PROJECT ALERT NOTICE (CA) California experiencing a wave of AR storms—Continued, Day 8

Date: Wed, 11 Jan 2017 15:58:09 EST

Summary: Multiple atmospheric rivers continue to bring heavy rainfall and snow to many parts of California this week.

Today, many streams are responding to heavy precipitation that occurred yesterday and overnight across much of central and northern California. Reports from the Center for Western Weather and Water Extremes show many parts of central California received between 8 to 15 inches of precipitation during the past 72-hours, with some parts receiving as much as 20 inches of precipitation.

Light to moderate rainfall is expected today for all parts of California, with snow accumulations at higher elevations. Flood and winter storm warnings remain in effect for central and northern California. Precipitation is expected to continue across the region through tomorrow. This precipitation, which adds to previous accumulations of rain and snow, will increase the potential for flash floods, landslides, and avalanches.

Currently, 64 percent of USGS streamgages in California are above 90th percentile of normal flow, with 41 percent of streamgages reporting the highest ever streamflow for the date.

The California Water Science Center (CAWSC) has 22 crews responding to this event today from the following service areas: Ukiah, CA (3); Redding, CA (1); Eureka, CA (1); Santa Cruz, CA (5); Redlands, CA (4); Santa Maria, CA (4) and Sacramento, CA (4). More crews are planned to deploy tomorrow.

The USGS Truckee Field Office is closed today due to power outages and road closures that resulted from blizzard and winter weather conditions. I-80 is closed in both directions between Colfax, Ca and the Nevada State line. These power outages are likely to continue for several days due to extensive damage to primary power transmission lines. The cellular network in Truckee is also down. No USGS gages in this service area use cellular data transmission, but interruptions in data are possible due to snow cover on equipment (antennas and solar panels) or battery failures at gages on backup AC power supply. The USGS webcam at Truckee River is currently not operational.

Traffic and road closures have been a challenge for many USGS crews. This morning, CalTrans reported numerous road closures across northern California due to flooding, landslides, rock slides avalanches, winter weather, and accidents. Flooding has closed Hwy 211 at Fernbridge where the Eel River exceeded flood stage. The USGS operates a streamgage and a webcam at this location: 11479560 Eel River at Fernbridge, CA; webcam: https://ca.water.usgs.gov/webcams/fernbridge/. This webcam has had over 107,000 views since these storms began last week.

A USGS crew of 4 hydrographers are being used to measure streamflow at two locations along the Eel River (11475000 and 11477000) where high flows pose multiple safety concerns. With stream velocities of over 250,000 cfs, two staff will operate the ADCP, one person will operate the laptop, and 1 person will be upstream to watch for debris. If crews are successful, these measurements could be the second highest at 11475000 and the third highest at 11477000.

The USGS operates several streamflow and precipitation monitoring stations in areas affected by runoff from wildfires in CA. A USGS precipitation alert station 384550122405101 located in the burn scar area of the 2015 Valley Fire (76K acres in Lake, Napa, & Sonoma Counties) recorded over 20 inches of rainfall since January 4 when these storms began. An alert streamgage located in this same burn area (11453250, Putah Creek at Middleton CA) recorded over 6.5 feet of change in stage over a 24-hour period on Sunday January 8, and over 9 feet of change in stage since these storm began.

Crews are out today measuring streamflow on the Carmel River at USGS streamgages located in the burn scar area of the 2016 Soberanes Fire (132K acres in Monterey County). The peaks in streamflow at these locations (11143200 and 11143250) are the highest recorded in nearly 20 years.

Many streams and rivers continue to flow above monitor or flood stage. The USGS streamgage 11335000 on the Cosumnes River—the only remaining unregulated river on the western slope of the Sierra Nevada—is above flood stage again today with recorded streamflow over 31,000 cfs, velocities not seen in over 11 years.

So far, no other streamgages have experienced damage or interruptions in data transmissions, besides the ones mentioned in previous Project Alerts. No safety issues have occurred during this series of storms and all staff have followed USGS field reporting and safety protocols. Updates will continue to be provided during the course of this event.