The recent flooding that occurred last October and November in Thailand was estimated to be one of the worst floods in decades. Thus, the Thai government together with the UNESCO Bangkok office organized a foreign expert mission to assess flood impacts in the Ayutthaya/Bangkok region. Zoran Vojinovic, PhD, from UNESCO-IHE was invited to join the group of foreign experts for a post-flood facts finding mission at the end of November.
Ayutthaya city, the former capital of the Kingdom of Siam, Thailand, was one of the many provinces devastated by this event. Concerns were raised that the floods could have affected the monumental structures which may no longer be strong enough to carry the weight of the pagoda that is centuries old.
Ayutthaya is located in the valley of the Chao Phraya River and it is uniquely characterized by the prang (reliquary towers) and gigantic monasteries. In 1991, its art and buildings were recognized internationally as a UNESCO World Heritage Site.
Vojinovic presented his findings to the group and explained that such flood management issues (together with other water-related management issues) in the Ayutthaya/Bangkok region must be approached from a holistic (or integrated) perspective and that the right mix of structural and non-structural measures must be sought at both regional and local scales.
He said the flow capacity of the waterways in Ayutthaya was estimated to be in the order of 1,500 cubic meters per second. The calculated inflow into the Ayutthaya region during the October flood event was at least two times larger than the flow capacity of the surrounding waterways.
This situation caused the extensive flooding and unprecedented impacts throughout the region. "This flood event illustrates some of the fundamental issues of flood risk and vulnerability in the Ayutthaya region and represents an immense challenge not only to planners, engineers and scientists but to the nation as a whole," he added.
"In the short-term, existing dykes can be improved or raised, canals should be dredged and portable dykes and pumps can be deployed. In the mid-term, some of the channels can be widened, multi-purposeponds can be built for water retention during the rainy season, and monuments can be flood-proofed," he said. "In the long-term, measures such as construction of diversion channels may be needed to counteract the mega-scale of floods as those that occurred in October/November 2011. Certainly, it is important to note that there is much to be gained from such physical engineering-based interventions, but without an appropriate inclusion of social and other aspects (e.g., cultural, historical, ethical and even political) into the analysis the potential interventions may be limited in their reach and their effect."
Therefore, Vojinovic stresses that for the development of sustainable and effective flood mitigation in the Ayutthaya region, different measures need to be considered which may range across different areas and disciplines. Certainly, this was a preliminary assessment and a more detailed study would be necessary to define those effective measures and to prioritize their implementation.