Chapter 4. Current Adaptation to Floods

Transcription

1 Chapter 4. Current Adaptation to Floods This chapter studies current flood adaptation strategies in land use planning and housing practices in the studied area. This is obtained through literature review on adaptation of land use and houses, site visits, sketches, and interviews of 47 households in the Mekong Delta. Figure 43 and Figure 44 present the location of the studied area and houses in the administrative and flood maps. Section 4.1 studies infrastructure development and its impact on floods while Section 4.2 examines the community in the studied area. Then, Section 4.3 explores adaptation of houses by analyzing houses from different aspects that have impacts on adaptation. Based on these analyses and evaluation criteria of safe shelter, ensuring connectivity, and supporting livelihoods, Section 4.4 discusses the limitations of current adaptation strategies. Figure 43. Location of the studied area and houses Source: NAGECCO (1998) 69

2 Figure 44. Location of studied area and houses studied in the flood map for year 2000 (based on maps of SIWRP) 4.1. Adaptation of land use: Infrastructure development dealing with floods This section studies the flood control planning and infrastructure in the studied area and its impacts on floods, socio-economic development and the environment Flood control infrastructure development Infrastructure in the Mekong Delta has been developed for flood control and agriculture intensification, especially since 1990s. In the studied area, year-round flood protection is provided in the urban areas, for main transportation systems, and the fruit tree areas. This is achieved by constructing full dykes 9, main roads or landfills higher than flood peak levels in 1996 and 2000 (Figure 45, Figure 46 and Figure 47). Full dykes protect the farms from floods completely, with the control of sluice gates and pumps, enabling three rice crops per year. Outside the above areas, 9 Full dykes (high dykes) are dykes constructed higher than peak flood levels, protecting the areas from floods all year round. They are usually combined with roads and residential dykes. 70

3 partial flood control solution, which protects the rice crops from early floods in August and late floods in November-December, is possible with semi-dyke systems (Figure 48). At the end of July and beginning of August, rice crops are ready for harvest, if floods happened early and there are no dykes, crops would be damaged. Therefore, semi-dykes are constructed around the level of floods in this time, protecting the areas from early floods. After harvesting, floods overflow semi-dykes into the fields. The semi-dykes also protect the farms from late floods in November December, so that farmers can start cultivating the next crop. Semi-dyke systems help decrease the flood duration for agricultural production, ensuring two crops of rice (SIWRP 1998b; To 1998). In the studied area, 67% of the dykes are semi-dykes with an average level of about 2.5 m.a.s.l, and the rest are full dykes with an average level of about 4.5 m.a.s.l. Moreover, there are more than 1000 man-made canals in the Mekong Delta, which have been used for flood drainage, irrigation, and transportation (Le et al. 2008). Figure 45. Preliminary design of dykes in Tam Nong District Source: MRC (2009) Figure 46. A main road combined with dyke in Tam Nong District (Tam Nong District, November 11, 2009) 71

4 Figure 47. Local road combined with semi dyke, canal system, and high elevated area in the studied area (Tam Nong District, December 01, 2009) Figure 48. Flood control infrastructure of the studied area in 2004 Source: SIWRP (2010) In the studied area, during , early flood prevention embankments were constructed, and the Tan Thanh Lo Gach canal was dredged (Figure 49). After 2000, major changes in infrastructure include further dredging of canals, and the expansion and raising of Road No. 30 to exceed the peak flood levels in 2000 (5.23 meters amsl at Tan Chau) (Figure 50). Soil obtained from dredging canals is used to elevate the roads, and to build embankments along canals and along residential areas (Le et al. 2008). 72

5 Figure 49. Infrastructural change in the Mekong Delta: (a) during Source: Le et al. (2008) Figure 50. Infrastructural change in the Mekong Delta: (b) after 2000 Source: Le et al. (2008) 73

