LSU researchers create first comprehensive storm surge database
Tropical cyclone-generated storm surges are among the most deadly and costly natural disasters to impact the United States. Storm surges occur as sea water is pushed up against a shoreline by hurricane winds, and are often the greatest threat to life and property from a hurricane.
Graphical representation of SURGEDAT database.
The Gulf of Mexico coastline is especially vulnerable to storm surge disasters. Based upon the risk of hurricane impacts in this region, two LSU researchers set out to synthesize historically available data on all notable storm surges that hit the Gulf Coast since 1880. Barry D. Keim, professor and graduate director of LSU Department of Geography and Anthropology and Louisiana state climatologist, and graduate student "Hurricane" Hal F. Needham pulled from 28 federal government sources including the National Hurricane Center and the U.S. Army Corps of Engineers, numerous academic publications and more than 3,000 pages of newspaper to create SURGEDAT, the first comprehensive storm surge database for the U.S. Gulf Coast.
"Over the last century, storm surge has caused substantially more deaths in the U.S. and beyond than hurricane winds or flooding rains," Keim said.
Where extreme tropical cyclone events can claim lives, destroy natural wildlife habitats and cost billions of dollars in damage, a database of past storm surges would permit researchers to better gauge risks and plan for infrastructures that promote resilience of local communities.
"When you look at this on a global scale, and the amount of these huge surge events that affect major cities like New Orleans and Houston, it’s a big issue," Needham said.
While a previously generated hurricane information database called HURDAT offers a collection of information on hurricane tracks and intensities in the Gulf Coast region, SURGEDAT is a novel database that uses highly credible historical data to identify the location and height of maximum storm surge levels associated with both mild and extreme tropical storm events. SURGEDAT provides information on past storm surges in a user friendly format, a visual and interactive map freely available online.
Most storm surge research is based upon computer models that predict surge heights based on several storm-related and external variables. These include, for example, maximum wind speeds, the size and forward speed of the storm and offshore water depth. However, SURGEDAT was the first surge database project to be built around historical observations."SURGEDAT should hopefully help people understand their risk and plan ahead."
— Hal F. Needham
"When we started this research in 2008, this approach was completely unique," Needham said. "Modeling is very useful, but you need to validate it with what’s happened historically. That is what we are trying to do here."
These historical observations may help improve storm surge modelers’ forecasts of future storm surges and potential damages caused by high tropical storm waters.
SURGEDAT is already providing surprising insights into storm surge climatology and the relationship between hurricane landfall, storm intensity and storm surge levels. For example, the database has blown away the stereotype that wind speed relates directly to storm surge level. Keim and Needham found that some tropical storms that produce only moderate wind speeds according to the Saffir-Simpson Hurricane Wind Scale can produce unexpected levels of peak storm surge due to their large and slow-moving nature.
"SURGEDAT is a snapshot of where the most vulnerability from storm surge is located worldwide," Needham said.
Certain areas prone to hurricanes may be more vulnerable from storm surge than others. SURGEDAT revealed that, rather contrary to common sense, storm surge height may be more related to the amount of time a hurricane spends over open water before striking a location than to number of hurricane strikes in a particular location. Despite the fact that the Texas, Louisiana and Mississippi coasts do not sustain as many hurricane strikes as many locations in Florida and Alabama, these coastlines generally observe the greatest storm surge magnitudes according to SURGEDAT.
Hurricane Ike's storm surge inundated portions of Orange, Texas, under more than nine feet of water, although this community was approximately 60 miles east of Ike's strongest winds and more than 20 miles inland from the open Gulf of Mexico. Ike's 17.5-foot storm surge ranks eighth largest along the U.S. Gulf Coast in the past 130 years. Hal Needham
For example, Hurricane Rita in 2005 produced a surge of approximately 15 feet at Cameron, La., and Hurricane Katrina in 2005 produced a disastrous 28-foot surge in Bay St. Louis, Miss. Keim and Needham point out that the high storm surges that impact these areas may be due to hurricane trajectories that approach from the south, providing ample time for these storms to generate high storm surges as they cross the Gulf of Mexico.
