Cao Lanh - The Mekong Delta's worst flood for 40 years has cost more than 250 lives and left hundreds of thousands of people homeless. Unusually heavy monsoon rains have inundated vast areas of Laos, Cambodia and Southern Vietnam. The relentless rise in the water level - five to 10cm (2-4 in) a day for the last two months - has submerged houses and cut off roads.