6 Impacts of flood control infrastructure on floods Figure 51, Figure 52, Figure 53, and Figure 54 illustrate average elevations of dykes in Tam Nong and Tan Hong districts, with simulated water levels in the historical 97 years under current infrastructure in the Mekong Delta. The average elevations of dykes in Tam Nong and Tan Hong are about 2.4 meters and 3 meters, respectively. These dykes can protect the area from the early floods in August, for roughly 90 percent of flood water levels simulated. This also implies that semidykes account for the majority of dykes in the studied area. Figure 51. Average elevations of dykes in Tam Nong District and simulated max water levels in the historical 97 years under current infrastructure situation Source: MRC (2009) Figure 52. Average elevations of dykes in Tam Nong District and simulated water levels in August in the historical 97 years under current infrastructure situation Source: MRC (2009) 74

7 Figure 53. Average elevations of dykes in Tan Hong District and simulated max water levels in the historical 97 years under current infrastructure situation Source: MRC (2009) Figure 54. Average elevations of dykes in Tan Hong District and simulated water levels in August in the historical 97 years under current infrastructure situation Source: MRC (2009) Figure 55. Flood control infrastructure in a nice flood 10 in the studied area 10 Nice floods have peak flood levels from 3.5 to 4.5 m, which bring fertile sediments, fishery resources, and renew the water and soil quality of the farmland (Please refer to Section for more details). 75

8 Figure 55 illustrates the flood control infrastructure in a nice flood 11 in transsections 12 of the studied area. It shows high elevated roads, elevated residential or urban areas, and areas protected by full dykes, which are higher than flood peak levels in 1996 or 2000, hence they are not affected by floods. It also shows that areas protected by semi dykes areas with low elevation of the roads and ground, and areas not protected are inundated by peak levels of a nice flood. Section further discusses how houses in these areas are affected by floods. Le et al. (2008) examined the impacts of infrastructure on floods in the Mekong Delta based on the analysis of flood variation from 1961 to 2004 and effects of infrastructure changes from 1996 to 2001 using hydraulic model HydroGIS. It is suggested that these engineering structures make the flood duration approximately 5 10 days longer and water level m deeper in some areas near or between the high embankment systems. Floods are reduced in areas protected by embankments and increased in water level and duration in other areas such as downstream of Dong Thap Muoi towards the Vam Co River, because the engineering structures make changes to the flow and obstruct drainage. Another impact is overbank inflow to Vietnam is decreased and water flow in the canals is increased, resulting in a trend of increase with progression in flood peaks downstream (Le et al. 2008). 11 Based on Tan Chau station s flood level, floods can be classified into four categories, including dreadful floods, damaging floods, nice floods and light floods when flood level is more than 5 m, 4.5 to 5 m, 3.5 to 4.5 m, and less than 3.5 m, respectively. The nice floods bring fertile sediments, fishery resources, and renew the water and soil quality of the farmland while the damaging floods or serious damage properties and infrastructure. The dreadful floods cause heavy human casualties and severe damage to infrastructure. In the light floods, fishery production decreases, the soil is less fertile, and salinity increases (Please refer to Section for more details). 12 The trans-section is combined from typical sections of houses in the studied area 76

9 Impacts of flood control infrastructure in the studied area Positive impacts Changes in infrastructure mentioned above have significant impacts on agricultural practices and flooding in the Mekong Delta. Flood control infrastructure in the studied area has benefited socio-economic development, protected people, infrastructure and houses, and supplied fresh water. Thanks to dyke systems and hydraulic constructions, rice production has almost quadrupled from 1974 to 2005 (Nguyen 2007a), and damages caused by floods have reduced substantially. Elevated roads ensure convenient transportation and connections of inhabitants to public services in the flooding season. Negative impacts Although the current strategy dealing with flood in the Mekong Delta is a combination of Living with floods and flood control, the numerous measures of flood control and underestimation of the complexity of the Mekong Delta s ecology have resulted in numerous drawbacks and challenges to the area s environment and flood regime. These measures have brought about a decrease in fishery resources and sediments in the flood control area (To 1998), as well as soil acidification, water pollution, and increase in insects and vermin in the rice fields. Recently, yields have decreased, in some cases to kg per 1000 m 2. Due to decrease in sedimentation, more chemical fertilizers and insecticides were used, leading to higher production cost and harm to the environment. In addition, full dyke protection may constrain water transportation (Le and Chu et al. 2007). In conclusion, the main strategies for coping with flood in the studied area are building semi-dyke systems to control early floods, and using canals for quick 77

