam standards in 1995 for aquaculture were: PO4, 0.01 mg/L; NO3, 0.05 mg/L The standards for swimming beaches in 1995 were: PO4, 0.065 mg/L; NO3, 0.05 mg/L (after Ninh et al 1995) PO4 NO3 Season River River mouth Coastal sea Dry season Flood season Dry season Flood season 0.12 0.448 0.307 0.728 0.07 0.224 0.144 0.121 0.03 0.077 0.090 0.085 Table 13 Total N and P in surface water at selected locations in the Mekong River delta These values are averages of monthly samples collected over a 24-month period ending in October 1994 Critical concentrations of total N and phosphate-P are generally considered to be 0.5 mg/L and 0.05 mg/L, respectively In these data, total N might reflect analysis problems From the Interim Report of the Sub-Institute of Water Resources Planning and Management World Bank (1996) Region\area Site Total N (mg/L) Total P (mg/L) Mekong River Tan Chau Chau Doc Hong Ngu Kien Binh Ho Phong Thoi Binh Thoai Son Tam Ngan 0.42 0.42 0.27 0.27 1.05 0.99 0.71 0.80 0.14 0.10 0.12 0.05 0.17 0.07 0.14 0.10 Plain of Reeds Camau Peninsula Longxuyen Quadrangle Table 14 Change in average content of oil in Vietnamese coastal waters (mg/L) from 1995–1998 The Vietnam standards in 1995 for aquaculture were 0.05 mg/L, and 0.3 mg/L for swimming beaches These average values were calculated from data of 16 national stations of environment observation (four stations for each area) measured every three months (after Dieu et al 2000) Area 1995 1996 1997 1998 Near shore of the northern part Near shore of the central part Near shore of the southern part Offshore area of oil exploitation and international shipping way 0.24 – – – 0.61 0.18 – 0.55 0.45 0.13 0.18 0.54 0.56 0.16 0.44 0.53 mouths of small rivers by sedimentation due to longshore sand drift in the dry season In November 1999, terrible floods along the central coast caused a great loss of life and destroyed considerable parts of the infrastructure Protected by the dike system, the coastal lowlands of the RRD are flooded only by local heavy rainfall Floods in the RRD are especially dangerous when waves linked with storm surges break the sea dikes, as happened in 1955 and 1996 Erosion/accretion In both the MRD and the RRD, which are known to have usually accreting coastlines, erosion has nevertheless occurred along one-fourth of the coastline of each delta Nowadays coastal erosion is a key concern, increasing in scale and amount with the resulting damage Overall, 243 coastal sites covering 469 km of coastline have eroded at a rate of 5–10 m/year Ninety-six of these sites have lost even more than km of coastline to erosion The longest eroded coastal stretch extends 60 km at Ganh Hao in the MRD and along the Bo De coast; some 36 km of coastline have been eroding at a rate of 30–50 m/year On average, 112 of coastal land has been lost each year for the last century Following is a discussion of the second longest eroding coastal stretch at Vanly in the RRD, which extends over a length of 30 km (Thanh 1995; Thanh and Huy 2000; Dien et al 2003) In the RRD, the Vanly coast has been eroding at a rate of 10–15 m/year during the last half century, even though dikes and embankments protect this coast Corresponding to the completion of the big Hoa Binh Dam in the Red River catchment at the end of 1989, the mean rate of coastal erosion increased from 8.6 m/year during 1965– 1990 to 14.5 m/year during 1991–2000 along the Vanly coast (Thanh and Chien 2002; Dien et al 2003) An effective means of protecting the area has not yet been found At present, two sea-dike systems are used Whenever the seaward dike system is damaged by erosion, a new dike system is built landward, and a great number of the inhabitants are forced to move Figure gives some detail on how accretion processes have been replaced by considerable erosion Coastal erosion has also long been a serious problem in the Bach Dang estuary in the north and in the Dong Nai Reg Environ Change (2004) 4:49–62 57 Original article Table 15 Change in average content of Zn and Cu in Vietnamese coastal waters (mg/L) from 1996–1998 The Vietnam standards in 1995 for aquaculture were 0.01 and 0.01 mg/L for Zn and Cu, respectively; and for swimming beaches, 0.1 and 0.02 mg/L for Zn and Cu, respectively These average values were calculated from data of 12 national stations of environment observation (four stations for each area) measured every three months (after Dieu et al 2000) Area Zn Near shore of the north part Near shore of the