The first "hard evidence" has emerged via NBC Bay Area that officials from the Santa Clara Valley Water District made a grave miscalculation last week about how much water they could safely release from the Anderson Reservoir without flooding downstream neighborhoods. The station obtained this email thread in which someone from the District admits to the mayor that the District's models "grossly overestimated" how much water they could release from the dam's spillway without triggering floods, perhaps by about 3,000 cubic feet per second.

As NBC's Stephen Stock reports, the amount of water spilling out of the dam since last weekend was the equivalent a large Olympic swimming pool every second.

San Jose Mayor Sam Liccardo had, since the major flooding began last Tuesday, questioned what had gone wrong and where, since it was clear that the deliberate release of water over the spillway had led directly to the swelling of Coyote Creek over its banks and into neighborhoods including Rock Springs in San Jose.

Because of the urgent need to release water from the reservoir — which topped 100 percent of capacity last week despite only having seismic tolerance to be at 60 percent — it seems that some flooding may have been inevitable. But residents were taken by surprise by the speed at which their neighborhoods saw rising floodwaters, some having to be rescued by boat late last Tuesday in the middle of the night. In total more than 14,000 people were forced from their homes, and it remains to be seen who will be on the hook for the widespread damage caused by all that contaminated water.

The Mercury News notes that there was also a clear failure in the emergency alert apparatus, as compared with the crisis at Oroville Dam just a week earlier.

When the Oroville Dam’s emergency spillway began to crumble earlier this month, phones throughout the region started blasting with emergency alerts, even sending shoppers at the local Wal-Mart to abandon their carts and flee.
When Coyote Creek in San Jose burst over its banks just over a week later, the first warnings for many residents that floodwaters were rising to their windowsills were rescue crews in boats knocking on their doors.

The Merc also obtained an email from 2:47 a.m. last Tuesday from a water district official who said that flow gauges along Coyote Creek were rising faster than predicted, and that flooding in the Rock Springs area was possible by 6 or 7 a.m. that day. Still, no warnings were sent out to residents.

Previously: 28 Horses Stranded, Left Behind In Contaminated Floodwaters In San Jose