10 flood water drainage. These may be good adaptive measures to deal with floods in the studied area as they have benefited agriculture development and reduced damages and loss of human lives, and damage to infrastructure and properties. Development of semi-dykes in the studied area is a better solution compared to fulldykes because it can both reduce damages and receive benefits from floods, which is critical to people s livelihoods. While drawbacks of full-dykes such as degradation of soil and water quality and fishery resources depletion result in difficulties for agriculture activities in the long term, semi-dykes cause these drawbacks to a lesser extent. Therefore, even with more pressure on agricultural production, full-dykes may not be an efficient solution for this specific area and any proposal to build full dykes should be carefully examined Adaptation of community Characteristics Unlike villages in the Red River Delta in Northern Vietnam which are closed by bamboos and walls, villages in the Mekong Delta are open. Villages are along the roads or the rivers, usually with one layer of houses and about 7 8 kilometers long, but the density is not high. Historically, when the farm land was not enough for the population, a part of the population moved to fresh land for cultivating and formed new villages (Figure 56 and Figure 57) (Phan 2004). 78

11 Figure 56. The formation of new village: when there was not enough land for farming, people went to fresh land Source: Reproduced from Phan (2004) Figure 57. The villages along the transport way Source: Reproduced from Phan (2004) Communities in the Mekong Delta are not affected crucially by bloodrelationship. However, family relatives support each other and respect the hierarchy. People in the neighborhood have a close relationship as they share the same experiences of traveling to fresh ground to cultivate and establish a new settlement. People in a village may have the same career, such as handicrafts The role of community in adapting to floods In the event of large floods that cause severe damage, the community plays an important role in the recovery of affected families and individuals. As new settlers who have changed fresh land into cultivated area, Mekong Delta dwellers have great empathy for each other s difficulties. They are generous and value friendship through mutual affection and a willingness to help each other overcome difficulties. People help in the dry season activities such as harvesting fishes, building and repairing houses. In adaptation to flooding, people help each other in preparation before the arrival of the next flood, during inundation, and after flood has receded. They may share food and houses, donate money, help repair and rebuild the houses. People also cooperate in work which benefits the community such as building and repairing dykes, village paths or bridges. There are also 79

12 programs in which the government and people in communities cooperate to build public infrastructure such as roads and hydraulic works, according to the motto Both the government and people work together (Le 2006a). In conclusion, communities in the studied area are open and settle along roads and canals. People have mutual affection and are helpful to each other, especially in hard times. Therefore, people are willing to support flood victims with whatever resources they have, including settlement, food, money, and labour to rebuild or repair houses. This spirit and practice of cooperation has contributed to the people's survival in the studied area Adaptation of houses in the studied area This section explores the adaptation of houses in the studied area. First, it examines housing characteristics, including the general layout of houses and types of houses (Section 4.3.1). Then, current adaptation of houses is analyzed from different aspects to figure out adaptation strategies of houses in the studied area (Section 4.3.2). Criteria to evaluate adaptation of houses to floods As stated by UN ESCAP (2011), the physical components of settlement comprise shelter, infrastructure and services. The house needs to satisfy the role of a shelter and connectivity to infrastructure and services. In the studied area, the house not only provides shelter, but being integral with infrastructure, form the basis of socio economic and communed activity. These functions are thus used as criteria to evaluate adaptation of houses in the studied area to floods. First, houses need to be safe shelters, protecting people from floods. Second, connectivity of houses to roads, 80

13 canals, farms, and services such as schools, markets, and healthcare centres needs to be secure in dry and flooding seasons. Third, the settlement has to collectively function as an entity to sustain and support all activities, including those relating to livelihoods Characteristics of houses in the studied area Layout of houses in the studied area The following provides an overview of houses in the upper Mekong Delta s deep flooding area. Elements of the typical layout of houses in the studied area include (Figure 58, Figure 59, and Figure 60): Main area (nhà chính/nhà trên): worship and living room (1) (Figure 61) Water floor (sàn nước), bathroom and WC (2) (Figure 65) Bridge area (nhà cầu) (3) (Figure 64) and/or ancillary area (nhà phụ) (5) (Figure 66): family room, sleeping area, rice storage area, kitchen Back area (nhà sau/nhà dưới) (Figure 63): kitchen, sleeping area (4) Verandah: the large front verandah is the space to relax, meet neighbours and guests, and also to work (Figure 62). There can also be side verandahs. These form the interstitial space between the house and outside environment, for cultural and climatic reasons. In addition, there are ancillary spaces outside the house to support people s activities and livelihoods, including small jetty, yard, garden, farm, pond, pigsty, hen-coop, and storehouse, etc. 81

