Flooding triggers call for alerts

FLAGSTAFF, Ariz. -- Recent flooding on the Havasupai Tribe reservation in the Grand Canyon has renewed talks of an alert system that could help tourists and residents evacuate more quickly.

Without many river or rain gauges upstream from the village of Supai, forecasters have a tough time determining when floodwaters might reach the remote community.

The home to the Havasupai Tribe is an area popular with hikers because of the towering blue-green waterfalls nearby.

Forecasters rely on a radar system to estimate the rainfall, but Supai is well to the northwest of the radar. While the estimates are good, at times "they're not perfect," said George Howard, warning coordination meteorologist for the National Weather Service in Flagstaff.

"The idea is, let's take some of the uncertainty out of this with the prospect of locating a gauge in a strategic position so we can time things more precisely," Howard said.

Thunderstorms last month sent a rush of water down Havasu Creek and led to the evacuation of hundreds of people from the canyon. Some trails and footbridges were washed out and trees uprooted. Authorities said Supai appeared to have sustained only minor damage.

Flooding in the early 1990s first prompted talks of an alert system that would allow the National Weather Service to access real-time data from stream and rain gauges to plot estimates of stream flows. Based on that information, the weather bureau could issue a flood warning and better determine when the village might be affected.

The canyon is accessible only by foot, helicopter or mule.

Former Bureau of Indian Affairs superintendent Bob McNichols said a system had been designed in response to the 1990s floods, but it never was installed.

"I don't know exactly why it wasn't," he said. "There is a real need for it."

Heavy runoff in 1993 caused the collapse of livestock tanks and earthen dams in Cataract Canyon, whose name changes to Havasu Canyon. The riparian vegetation that survived a flood the year before was damaged again downstream from Mooney Falls, one of several waterfalls that cascade into blue-green waters.

Cassandra Anderson, Arizona flood warning coordinator, said the state has plans to reach out to tribes to help link them to a statewide flood warning network, but she wasn't sure of the time frame.

A rainfall station at Supai was discontinued in 1987, and the nearest river gauges are downstream from the village and at the head of Cataract Creek, about 35 miles upstream from Supai.

During flooding that began Aug. 16, radar had estimated up to 3 inches of rain, prompting flash flood warnings that afternoon, Howard said. The weather service notified the tribe and law enforcement agencies of a potential flood, and most tourists were able to catch a helicopter ride to the rim.