The Ministry of Land in Tonga says the new drainage system in the capital was not built to cope with the magnitude of rain that has fallen in the past two weeks.
Flooding from heavy rains has forced some schools and businesses to close and has caused concern over the number of potential breeding grounds for mosquitoes.
The director of the ministry's urban planning unit, Tukua Tonga says the team behind the multi-million dollar new system built two years ago, had not anticipated the volume of rain, so the system lacks the capacity to process it.
"The design calculation wasn't in place for continuous rainfall that we're in second week now. That kind of calculation nobody really foresaw for engineering purposes. And hence we're redesigning everything else in terms of climate proofing to ensure that we address these issues."
Tukua Tonga says the ministry of land will engage the ministry of infrastructure to solve the drainage problem.