Residents and activists posted photographs and video online showing water from torrential showers carrying accumulated waste down streets in the early morning outside Beirut and beyond.
The crisis sparked a protest movement led by the "You Stink" activist group, which brought thousands of people into the streets for several weeks of demonstrations protesting the government's failure to solve the problem.
And elsewhere, residents and municipal workers used bulldozers to push dispersed trash back into piles after the rains stopped.
The scenes come three months into a crisis precipitated by the closure of Lebanon's largest landfill in July, and the government's failure to find an alternative.
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The cabinet in early September approved a plan that involved finding new sites for landfills and temporarily reopening the closed Naameh site for the immediate disposal of already-accumulated waste.
But the plan has run into a series of obstacles, including the refusal of residents around Naameh to allow its reopening and protests by people living near prospective new landfill sites.
Activists and several ministers have long warned that the arrival of winter, which often brings heavy rains to Lebanon, risked dispersing months worth of trash that has accumulated in open dumps.
"You Stink" activists wearing protective suits and facemasks sorted trash that had washed into the Beirut river from piles where it has been dumped along its banks on Sunday.
"We are proud to be 'waste workers' in this country, for trash, corruption, and the corrupt," the group wrote on its Facebook page.
It accused Lebanon's politicians of doing nothing "while the country drowns in their trash as a result of rampant, criminal corruption and inaction."