MARK BENNETT: The Flood of ’08 left its mark, but will it make it into history books?

By Mark Bennett
The Tribune-Star

TERRE HAUTE June 07, 2009 12:02 am

— The Great Flood of 2008 will remain an upper-case memory for many Vigo Countians.
We’ll tell, and retell, the stories of what happened to us last June 7. Some, determined to mark history, already have scrapbooks of photographs from that weekend, with images of roads turned to rivers, rooftop rescues, sump pumps sucking up water, collapsed basement walls, mounds of soaked belongings on front porches, sandbags, sweat, tears and prayers.
It was all real. We saw it, and lived it.
Our future recounts of those events caused by Mother Nature are also subject to the weaknesses of our human nature.
In other words, as years pass, we may embellish a bit about the scope of this disaster.
The level of flooding that day reached historic levels in some places. In others, the scope and force of the high waters were far less rare.
In Vigo County, the term “100-year flood” cropped up a lot after June 7. That terminology is deceiving. Statistically, it means a flood of a certain magnitude has a 1 percent chance of occurring at any time. On average, that type of flood would happen once every 100 years. Thus, the label “100-year flood” became common.
Of course, nature isn’t driven by statistics. Iowa, for example, experienced two 500-year floods — those with a 1-in-500 chance of occurring — in a 15-year span (1993 and 2008).
Here, last June, the flooding along Honey Creek that devastated homes, businesses and farms in Terre Haute and southern Vigo County, was described as a 500-year, or perhaps even a 1,000-year, caliber event for that particular stream. Both terms were used by local officials at last week’s announcement by U.S. Agriculture Secretary Tom Vilsack that $3.3 million in federal stimulus funds would go toward completing the Honey Creek-Vigo Conservancy District Watershed project along Thompson Ditch.
But when it comes to this area’s most famous body of water, the Wabash River, the date June 7, 2008, won’t stand out in the history books.
“It’s basically around a 10-year flood,” said Robert Holmes, the national flood specialist for the U.S. Geological Survey.
In fact, Holmes said, statistically, the recurrence rate for the ’08 flood is closer to a once-every-eight-years event for the Wabash in Terre Haute.
It all boils down to numbers.
The USGS has monitored the Wabash at its Terre Haute station for 116 years. The flood of record occurred on March 26 and 27, 1913, when the river crested at 31.1 feet. On that day 96 years ago, the Wabash overflow swamped vast sections of the city and Vigo County, from Collett Park to West Terre Haute to Prairieton. The surging river was measured at 245,000 cubic feet of water per second, Holmes explained. (A cubic foot of water is about 7.5 gallons. Thus, that volumetric discharge in 1913 was around 1.8 million gallons per second.)
By contrast, last June’s river stage was around 92,400 cubic feet of water per second, almost one-third less than in 1913. The river crested at 25.16 feet, according to the USGS.
The USGS maintains a ranking of the most high-volume flooding or river stage for each year at the Terre Haute measuring station (and every other USGS station around the country). On that chart, the June 8, 2008, flood on the Wabash stands at No. 26 out of 116 years.
Thank goodness, the Wabash did not experience a 500- or 1,000-year flood, as its smaller tributary Honey Creek did.
“If we’d have had that 1913 flood, that was more than twice the amount of water,” Holmes said.
The fact that the Wabash rose at less historic levels than smaller streams in the county doesn’t surprise Robert Houghtalen, a professor of civil engineering at Rose-Hulman Institute of Technology, who specialized in hydrology. He also pointed out that, even along Honey Creek, people should not assume the 2008 flooding won’t recur for another 100, 500 or 1,000 years.
“They might think, ‘We got a 100-year event on Honey Creek, and I won’t have to worry about that for another 100 years,” Houghtalen said, “and nothing could be further from the truth.”
So, as the community reminisces, reflects and recovers, we should prepare for the unexpected, too.

Mark Bennett can be reached at (812) 231-4377 or mark.bennett@tribstar.com.

What happens as the Wabash River rises?
A look at what is occurring as the Wabash River reaches various stages in feet.
12.0 — River is bankfull to slightly overflowing. Flooding of a few low-lying fields is in progress.
14.0 — Agricultural flooding begins along west bank across from Water Works, southwest Vigo County and northeast Crawford County, Ill. Low county roads in these areas begin to flood. Old Darwin road begins to flood near Darwin, Ill., and northeast Crawford County.
16.0 — Lowest river cabins across from the Wabash Generating Station begin to flood. Flooding of agricultural land along U.S. 63 north of Terre Haute, west bank of river and in southwest Vigo County occurs. County roads flood in southwest Vigo County.
18.0 — Residential property of about 50 river cabins begin to flood. North Lake and Izaak Walton Areas near West Terre Haute begin to flood. Flooding closes more county roads. Lowland agricultural flooding is in progress.
18.5 — The Wabash River extends to Interstate 70 Mile Marker Number 4 from its west bank in the Terre Haute/West Terre Haute area.
19.5 — Pottsville Street just northwest of Terre Haute is flooded. Lowland flooding in progress with several river roads flooded in Clark County, Ill.
20.0 — Access to North Lake and Izaak Walton Areas nearly impossible by land vehicles. South Lake Area and 10 homes near Fort Harrison Country Club begin to flood. Water is at critical stage for a few agricultural levees.
22.0 — Water is at or near critical stages of many agricultural levees. Flooding of about 10 residential properties in South Lake area begins. North Lake and Izaak Walton are now a part of the Wabash River. West Road in northern Vigo county floods. Floodwaters surround homes in lowest areas near Fort Harrison Country Club.
23.0 — Extensive flooding is in progress. Greenfield Bayou levee may leak. South Lake Area extensively floods. Many local roads are under several feet of water.
24.0 — A few agricultural levees fail. Water enters about 50 homes in the North Lake, Izaak Walton, South Lake areas and near Fort Harrison Country Club. Some evacuations are necessary. Significant flooding in progress in industrial area on east bank near I-70.
26.0 — At least 5 agricultural levees fail. Most residents in the North Lake, Izaak Walton, South Lake areas and low structures near Fort Harrison Country Club leave or evacuate. Most of the east bank from US 40 to I-70 floods. Significant backwater affects gravel pit operation along Lost Creek in North Terre Haute.
28.0 — A major flood is in progress. Gravel pit operation in North Terre Haute along Lost Creek is flooded. Commercial property and industrial property along east bank from US 40 to I-70 begins to flood. Water flows over US 150 north of West Terre Haute.
29.0 — Sandbagging necessary at the Terre Haute Water Treatment Plant. Flood waters will begin to enter the Water Treatment Plant at 29.5 feet. Residential and commercial areas affected in Terre Haute and the West Terre Haute areas. Taylorville (Dresser) is very extensively flooded. US 150 and possibly US 40 are flooded.
30.0 — Record to near-record flood is in progress. Industrial and commercial areas along east bank of Wabash River from U.S. 40 to I-70 floods. Floodwaters are at the top of levee protecting Taylorville. Extensive flooding along Lost Creek possibly threatens residential and commercial areas in northern Terre Haute. Sandbagging of Terre Haute Water Treatment Plant is necessary.
31.0 — Taylorville (Dresser) is totally destroyed. Industrial and commercial area from US 40 to Interstate 70 floods extensively. Extensive flooding along Lost Creek may threaten residential and commercial areas in Northern Terre Haute.

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