Story highlights

NEW: More than 100,000 people are in shelters, the Philippines' emergency management chief says

NEW: Early estimates are that damages will exceed $114 million, official says

Floodwaters have inundated towns in central Luzon

Manila, Philippines CNN  — 

Flood waters unleashed by a deadly, slow-moving typhoon have invaded more and more towns in the northern Philippines, forcing people to clamber onto rooftops to await rescue.

Typhoon Koppu began its multiday battering of the region over the weekend, killing at least two people, injuring five others and driving 20,000 residents from their homes.

At least 18 people – all but one in Luzon, the Philippines’ largest and most populous island – died as a result, Philippines’ disaster management agency director Alexander Pama said. Another 16 were injured, while one person was missing Tuesday.

The storm, known as Lando in the Philippines, has directly affected more than 550,000 people, with more than 107,000 taking refuge in shelters as of Tuesday.

The storm came ashore early Sunday at super-typhoon strength, ripping roofs off buildings and uprooting trees in the coastal province of Aurora.

It lumbered around Luzon at an excruciatingly slow pace, setting off floods and landslides across the rugged terrain.

The entire town of San Antonio in central Luzon has been engulfed by flood waters, Mayor Antonino Lustre said early Monday, according to CNN affiliate ABS-CBN. Rescuers were unable to reach some areas of the inundated town where residents were stranded on roofs, the broadcaster reported.

Flood waters have wreaked havoc in many other towns elsewhere in Nueva Ecija province, Gov. Aurelio Umali said, according to ABS-CBN.

“We know a lot of infrastructure has been destroyed, (and) some hasn’t been estimated yet,” he said. “Also, the (damage cost for) private properties like houses are still not included.”

Towns reportedly cut off by landslides, floods

The storm packed maximum sustained winds of 240 kilometers per hour (150 mph) when it slammed into the eastern coast of Luzon, according to the U.S. military’s Joint Typhoon Warning Center, although the Philippines’ national weather agency measured the winds as significantly weaker, at 185 kilometers per hour.

Roads and communications have been cut off by flooding and landslides in three towns in Aurora province, including Casiguran, where the typhoon made landfall, authorities reported.

“Based on the report of the Philippine Army, there were many houses destroyed and trees uprooted in the three towns,” the official Philippines News Agency said. The army and other agencies are trying to clear the routes to Casiguran, which has about 25,000 inhabitants, and the other towns, Dinalungan and Dilasag, it reported.

By Tuesday, all roads to and from Casiguran were again passable, according to Nigel Lontoc, a civil defense official in central Luzon. Authorities had packed food for about 1,000 families in the hard-hit community.

In Baler, another town in Aurora, CNN Philippines reporter Paul Garcia said there was flooding in several neighborhoods. Surprised local residents said that while storms are common in the area, flooding is not, Garcia reported.

The heavily populated region around Manila, the Philippine capital, isn’t in Koppu’s direct path, but it’s still getting lashed with wind and rain.

One of the two people so far reported killed, a 14-year-old boy struck by a falling tree, was in the Manila suburb of Quezon City. The other person killed was a 62-year-old woman hit by a wall that collapsed in Subic, which lies northwest of the capital.

Huge rainfall expected

A big concern is the extreme amounts of rain Koppu is expected to unleash. Flooding has struck Cabiao, Jaen and Santa Rosa.

“The big story out of this storm is definitely going to be the rainfall totals,” said CNN meteorologist Allison Chinchar. Some areas are forecast to receive more than 1 meter (39 inches) of rain by the end of Wednesday.

The typhoon is predicted to dawdle across northern Luzon for several days because of a ridge of high pressure over China blocking its progress farther north. That gives it longer than usual to soak the region’s mountains and swell its rivers, threatening people who live downhill and downstream.

“That’s where the problem with the flash flooding comes in, because when you have all of this rain that keeps coming down over the same places over and over, that is likely to trigger mudslides and landslides in addition to flash flooding problems in … some of the low-lying areas,” Chinchar said.

Officials reported dozens of flight cancellations, thousands of people stranded in ports and many municipalities without power.

‘The bowling alley for typhoons’

Situated in the Western Pacific, the Philippines is frequently hit by typhoons.

“They’re located in the belt basically between the equator and the subtropics. You might consider it the bowling alley for typhoons moving across the Pacific,” said Bob Henson, a weather and climate science blogger for Weather Underground.

“It’s considered to be the most vulnerable large nation on earth for tropical cyclones,” he said.

The deadliest storm to hit the country in recent years was super Typhoon Haiyan, which left more than 7,000 people dead or missing in November 2013.

Haiyan, one of the strongest storms ever to make landfall, was a different beast from Koppu, however. It generated a devastating storm surge that flattened entire neighborhoods in the densely populated coastal city of Tacloban before moving quickly over other areas of the central Philippines.

Journalist Arlene Espiritu reported from Manila, and CNN’s Jethro Mullen reported and wrote from Hong Kong. CNN’s Greg Botelho, Chieu Luu and Kim Hutcherson contributed to this report.