center part Near shore of the south part Cu 1996 1997 1998 1996 1997 1998 0.0053 0.0233 0.0219 0.0465 0.0287 0.0219 0.0538 0.0185 0.0473 0.0078 0.0055 0.0168 0.0066 0.0051 0.0093 0.0086 0.0042 0.0064 Table 16 Changes in some key parameters of water quality in the coastal area of North Vietnam from 1995–1998 The Vietnam standards in 1995 for aquaculture were: DO, mg/L; NO2, 0.002 mg/L; PO4, 0.1 mg/L; SiO3, mg/L; Coliform, 1,000 MNP/100 ml The standards for swimming beaches were: DO, mg/L; NO2, 0.001 mg/L; PO4, 0.65 mg/L; SiO3, mg/L; 1,000 MNP/100 ml; After Dieu and Hoi (1999) Parameter Unit 1995 1996 1997 1998 DO NO2 PO4 SiO3 Coliform mg/L mg/L mg/L mg/L MNP/100 ml 7.53 0.0049 0.0098 0.3140 – 7.06 0.0050 0.0065 0.5990 773 7.01 0.0088 0.0177 0.9570 804 6.28 0.0115 0.0224 1.1875 866 estuary in the south, regions where population density is high Along the central sandy coast, erosion localized in both time and place happens suddenly In general, the erosion rate ranges from 1–5 m/year, but sometimes it is as much as 10–15 m/year Typical eroded coasts are found at Canh Duong, Thuan An, and Phan Ri In the MRD, coastal accretion has occurred on the Camau Peninsula at a rate of 50–80 m/year, with a maximum rate of 150 m/year, while the peninsula expanded seaward at a rate of 122 ha/year between 1885 and 1985 (Nguyen et al 1999) The RRD has expanded seaward 27 m/year at a maximum rate of 120 m/year, and 360 ha/year have been added to this delta In the deltas, deposition provides us with the precious resource of land However, sedimentation is a major risk, which has become more extensive recently (Thanh 1995), having a particularly negative impact on marine ports and harbors Haiphong is a typical example: for more than a century, it was the biggest port in Vietnam, but recently big ships have not been able to reach the port owing to the heavy sedimentation in its channel caused by the building of the Dinh Vu coastal dam This dam has closed the Bach Dang estuary, blocked the discharge of sediments from a natural tributary, and concentrated sediments into the shipping channel Along the central coast, longshore sand drifts generated by wave action have closed lagoonal inlets and the mouths of small rivers, leading to coastal floods, the freshening of saltwater lagoons, and the loss of water on its way to the sea; for example, the closure of the Tu Hien inlet in Tam Giang lagoon pressures, saltwater now penetrates 30–50 km up the Red River and 60–70 km up the Mekong River More than 1.7·106 of land has been affected by saltwater intrusion in the MRD; this area is predicted to increase to 2.2·106 in the near future if suitable management practices are not implemented In recent decades, the 1& salinity contour (isohaline) has moved landward by 4–10 km in the northeast part of the RRD Owing to gradual saltwater intrusion landward, salinity has also increased everywhere in the MRD during the dry season, reaching its maximum in March and April every year A comparison of the 4& salinity contours during the 20 years between 1978 and 1998 revealed movement of approximately 20 km landward (Nguyen et al 1999) Most of the Mekong water during the dry season comes from the upper reaches of the river in China A combination of factors such as the decrease in river-water discharge caused by dams, irrigation and the sea-level rise may have led to more saltwater intrusion, which is a serious problem not only for coastal agriculture, but for other economic sectors as well Along the central coast, the Thua Thien Hue Province with a population of nearly one million, also suffers from fresh water shortage for agricultural, domestic, and industrial uses because of saltwater intrusion in the valley of the Huong River, a small river, during the dry season Environmental pollution For the most part, coastal and marine environmental quality with respect to contaminants is still rather good, although varying levels of pollution have been recorded at some sites resulting from contaminants produced by huShifts in the saltwater–freshwater boundary man activities in catchments or in coastal or marine areas Flood-related water freshening has caused losses in the (Ninh et al 1995; Hoi et al 1997) Among those, oil polcoastal fishery, including both the fishery catch and mar- lution is locally a comparably serious problem (see Fig 3) ine and brackish water aquaculture Because of tidal This pollution is generated mainly by activities off shore 58 Reg Environ Change (2004) 4:49–62 Original article Fig Coastline change by erosion and accretion in the Red River Delta (after Dien et al 2003); the detailed map on the left features the change from accreting to eroding processes along Vanly coastline between 1930 and the recent past After completion of the Hoa Binh Dam at the end of 1989, erosion rate increased even here from 8.6 m year)21 (1965–1990) to 14.5 m year)1 (1991–1998) and affects the coastal zone especially through the water transportation pattern In waters close to the coast, the oil content exceeds the Vietnamese standard of 0.05 mg/L for fisheries and even the standard of 0.3 mg/L for domestic activities at some sites In the offshore waters, an oil content of more than 0.05 mg/L up to a maximum of 0.4 mg/L, has been recorded at 10% of the sampled stations Pollution from heavy metals such as Fe, Zn, Cu, Cd, Reg Environ Change (2004) 4:49–62 59 Original article Hg, As, and Pb is not yet widespread, but the concentrations of these pollutants may be increasing in coastal waters, sediments, and wildlife Fe, Zn, and Cu pollution has been confirmed at several sites Similarly, pollution of organic matter is distributed locally, but is heavy at some sites In general, pesticide residues have been below standard limits, although evidence for their accumulation is widespread and they exceed standard limits in several places; for example, in the coastal zone of the RRD Residues of ten organochlorinated pesticides such as HCB; Lindane; Aldrin; 2,4Õ-DDE; Dieldrin; 2,4Õ-DDD; Eldrin; 2,4ÕDDT and 4,4Õ-DDT have been found in estuarine water and sediments (Cu 2000) Eutrophication is a problem in southern Vietnam where nutrients such as phosphate (PO43)), nitrogen (NO2), NO3)), and organic matter are produced as waste from domestic activities, agriculture, and aquaculture The widespread occurrence of diseases in brackish water aquaculture in the south may be related to eutrophication and to red tides In 1996, the brackish water shrimp aquaculture industry in the MRD lost hundreds of millions of dollars owing to the expansion of eutrophication and toxic algal blooms Some shellfish have been poisoned by toxic phytoplankton, but, unfortunately, no scientific studies of this problem have yet been conducted In the coastal areas of central Vietnam, where many small rivers enter the sea, environmental quality is still rather good and coastal pollution is not yet severe, thanks to the lower economic and population pressures in this region (Hoi et al 1997) Unusual changes in suspended sediment distribution (here also reviewed in the context of pollution) have caused increased turbidity at swimming and resort sites such as Doson Beach This is one important reason for the loss of first class coastal tourism category of Doson Beach in North Vietnam Impact on fisheries The total estimated standing stock in Vietnamese seawater is about 3.4–3.5 million t and the annual potential yield is about 1.4–1.5 million t Especially the coastal zone (estuaries, bays, and lagoons) is the site of breeding and spawning grounds essential to sustain natural fishery production Pollution and loss of habitats in this zone have degraded the living resources for coastal and offshore fisheries Coastal fishery resources have been overexploited, while offshore ones have not yet been well exploited (Thuoc 2001) Dams in the catchments have also obstructed the migration for the spawning of some fish species, for example, Clupanodon thrissa and Maerura reeversii, so that these fishes are now rare The breeding success of migrating fish has been cut by around 50% because of dams in the Red River catchment Combined with over-exploitation, the coastal changes have threatened the survival of many marine species, including 98 species recorded in the Vietnam Red Book (the Vietnamese list of endangered species; Ministry of Fishery 1996) At the important fishing grounds, fish stocks have decreased by up to 25–30%, and even 50% in some sites (Thuoc 2001) An initial calculation shows that during the 60 Reg Environ Change (2004) 4:49–62 last decades, the total fish stock in the Tonkin Gulf (part of the Vietnamese Sea) has been reduced to some 185,500 t, equaling only 24.6% of the original total stock observed during the 1960s–70s The impact of building and operating the Hoa Binh Dam has brought this reduced amount back even further to 42,655 t, resulting in a financial loss of at least 27.6 million US dollars per year