Surges are the Overlooked Storm Threat — But Not for Much Longer

Posted on September 12, 2013

by Hilton Collins, via EMERGENCY MANAGEMENT

Storm surges are a coastal threat that few taxpayers understand. A surge strikes when a storm causes seawater to rise above the normal predicted tide level. The surge itself consists of extra water that’s been added on top of the tide, and the combination of the two bodies of liquid can spell doom for coastal residents.

Hurricane Katrina, for example, killed more than 1,800 people in 2005, and the National Hurricane Center attributes many of those deaths to the resultant storm surge. Surge flooding of about 25 to 28 feet above the normal tide level struck the Gulf Coast and caused an estimated $75 billion in damage in the New Orleans area, the costliest hurricane on record.

But according to some of America’s most prominent weather experts, storm surges are often overshadowed in the public consciousness by the disasters that create them.

 “People by their very nature think wind first. You hear ‘hurricane,’ you think wind. They’re not thinking water,” said Jamie Rhome, the National Hurricane Center’s team lead on storm surges.

 Bryan Koon, director of Florida’s Division of Emergency Management, agreed.

 “A 100-mile-an-hour wind, 150-mile-an-hour wind — people understand wind, but when you start talking about storm surge, we start using terms like ‘above ground level’ [and] ‘base elevation,’” Koon said. “It quickly gets complicated and as a result, there’s less conversation about it, simply because it doesn’t register as much.”

 Government agencies are working diligently to increase storm surge awareness and education. The National Hurricane Center, a division of the federal government’s National Oceanic and Atmospheric Administration (NOAA), is developing storm surge warnings, separate from hurricane warnings, to be ready by 2015, and Koon said Florida is one of several local governments that is developing strategies to publicize storm surge and evacuation zone information.

Under the Radar

Multiple factors contribute to storm surges, which makes them more mercurial and difficult to predict than the forces that generate them. When wind moves in a cyclone around the eye of a storm, the force pushes water to shore and creates the surge, but the surge’s power depends on the storm’s characteristics, which can vary over the disaster’s duration. These features include the storm’s size, forward speed, angle of approach to the coast and central pressure.

Surges’ destructiveness also depends on the land features they hit. If an area has a shallow continental slope, the storm surge will potentially be greater than if the slope were steep. A shallow slope allows water to more easily wash onto shore, but a steeper slope can create a groove that catches more water than it allows to flow. The Louisiana coastline’s shallow continental shelf can produce a high storm surge, as it did in Katrina’s case, but a storm surge that strikes Miami Beach, Fla., which has a steep continental slope, may be much lower.

Consequently, storm surges don’t always match the severity of their accompanying storms, and sometimes storms don’t bring surges at all. This means that storm surges are often overlooked while the severe weather behind them always receives attention.

“In Florida, you get a lot of hurricanes without storm surge, so it’s not something that people always tie together, or if you do, it’s often such a small storm surge that it doesn’t go very far inland and most people are unaware of it,” Koon said. “You get the occasional giant ones like you did with Katrina, so oftentimes when people think hurricanes, they’re not thinking storm surge because it doesn’t always correlate with that.”

Koon also feels that the media focuses on wind damage more than water damage because wind is easier to observe. Reporters can stand near strong winds, but they can’t stand near 20 feet of water rushing onto shore.

“You get reporters standing there with wind blowing them sideways, but, because they would be dead, you don’t get people standing up saying, ‘Here, the water’s 20 feet higher than it normally has been in this location,’” he explained.

Rhome said that reporters don’t understand water events as well as they do wind events. “Your on-camera TV people; they’re meteorologists comfortable with wind. They’re not oceanographers, so they’re not as comfortable with water,” Rhome said.

 Changes Ahead

 Efforts are under way to improve storm surge warnings and demystify the nature of these events to the public.

The National Weather Service, another NOAA division, plans to create experimental storm surge watches and warnings by 2015, and the National Hurricane Center has updated its existing storm surge modeling program on faster computers to help emergency managers update evacuation plans more quickly.

The center’s surge model is called SLOSH, which stands for Sea, Lake and Overland Surges from Hurricanes. Center personnel use it to calculate surge levels in advance for nearly 40 areas around the world, including the Gulf and East coasts. They run hurricane simulations for all categories of storms, and faster computer modeling means that the center can run more surge scenarios than in the past. Emergency managers use these models to prepare evacuation zones before storms hit.

These efforts will lead to the government’s creation of a separate warning system for storm surges specifically. Currently hurricane warning and advisories dominate the emergency preparation process, and no sophisticated system exists for storm surges specifically. The much-used Saffir-Simpson scale, which measures wind speed, is what’s used to determine hurricane categories, but it overlooks the power of surge water.

The Hurricane Center is also coordinating with multiple governments across federal, state and local levels to improve public advisory language pertaining to storm surges in order to better educate the world about the danger, an improvement over how it’s been done in the past.

“We probably haven’t done a great job of educating people exactly what a storm surge is,” Koon said.

To change that, NOAA is working with social scientists to assess the language and dissemination methods for any future public service messaging. The idea is to consider the public first before messaging is developed, as opposed to an approach where climate specialists develop sophisticated language first without considering  how confusing the jargon may be to others outside of the scientific community.

“Historically the weather service would do an excellent job of designing a product or service that fit its needs,” Rhome said. “Well the average person doesn’t have an advanced degree in physical science, so that product may or may not be clear to them.”

 These messaging changes will include using “high” to describe water levels more often than “deep” is used, since the general public typically associates “deep” with ocean depth as opposed to how deep water will be from a storm surge when it hits the land.

 “Communication experts work with our constituents directly to design what will ultimately be a new suite of forecast products and services for storm surge.”

He claimed that some of the language and dissemination changes have already commenced, which comprises more visuals, like videos and graphs. He may or may not have been referring to the eye-catching material on NOAA websites, like video on the Ocean Today website, or the wealth of visuals and models that abound on the Hurricane Center’s storm surge information page.

Recent disasters like Hurricane Katrina have prompted these changes in warnings and public messaging, but so has the increase in the numbers of residents moving to coastal communities.