Improved flood forecasting keeps cities ahead of the game
FARGO – You might say that hard-won wisdom acquired from fighting floods flows downstream.
That’s a way of saying the record 2009 Red River flood in Fargo drew upon lessons learned in the 1997 flood that devastated Grand Forks-East Grand Forks.
In turn, the lessons learned in Fargo in 2009 and 1997 helped Bismarck fight the historic 2011 Missouri River flood.
The Red River Valley, in fact, has become a veritable flood-fighting laboratory. Experience has stacked up like sandbags.
Take flood forecasting, which provides the essential intelligence for tactical flood fighters in the field.
Crest forecasts for the cantankerous Red River were significantly changed following the 1997 flood that devastated Grand Forks-East Grand Forks.
The changes are so significant that hydrologist Andrea Holz regards the forecasting reports that were the norm before that watershed event 15 years ago as from another era.
In the past, the weather service flood forecast consisted of two predicted flood crests – one assuming a spring melt with no further precipitation and another assuming normal precipitation.
Besides failing to account for above-normal precipitation – a common element of floods – the problem with the old forecasts was that officials and property owners tended to regard the two predictions as firm numbers.
In the case of the 1997 Grand Forks flood, the crest forecast range ran from 47.5 feet to 49 feet – well below the record peak of 54.35 feet.
Following that disaster, which flooded much of the city of Grand Forks and most of East Grand Forks, the weather service started using forecasts with a range of possible crests, each carrying a probability of occurring.
So-called “probabilistic forecasts,” which are issued before water starts moving and hydrologists can make an actual crest forecast, convey to the public the uncertainties that plague forecasters.
“In the olden days, which is what we call them now, it was just these two numbers, and people put a lot of stock in those two numbers,” Holz says.
“Now it’s 60 numbers,” she adds. That’s a reference to the 60 years of detailed flooding data built into Red River flood forecasts, reflecting the full range of recorded possibilities.
The switch to “probabilistic” forecasts gave flood fighters an early warning that a major flood was on its way. But the forecasts kept ratcheting up dramatically, and hydrologists since have been working to refine their predictions.
Now the weather service’s river forecast center has the ability to run a forecast model developed by the Army Corps of Engineers along with its own model.
That helps to provide a more detailed picture of how water flows over the landscape, better allowing flood fighters to pinpoint problem areas, Holz says.
Every flood is different, as the saying goes, and every flood provides a new set of lessons.
The jarring necessity of suddenly having to fight a record flood forces communities to identify vulnerable areas.
The Bismarck-Mandan area provides a case in point. The cities learned some lessons last summer when residents found themselves battling a record flood on the Missouri River.
Long accustomed to the protection provided by Garrison Dam, residents of areas that never had flooded since the dam was built in the 1950s suddenly had a flood battle on their hands.
Fargo officials lent a hand and shared their expertise.
The city sent sandbags as well as machines to make sandbags, and sent along public works staff to help operate the “spider” bagging machines, as well as provide advice about placement.
“Certainly that was a great assistance,” says Jeff Heintz, public works operations director for the city of Bismarck. “They’ve done it so many times in recent years they’ve really got it down.”
A consulting engineering firm is helping Bismarck to develop a flood-fighting plan. It will be ready in time for next spring, in case it’s needed.
“I think we have a good idea now where we’d have to move those resources in the future,” Heintz says.
One lesson Bismarck is learning from Fargo and Moorhead that it can apply to the next flood fight: It’s better to work together, as neighbors, on mutual flood protection rather than erecting individual defenses.
“I think the people in Bismarck are seeing that,” Heintz says. That was a lesson two of his own children, who attended college in Fargo and Moorhead, brought home.
Bismarck learned other lessons as well, such as making sure that storm sewer outlets are covered to prevent floodwater from backing up into the city.
“The guys who came out from Fargo were a lot of help,” Heintz says. “If this ever happens again, we’ll be able to provide a lot more confidence for residents.”
Public safety and emergency management officials all follow the same protocols for managing disasters.
The system originated in California, where firefighters had to battle major wildfires, and was extended to fighting tornadoes, hurricanes, blizzards and floods, Greg Gust, a weather service meteorologist says.
In the same fashion, other areas of North Dakota and Minnesota have looked to the Red River Valley for advice and models in fighting floods, he says.
“In a practical sense, it’s real people having real experience,” Gust adds. “The result is, they know who to call for help.”
Long-term probabilistic forecasts aren’t yet available for the Missouri River, but hydrologists are working on making them available, probably between 2015 and 2020.
The project is intricate because it involves getting a better handle on inflows to the six dam reservoirs, and taking into account complex dam operations.
Fargo-Moorhead has all sorts of flood-fighting experience but still is working to improve its protection. The cities are working to build defenses for a 100-year flood as interim protection against the 500-year solution a diversion channel would provide.
“The thing that keeps lurking out there is having a flood level that would exceed the 2009 flood,” says Fargo Mayor Dennis Walaker. “That would be very, very difficult. But that’s where we’re trying to get.”
One of the biggest lessons comes from watching the devastation that occurs in places that lose a flood fight.
Grand Forks-East Grand Forks took years to rebound from the 1997 flood, and Minot will take years to recuperate, Gust says.
“Certainly they learned that you don’t want to lose the fight,” he adds. “The human impact, the economic impact – it takes a long time to recover.”
Patrick Springer reports for The Forum of Fargo-Moorhead.