for the fish industry As a consequence, the production costs per ton of fish increased by 9.2–11.5% (Thanh and Chien 2003) In general the degradation of coastal ecosystems—water freshening, turbidity, eutrophication or nutrient loss, pollution, and loss of habitat—leads to disruption of the ecological balance and to decreases in biological productivity and biodiversity The quantity of commercially valuable fish, shellfish, crustaceans, etc has decreased in marine fishery, while brackish water and marine aquaculture has begun to suffer from diseases caused by environmental changes and pollution Impact–response relation Vietnam is a developing country, and its economy has developed quickly during the last decade as a result of VietnamÕs policy of openness and renovation The Vietnamese coastal environment is very sensitive and its tropical coastal ecosystems, especially its coral reefs, mangroves, and seagrass beds are particularly vulnerable to forces resulting from human activities and global change processes The Vietnamese coastal environment is facing emerging problems such as an increase in risks/ hazards, habitat loss, a decrease of living resources, and pollution The economic and population pressures resulting from development in the coastal environment and its affected ecosystems increase over time It is predicted that the number and scale of developmental projects supported by domestic and overseas investment will increase dramatically in the near future Coastal economic activities such as port and maritime activities, oil and gas exploitation, construction, aquaculture, and coastal tourism will increase in the next decade In catchments, major industrial development, particularly the construction of big dams for hydraulic power and irrigation, and the use of chemical fertilizers and pesticides for agriculture will have a strong impact on the coastal environment Additionally, risks and hazards at coasts associated with climate change may increase If coastal environmental protections are not implemented effectively, the social and economic development of Vietnam will not be sustainable, the natural coastal resources will be reduced, and the peopleÕs quality of life will not be maintained For these reasons, the protection of the Vietnamese coastal environment, including the prevention, control, and mitigation of negative impacts is an urgent issue In response Vietnam has implemented various coastal environmental protective measures, including establishing organizational mechanisms and a legislative basis, building national capacity, formulating national plans and strategy, implementing environmental projects, and strengthening its international cooperation The most important legislative base for environmental protection is the Law on Environmental Protection, passed in 1993 by Original article the National Assembly, and Decree No 175 issued by the government in 1994, which implements the Law on Environmental Protection The Ministry of Science, Technology and Environment of Vietnam is responsible for environmental management Under the Ministry, the National Environmental Agency is responsible for making policies, strategies, and regulations for environmental protection and sustainable development, focusing on the control of pollution and natural conservation Establishing national strategies and plans has been a very important aspect of VietnamÕs efforts to implement coastal environmental protection The National Plan for Environment and Sustainable Development (1991–2000) has been adopted During the last decade, many projects concerning coastal environmental protection for sustainable development have been implemented under this plan The National Strategy on Environmental Protection Toward 2010, in which the protection of the coastal environment is paid special attention, is being refined for submission to the government Measures for the protection of the Vietnamese coastal environment have achieved initial success, but with some limitations In particular, that coastal environmental management has not been combined with catchment management is a very important reason for these limitations In fact, this is one of the key recommendations of the LOICZ scientific synthesis currently underway (see http://www.nioz.nl/loicz/ for more information) However, this is of course not unique to Vietnam but a rather widespread shortcoming of a global scale Coastal environmental protection cannot be achieved completely