The floods in Moshi, near Mount Kilimanjaro, mostly affected residents who had previously been hit by drought, which had threatened up to 11 million people with starvation.
James ole Millya, Moshi rural district commissioner, said on Monday: "I think we have more than 19,000 displaced. Up to now there are 998 houses that are under water."
He said more than 1,495 hectares of land was under water and 84 families had been moved to government institutions.
The floods, which ravaged the area last week, also destroyed crops in the fields as well as harvested produce, including maize, rice, millet and beans.
"There are some people whose food was stored indoors, which has been destroyed by the rains," ole Millya said.
Floodwater had also filled pit latrines and contaminated drinking water.
"At the moment, water for domestic use is definitely a problem. Our health authorities have contained the situation and so far we have not had any disease outbreaks," ole Millya said.
In recent months, flooding has also affected Tanzania's neighbours, Kenya, Zambia, Mozambique and Malawi.
Besides Tanzania, the flood has
affected at least four nations
In related news, the UN food agency has appealed for $16.6 million to feed more than half a million Tanzanians facing severe hunger due to the drought.
Patrick Buckley, the World Food Programme (WFP) representative for Tanzania, said in a statement first published on Thursday: "With more than half a million people in dire need, we really need funding now for this new emergency operation.
"If we are to help these families - whom we should start feeding as soon as possible - we need the international community to make rapid contributions," he said, adding that the agency required 33,900 tonnes of maize for the vulnerable population from May until September, when needs would be reviewed.
In a statement distributed on Friday, the agency said that in 2005 food production fell by between 50 and 70% as a result of low rainfall, and that this year's annual long rains had been below normal.