Flood shows wa­ter’s power to re­carve land

Austin American-Statesman - - FRONT PAGE - By Pa­trick Ge­orge

SAN MAR­COS— A year af­ter Mark Fon­stad be­came a geog­ra­phy pro­fes­sor at Texas State Uni­ver­sity in 2001, he got the chance to do re­search on some­thing for which no one could have planned.

In the sum­mer of 2002, a flood that re­shaped the area’s ge­o­log­i­cal land­scape on a scale that nor­mally would have taken thou­sands of years

hap­pened prac­ti­cally in his back­yard.

Mas­sive rain­falls around the July Fourth week­end that year caused a reser­voir on the Guadalupe River to over­flow. Flood­wa­ters tore through a gorge at the base of Canyon Dam, car­ry­ing mas­sive boul­ders as if they were peb­bles, scour­ing the walls and deep­en­ing the val­ley as they went.

The wa­ters caused $87 mil­lion in dam­age and de­stroyed or dam­aged al­most 500 homes. They also carved a

Con­tin­ued from A1 large, pic­turesque canyon into the land­scape.

“This was so huge, it changed ev­ery­thing at once,” Fon­stad said.

The data col­lected by Fon­stad and his re­search part­ner, Michael Lamb of the Cal­i­for­nia In­sti­tute of Technology, on the area be­fore, dur­ing and af­ter the flood has ap­pli­ca­tions here on Earth — and on Mars.

The re­search can be used to de­ter­mine how un­sta­ble a river is and whether its wa­ters could erode rock 10 feet deep, in­for­ma­tion that would be use­ful in mak­ing en­gi­neer­ing de­ci­sions, such as whether to build a bridge over a “prob­lem river,” Fon­stad said.

The re­searchers also hope their work will of­fer in­sight into how the canyons on Mars were formed.

To un­der­stand how a Cen­tral Texas flood can be tied to the Red Planet’s geog­ra­phy, one must go back to 2002.

Thanks to a wet spring, Canyon Lake — nor­mally at 909 feet — was al­ready full. Then, on June 30, rains swept in from the Gulf and stalled over the Hill Coun­try for five days, drop­ping up to 45 inches in ar­eas north and west of San An­to­nio. Lo­cal­ized rain­fall com­bined with runoff from up­river, push­ing things over the edge.

When the lake reached 943 feet, the U.S. Army Corps of En­gi­neers opened the flood- Re­searchers hope their work will of­fer in­sight into how Red Planet canyons were formed. gates at Canyon Dam full blast in an at­tempt to re­duce the vol­ume of wa­ter head­ing to­ward the spill­way, the part of the dam that al­lows con­trolled over­flow and helps pre­vent wa­ter from top­ping the dam.

Bil­lions of gal­lons of wa­ter spilled forth from the side of the dam and tore into the Guadalupe River.

“It was very dra­matic. It went over at very high speeds,” Fon­stad said.

The lime­stone walls of the val­ley be­low were very weak, made up of loosely con­nected blocks, Fon­stad said. The flood­wa­ters picked up about 70,000 tons of rock and car­ried them down­stream, carv­ing 70 feet deep into the canyon floor in some places.

The tor­rent un­cov­ered fos­sils, an­cient shells and fresh­wa­ter springs.

Fon­stad and Lamb com­pared to­po­graph­i­cal im­ages to de­ter­mine how much earth had been washed away be­low Canyon Dam. Fon­stad said that us­ing data col­lected on the Guadalupe River flood, he and Lamb can es­ti­mate the size of floods on Mars and how much rock was in­volved to cre­ate that planet’s many canyons and gorges.

Their re­search was re­cently pub­lished in the jour­nal Na­ture Geo­science.

“There was a tremen­dous amount of wa­ter” on Mars, Fon­stad said. “It prob­a­bly wasn’t cre­ated by sur­face rain, but pos­si­bly snow melt or ground­wa­ter.”

Brian Hynek, an as­sis­tant pro­fes­sor of geo­sciences at the Uni­ver­sity of Colorado, re­cently pub­lished a study say­ing that a vast ocean prob­a­bly cov­ered one-third of the sur­face of Mars about 3.5 bil­lion years ago.

The quest to find liq­uid wa­ter on Mars, or prove that it once ex­isted, cap­ti­vates sci­en­tists be­cause on Earth, where there is wa­ter, there is life. Hynek said track­ing wa­ter on Mars is key to trac­ing the pos­si­ble devel­op­ment of life there.

“Un­der­stand­ing the his­tory of wa­ter on Mars is pretty im­por­tant (to de­ter­mine) if life is there, or ever was there,” Hynek said.

The study shows how events on Earth can be ap­plied to other worlds, Hynek said. “Mod­el­ing the Earth’s cat­a­strophic floods is a great way to look at Mars.”

Larry Kolvo­ord

Flood­wa­ters, which caused $87 mil­lion in dam­age, picked up about 70,000 tons of rock, cut­ting 70 feet deep into the canyon floor in some places.

Michael Lamb

Mark Fon­stad

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