Thousands of Pakistanis are fleeing their homes in southern coastal areas as floods sweep down from the north. The vast body of flood-water that has swept the length of Pakistan is now threatening previously unaffected communities in Sindh province, at the country’s southern tip. The authorities have been organising a mass evacuation from the town of Thatta – near the mouth of the Indus delta – and surrounding villages. At the moment, all that stands between locals and the vast weight of water is an embankment which has started to crack in places. If it bursts, the whole area could be submerged. In the north, workers have begun clearing up as the floods recede. The UN has appealed for more helicopters to reach 800,000 people who are cut off. Doctors in many areas are struggling to cope with the spread of water-borne diseases such as diarrhoea and cholera. The UN says more than 17 million people have been affected by the monsoon floods, and about 1.2 million homes have been destroyed.