in Vietnam without international cooperation The government of Vietnam has strengthened international environmental cooperation by joining many international agreements and protocols related to the environment, including the coastal environment, for example, the London Convention on Dumping at Sea and the Convention on Marine Pollution (MARPOL) These protocols and agreements serve as the legislative basis for VietnamÕs rights and responsibilities regarding environmental protection in international relations Some cooperative international projects have achieved good results However, international cooperation on coastal environmental protection has been modest The strengthening of cooperative, i.e., truly interdisciplinary research, should be considered as a strategic solution for implementing effective protection of the Vietnamese coastal environment in the future Discussion Vietnam is a tropical country located on the eastern Asian coast, where the Red and Mekong rivers—two of the five largest rivers in eastern Asia—discharge into the sea The catchments of these two rivers include parts of six countries; their water and sediment discharges greatly influence the coastal seas of many countries in the region Because of its rich natural resources and other favorable natural conditions, the Vietnamese coast has become a zone of active economic development facing a rapid increase in population density Human activities such as upstream deforestation, the destruction of mangrove swamps, dike and dam building, channel dredging, agriculture, aquaculture, and industrial and domestic activities in both the coastal zone and the river catchments have strongly influenced the Vietnamese coastal environment In terms of the Land–Ocean Interactions in the Coastal Zone (LOICZ) program, the impact of these activities includes changes in the supply and distribution of water, sediments, and nutrients; changes in the relationships and balance among dynamically interacting factors and processes; and changes in the quality of the coastal and marine environments due to the increased use and accumulation of pollutants and the loss of habitats These impacts have resulted in increasing unpredictability and severity of coastal problems such as floods, erosion, sedimentation, and saltwater intrusion; environmental pollution from, for example, oil, organic matter, pesticide residues, and, to varying degrees, heavy metals; and the degradation of ecosystems with accompanying decreases in biodiversity and fishery productivity Of course, these impacts are also the result of human influence in the other countries as well as those in Vietnam through which the Red, Mekong, and other small rivers flow From the above-mentioned knowledge, a thorough and comprehensive approach needs to be distilled, allowing for sustainable use of ecosystems relying on conserved natural resources and environmental services of the Vietnamese coastal zone Scientific information of this kind has been an effective contribution towards policy making processes, the development of resolutions and the isolating of possible patterns of balanced eco-social development and protection of natural environment However, as seen here, for the purpose of integrated coastal management and sustainable development, many limitations still exist in scientific information concerning the Vietnamese coastal environment and resources for an appropriate full analysis in light of integrated land–ocean interactions science These limitations are, firstly, gaps of recent data and information; secondly, lack of spatial and temporal synchronization of research and applied scales hampering the detection of changes in natural resources and the environment; and thirdly, limitations in publication and exchange of data Up till now, in the coastal zone including the human dimension in Vietnam, there is no coherent research agenda in terms of earth systems sciences Of course Vietnam has implemented coastal environmental protection However, it is necessary to carry out more detailed, integrated and comprehensive investigations and to build up a monitoring scheme focused on coastal nutrients, pollutants, material fluxes and coastal interaction processes that have been impacted by both human activities and climate change This will also allow a full appreciation of the existing information and a better quantitative idea of changes in the past decade Hope is expressed that through international cooperation