A federal agency listened to business leaders, the City of Nogales and Santa Cruz County and approved an appeal to a new set of flood-plain maps for the county, said John Hays, county flood-plain manager.

The Federal Emergency Management Agency (FEMA) approved an appeal the Nogales and Santa Cruz County Port Authority submitted last winter, Hays told the Santa Cruz County supervisors on Sept. 2.

“The appeals did result in areas of deeper flood waters than the original preliminary Digital Flood Insurance Rate Maps (DFIRMs),” Hays wrote in his report.

This means that FEMA must restart the process of review and appeal for the areas affected by the increases in water elevation �“ certain properties adjacent to the Nogales Wash, Ephraim Canyon and Potrero Creek, Hays said. But the new maps will probably not be available until the end of December.

Hays predicted that the final maps would not become effective before April 2011.

In September 2008, FEMA released the preliminary maps for Santa Cruz County, updated from the 1970s by a contractor called Stantech, Hays said in an interview. FEMA required the update for residents to continue to participate in the government-subsidized National Flood Insurance Program.

The maps represent an educated guess about where water will flow in a 100-year flood, Hays said. It’s a major event that has a 1 percent chance of occurring in any given year.

They predicted up to eight feet of water flooding from the Nogales Wash onto certain properties on Grand and Morley avenues and surrounding streets.

Chipping in

This alarmed local businessmen who believed it would stifle building in downtown Nogales. They brought the issue to the Nogales City Council and the county supervisors, who agreed to chip in for an appeal of the maps. On behalf of the city and county, the Port Authority contracted with CMG Drainage Engineers Inc. of Tucson to develop alternative flood-plain maps for Nogales.

“I think we’ve ended up with quite a bit of improvement,” businessman Joe Barr told the supervisors.

There’s no real difference between the validity of the mapping done by Stantech and CMG, Hays said. “It’s a matter of the modeling technique used.”

Stantech used a technique that FEMA said they would accept at the time, Hays said. But new staff at FEMA accepted the model CMG used for the appeal.

“You’re trying to model the real world using a simplified model,” Hays said. “All this presupposes nothing changing between the mapping and the flood occurring.”