Trends: socio-economic, climate change
Similar to other evolving mega-cities in South-East Asia, Ho Chi Minh City has experienced rapid changes in recent decades. The city’s population has more than doubled from 3.9 million in 1989 to approximately 8 million inhabitants in 2010. The regional economy has continuously grown with double-digit growth rates and HCMC contributes nearly 30% to the national GDP and received 37% of total foreign direct investments in 2009. In addition to a substantial increase in population density, HCMC’s rapid growth resulted in expansion of urban areas on low-lying marsh land. Today, approximately 60% of the urban area is located less than 1.5 Meter above sea level, making it highly vulnerable to projected sea-level rise.
Urban flooding has become a wide-spread phenomenon and a major concern in HCMC in recent years that has been accompanying the city’s rapid growth. Especially since the beginning of the 1990s the amount of flooded locations, flood frequencies and flood duration has steadily increased and has caused substantial economic and social losses, such as damage to infrastructure and assets, water pollution as well as traffic jams. The floods are caused by a combination of factors. First, low lying areas to the south of the city are impacted by tidal peaks, which are projected to increase under climate changes. About 20 sites are currently inundated on a monthly basis as a result of high tides. Second, frequent flooding results from a combination of heavy rainfall events and an insufficient drainage system. The heavy rainfall event of 127mm (5 inches) on May 16th, 2004, for example caused more than 100 small-scale floods. Third, HCMC is prone to river flooding, which also affects the upstream areas that are situated on slightly higher grounds. As river levels increase due to embankment and sea level rise, this problem is growing.
Vietnam in general and HCMC in particular have been identified as one of the most severely affected places by future climate change and especially sea level rise. During recent decades, changes in the regional climate have already been observed. The average annual temperature has increased by 0.6 degrees during the last seven decades. Whilst the annual volume of rainfall has remained fairly stable, the number of heavy rainfall events (>100 mm/3.94 inches of rain) has increased remarkably. The increase of heavy rainfall events coincides with the rapid urbanization process in the last 20 years and has been attributed to the so-called urban heat island effect. The sea level rose by 20cm in the last 50 years with a rate of about 3mm (0.1 inch) per year during the period 1993- 2008. It is projected to rise another 28 to 33cm by 2050, posing a major challenge to low-lying HCMC. That is even increasing with the land subsidence of several centimetres per year in some parts of the city.
Another problem HCMC is facing is the salination of the grounds, which can affect the agricultural activities in the city. Although this does not immediately affect the livelihood in the city it is a problem which has to be taken into account.