Haiyan's Storm Surge: A Detailed Look

The Philippines is a nation used to seeing devastating typhoons. Between 1984 and 2012, the Philippines saw seven tropical cyclones that killed at least 1,000 people. In all of these storms, it was destructive flooding due to heavy inland rains that was the main killer. This is in contrast to the Atlantic basin, where storm surge from the ocean has historically been the main killer. That's due, in part, to the fact that the Philippines gets hit more often by intense tropical cyclones than any place in the world, and this has influenced settlement patterns. The portion of the coast most prone to typhoon strikes--the east coast of Luzon Island--is not heavily populated, and does not have any major cities at low elevation that are prone to large storm surges. The islands of the Philippines farther to the south, like Leyte, Samar, and Mindanao, are hit far less often, since they are closer to the Equator, where typhoons have a tougher time getting spinning due to the lack of an extra boost from Earth's rotation. This relative lack of typhoon strikes has allowed more settlement on the east coast, and Tacloban (population 221,000) is the largest city on the Philippines' east coast. Tacloban also happens to be low-lying, with much of the city at less than ten feet elevation. It's position at the pointy end of a funnel-shaped bay makes its location particularly vulnerable to storm surge, since the topography acts to concentrate water at the apex of the funnel. The occurrence of a massive storm surge disaster in Tacloban was only a matter of time, and that time happened to be November 8, 2013, during Super Typhoon Haiyan.


Video 1. Nickson Gensis, Plan Philippines Community Development Worker, filmed from the top flood of a boarding house what is probably the most remarkable video of storm surge ever taken, during Super Typhoon Haiyan in Hernani, in Eastern Samar, Philippines. Australian tropical cyclone expert Bruce Harper had this to say about the remarkable "tsunami-like" storm surge observed at 46 seconds into the video:

This site at Hernani is quite exposed on the eastern coast of Samar, and has a fringing reef. My guess is that we are seeing the sudden exposure to deep water ocean swell waves that were triggered by the tide and sea level increase due to the storm surge. There is a critical water level where waves impacting on reefs can suddenly cause a massive increase in wave setup in the form of a tsunami-like effect such as we see in the video. A similar effect was reported at Basey, ten miles to the northeast of Tacloban across the San Juanico Strait, in this news report: "Edgar dela Cruz, 45, of Barangay Mercado, recounted to The STAR the sight of what looked like a tsunami. During the strange lull in the typhoon, he went out of his house. Jinamok Island was a kilometer across the sea from his village, he said. The sea receded about halfway to the island. 'There was a kind of low black cloud moving toward us,' Dela Cruz said. 'We heard a loud boom, like an explosion. And then we saw the giant waves--four giant waves--it was horrible.' Their house was destroyed. He said he and his family escaped with only the clothes on their backs." In this case, the reports suggest that northeast winds ahead of the center of Haiyan caused an initial “negative surge” effect in the shallow waters in this area, followed by the winds turning to E and SE as the center came closer. You can then develop quite a gradient in the water levels capable of producing this effect. The fast speed of the storm may also have contributed to this specific phenomenon. Andrew Kennedy, Associate Professor in Notre Dame's Department of Civil & Environmental Engineering & Earth Sciences wrote this email to me: "My student, Yao Zhang, has been doing some preliminary estimates of the waves and surge at Hernani, Eastern Samar, using a one-dimensional Boussinesq model. These show periodic surges and recessions very similar to those seen by Nickson Gensis in the video you referenced. Magnitudes are quite large--over 5 meters--which does not include any initial storm surge. I would not take all of the simulations as being perfectly accurate, since we do not have perfect bathymetry and incident waves. In any case, Yao has made a video of one of his model runs and it may be seen at http://www.youtube.com/watch?v=KPYGQCE3778." The middle plot is a zoomed-in version of the larger-scale version shown in the top panel.

Why wasn't Tacloban prepared for Haiyan's storm surge?
At this writing, at least 7900 people are dead or missing from Haiyan, making the typhoon the deadliest disaster in Philippine history. The vast majority of these deaths were due to storm surge. The Philippines have never had a storm surge disaster responsible for killing hundreds of people in living memory, and thus is was difficult to communicate the danger. As early as 36 hours before the storm, advisories from the Philippine meteorological agency, PAGASA, were predicting a storm surge of 15 feet for Tacloban. That should have been enough to trigger a mass evacuation of low-lying areas of Tacloban, yet this did not happen. As senior presidential aide Rene Alemendras said, "I was talking to the people of Tacloban...they said 'we were ready for the wind. We were not ready for the water."


Video 2. This animation by Deltares shows computed storm surge levels and wind vectors as Super Typhoon Haiyan makes landfall near Tacloban City, The Philippines. Surge levels were computed using Delft3D two days after landfall. The wind fields are based on Joint Typhoon Warning Center data, and generated a simulated storm surge of over 16.4 feet (5 meters) for Tacloban.

How high was Haiyan's storm surge?
According to storm surge expert Dr. Hal Needham, the record highest storm surge in modern history in East Asia was 24 feet (7.3-meters) in 1897 on Samar Island, Philippines--the same location where Haiyan initially hit. He estimated that Haiyan's surge was very close to that at the Tacloban Airport: 21.3 feet (6.5 meters). Storm chaser Josh Morgerman of iCyclone.com rode out the storm in a hotel a mile northwest of the airport, where the surge may have been even higher, due to the shape of the coast. He stated in an email to me that "we determined our location to be at 26 ft (based on USGS data), and we flooded to a depth of about 4 ft, suggesting a whopping 30-ft surge. (Afterward, I had a geography expert research this, and he came up with the same value for our location—8 m or 26 ft.)" A storm surge of 21 - 30 feet hitting densely populated Tacloban, which did not fully evacuate low-lying areas, was bound to cause thousands of deaths.

A detailed look at Haiyan's storm surge
Hurricane scientist Margie Kieper, who wrote a remarkable analysis of Hurricane Katrina's storm surge for wunderground, also studied Haiyan's storm surge in detail. The rest of this post is her analysis.

You know the more I reflect on the surge damage from STY Haiyan the more I realize this is an enormously extensive surge. Even considerably far north of the eye along Eastern Samar's Pacific coast water came inland with enough height and velocity to destroy all coastal towns. And in the Gulf of Leyte, the surge damage along the coast was just as extensive and dramatic. Unfortunately, there seems to be only the one main coastal road ringing the island of Samar, to provide access to all these coastal communities.


Figure 1. Locations in the Philippines where a significant storm surge from Super Typhoon Haiyan was observed.

I just don't think I have ever seen anything on par with this. And this was a primarily rural area with small towns, not a developed coastline as with Katrina, Ike, etc. Haiyan's surge was most severe in Leyte, Samar, and Eastern Samar bordering the Gulf of Leyte, and the Pacific Coast of Eastern Samar (see map). Surge heights were on par with forecasts publicized by Philippines meteorological service, and may even have been a little higher than the forecasts. Their surge numbers were generated using the Japan Meteorological Agency (JMA) Storm Surge model using JMA forecast data and WXTide results. The model predicted 15 feet (4.5 meters) for Tacloban, and an estimate of about 21 feet has been suggested by Dr. Hal Needham on stormsurge2010.blogspot.com.

The storm surges at Tacloban and across the bay at Basey have been well-documented in the news. But along the Leyte coast south of Tacloban, the communities of Palo, Tanauan, Tolosa, and Dulag also received significant surge. Coastal communities along the northern shore of the Gulf of Leyte, and the connecting road, which runs in many places right along the shore, were all also destroyed by surge. Here, also, bridges along the coastal road such as at Lawaan, were also destroyed. In Samar, Basey and Marabut were heavily damaged by surge.


Figure 2. Storm surge damage from Haiyan in Palo, near where the center of the eye passed. This location is just south of Tacolban on Leyte Island. Image credit: rappler.com.


Figure 3. Storm surge damage from Haiyan in Tolosa, just south of where the center of the eye passed. This location is south of Tacolban on Leyte Island. Image credit: rappler.com.


Figure 4. Storm surge damage from Haiyan in Hernani on Samar Island. Image credit: rappler.com.


Figure 5. Storm surge damage from Haiyan in Lawaan on Samar Island. Image credit: rappler.com.


Figure 6. Storm surge damage from Haiyan in Marabut on Samar Island. Image credit: rappler.com.


Figure 7. Storm surge damage from Haiyan on Victory Island, Samar. Image credit: Getty Images.

Eastern Samar Representative Ben Evardone, in an interview with Rappler, noted that eleven out of the 23 municipalities in Eastern Samar were devastated by the storm, plus the Borongan City and the island of Homohon: Lawaan, Balangiga, Giporlos, Quinapondan, Macarthur, Hernani, Balankayan, Maydolong, Salcedo, Mercedes, and Guiuan. After a helicopter survey, he told reporters, “There is no more Eastern Samar province. You cannot recognize it. The devastation was horrific."

One other location that had extremely high surge was Hernani, facing the Pacific Ocean north of Matarinao Bay, where the storm surge was described as being two stories high. Hernani and Balangkayan are described as "destroyed" by the surge, and photos from Rappler's Franz Lopez bear this out (the entire photo essay can be seen at http://www.youtube.com/watch?v=fTrNTNNiIQA ). The surge obliterated the "first two rows" of houses along the shore at Balangkayan and eroded the beachfront there.

North of Hernani, along the Pacific Coast of Eastern Samar, surge destroyed bridges at the capital Borongan and at General MacArthur. The governor of Eastern Samar was not familiar with the term "storm surge" and was quoted as saying, "Nobody expected the sea water to surge through the towns. Usually, typhoons here just bring rain. Those who live near rivers and rice fields, they’re the ones who are asked to evacuated. Those living near the shoreline, that’s unexpected." In other words, they were familiar with freshwater flooding issues from heavy rainfall, but not familiar with storm surge. A resident of Maydolong, north of Balangkayan, described the damage as similar to a nuclear bomb, an analogy commonly invoked to describe surge damage. These areas also received strong winds which resulted in flying debris in the air at the same time the surge was moving inland. South of Hernani, in Guiuan, homes right on the coastline or built on peninsulas little more than sandbars, known in the U.S. as being in the "velocity zone", were also obliterated by water.


Video 3. The storm surge in Tacloban, Philippines during the landfall of Super Typhoon Haiyan is captured at about the 3:30 - 4:20 mark in this video shot by ABSCBN News of the Philippines.

The 1912 typhoon that devastated Tacloban
Haiyan is not the first typhoon to devastate Tacloban. The Philippine Star reported on a November 26, 1912 typhoon that struck the city. The news story from the Washington Herald that they cite reads: "That 15,000 persons were probably killed and wounded in a typhoon...probably half the population of the two cities had been lost." A pressure trace from the city showed the pressure fell to an impressive 924 mb during the typhoon. However, weather maps of the event show that the eye of the typhoon may have passed just north of the city, preventing a massive storm surge from hitting. There were three New York Times articles about this typhoon, one reporting about 300 killed, and another reporting, "Despite the enormous damage in Tacloban, the capital of Leyte, the fatalities there were less than a dozen." Thanks go to hurricane scientist Sim Aberson of NOAA's Hurricane Research Division for this info.

Jeff Masters and Margie Kieper