A few years ago, while state climatologist Barry Keim was working on a project involving storm surges produced by tropical storms, fellow researchers asked him for access to a storm surge database.
The problem was, there was no database of historical storm surges, he said.
Although storm surge computer models are commonly used to forecast what height a storm surge could reach along portions of the coast for a particular storm, there was no historical database on storm surges that had formed in the past.
Then in 2008, LSU graduate student Hal Needham approached Keim and said he was interested in doing a project about past storm surges, and a partnership was formed.
Needham scoured government documents, academic papers, books and newspaper articles to put together a database of storm surge heights from 1880 through 2011.
“Generally, when talking about storm surge, it’s all been modeling,” Needham said. “What we have here actually happened.”
The result was SURGEDAT, a database of historic storm surges in the Gulf of Mexico. They were very close to calling it the “Water Height Observation Data,” or WHODAT, Keim said with a chuckle.
Within the 132 years of data, Needham restricted the search to storm surges above 4 feet because at that time, the National Hurricane Center considered a 4-foot surge as being associated with a Category 1 hurricane.
Since then, the National Hurricane Center has made the category scale for hurricanes based only on wind speed and have warned that storm surge can vary widely despite the category of storm.
A storm surge is the height of the water above normal tides but doesn’t include the waves that can ride on top of the surge.
After the initial map was put together, researchers saw that storm surges are relatively low in height on the western coast of Florida when compared with those on the Mississippi and southeast Louisiana coasts.
“The top two (storm surge heights) were both in Pass Christian, Miss.,” Needham said. “There are physical reasons some areas get more extreme storm surge.”
The coastline of Mississippi gets higher storm surges, in part, because the water off the coast is shallow, causing the storm water to pile up, and because the geography of the coast causes water to get trapped.
In Louisiana, storm surges can be larger because storms travel a longer distance, generally, and have more time to build up more surge.
“When approaching Louisiana, they’re going over open water for two days,” Needham said. “Which is plenty of time to push more water.”
Using this information, Keim and Needham set out to determine how often a storm surge of a particular size would return to the Gulf of Mexico coast.
For example, they calculated the height of a 100-year storm surge would be about 27 feet when averaged across the coast.
In the meantime, another graduate student also worked on a storm surge project along the east coast of the U.S., and then the mapping of historical storm surges started going global, Keim said.
“We were curious how to assess Gulf surges as they relate to the rest of the world,” Keim said.
The work is still in progress and the two are currently working with researchers in other countries to get better information on historical storm surges around the world.
“This is by no means complete,” Needham said of the database.
Looking at the height of storm surges worldwide, the Gulf of Mexico coast is about second.
First is India and Bangladesh where some storms produce more than 40 feet of storm surge, Needham said. In fact, the largest storm surge reliably recorded was 44.9 feet in 1876 in Bangladesh, Keim said.
Third place is on the east coast of Australia, with fourth place a tie between the East coast of the U.S. and eastern China, Needham said.
The project they mapped just notes where the peak storm surge of any particular storm was located. For example, storm surge impacts from Hurricane Ike in 2008 were felt all along the coast, but their current project only counts where the peak storm surge was measured in Texas, Needham said.
The next project will catalog storm surges at different areas along the coast. For example, a person will be able to click on a particular town and see historic storm surge levels from a variety of storms over time, Needham said.
More information about the historical storm surge database along with an interactive map can be found at http://surge.srcc.lsu.edu/.