14 Figure 58. General layout of houses in the Mekong Delta s deep flooding area Figure 59. Plan of a house in the Mekong Delta s deep flooding area 82

15 Figure 60. Exploded axonometric of a traditional house on stilts in the studied area 83

16 Figure 61. The living room and worship area (Phu Cuong Village, Tam Nong District, November 29, 2009) Figure 62. The verandah (Phu Cuong Village, Tam Nong District, November 29, 2009) Figure 63. The kitchen (Phu Cuong Village, Tam Nong District, November 29, 2009) Figure 64. The bridge area (Phu Cuong Village, Tam Nong District, November 29, 2009) Figure 65. The water floor, bathroom and WC (Phu Cuong Village, Tam Nong District, November 28, 2009) Figure 66. Ancillary area (Phu Duc Village, Tam Nong District, November 28, 2009) Figure 67. A pigsty (Phu Duc Village, Tam Nong District, November 28, 2009) Figure 68. A store house (Phu Duc Village,Tam Nong District, November 28, 2009) 84

17 Types of houses in the studied area a. Type A traditional house on stilts This type of house is popular in the upper Mekong Delta s deep flooding area due to several advantages. First, the floor level of these houses is raised high on stilts to avoid the floods. Second, the houses are convenient for farming and fishing activities in dry and flooding seasons. The ground floor can be used for storing farming and fishing tools; in some cases, this space can also be used as living space in the dry season. Other spaces used for storing harvested rice are the bridge area, ancillary area and back area. Third, the local culture is integrated with this traditional layout. There are spaces like the altar in the center of the large living room, the large verandah as a space for informal guests, the bridge area for family activities, and the water floor for washing activities. Figure 69. Type A houses (Phu Duc Village, Tam Nong District, November 28, 2009 (left) and Long Khanh Village, Hong Ngu District, December 05, 2009 (right)) Figure 70 shows photos of a traditional house on stilt in the studied area. The house has a small jetty connected to canals. The ground floor is used to store farming and fishing tools. The elevated front ground ensures connectivity of the house to the roads and can be used for drying husks and fishes. The house includes the main area with living and sleeping rooms, the bridge area for family activities 85

18 and storing harvest, the back area for kitchen, water floor and toilet, and a large verandah with a tea table for informal guests. Perspective of the house The house s small jetty The ground floor is used as storage space The spacious living room with altar Figure 70. Photos of Type A House (Tam Nong District, November 29, 2009) Figure 71 and Figure 72 illustrate activities of a Type A house in the plan in the dry and flooding seasons. Figure 73 and Figure 74 illustrate its activities in the section in the dry and flooding seasons. It can be observed that there are changes of livelihood activities between the dry and flooding seasons. 86

19 Figure 71. The plan of a Type A house in dry season Figure 72. The plan of a Type A house in flooding season 87

20 Figure 73. The section of a Type A house in dry season Figure 74. The section of a Type A house in a nice flood 88

21 b. Type B temporary house on stilts This type of house is popular in the upper Mekong Delta s deep flooding area. They are temporary houses on stilts which have quite similar advantages like Type A houses, but they are less durable and spacious, although more economical. The houses are built of low quality wood and temporary materials such as thatch and metal panels. The durability of this type of house is a concern in dealing with storm surges and strong winds, especially during the flooding season. Figure 75. Type B houses (Phu Tho Village, Tam Nong District, December 01, 2009 (upper left and lower right), Binh Thanh Village, Hong Ngu District, December 04, 2009 (upper right), and Tam Nong District, November 27, 2009 (lower left) 89

