Towards the methodology for flood risk assessment on cultural heritage sites [Case study : Ayutthaya world's heritage site]

Evolution of the humankind implies the transfer of knowledge from those whom generation after generation have discovered and learnt the principles that governs the laws of science and the arts. In past times, the roots of this wisdom were concentrated in historical sites of enormous cultural value. Sites which in today's picture are threatened by unavoidable natural hazards, and flooding is not the exception. In this field, it is our responsibility to contribute in the defense and conservation of these outstanding locations full of thoughts, emotions and human expressions. Flooding is mostly appraised through flood risk assessment protocols, where the aim is to identify areas at risk of inundation and to undertake mitigation measures. This is conducted in order to minimize risk under acceptable limits. However, until now, the approach has been done mostly based on economical impacts and everything embraced within it, whereas and the integration of intangible values attached to cultural heritage sites is certainly an area with a wide range of knowledge to be developed. The present research proposes a feasible methodology to assess flood risk on cultural heritage sites in order to consider their impacts and invites their consideration into discussion during the process of decision making. Roughly, the methodology consists of a scored value approach of assets depending of their relevance in cultural, religious, and archaeological contexts. Similarly, vulnerabilities are classified depending on the exposure and susceptibility of the assets. Furthermore, hazards are identified through the use of modelling practices and are scored based on a qualitative assessment for the scope of evaluating flood risk. As a case study, the research focuses on the Historic City of Ayutthaya, in Thailand; which since 1991 became one of the World Heritage Sites of UNESCO. Ayutthaya Heritage Site and neighbour areas are located in a low-land surrounded by the Lopburi River to the north, Pasak River at the east and Chao Phraya River from west and south, making it highly susceptible to floods. The region faces almost every year flood-related issues during the rainy season. The impact and risk assessment of flooding in Ayutthaya is conducted using a hydrodynamic 1D-2D model. MIKE FLOOD is utilized to perform simulations for multiple scenarios which involve the identification of mitigation measures and adaptation to Climate Change. The model was setup with the available data, and used some information generated from ArcGIS and complementary tools. The results of this research show the feasibility to incorporate the value of cultural properties for identifying areas at risk. However, it should be noted that due to the subjectivity of the topic, many different discussions can be derived from the results. As an example, it can be pointed out that for the study area, it was found out that the combination of different mitigation measures, for a series of rainfall events equivalent to 50 and 100 years return periods, is the most effective alternative to reduce the potential damage to the cultural heritages in the site of Ayutthaya