Getting to the anatomy of a flood forecast
The sets of eyes most keenly focused on the Flood of 2008 are six miles from the Mississippi River.
In a stand-alone building on the grounds of the Davenport Municipal Airport, weather, hydrology and information technology experts from the National Weather Service have been as in demand as sandbags and gawking space on the skybridge.
One might lovingly categorize the collection of NWS experts as “geeks.” If the definition of a “geek” is someone who has an intellectual enthusiasm for computers and scientific information, the office at the airport could be Geekville. And hydrologist Ray Wolf could be mayor.
He pointed to one of the five computer monitors that frame his desk and work area Wednesday, explaining what all the pretty colored lines and graphics mean.
“Blue represents moderate flooding,” he began. “Purple represents major flooding, and, as you can see, we’re in the major.”
This I knew. But my knowledge of flood forecasting pretty much dries up there. Wolf is all over it.
For instance, have you ever wondered how the Weather Service can predict the level of a crest (within at least a couple tenths of an inch) several days before the water actually gets here?
For starters, they get river level readings from points all up and down the Mississippi. At Lock & Dam 15 at Davenport and Rock Island, for instance, the gauge is at the Arsenal’s visitor’s center, and the reading is sent up to a satellite and retrieved from there.
More data comes from the U.S. Geological Survey, which I’m not smart enough to explain.
Engineers and hydrologists then can forecast the amount of water flowing past a certain point, taking into consideration the flow from tributaries, such as the Wapsi.
They also take into account how much rain is expected to fall. This is tricky, because no one can be entirely certain where, exactly, the rain will land. In the Quad-Cities, for instance, it can rain in Davenport, but not in Moline. Davenport rainfall would affect Duck Creek, while rainfall in Moline would affect the Rock River.
All of these variables, along with others from around the nation, are poured into the brains of people like Wolf who then turn the data into a forecast.
Voila!
Of course, it’s not really that simple, but new relationships between the NWS and the U.S. Army Corps of Engineers, along with new technology, make the turn-around time for accurate forecasting much quicker than it was in the record Flood of 1993.
Wolf, who cleverly came to Davenport in 1994, said this of the people in his office: “We look at ourselves as a public safety agency just like police or fire.”
As with any such agency, the NWS is loaded with jargon. A flood, for instance, is a “hydrology event.”
One of the biggest challenges for people like Wolf is simplifying complicated, scientific data in a way that laymen will understand. And he’s not just talking about me. The NWS team also has to simplify its message for at least 20 other agencies that have been involved in daily conference calls since the flooding started.
Wolf began his briefing Wednesday with roll call, rattling off the names of 16 Iowa counties, the state of Iowa, the Corps of Engineers, the Federal Emergency Management Agency and the Emergency Services and Disaster Agency — all of whom were on the phone for the latest river news. Wolf took the data he spent the earlier part of the day analyzing and filled in the folks who have to be prepared to deal with whatever is coming.
“The crest has passed throughout the Quad-Cities, and the tributaries have crested,” he said. “The issue is going to be rainfall over the next several days. We’re good to go with no rainfall for the next 24 hours. Thursday and Friday are a point of concern for us, however. The one to two inches we’re expecting north of I-80 are not included in the current forecast. Keep that in mind.
“I think it’s almost a certainty the rainfall will sustain the river levels. A significant secondary crest is an uncertainty.”
In other words, the Hydrology Event of 2008 may not be quite over.
Barb Ickes can be contacted at (563) 383-2316 or bickes@qctimes.com.