22 Figure 76. Plan of a temporary house on stilts in Phu Tho village, Tam Nong District in dry season Figure 77. Section of a temporary house on stilts in Phu Tho village, Tam Nong in a nice flood 90

23 c. Type C old house This type of house can be found at Long Khanh Island in the upper Mekong Delta s deep flooding area. Due to the fertile soil in this area (natural levee) and higher level of land, many houses are garden houses and the level of the houses on stilts is low compared to houses in other areas. These houses have been built for a long time, with several houses aged over 50 years. These houses were built by wealthy people, using high quality wood such as Xylia xylocarpa (căm xe), Lagerstroemia calyculata (thao lao), cà chất 13, Pterocarpus macrocarpus (giáng hương). Figure 78. Type C houses (Long Khanh Village, Hong Ngu District, December 04, 2009) d. Type D houses on elevated ground Houses built on elevated ground are quite similar to houses in the Mekong Delta s non-flooding area. They are usually connected directly to elevated roads or elevated front ground, hence they are almost not affected by flood. 13 Vietnamese name of the wood 91

24 Figure 79. Type D houses (Phu Tho Village, Tam Nong District, December 01, 2009 (left) and National Road 30, November 27, 2009 (right) e. Type E floating house Floating houses are used for fishing homesteads and for people who do not own land. However, most families living in floating houses prefer to live on the land. This type of house may be an option for future adaptation. Below are some characteristics of these houses. Water pipes, barrels and bamboos are put into a frame to keep the houses floating. Light materials are used for other components of the houses. In the flooding season, people move the houses towards the river banks as the water flows swiftly in the flooding season. People travel by boats. For houses near the river banks, they have a small wooden path on barrels connecting them to the land. 92

25 Figure 80. Type E houses (Da Phuoc Village, An Phu District, An Giang Province, December 07, 2009) Figure 81. Section of a floating house in Chau Doc 93

26 Figure 82. Plan of a floating house in Chau Doc f. Type F houses in residential dykes and clusters The government provides these houses to resettle inhabitants from the deep flooding areas that are vulnerable to flood. This type of house and its advantages and disadvantages are discussed in detail in Section Houses in residential dykes are preferred to houses in residential clusters because the quality of infrastructure is better and people s lifestyles are less affected. People may engage in animal husbandry (illegally) and gain direct access to the 94

27 canals. The residential dykes are usually nearer to people s former habitats, so they can better sustain livelihoods. If they have some land, it is convenient for them to connect to their farms. If they are landless, it is easier to sustain relationships for their hired on-farm and off-farm jobs. Figure 83. Type F houses (Tram Chim Town, Tam Nong District, December 02, 2009) Figure 84. Plan of a house in residential dyke in Tam Nong District Figure 85. Section of a house of in residential dyke in Tam Nong District, year 2000 peak flood level 95

28 In summary, in order to raise floor levels to adapt to floods, houses on stilts or elevated grounds are built. Houses built by the people also support livelihoods activities in the dry and flooding seasons. For all of these types, people flexibly arrange spaces in and around the houses for livelihood activities such as spaces for working, storing tools and harvests, and drying yards. Floating house is an interesting type because their floating characteristics can be applied as an adaptation measure to floods in the future Current adaptation strategies of houses This section analyzes how houses adapt to floods in terms of location and settlement patterns, elevation, durability and housing construction, flexibility, landscape, and other criteria (land ownership, main source of income and wealth), which are the issues that affect adaptation of houses to floods Location and settlement patterns This part describes locations of houses and their connections to roads, canals and farms and how houses are affected by floods. a. Relative location of houses to roads and dykes In the studied area, houses settle along high elevated roads, low elevated roads, in flooded areas, in protected areas (full-dyke and semi-dyke), and in residential dykes and clusters. Figure 86 illustrates houses in different location with different flood levels in history. It shows that location has critical impact on houses in the flooding season, mainly due to impact of floods on transportation and the connectivity of houses to public services. The followings discuss in detail how location affects the impacts of floods on houses. 96

