2.1. Deltas

The deltas are characterised by very high population densities and major cities, quite often capitals, and are associated with intensive rice-growing. This does not exclude, for reasons mentioned above, the existence of rapidly developing pioneer fronts close to the coastal lines. The dominant ethnic groups make the majority in the deltas. Yet we can find there pockets of minorities: foreigners in the cities, if not people who represent the remainder of a late assimilation of the deltas in the centre of the countries. This dense human presence is yet associated to a physical environment which increases the dangers by the conjunction of cyclones, floods, high tides, storm surges and if not, local tsunamis. International openings increase the vulnerability while modifying the previous danger management measures as can be seen by the development of Hanoi that has been faced with an evolutive management of the dykes network.