Wednesday, Aug. 20, 2003 | 11:20 a.m.
Despite the images of people being plucked from the roofs of their submerged cars on roadways turned into rivers, the flood control system built in the Las Vegas Valley over the last 16 years worked, officials said.
The problems were that it is $1.7 billion away from being finished, and the portions of the system that are in place were simply overwhelmed by the amount of water that fell in a short period of time in the northwest late Tuesday afternoon, authorities said.
"We had no facilities that failed," said Betty Hollister, spokeswoman for the Clark County Regional Flood Control District. "Every detention basin and channel in place now worked as designed."
Even at the twin detention "cells" dubbed Gowan North worked, Hollister said. Gowan Road was one of the areas that suffered some of the worst flooding and several people along that road were nearly swept away before being lifted off their vehicles by helicopter crews.
Nevertheless, Gowan North "did not overflow," she said.
The rainfall surpassed the benchmark of a "100-year" flood, which is marked by 1.8 inches of rain falling in a 20-minute span. Rain gauges measured as much as 2.8 inches of rain in a 20-minute period.
The flooding in the Gowan Road area was due to the inlets to the detention basin being overwhelmed by the storm. More work will come to divert water from the site, part of 25 years of effort still planned by the flood control district.
The district was formed in 1986 and funded with a one-quarter cent sales tax. Since 1988, when construction began on the first flood-control structures, the agency has spent about $840 million, including about $180 million in federal dollars.
As of June 2003, there were 62 completed detention basins and about 350 miles of channels and storm drains on-line throughout Clark County. The district plans to spend another $1.7 billion building, coincidentally, another 62 detention basins and 476 miles of channels.
District officials pointed to the lack of flooding Tuesday in areas hard hit by the July 1999 flood as a measure of their success.
That was when Las Vegas' worst flooding on record occurred. Two people were killed and the area suffered $22 million in damage, earning a federal disaster area designation.
As was the case Tuesday, some parts of the Las Vegas Valley received more three inches of rain within a few hours during the July 1999 floods.
Mayor Oscar Goodman said he thought Tuesday's storm packed a bigger punch than 1999's, but the difference was in 1999 all washes in the valley were running full. Tuesday night, it was mainly the northwest that was deluged, and the drainage improvements built since July 1999 lessened the impact, officials said.
Among the projects completed in the the last year was the Interstate 15 Freeway Channel System, the District's largest single project to date. It was mostly completed by the beginning of this year's flash flood season. The project is designed to address the flooding problems that regularly turned the underpass at Charleston Boulevard and I-15 into a lake.
It also was designed to handle long-standing flooding problems along Western Avenue, Wall Street, Industrial Avenue and Oakey Boulevard and was designed to reduce flooding in the surrounding neighborhoods.
Improvements to the Flamingo Wash near Boulder Highway, an area that suffered much of the estimated $20 million in damage from the July 1999 flood, were also largely completed before the start of this year's flash flood season. Three new detention basins in Henderson, the Flamingo Wash at Spencer Street, and three areas along Duck Creek also received improvements.
District General Manager Gale Fraser had previously planned to go out of town today -- to Reno, to meet with the U.S. Army Corps of Engineers, state and Clark County officials for the 100th monthly meeting of the Tropicana and Flamingo washes flood control efforts.
About 75 percent of that work has been funded with federal dollars through the Corps of Engineers, Hollister said.
"We're just two years away from wrapping up all that work," she said.
National Weather Service meteorologist Andy Baily, in his Las Vegas office, said residents and visitors of Southern Nevada will never be able to completely relax. Some storms will always be able to overwhelm, at least temporarily, the work of man, he warned.
But he said Tuesday's floods could have been much worse.
"The flood control district has done a tremendous job for the area, but it is very difficult to defeat nature," Bailey said.
The National Weather Service had not even forecast any rain in Las Vegas for Tuesday. It wasn't until the afternoon that the gathering storm became evident.
Mid-summer -- "monsoon season" -- thunderstorms like Tuesday's are notoriously difficult to predict. The intensity of the rainfall also can vary greatly from one area to another just a few miles away, and that was also the case Tuesday night.
The threat of floods is present throughout the year in Las Vegas and the Mohave Desert, but the worst risk is from July through September.
During the hottest summer months, the usual west-to-east movement of weather from the Pacific Ocean can be disrupted. The heat of the southwest desert creates a low-pressure gradient, pulling moist air from Mexico north.
The monsoon effect can cause flooding throughout the West, but it usually occurs over the Four Corners region where New Mexico, Colorado, Arizona and Utah intersect. Sometimes, however, the monsoon moves west. When it does, Southern Nevada can get hammered.
Daytime heating can exacerbate already humid conditions, sparking thunderstorms that generate inches of rain in minutes and flooding that can send walls of water down normally dry washes and streets -- the classic desert flash flood.
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