FOR IMMEDIATE RELEASE
NOVEMBER 23, 2005
Project maps underwater landscape for better storm surge evacuation plans, safer oceanic drilling and lessons for schoolchildren
COLLEGE STATION, TX — As one of the busiest and most catastrophic hurricane seasons ever recorded finally draws to a close, researchers at Texas A&M University are finishing a project that may someday make it easier to model the tremendous storm surge from these powerful storms.
In a project funded by the Texas Sea Grant College Program, marine geologists Dr. Troy Holcombe and Dr. William Bryant are combining soundings from the Gulf of Mexico and topographic information from coastal areas in Texas and Louisiana to make it easier to model the massive storm surge that is part of such huge storms.
The researchers are pulling together data from a patchwork of soundings — literally millions of data points collected by the NOAA’s Office of Coast Survey over the past 100 years — from throughout the Texas-Louisiana Continental Shelf and upper Continental Slope, including bays and estuaries, to create the first detailed, easily readable and readily accessible maps of bathymetry, the topography of the land under water. A third researcher, geographer Dr. Sarah Bednarz, is synthesizing their results to create curriculum items for teachers in grades 6 through 12 in Texas and Louisiana to use in the classroom.
The continental shelf is a gently sloping extension of the coastal plain. Along the northwest Gulf of Mexico coastline it extends 170 to 400 km out to a depth of 90 to 150 meters. At the edge of the shelf, at a marked break in the angle of descent, begins the continental slope, a steeper drop to deeper waters. Much of the commercial activity of the Gulf — oil platforms, pipelines, fishing — takes place along the shelf, and Texas and Louisiana share one of the most intensely used shelf areas in the world.
“Bathymetric maps are very useful for ocean engineering and construction — people who are deciding about laying a pipeline need good bathymetry of the shelf area to go along with information about the character of the bottom sediments,” Holcombe says. “Also, if you’re going to anchor a drilling platform, you need good bathymetry along with information about the strength of the sediments in the area in order to build a safe platform and decide where the best place to locate it will be.
“On the other end of the spectrum you have the fishing folks, who like to have bathymetry, particularly in the search for species whose habitat is depth-dependent,” he adds. “On the Gulf coast shrimp are found mostly out to 50 meters, so there’s not much point in trawling for shrimp if you’re deeper than that. Many fish hang around reefs and banks on the outer shelf, so good maps of those are useful for fishermen.”
Bryant notes that recreational users, including fishermen and divers, also value good bathymetry.
“A lot of sports fishermen like to fish on bathymetric highs, which are known for the community of fish they attract. And the corals around and on the highs attract more and more people for recreational diving,” he says.
The combination of the bathymetry with existing maps of land topography along the coast has obvious applications for those who model storm impacts, especially the storm surge from a hurricane or tropical storm.
“To determine how high the surge will get — to determine how far the water is going to run up on the land — you need to know the bathymetry plus you need a good map of the land topography,” Bryant says.
Holcombe explains that storm surge models have never used bathymetry in this detail. Before this project, accurate bathymetric maps of the whole region were not available because the technology to do it in a cost-effective manner didn’t yet exist.
“We’ve had the expertise, but until about 10 years ago, you didn’t have the computing power to deal with this, and until about 20 years ago you didn’t have the data in digital form,” Holcombe says.
He predicts that once the bathymetry is completed in early 2006, modelers will begin to incorporate it into their projections.
“In a case where you have a hurricane or other storm coming in from this position in this direction at this speed, with the model you can run it across the shelf right into a bay and up the estuary, and you see what happens to the storm surge,” Holcombe says. “This may turn out to be one of the most important uses for new bathymetry.”
Bryant says that tsunamis present another danger, one that could send a large run-up of water from the Gulf onto the coast.
“There’s not a lot of naturally occurring seismic activity within the Gulf of Mexico, but there are indications from the bathymetry that large landslides have occurred in the past along the shelf edge. There are large masses on the Continental Slope and the Sigsbee Escarpment that have failed, and if they fail at the right time and the right place they can create a tsunami,” he says. “This has occurred on the Mississippi fan, which may have created quite a tsunami tens of thousands of years ago — it can always happen again.”
Bednarz’s challenge is to transform the bathymetry of the continental shelf and upper slope being developed by Holcombe and Bryant into a form that Texas and Louisiana teachers can use in the classroom.
“I began by looking at the curriculum in science and social studies for Texas and Louisiana — where are the opportunities for teachers to use this information?” Bednarz says. “Too much curriculum material is developed on esoteric things that aren’t relevant to what teachers are going to teach about. They’re great materials but they’re never implemented. So as much as possible I wanted to find a niche for this material, a way to combine it with what’s going on in the curriculum.”
She has designed five lessons that can be used in grades 6 through 12. They include an example of bathymetry that students can model with clay or paper that connects the bathymetric data to a hands-on understanding of the underwater landscape.
“When kids see the ocean they just see the top of the water, and they do not understand that there’s anything under the water,” she says. “They know and have experienced the shore — it’s flat and sandy — but they don’t understand that deep down underneath the ocean there are landforms, and the processes that created those landforms underwater are related to the processes on land. There’s a whole rich geography of what goes on under the water, and the first activity is to introduce students to the idea of bathymetry and what the bathymetric map is all about.”
Other lessons incorporate computer programs and PowerPoint presentations about the Gulf of Mexico, including one developed by Holcombe showing how coral reefs are formed on salt domes. Another lesson focuses on the importance of underwater salt domes in oil production.
In addition to the curriculum materials being designed by Bednarz, the study will yield one or more CD-ROMs of bathymetric images, including a continuous map with 1-meter contours of the Texas/Louisiana continental shelf and upper continental slope that also includes land topography and shoreline details. They have completed some larger panels of bathymetry at half-meter contour intervals showing more detail of features such as the reef terraces at Flower Garden Banks and the nearshore areas. The maps will be available for download from the Texas Sea Grant website at http://texas-sea-grant.tamu.edu/pubs/Bath.php; some images are already available at the gallery there. The images will be freely available to researchers, government agencies, coastal resource managers, educators and the public.
After they have completed this bathymetry project, the researchers say they would next like to map the shelf and upper slope for the rest of the states along the Gulf of Mexico, now that the technology exists to make it a reasonably cost-effective process.
“We’re closer to having the bathymetry faithfully reproduce the bottom today than we ever have been,” Holcombe says. “In the past, with a pencil and a bunch of soundings on a sheet of paper, there was a big gap between the data on the one hand and the bathymetry on the other. But that gap now has been narrowed a great deal. With better data and evolving technology, we’re able to get credible bathymetry out of the sounding data without resorting to elaborate interpretation in many areas.
“There is much interest in having a good map of the bathymetry. It provides a base map for further studies of everything that involves the ocean environment on the shelf.”
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For additional information, contact:
Dr. Troy Holcombe, Department of Oceanography
Texas A&M University
979-845-3528
tholcombe@ocean.tamu.edu
Dr. William Bryant, Department of Oceanography
Texas A&M University
979-845-7211
wbryant@ocean.tamu.edu
Dr. Sarah Bednarz, Department of Geography
Texas A&M University
979-845-1579
s-bednarz@tamu.edu
NR 5-14
Powell 11/23/05
The Texas Sea Grant College Program is a partnership of university,
government and industry, focusing on marine research, education
and advisory services. Visit our web site at http://texas-sea-grant.tamu.edu
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