The disaster washed way villages and some of the Honiara's critical infrastructure.
Foreign aid is slowly arriving but there are now fears disease outbreaks could add to the scale of the disaster in Australia's tiny Pacific neighbour.
Listen: Disease outbreak fears in Solomons flood clean-up, Stefan Armbruster reports
It is a natural disaster on a scale never before witnessed in the Solomon Islands.
Flash flooding on the main island of Guadalcanal caught people living in settlements and squatter camps on the river banks of the capital Honiara by surprise.
The Mataniko River swept villages out to sea and destroyed one of the main commercial districts, Chinatown.
Ben Afuga is the CEO of civil society group Forum Solomon Islands International who began relief operations before help from aid organisations and the national government arrived.
"This is one of the worst disasters that has ever hit the country, especially Honiara, which has caused some devastating damage to the infrastructures," he said. "Up the Mataniko River there's a lot of settlements by the river banks, all those settlements have been washed away by the floods."
The relief effort is underway but in a country with few resources.
People are picking through the debris of the flood with their bare hands, looking for those lost.
About 19 have reportedly died, but many are still missing.
Residents scour debris in Honiara. (Photo credit:Jay Liofasi)
Cameron Vudi, the Red Cross Solomon Islands disaster relief manager, says they are only now getting an accurate picture of how many people are affected in the capital alone.
"From the last count it is roughly between the 9,000 and 10,000 mark," he said, "and there's a lot of these people who have lost their homes and their assets and that and we have to remember apart from Honiara, there are also communities in Guadalcanal province which is outside of Honiara."
Cameron Vudi says there is now a new threat emerging - diarrhoea, malaria and dengue.
"We have been working closely with the health authorities and they have said there might be some indication of outbreaks. I can't confirm if there are outbreaks already, but there are indications there might be because of the situation in the evacuation centres."
Aid is slowly trickling in from overseas.
Australian and New Zealand air force transport planes have landed with supplies and personnel.
Australia has promised $400,000 in aid and is assessing any further response.
Forum Solomon Islands International's Ben Afuga says much more is needed.
"Well the immediate need now from our own assessment is food and clothing, food, clothing and water.
"I should say we desperately need support from other governments and other aid donors. I don't think we have the capacity in terms of resources to deal with the situation now."
In Brisbane, home to Australia's largest number of Solomon Islanders, they are doing what they can to help says community leader Charles Tema.
"So currently we'll still be taking up food collections and donations, so looking at non-perishable items as well, we have set up collection points in the north side and south side of Brisbane," said Mr Tema. "So all this information is placed in our Facebook page, which is the Solomon Islands Brisbane Community FB page."
Amid the carnage and desperation in Honiara, there were initially reports of looting.
Ben Afuga says that is not what happened in Honiara's Chinatown, which has previously been the target of rioting against Chinese business interests in the country.
"I think it was a very minor incident that happened at the Rainbow shop. The building that housed the shop was slowly eaten away at the back by the river," he said, "that caused the owner to, thought that he might lose everything so he thought it might be useful for people to take that things being washed down the river."
Ben Afuga says the Chinese community has been contributing to the relief effort, despite having lost so much in the flood.
Flash flooding in Honiara leaves behind a trail of destruction. (Photo credit: Jay Liofasi)
"In terms of the Chinese support for the victims, there has been a lot of support. I heard of a story yesterday the some Chinese cook food and take them to one of the evacuation centres."
With the death toll mounting, questions are being asked what caused this unprecedented flooding.
Ben Afuga says the finger of blame is being pointed at the country's often unfettered logging by foreign corporations.
"If you walk to the beaches are more like ah, you will see a lot of logs on the beach, and I also understand a lot of the victims have been killed by the logs, one of the victims says four logs came and took away his house."
But that's an issue for another day.
With the weather clearing, the focus in the Solomon Islands is on the relief operation.
The tropical low that caused the flooding has moved west towards Australia.
Category One Tropical Cyclone Ita is expected to hit Cape York in far-north Queensland later this week.