29 Houses along high elevated roads (higher than the peak flood levels in 1996 or 2000) The levels of main roads were constructed over the peak flood level in 1996 or Since then, houses along high elevation roads have not been affected substantially by floods. These houses have good connections to infrastructure and public services such as schools, markets and healthcare centres, and facilities such as electricity and piped water, as these facilities are usually provided together with the main transport system. In addition, their daily activities, except agriculture production, are not considerably influenced by floods. Houses along low elevated roads (lower than the peak flood levels in 1996 or 2000) Low elevated roads may be inundated in the flooding season. As a result, people may encounter difficulties in connecting to infrastructure and facilities to some extent. In the case that the road is inundated deeply, water transportation becomes predominant in the flooding season. However, most roads in the studied area are relatively high compared to the average flood level, so houses have not been significantly affected in recent years. Houses in areas protected by dykes Majority of dykes in the studied area are semi dykes (Section 4.1). Houses in semi-dyke protected areas are protected from early (August) and late (November and December) floods. Meanwhile, houses in full-dyke protected areas are not affected by floods, but in the long term, agriculture production may be negatively affected due to loss of sediments, increase of vermin, and reduction of fishery resources. 97

30 Houses in flooded areas For houses that are surrounded by floodwater, water transportation becomes predominant. Houses in these areas have difficulties connecting to infrastructure and facilities, and may have limited access to electricity and piped water. However, these houses are the minority in the studied area, due to their inconvenience and danger, and resettlement in residential dykes and clusters. Houses resettled in residential dykes or clusters People who have resettled in residential dykes and clusters are not affected by floods because the level of houses and roads is higher than the highest flood level in history. However, these houses have a poor quality of construction. The infrastructure, including the drainage systems and piped water supply systems, is inadequate. The people may also have difficulties in sustaining and improving their livelihoods. In summary, the location of houses considerably affects the extent of impacts of floods on houses, especially the connectivity of houses to the transportation system and public facilities, and the livelihood activities of the inhabitants. Houses in flooded areas, areas protected by semi-dykes, and houses along low elevated roads are most affected by floods. 98

31 Figure 86. Locations of houses in the studied area in dry season and flood in 1998, 2000, 2009 Figure 87. Settlement patterns in dry season, nice flood and flood in

32 b. Settlement patterns Settlement patterns represent the connections among houses, roads, canals and farms, which means the connections of houses, infrastructure system, and livelihoods. Therefore, it determines the extent of impact of floods on access to transportation and services, people s daily activities and livelihood activities such as farming and fishing. In the studied area, most houses and buildings are along the roads, canals and rivers due to travelling convenience, especially in the flooding season. Figure 87 shows different settlement patterns in the dry season, and a nice flood and the flood in It can be interpreted that houses with access to both roads and canals have the most advantageous connections to transportation, and also farms. Meanwhile, houses in the infield areas are most affected by flood due to limited connections to transportation, but have easy access to surrounding farms for farming and fishing activities. Houses in infield areas are the minority in the studied area. Settlement patterns in the studied area are examined in greater detail below. Group 1: Houses that are directly connected to roads and canals This group of houses has both access to land and water transportation in dry and flooding seasons. It is convenient for them to access farms and transport heavy things such as farming tools, fertilizer and harvests. Connectivity of these houses to services and facilities is also advantageous (Table 7). 100

33 Table 7. Settlement patterns of houses directly connected to roads and canals Settlement pattern Section Photo Canal Road House (Farm) Road House Canal (Farm) Road Canal House (Farm) (Photos were taken in Tam Nong District, November 2009) Group 2: Houses that are directly connected to the road This group of houses has access to land transportation but limited access to water transportation. In some cases, they can use nearby canals to travel. In the flooding season, people can go fishing from nearby canals or inundated farms (Figure 88 and Figure 89). 101

34 Figure 88. Road House Farm pattern Figure 89. Houses of the pattern Road House Farm (Tam Nong District, November 29, 2009) Group 3: Infield houses These houses are surrounded by farms and have limited access to both land and water transportation. Small dykes in the fields connect people to the roads in the dry season, and boats are used in the flooding season for transportation and fishing. Figure 90. Houses in the farm (Thuong Phuoc Village, Hong Ngu District, December 03, 2009) 102