The river capitals Phnom Penh and Bangkok are subject to very high stresses in their urban development. They have expanded behind the bank of the rivers with dikes and embankments on the river floodplains. So they are very vulnerable to natural disasters such as flooding. Since the early 1970s, it is now common to assimilate a city to a system, closed (Forrester W.J. 1969) or opened (Rosnay de J. 1975). The major crisis suffered under the Khmer Rouge regime damaged hydraulic networks. Moreover, most of the city dwellers and elites were killed in a genocide charge of 1.7 million victims. Why can we talk about resilience for this city-system since 1979? We define resilience as "the ability of a system to integrate a disruption in its run, without changing the qualitative structure" (Holling C.S. 1973). More recently, in Phnom Penh and Bangkok, speculative projects to private investors reject in the outskirts of cities the poorest populations. The consequences are social, but also environmental. Firstly the peripheral areas, in contrast to the city center, having no embankments, are prone to flooding, with no proper drainage systems. Secondly the proliferation of high-rise towers worsens the process of subsidence and flooding vulnerability of cities. Why speculative urban projects of the private investors located in the central and the peripheral areas (i.e. new skyscrapers and new towns) are they going to worsen the vulnerability of cities to flooding?