PROJECT ALERT NOTICE (CA) Post-flood work in California following flooding, debris flows, and mudslides

Date: Wed, 10 Jan 2018 15:50:16 EST

Summary: Rivers are receding today as a major storm moves out of California and leaves behind the remnants of flooding, mudslides, and debris flows in areas within and downstream of recent burn areas.

Today, rivers are receding as the storm system that brought flooding, mudslides, and debris flows to fire-affected parts of southern California moves out of the area. Lingering showers are expected through tonight, with generally dryer conditions forecast for the next few days.

The USGS California Water Science Center (CAWSC) has 5 crews out today doing post-flood work; 2 of the 5 crews are working specifically in the Thomas Fire burn area making recessional measurements, repairing equipment, and flagging high water marks (HWMs). A mudflow from the Thomas Fire burn area dislodged equipment and buried the orifice at USGS streamgage 11114495 on Matilija Creek. A crews is working today to repair this gage, get the data back online, and flag high water marks for peak-flow estimation. Crews will also be servicing USGS streamgage 11119500 on Carpenteria Creek. This gage is located just south of Montecito, CA where a deadly mudslide occurred yesterday in the early morning. Runoff from this storm produced record peakflow at Carpenteria Creek, a site with 74 years of record, and resulted in flooding that closed HWY101. Yesterdays record peakflow recorded at Carpenteria Creek is 60% higher than the peak of record in 1971; however, it’s not clear how much of that rise in stage was caused by water as opposed to the slurry of water, mud, and debris that moved through the channel.

Yesterday, about 40 streamflow discharge measurements were made at approximately 30 different locations in California by the 19 crews deployed by CAWSC for flood response. Flood response work included streamfow rating verification measurements in fire-affected locations of northern and southern California, and sediment sampling for load estimation following the first major storm of the season.

Additional CAWSC crews will be deployed over the next week to complete HWM flagging in response to this storm event. No safety issues have occurred during this event and all staff have followed USGS field reporting and safety protocols. In anticipation of this storm, staff were reminded of safe working practices and the potential hazards that can be expected when conducting field work in fire-affected area.