Fears that crushing waves and powerful rains from El Niño would erode the coastal bluffs in Pacifica — where several vacant apartment buildings and homes have been left teetering for years — were realized this weekend.

The city declared a state of emergency Friday in part because of accelerated erosion to the cliffs along Esplanade Avenue and Palmetto Avenue, where two properties in recent days were evacuated.

Those homes joined scores of other units that have been abandoned because of erosion, including the apartments on the 300 block of Esplanade Avenue that were evacuated in 2010 after heavy storms in 2003 began shearing off huge chunks of the cliffs.

Other areas along the bluffs have given way in the past 10 days as several heavy storms and waves slammed the shoreline, city officials said.

Officials have worked to preserve the delicate sandstone bluffs by piling rock on the beach below, drilling reinforcement rods into their sides and covering the cliff faces with reinforced concrete.

Those ledges had remained relatively intact during California’s four-year drought until this month, when unceasing El Niño-driven storms began to sweep through.

YouTube user Duncan Sinfield posted drone video Saturday that captured a large chunk of the cliffside breaking off under the apartments on Esplanade, as large waves crashed below.

Farther south, along the 1000 block of Palmetto Avenue, the earth under several homes crumbled in recent days, leaving parts of the houses and their back patios hanging precariously over the edge.

Officials in Pacifica have been scrambling in recent days as many areas in the city have taken a beating from the ocean. On Friday, the city manager, who serves as director of emergency services, declared a local state of emergency.

The Pacifica Pier — a favorite spot for anglers and tourists — sustained damage and was partially closed, while last week, part of the walkway along the seawall at Beach Boulevard gave way.

“El Niño is hitting the City’s coastline very hard and creating almost daily reports of impacts to both public and private property,” Pacifica City Manager Lorie Tinfow said in a statement.

The latest in a series of January rainstorms to hit the Bay Area dried up over the weekend. Skies will remain clear until the middle of the week, when another round of rain is expected to come through, forecasters said.

Evan Sernoffsky is a San Francisco Chronicle staff writer. E-mail: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky