Researcher Estimates Philippines Storm Surge Height from Denmark

After a major coastal flooding event, we want to know the maximum water height in various locations. Such information helps us better understand the process that triggered the event, and also helps us learn about localized flooding patterns.

Post-storm field surveys generally rely on trained field teams to go into an area and measure high-water marks. Such teams are generally looking for various clues that indicate the maximum water height. Signs on the landscape include the height of rafted debris, damage trimlines, tree bark removal, as well as mudlines or waterlines inside or outside standing structures.

Massive storm surges are so catastrophic that they destroy tide gauges as well as most buildings, making it difficult to obtain high water marks. After such disasters, measuring the height of tree bark removal is sometimes the best way to estimate surge heights. Photo: Noel Celis/ AFP/ Getty Images

A researcher from Denmark has already begun analyzing photographs for evidence of high-water marks, following Super Typhoon Haiyan’s massive storm surge in the Philippines. Aslak Grinsted, assistant professor at the Centre for Ice and Climate, at the Niels Bohr Institute, in Copenhangen, Denmark, has estimated the height of tree bark removal in numerous photographs from the impacted area. Such analysis is very valuable, because it provides some of the earliest estimates of surge height in the region.

Aslak Grinsted, assistant professor at the Centre for Ice and Climate, at the Niels Bohr Institute, has begun estimating  Haiyan's storm surge level by analyzing the height of tree bark removal in photos

Aslak sent me several photos earlier this week. Note the utter devastation in these photographs, as well as the fact that few structures remain standing to provide water lines or mudlines. In such massive surges, the height of tree bark removal often provides the best estimate of water levels, as debris floating on the top of the water column during the surge event rubbed off the tree bark.

Image #1 from Aslak Grinsted

Image #2 from Aslak Grinsted

Image #3 from Aslak Grinsted

Aslak compared the height of tree bark removal to the height of people in some of the photographs. In one photo, he estimated the height of tree bark removal to be approximately 2 human heights, while he estimated a water level of 2.5-3 human heights in another photo. If we assume the average human height in this area to be approximately 1.7 m (5 feet 7 inches), these approximations would provide estimates of surge levels reaching 3.4 m (11.2 ft) and 4.25-5.10 m (13.9-16.7 ft).

In order to accurately estimate the storm surge height, it is necessary to know the ground elevation for each observation, because storm surge is measured as the water height above the predicted tide level. Field teams will eventually provide accurate measurements, but in the meantime, online crowdsourcing may provide the best method for early surge estimates.

Here are some questions you could help with:

•  In the photos that Aslak used to identify tree-bark removal, does anyone know the name of the location and/or the approximate ground elevation?

•   Have you seen any photographs that contain clear signs of tree bark removal, rafted debris, mud lines, water lines, or damage trimlines on buildings/ structures?

If so, please send photos to Hal Needham at the following email: hal”at”srcc.lsu.edu. Please make sure to provide a citation and weblink for any photographs, if possible.

Aslak’s initial work this week has shown us the potential for all of us to participate in post-disaster field work, even from across the globe. As our world becomes more connected, opportunities should continue to open up for increased collaboration after such catastrophes.