At least 104 people have died, 99 people are still missing and thousands have been left homeless by the waters, which have since begun to recede.
The majority of deaths occurred following a landslide in the central of area Kegalle which devastated three villages and there is a warning of a risk of further landslides.
The Church of Ceylon has been distributing - with support from Us (the United Society) - toiletries, boots, medicines, cooking utensils, bedding, chlorine and cleaning materials.
Us is reporting an "urgent need" to initiate environment clean-ups and waste management schemes to stop disease spreading.
It is believed families forced from their homes by floods have been living in locations including temporary camps, schools, religious buildings and community centres.
A statement on the Diocese of Colombo's website reported: "The flooding and landslides have wreaked havoc across the country. Many casualties have been reported and dozens are missing under the mud of a landslide at Aranayake.
"We are very grateful to everyone who has contributed generously in cash or kind or by volunteering their time."
The economic cost of the flooding is expected to be significant, with the Sri Lankan government estimating up to 30,000 businesses may have been affected.
Us says "now, the church is focused on supporting families in the villages of Puttalam, Chilaw, Urubokke and Dandugama.
"Looking forward, the church will be involved in assisting with the rehabilitation and reconstruction of communities as they rebuild livelihood activities."