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Description of Study Sites in the NCAP Vietnam Project

Multiple Authors

Thua Thien Hue Province, Huong River Basin and Phu Vang districts

Figure 1: Location of Thua Thien Hue province in Vietnam and the surrounding regions(Source: Phong Tran et al. 2007)

Thua Thien Hue (TTH) is a province in the coastal zone of northern central Vietnam, located between 15059′-16048’N and 106025′-107051’E. It is bordered on the east by the East Sea of Vietnam (South China Sea) and on the west by Laos (Figure 1). The province has a varied geography including forested mountains and hills, rivers, streams, (rice) paddy fields, coastal lagoons and marine areas. Lying on the east-west corridor connecting Myanmar, Thailand, Laos and Vietnam with the South China Sea, Thua Thien Hue is one of four provinces of the Central Key Economic Zone and is one of the most famous cultural and tourism areas of the country (TTHPPC, 2005).

Thua Thien Hue has an area of 5,053km2 and is divided into nine administrative districts. In 2006 the population of the province was estimated at 1,150,000 inhabitants, with about 300,000 of these living in or around the ancient capital of Hue (TTHPPC, 2005; Phong Tran et al, 2007). Much of the province’s infrastructure and industry lies in the coastal plain and most of the population lives within 25km of the coast (TTHPPC, 2004). As such, Thua Thien Hue is at high risk from disasters and other climate change-related impacts.

Figure 2: Thua Thien Hue topography and the Huong River Basin

The Huong River Basin is the largest basin in Thua Thien Hue Province. It has a length of 104km and three main tributaries: the Ta Trach, Huu Trach and Bo Rivers (Figure 2). The total area of the basin is approximately 2,830km2, among which more than 80% consists of mountainous and steeply hilly terrain (the average basin altitude is 330m and the average basin slope is 28.5%). The Huong River Basin is located in the specific monsoon climate zone of central Vietnam with a severe meteorological regime: a long dry season followed by a short rainy season with often very intense rainfall. Almost all of the record rainfalls measured in Vietnam have been in the Huong River Basin. The highest rainfalls on records are in Thua Thien Hue: daily – 731.3mm, monthly – 2,451.7mm and annual rainfall – 5,910.7mm (Nguyen Duc Ngu et al., 2004).

The Huong River Basin contains a unique ecosystem of national importance – the Tam Giang-Cau Hai lagoon, which is the largest lagoon system in Vietnam and in southeast Asia. 24,876ha of the Tam Giang-Cau Hai lagoon were included on a list of 16 proposed wetland and marine protected areas in Vietnam in 1998 (TTHPPC, 2004). However, due to the changing environment and poorly planned expansion of the aquaculture sector, the ecological integrity and water quality of the lagoon system has rapidly degraded. In addition, construction of a major anti-salinity weir in the Huong River is decreasing downstream freshwater flows and is impacting on the fauna and flora in the lagoons.

The Huong River is also the main source of irrigation water for agriculture and aquaculture, provides the water supply for industry, energy generation, municipal and civil use, and supports the existence of various ecosystems and wildlife on a large scale. Consequently, demand for its water is very high. In addition, there is dense human settlement in the Huong River plain and coastal area, with the majority of the population living near the poverty line and whose livelihood strongly depends on the river basin’s natural and water resources. The seasonal distribution of water resources in the basin is not consistent. Very high discharge in the rainy season causes flooding and inundation whilst low flow in the long dry season often causes a water supply crisis. Potential impacts of climate change and consequent water demand pressure would only exacerbate such crises, increase water pollution and saline intrusion and contribute towards ecological and wildlife degradation.

Phu Vang is a coastal district in the lower part of the Huong River with a diversity of landscapes: mixed low-lying agricultural land and aquaculture ponds cover the river estuary and part of the above-mentioned Tam Giang-Cau Hai lagoon. Phu Vang is among the most vulnerable districts in the province, bearing the burden of untimely pressure from both the ocean (typhoons, storms, sea level rise and saline intrusion) and the river (flood and drought). The low level of local people’s awareness and their very limited sources of income, along with their unwillingness or inability to resettle, all contribute to the huge loss of human lives and properties in the case of a large storm or flood. In the 1999 flood, 64 households of Hoa Duan village located in the lagoon were washed out to the sea and hundreds of people died or remain missing (Phu Vang DPC, 2006). Since ancient times, Thua Thien Hue Province and the Huong River Basin have been recurrently affected by many types of climate-related disasters such as typhoons, storms, floods, droughts and landslides. Recently, such disasters have increased in both frequency and intensity, causing significant socio-economic turbulence and loss of life, seriously damaging upstream and downstream infrastructure and ecology, impacting on World Heritage Sites and destroying people’s livelihoods and properties (Maarten Scheffers, 2005). Table 1 below summarizes the enormous losses in Thua Thien Hue Province caused by recent severe flooding events in October 1983, September 1990 and November 1999 (DMFSC, 2002; CCFSC, 2006).

Table 1: Flood-related losses in Thua Thien Hue Province, Vietnam

No Losses and Damages Oct 1983 Flood Sept 1990 Flood Nov 1999 Flood
1 Number of People dead/missing 30 5 127
2 Rice Paddy 6,152ha 7,066ha 28,799ha
Damaged/inundated subsidiary crop area 8,754ha 1,994ha 8,747ha
Damaged industrial crop area 65ha 1,577ha 4,073ha
Fields swept away/filled up 30ha 370ha
3 Infrastructure
Collapsed houses 1,340 735 7,121
Hospitals 52 91 119
Irrigation Structures
Soil swept away 1.24mil. m3 1.29mil. m3
Stone swept away 1,050 m3 1,265 m3
Concrete 340 m3 151 m3
Transport Networks
Soil 821,000 m3 742,000 m3
Concrete 198 m3 285 m3
Damaged bridges 54 55
Electrical cable poles 32 35
4 Other properties
Sunk boats 915
Dead buffaloes/cows 425 heads 270 heads 1,645 heads
Dead domestic animals (others) 170,000 194,210 319,377
Monetary value (with USD approximates) 75 bill. VND (5.6 mill. USD) 120 bill. VND (8 mill. USD) 925 bill. VND (60 mill. USD)

Figure 3: Climate related disasters and environmental change in different parts of the Huong River Basin (Source: Phong Tran et al., 2007)

Hue City and the Huong River are both World Heritage Sites and famous tourist destinations, providing income for an increasing number of local people. Protection and adaptation measures for the Huong River system to help address negative changes are very important economically in the context of the above. To better preserve the world heritage and landscapes of Hue City, adjacent areas and the Huong River, it is not appropriate to build dykes along the river or an embankment system around Hue City and the historical sites, so flooding usually spreads across very large areas. In addition, the topography of the Huong River Basin changes rapidly from the upstream mountainous zone to the plains and large lagoon system, with hardly any transition area, resulting in high runoff/flow in the rainy season and extensive floods and inundations downstream.

During the dry season, the prolonged low rainfall causes salinity to intrude far upstream, badly affecting agriculture, lagoon ecology and aquatic resources. The saline intrusion can reach Bach Ho Bridge, more than 10km from the Huong River estuary, where the intake for Hue City’s water supply system is located. Moreover, the upstream ‘slash and burn’ cultivation practices and rapid deforestation together with the geographical and meteorological characteristics of the basin are causing more erosion, creating increased risk of land slides and flash floods in the mountainous areas (Figure 3).

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