If the city less than 10 meters above sea level, then the city is facing the possibility of a great flood in the world 2% of the total area of 10 meters above sea level living below 10% of the population, the world's 20 most populous cities in 13 in the coastal areas.
If the city less than 10 meters above sea level, then the city is facing the possibility of a great flood。In the world 2% of the total area10 meters above sea level living10% of the population ，13 cities of the world's 20 most population cities in the coast.