"Storms that track across the open water for long periods of time push a tremendous amount of water as they come toward the shore," Needham said.
SURGEDAT data also reveal that shallow waters and the inward curve shape of bays produce greater storm surge heights. Needham describes the shallow water storm surge phenomenon as similar to what happens if we were to drop a boulder in an aquarium.
"The water is going to splash out because it is so confined, it can’t redistribute," Needham said. "But if I drop a boulder into a swimming pool, you will see a little wave that spreads out from the point of impact. Where you have deeper water, for example off the South Texas Coast, water displaced by storm events can better redistribute through underwater currents. However in shallower waters, for example off the Mississippi coast, the displaced water has nowhere to go, so it just goes up."
While many Gulf Coast inhabitants have the impression that storm surge natural disasters are random – that they can happen anywhere along the coast – this impression is not completely true.
"What most people think is that you either get hit by a hurricane or you don’t, but we are seeing that some places will get hit by a hurricane and there will be a massive storm surge and flooding, while other places will get hit and there will be minimal storm surge," Needham said. "The big picture here is that there is a pattern to storm surge events. Your vulnerability along the Mississippi coast is very different than your vulnerability in Tampa. This should hopefully help people understand their risk and plan ahead."
The SURGEDAT database is providing new insights into storm surge climatology and where surges are most likely to occur.
"When I started this research, I thought it was a crazy coincidence that the two biggest storm surge events we’ve seen – surges from Hurricane Camille in 1969 and Hurricane Katrina in 2005 – happened in the same location," Needham said. "This gives support to the idea that there is a pattern here, that this isn’t random."
These results have implications for heightened vulnerability and need for resiliency planning in particular areas of the Gulf Coast.
Although Hurricane Ike's storm surge was the highest along the Texas Coast, much of coastal Louisiana experienced flooding as well. Storm surge pushed in more than 25 miles in Southwest Louisiana, submerging this sign in Lake Charles, La.Hal Needham
"Mississippi and Louisiana – for every storm these areas are more vulnerable because the waters off their coasts are so shallow," Needham said. "The vulnerability here stems from the coastal profile, which doesn’t change from one storm to the next, it’s always the same."
In a new project that is undertaking the calculation 100-year storm surge levels for various locations worldwide, Keim and Needham show that southeast Louisiana and Mississippi are home to some of the highest 100-year storm surge levels along the Gulf Coast.
When research on SURGEDAT was published in the International Journal of Climatology in 2011, the database already contained information on location and height of peak storm surge for 195 surge events from 1880 to 2011. The project has now expanded beyond the Gulf Coast, incorporating hundreds of sources to generate a global dataset and map.
"We're currently seeking international partners to assist us in building the database in places other than the U.S.," Keim said.
SURGEDAT currently provides an interactive map showing locations of more than 400 peak surge events along the Gulf Coast and worldwide. The coordinates for each surge event are plotted in a Geographic Information System, or GIS, with each surge event represented by a circle on the map. Larger, darker circles represent larger surges.
Future additions to the database are also underway, including documentation of flooding and calculation of return periods for various storm surge levels.
"Within the Gulf of Mexico, we're currently making an effort to build complete surge envelopes to document the full extent of the surge flooding," Keim said.
Tropical cyclone-generated storm surge is a complicated hazard, one that many coastline inhabitants and even emergency personnel don’t fully understand. SURGEDAT, now an international database that draws awareness to past occurrences and brings together information from hundreds of discrete surge events, can help citizens and officials better prepare for approaching storms and plan evacuations.
"Hal has done an amazing job developing SURGEDAT," Keim said. "The database is unique and will have many applications in assessing surge risks in the Gulf and around the world."
The database may also help researchers better predict and prevent surge disasters in the future, as Keim and Needham plan future research to analyze the relationships between hurricane characteristics and storm surge heights.
As a part of the project, Needham maintains a Storm Surge Blog on the SURGEDAT website, providing information related to storm surge climatology and discussing storm surge history and forecasts in promoting public awareness in the U.S. Gulf Coast and worldwide. Keim and Needham hope that SURGEDAT will promote a better understanding and public awareness of storm surge climatology.