an effective resolution can be found to respond to this demand The strengthening of cooperative and Reg Environ Change (2004) 4:49–62 61 Original article interdisciplinary research, as promoted for instance in the Ministry of Fishery (1996) Aquatic resources in Vietnam Agriculture Publishing House, Hanoi, 616 pp old and even more the ‘‘new’’ IGBP/LOICZ framework should be considered as a strategic scientific underpinning Nguyen VL, Ta TKO, Tateishi M, Kobayashi I (1999) Coastal and saltwater intrusion on the coastal lowlands of the for the future implementation of effective protection of the variation Mekong River Delta, southern Vietnam In: Saito Y, Ikehara K, Vietnamese coastal environment Katayama H (eds) Land–sea link in Asia, STA (JISTEC) and Geological Survey of Japan, Tsukuba, pp 212–217 Ninh PV, Quynh DN, Manh DV (1992) Typhoon surges in Vietnam and their regime characteristics Proc Nat Sem Coast Res Man, Hanoi, 17–19 September 1992, pp 81–87 Ninh PV, Gian TX, Tuong NV (2001) Marine pollution from pollutants discharged by rivers In: Thanh DN (eds) Reports from national programs for marine research T.IV University, Hanoi: pp 223–234 Pho NV (1984) Streams in Vietnam Science Publishing House, Hanoi, 209 pp Cu ND (2000) Some results in environment geochemistry of river Thanh TD (1995) Coastal morphological changes concerning the mouths in Vietnam In: Hoi NC (ed) Marine resources and management of the coastal zone in Vietnam Proc Coastal environment, vol VII Science Publishing House, Hanoi, pp 74– Changes, Bordeaux, 10–16 February 1995, pp 451–462 89 Thanh TD, Chien DD (2002) Influence of catchment dams on the Cuong NM (1997) Forest mapping in Vietnam In: Remote coastal environment and ecosystems In: Tien NV (ed) Marine sensing for tropical ecosystem management United Nations, resources and environment, vol IX Science and Technology, New York, pp 47–59 Hanoi, pp 121–136 Dien TV, Thanh, TD, Thao NV (2003) Monitoring coastal erosion Thanh TD; Chien DD (2003) Initially impact assessment of Hoa in Red River Delta, Vietnam: a contribution from remote Binh Dam on the fishery resources in coastal sea In: Tien NV sensing data Asian J Geoinform 3(3):73–78 (ed) Marine resources and environment, vol X Science PubDieu LV, Hoi NC (1999) Assessment of the change tendency of lishing House, Hanoi (in press) some water quality factors in the North coastal waters of VietThanh TD, Huy DV (2000) Overview on the risks of coastal nam In: Hoi NC (ed) Marine resources and environment, vol erosion and sedimentation in Vietnam J Sci Activities 1:26–27 VI Science Publishing House, Hanoi, pp 19–26 Thuoc P (2001) Scientific bases for sustainable management of Dieu LV, Trang CT, Luu VT (2000) Some remarks on the tencoastal zone fisheries resources in Vietnam In: Chung BD (ed) dency of marine environmental quality change in Vietnam In: Marine fisheries research, vol II Agriculture Publishing House, Hoi NC (ed) Marine resources and environment, vol VII SciHanoi, pp 279–300 ence Publishing House, Hanoi, pp 125–135 Thuy NN, Khuoc BD (1994) El-Nino phenomenon, global climate Hau LP, An TV, Hop LP (2002) Change in estuaries of Bac Bo warming, and sea level in Vietnam sea and South China Sea plain Constructional Publishing House, Hanoi, 172 pp Meteorol Hydrol 5:16–23 Hoi NC, Cu ND, Luong PV, Thanh TD, Yet NH (1997) Status of World Bank (1996) Vietnam water resources sector review Secoastal and sea environment in Vietnam Technical report, lected working papers of the World Bank, ADB, FAO/UNDP and Haiphong Institute of Oceanology NGO Water Resources Sectoral Group, Hanoi, 340 pp Hong PN, San HT (1993) Mangroves of Vietnam IUNC, Bangkok, 173 pp Acknowledgments We are indebted to Dr Hartwig Kremer of LOICZ-IPO for encouraging us to submit our paper for this special issue and for his kind support References 62 Reg Environ Change (2004) 4:49–62 ... strategies, and regulations for environmental protection and sustainable development, focusing on the control of pollution and natural conservation Establishing national strategies and plans has... data and information; secondly, lack of spatial and temporal synchronization of research and applied scales hampering the detection of changes in natural resources and the environment; and thirdly,... cooperation by joining many international agreements and protocols related to the environment, including the coastal environment, for example, the London Convention on Dumping at Sea and the Convention