The Rivers State government claims the demolition of the waterfronts is necessary to implement the Greater Port Harcourt Master Plan, an urban renewal project launched in 2009.
The development of the waterfront promenade is a central feature of the Master Plan - which encompasses the whole city - but full details have not been made public.
"None of the affected communities have been adequately consulted about these urban renewal plans and this has resulted in a great deal of uncertainty and insecurity," said Tawanda Hondora.
"These planned demolitions are likely to plunge hundreds of thousands of Nigeria's most vulnerable citizens further into poverty," said Tawanda Hondora, Amnesty International's deputy Africa Program director.
"The government should halt the waterfront evictions until they ensure they comply with international human rights standards."