Damage caused by an hour's worth of rain has sparked fears of what the upcoming monsoon could bring for Rohingya refugees at Bangladesh's packed refugee camp.
A single downpour last week left shelters damaged, while cars laden with supplies were bogged in mud and minor flooding hit camps where more than 700,000 refugees reside since fleeing troubled Myanmar.
Oxfam aid worker Dorothy Sang says preparations have increased for the monsoon season beginning in late May and ending in September.
Two and a half metres of rain is expected to fall within three months.
"There are grave concerns floods or landslide could cut vulnerable people off from accessing key drinking water sources and aid distributions, which could be fatal," said Ms Sang, Oxfam's Rohingya Response Advocacy Manager.
Anywhere from 100,000 to 150,000 refugees are in the monsoon season's direct firing line, living in flimsy shelters in areas that would be hit hard by heavy rainfall.
Once the wet weather arrives, refugees will also face waterborne disease outbreaks particularly cholera and diarrhoea.
Oxfam Australia's Humanitarian Manager Meg Quartermaine says urgent plans have been made to move the refugees most at risk, with the Bangladesh government recently expanding the camp boundaries and providing expertise on monsoonal flooding.
"Land is at a premium, everywhere you look there's people," Ms Quartermaine told AAP, following her visit to camps near Cox's Bazar this week.
"That's what the concern is - the scale of this population. We have hope that there will be minimal damage and lives lost."
Oxfam has focused on producing large amounts of clean drinking water by building water treatment plants, building faecal waste treatment plants and educating refugees about hygiene practices to help stem the tide of any disease outbreaks.
Hygiene kits have been distributed and refugees have been keen to learn about the importance of hand washing and what to do if a family member becomes unwell, Ms Quartermaine said.
"It's a population who have experienced a great deal. They are frightened, frightened people...they are concerned about their overall wellbeing."
The refugees poured into Bangladesh to escape a military crackdown in Myanmar, where it's reported the military committed atrocities such as mass rapes, murders and burning villages.
The United Nations has described the situation as a "textbook case of ethnic cleansing".
