The military is involved in the effort to reach thousands cut off amid a looming threat of disease in the Indian Ocean island.
More than half a million people in Sri Lanka have been displaced by devastating floods following several days of torrential rain.
At least 180 people have died and search and rescue teams are looking for more than 100 who are missing.
While the streets of Colombo are under water, towns and villages on the Indian Ocean island have suffered landslides. In Ratnapura 70 kilometres from the capital more than 70 were killed and the numbers are still rising.
The waters have receded but the mud has done untold damage.
“There were trees here. This was a beautiful mountain with thickets, we never thought such a disaster would happen here. The two houses which were up there are deep under the mud,” said resident Vijay Thunga.
“We are used to rains and flooding in our area. But this year it has been unusual. We have never experienced such floods in 70 years in this village,” added another local man, Mudith Sumanasekara.
Efforts to reach isolated villages have been hampered by the conditions, although tens of thousands of people have been relocated to temporary shelters.
Amid warnings of more bad weather and a looming health threat from potentially fatal diseases such as dengue fever, the United Nations and the World Health Organization (WHO) have pledged aid, as have several countries.
Latest update on #SriLankaFloods from
UNSriLanka</a> 75,000 people displaced & more rain forecast over coming days <a href="https://t.co/ekqGO6ZHrE">https://t.co/ekqGO6ZHrE</a></p>— UN OCHA Asia Pacific (OCHAAsiaPac) May 30, 2017