"The year 2022 has witnessed most flood incidents in recent history, which has caused massive destruction of farm lands at the point already close to harvest season," Buhari said in a letter read by the Senate President to lawmakers.
Buhari said the new spending will be financed through domestic borrowing, which will raise the deficit for 2022 to 4.43% of GDP.
The government expects the deficit to widen to 4.78% in 2023 as spending rises in an election year in which Buhari will not stand for re-election to due term limits.
"This may compound the situation of hostility and aggression in the country," he said.
Severe flooding this year has destroyed farmland, roads and dams, raising food security concerns as high food prices add to concern over double-digit inflation.
Nigeria is also battling with insurgents in the northeast and crude oil theft in its oil-producing regions in the south which has slashed oil output and government revenues.