(CNN)The first monsoon rains have hit camps housing hundreds of thousands of Rohingya refugees in Bangladesh, causing the death of one young child, and destroying hundreds of makeshift shelters, as aid agencies warn of a humanitarian catastrophe as the wet season gets underway.
Rohingya 'living on sandcastles' as first monsoon rains hit fragile camps
UN refugee agency UNHCR reported that "large areas of the camp were underwater," following the downpour, which has so far caused 21 landslides, according to agency estimates.
"Rain came down in sheets all last night," said UNHCR spokeswoman Caroline Gluck, adding that landslides will continue as "the land has been stripped of all vegetation, to make way for the building of makeshift homes. People are practically living on sandcastles."
Around 2.30 a.m. Monday morning a mud wall in a shelter in the Kutupalong camp collapsed, killing a 3-year-old boy and injuring his mother, Rezaul Karim, of Bangladesh's Ministry for Disaster Management and Relief and manager-in-charge of the camp, the largest in Bangladesh, told CNN.
As many as 300 family shelters have been damaged, according to Bangladesh's Ministry for Disaster Management and Relief.
The rains will potentially imperil upwards of 200,000 Rohingya refugees huddled in low-lying makeshift camps along the country's eastern border. The monsoon season typically lasts until around October.
More heavy rain is forecast for coming days.
Hundreds of thousands of Rohingya -- an ethnic Muslim minority -- have fled Buddhist-majority Myanmar into neighboring Bangladesh since August 2017, bringing with them stories of murder, rape and the destruction of villages at the hands of the military.
The UN and the United States say they believe the violence against the Rohingya constitutes ethnic cleansing, a charge denied by the Myanmar government.
As many as 200,000 of the estimated 700,000 refugees living in squalid, precarious shelters are at risk of the heavy, seasonal rains, according to the Inter Sector Coordination Group, an interagency group headed by the International Organization for Migration (IOM) and UNHCR. Of these, 25,000 are considered to be "at very high risk."
The Group estimates that, since May 11, over 2,000 shelters have been damaged by high winds, storms, and landslides, with almost 19,000 individuals affected. On June 10 alone, 60 incidents affecting over 9,000 individuals were reported.
As of June 3, 28,153 Rohingya have been relocated from risk areas and to allow for infrastructure work.
A road constructed by the Bangladeshi army in the camp has been severely damaged by rain, According to UNICEF spokesperson Alastair Lawson Tancred said.
"All vehicles apart from those carrying essential medical supplies have been prevented from using it," he added.
In April as the first pre-monsoon rains began to fall, Daphnee Cook, Save the Children's media and communications manager, told CNN that "if a big storm hits the camps, it would be nothing short of disastrous."
Hillsides around the camps have been denuded of trees, which has left the underlying soil vulnerable to landslides. The camps' sewage and drainage systems, which are rudimentary, are also prone to failure, meaning that the spread of water-borne diseases like cholera is likely.
Aid groups warn that, in addition to the risk of flooding and landslides, water-borne diseases are a huge worry for those in the camps.
"With the flooding and accumulation of stagnant water, water- and mosquito-borne diseases are all the more likely to spread because of the refugees' severely overcrowded living conditions and very poor sanitation," said medical aid group Medicines Sans Frontiers (MSF) emergency coordinator in Cox's Bazar, Francesco Segoni.
Earlier in the year the government allocated 500 acres of new land to house relocated refugees, "which is massively welcomed, but we still believe the sites are not large enough to move everyone who needs to be moved," Gluck told CNN at the time.