Résumé
Deltas are environments that combine opportunities and vulnerabilities. They are ideal places for shipping, maritime trade and commerce, fertile for agriculture, and rich in water and biodiversity, but their environmental characteristics also pose specific constraints. As Bangkok has urbanised and co-evolved with its deltaic environment, the megalopolis has had to manage its exposure to floods and tides, coastal erosion, saltwater intrusion, water pollution, land subsidence and the supply of drinking water. In order to identify the physical and institutional constraints to sustainable urbanisation, this thesis aims to understand the joint transformations ─ both environmental and socio-political ─ induced by water challenges, through an analysis of governance 'in action', manifested by decision-making processes unfolding in a context of a plurality of actors, institutions, ecological ramifications, spatial and administrative scales, norms, narratives, representations and imaginaries. This multi-level governance (we consider the 'vertical' interactions between global players, the State, the BMA (Bangkok Metropolitan Administration) and local administrations) intersects and merges with 'horizontal' governance, which brings together private players (industries, consultancies, lobbies), civil society (NGOs, collectives) and the academic sector.The central hypothesis of this thesis is that the clarification of governance, through the analysis of decision-making processes around water-related projects and public policies, makes it possible to account for the environmental and socio-political transformations geared towards maintaining the capital's prosperity in the face of the hazards of the delta and the economic competition between global megacities. These transformations are explained through three case studies that illustrate the formulation of public problems and their controversies: 1) the enhancement of the banks of the Chao Phraya River through a promenade project; 2) the management of groundwater in relation to the phenomenon of land subsidence; 3) the protection of the capital from flooding through canals designed to divert flood flows away from the city.The fluidity of water links the atmosphere, the underground and urban surfaces to the human and non-human inhabitants of the delta, and constitutes a material witness that enables us to empirically grasp the complexity of hydro-social interactions. The environmental transformation of Bangkok is not only the consequence of urbanisation, presented as uncontrolled or inevitable, but also the result of a bundle of political and financial interests that are constantly reshaping the flow and spatial distribution of the benefits and costs associated with the transformation of the aquatic environment and the hydrological cycle. The analysis highlights the BMA's limited decision-making autonomy in the face of a centralised state that retains most of the power to influence public policy, reveals the central importance of the academic sector in debates and decision-making, highlights the role of visual media in enlisting stakeholders (the imagineering process), and underlines the multi-scalar nature of the composition of stakeholder coalitions and their reconfigurations.