DESERT CENTER (AP) — The interstate bridge that washed out in the desert between Los Angeles and Phoenix easily withstood its daily load of thousands of cars and trucks, but the pounding of a powerful flash flood scoured away the land where the bridge was anchored, officials said Monday.

The flood severed a highway vital to the movement of people and commerce between two of the nation’s largest cities. On an average day, the interstate carries about 27,000 vehicles in either direction.

Water rushing through a normally dry desert gully eroded the land around the Interstate 10 bridge, causing one side of the eastbound span to collapse and forcing the indefinite closure of the westbound span.

While the bridge should have been fine if the flood came straight down the gully, this time it swept down at an angle that pushed the water to one side, digging away the soil at the gully’s edge where the bridge reconnected with the road bed, according to California Department of Transportation spokeswoman Vanessa Wiseman.

Caltrans was not yet sure why the flow was redirected, but such changes are not unusual in sandy desert soil, she said.

Nine inspectors fanned out Monday to check all 44 bridges along a 20-mile stretch of I-10 after a second bridge showed signs of damage following the storm Sunday, according to the Caltrans. They also planned to inspect bridges across the large swath of Southern California where the remnants of a tropical storm off Baja California dumped unusual July deluges.

No timeframe was given for when either direction of the interstate would reopen. One driver had to be rescued Sunday from a pickup that crashed in the collapse and was taken to a hospital with moderate injuries, the Riverside County Fire Department said.

When inspectors visited the bridge in March, they found no structural issues, according to Caltrans. The eastbound span was deemed “functionally obsolete,” a label Caltrans spokeswoman Wiseman said reflected not its strength or durability but the fact that its 1967 construction style requires motorists to slow as they approach.

Many motorists speeding through the desert might cross the bridge without knowing. It spanned a shallow desert gully, perhaps just 60 feet wide. Such washes, as they are known, streak the desert floor and flash to life as rains are funneled into them much like tributaries can swell a river.

The bridge about 50 miles west of the Arizona state line washed out as rain was falling at a rate of 1.5 inches an hour. A total of 6.7 inches fell Sunday in Desert Center, said National Weather Service forecaster Ken Waters. Showers and thunderstorms in drought-stricken southern and central California set rainfall records in what is usually a dry month.

The rainfall was unlikely to offer much benefit for the drought-stricken state’s water supply, most of which originates far from the desert, in the Sierra Nevada and Rocky mountains.

In a place of extremes — where it may not rain for months and then rain so much that walls of water change the landscape — the loss of a short bridge caused long lines of traffic and huge headaches.

Clarin Sepulveda, her husband and her 16-year-old daughter were on their way back to Los Angeles from a weeklong vacation in El Paso when the bridge collapsed a mile ahead of them.

They sat on the freeway for two hours before word about what had happened started spreading among drivers. There was no cellphone service along the remote stretch of road. Sepulveda said her family and many other cars began crossing over into the median to head back eastbound, some getting stuck in mud as rain poured down.

They spent the next three and a half hours trying to take two alternate state highways, only to be turned back because of flooding. They finally gave up and snagged one of the remaining motel rooms in Blythe, California, about 50 miles away on the border with Arizona.

“It was stressful and extremely inconvenient,” Sepulveda said Monday as the family was back on Interstate 10 after having to detour around the closure.

The road’s rupture means longer-term inconveniences for those who live in the region.

Diana Valenzuela, a clerk at the post office in Desert Center (population about 200), said she would typically drive 50 miles west to Indio to shop at grocery and department stores.

With detours along desert roads, a trip that normally takes 45 minutes “will now take 3 hours,” she said.