Xasáuan Today

Big Sur Rain

Shortly before 3:00 pm this afternoon, the Big Sur River pushed its gauge above the 10 foot level that marks the official flood stage. The gauge was at 10.04 feet by 3:00, or 4,250 cubic feet per second. The river reached a peak flow of 4,950 cfs last Wednesday (10.54 feet).

Heavy rain is still falling over the Big Sur watershed at this time, but should begin decreasing soon as the storm moves off to the south. The watershed is small, so the river won’t keep rising for long, once the rain relents. Serious flooding is unlikely to occur until the gauge height exceeds 11 feet.

3:30 pm Update: River now at 5,250 cfs (Gauge height 10.75). That’s an increase of 1,000 cfs in half an hour.

4:00 pm Update: River now at 6,020 cfs (11.26 feet). Still rising quickly, though not as quickly. This is the largest flow the Big Sur River has seen since 6,590 cfs was recorded in February, 1998. Radar suggests heavy rain is still falling in the Big Sur watershed.

4:45 pm Update: River now at 6,420 cfs (11.53 feet). Rain may be easing some.

5:00 pm Update: Latest reading is 6,620 cfs (11.66 feet). This exceeds the 1998 flow and is the third highest flow ever recorded on the Big Sur River (after 1978 and 1995).

5:15 pm Update: Now the second largest flow ever recorded on the Big Sur River at 6,700 cfs (11.72 feet). With rain beginning to recede, there’s not much chance of it matching the 1978 flow of 10,700 cfs, I’m glad to say. Flows have been recorded since 1950.

5:30 pm Update: Still inching upward. Now 6,790 cfs (11.78 feet).

5:45 pm Update: 6,820 cfs (11.80 feet). How high will it go?

6:00 pm Update: Still 6,820 cfs at 6:00 pm. Have we finally found the peak?

6:15 pm Update: Yes! The river is now receding. 6,790 cfs (11.78 feet) at 6:15.

Heavy overnight rain falling on the Soberanes Fire burn scar has pushed the Big Sur River Gauge over the 10 foot level that is considered flood stage. The current level (at 6:00 am) is 10.48 feet. This translates to a flow of 4,860 cubic feet per second; essentially matching the 4,900 cfs peak flow of 2012 (which did not result in serious flood damage). The highest flow recorded at the Big Sur River Gauge, following the Marble Cone Fire in 1978, was 10,700 cfs.

The Big Sur River, with its smaller watershed, reacts to rain more quickly than the larger coastal streams. The Carmel River at Rosie’s Bridge is at 1,170 cfs and rising (peak flow there was 16,000 cfs in 1995).

The Arroyo Seco River Gauge is still only showing 161 cfs, but with some portions of its watershed receiving over 7 inches of overnight rain, the water will be rising quickly this morning.

The parched San Antonio River, which only began flowing past the gauge site on December 31, has only risen to 37 cfs… so far.

The Nacimiento River is at 4,350 cfs, an inconsequential amount for a stream that sometimes produces flows in excess of 50,000 cfs.

7:00 am Update: The Big Sur River is now above its 2012 peak; at 4,950 cfs (10.54 feet). The Arroyo Seco is at 1,140 cfs.

7:30 am Update: The Big Sur River has begun to drop. It’s currently at 4,720 cfs (10.38 feet). The Carmel River is up to 1,790 cfs. The Arroyo Seco is up to 1,990 cfs. The Nacimiento is up to 5,540 cfs.

9:30 am Update: The Big Sur River, at 9.95 feet (4,130 cfs), is no longer above flood stage. The Carmel River is at 2,630 cfs. The Arroyo Seco River has jumped to 7,560 cfs. The San Antonio River is barely changed at 39 cfs; and the Nacimiento now has the greatest flow, with 7,800 cfs. Some of the wettest spots along the Coast Ridge have received over 10 inches of rain since this storm began.

1:30 pm Update: The peaks have now past on the local streams. It looks like the Nacimiento and Arroyo Seco rivers got up into the neighborhood of 12,000 cfs, or so, and the Carmel to around 2,700 cfs. The San Antonio, which must be dumping a lot of water into its bone dry aquifer, is still only pushing 41 cfs past the gauge.

With an even wetter storm forecast for this weekend, it would be prudent for those who live near streams to prepare for debris flows and the possibility of record, or near record, water levels.

Once saturated, scorched slopes like these, can produce dangerous debris flows. It just has to rain hard enough and long enough.

The atmospheric river type storm that swept through the Santa Lucia Mountains yesterday produced close to the advertised 6 inches of rain at the wettest Coast Ridge spots, but produced relatively little run off and no serious debris flow problems.

While slides predictably closed Highway One on the South Coast (it will probably reopen later this afternoon), the larger streams pretty much shrugged the event off.

The Big Sur River peaked at over 1,000 cfs last night, but its channel can accommodate many times that much water without difficulty. For comparison, during the storms following the Marble Cone Fire, in January 1978, the Big Sur River reached a record 10,700 cfs.

The Nacimiento River, whose watershed did not burn, reached the highest flow of any Santa Lucia stream early this morning, with around 2,500 cfs. That is a relative trickle for a stream that has produced flows exceeding 50,000 cfs during extreme rain events. No water has, so far, even reached the bone dry San Antonio River gauge.

As the twelfth, and hopefully final, week of the Soberanes Fire begins, 132,100 acres have burned and containment has reached 98%.

Some of the best information currently available on the state of the burned area is contained in the recently released Soberanes Fire Watershed Emergency Response Team (WERT) Report.

The first significant rain of the season may arrive during the coming week. Hopefully, it will be enough to put the fire definitively out, but not enough to set off damaging debris flows in denuded watersheds.

Update: The Soberanes Fire was declared 100% contained on Wednesday, October 12, 2016; almost a full 12 weeks after it began on July 22.

September 30, 2016

View up Piney Creek at the fire’s eastern corner. Spotting over the line was still creating headaches there last week, but all is quite now.

As week eleven begins, the official numbers for the Soberanes Fire stand at 132,069 acres and 92% containment. Full containment is expected by noon on October 15, but could certainly come sooner, as only scattered hot spots and occasional interior flare ups remain.

There could be more of these today and tomorrow, as another wind event is expected this afternoon and evening, but the containment lines are unlikely to be challenged.

Important caveats: Please note that the squares on the heat detection maps represent the expected margin of error, not the size of the area burned. In other words, the detection could have come from anywhere within the square. Also be aware that false detections do sometimes occur. An outlying or “over the line” heat detection is not, by itself, a confirmation that there is fire in the area indicated. In addition, the satellites do not detect heat everywhere that fire exists. Creeping, backing or smoldering fire is often not detected. Finally, the detections are only snapshots of moments in time. Flare ups that occur before or after a satellite pass may be entirely missed.

Also be aware that yellow squares disappear from the map after 6 days. These are not maps of the area burned since the fire began, just maps of where heat has been detected during the past week. Read the rest of this entry »