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SBitz
Jan 5, 2018, 3:01:57 PM1/5/18
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Here's a new Topic for info related to flood risk, preparation, and updates should flooding or other problems arise from the predicted potential for heavy rains the week of Jan 8, 2018 or future storms.
SBitz
Jan 5, 2018, 3:22:15 PM1/5/18
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As noted extensively in prior posts, the Thomas Fire burned a massive area placing many large watersheds at risk for flooding. Potential effects of heavy rain include not just flooding, but intense flash floods, debris flows, water toxicity, loose boulders, mudslides and many other hazards. The biggest problem with heavy rain right after the fire, is that the soil surface can actually repel water so that the portion normally absorbed simply heads straight downhill. Even after soil begins to absorb water, there's no vegetation to stabilize soil. SB County has just held a press conference on this topic, and KEYT has a link for watching the entire presentation. I don't have time to watch it, so if you do please post a summary or anything else you find (if you're not a Member, we'll process your free application when we can).
Meanwhile, here's the part of a map prepared by SB County covering the South Coast with flood risk areas in blue:
As you can see, Carpinteria, Toro Canyon and Montecito are all at risk. To view the interactive version of this SB County map where you can zoom in on your particular area of interest, click here. For the SB County page on Flood Prep, click here.
Meanwhile, here's the part of a map prepared by SB County covering the South Coast with flood risk areas in blue:
As you can see, Carpinteria, Toro Canyon and Montecito are all at risk. To view the interactive version of this SB County map where you can zoom in on your particular area of interest, click here. For the SB County page on Flood Prep, click here.
topix
Jan 8, 2018, 12:09:52 AM1/8/18
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If you are looking for realtime rainfall levels, go to https://rain.cosbpw.net/home.php
It's a handy source for finding out how much rain has fallen in the past hour/3 hours/day etc, and also what the current levels are at the reserviors. They have recently added the burn scars to the map, so you can better assess when/where mudslide threats are developing.
And here's a map of the new (post-fire) evacuations that were just issued due to the rain expected on 1/8/2018. Fingers crossed that the dirt will stay far away from all the SBitz'ers
https://www.google.com/maps/d/u/0/viewer?mid=1MsfIfBPYO0JcSprEno-QPWR2-POpliv2&ll=34.449200353180686%2C-119.56311619001309&z=10
It's a handy source for finding out how much rain has fallen in the past hour/3 hours/day etc, and also what the current levels are at the reserviors. They have recently added the burn scars to the map, so you can better assess when/where mudslide threats are developing.
And here's a map of the new (post-fire) evacuations that were just issued due to the rain expected on 1/8/2018. Fingers crossed that the dirt will stay far away from all the SBitz'ers
https://www.google.com/maps/d/u/0/viewer?mid=1MsfIfBPYO0JcSprEno-QPWR2-POpliv2&ll=34.449200353180686%2C-119.56311619001309&z=10
SBitz
Jan 8, 2018, 3:43:58 PM1/8/18
to Santa Barbara CitiZen Network
I hope everyone's safe tonight, because the latest official rain forecasts on the Thomas Fire area are still very intense. Often the long range forecasts don't pan out and tend to err on the side of caution to protect life and property. Because the strongest rain is expected while most people will be sleeping, this accurate forecast is life threatening. Imagine thousands of gallons of concrete coming down a steep slope toward your home at 20mph. This is now a very real possibility for tonight, in areas below burned hillsides. It won't just be a flash flood situation, because the soil won't have absorbed much of the rain and the flow will pick up lots of debris. This could be a debris flow similar a tsunami or the one from Mt. St. Helens' eruption. You may have heard about the one in Sycamore Creek a decade or so ago, that killed a recently retired judge. We ourselves saw cars going down the creek.
Today's (Monday 01/08) 10am NOAA / National Weather Service forecast maps are predicting a total of 7 inches of rain along the SB/Ventura County line in the period ending 4pm tomorrow. That's a lot of rain on scorched earth. The rain area is of course much larger than just the area burned along the county line going North from Carp, and some of the strongest rain is exactly on the largest burned areas. I've sometimes used these maps for planning long flights, and have found them generally pretty accurate this close (~24 hours) to the forecast date. Here are the maps of total rainfall expected in six hour periods, adjusted to make some landmarks more visible. The colors aren't terrain, they depict the amount of rain with lighter green indicating smaller amounts. First the map for the 6 hours between 10am this morning and 4pm this afternoon, with the darkest green areas expecting about 0.8" of rain.
Things start getting scary after dark, with another two inches or so expected by 10pm.
Almost three inches of rain in 12 hours (probably 8, since most of it is likely to start in the afternoon) on scorched soil would be likely to create high risks to life and property. But look at what's next. Here's the forecast map for the next six hours until 4am when few people would likely be awake.
Those red areas are expected to get 4 inches more rain in six hours. Since the heaviest rain may come in the wee hours, it could easily be an inch per hour on the Thomas Fire area. Not good for anyone or anything in or below those watersheds. Unlike the fire, things could change far too quickly to get out of the way.
By tomorrow morning we'll start to find out if the forecasts are accurate, as rainfall diminishes to another inch by 10am Tuesday.
Again, most of that will probably happen before sunrise just after 4am. After 10am Tuesday the longer range prediction (more than 24 hours from this Monday 10am forecast) calls for only a quarter of an inch more rain as we find out what happened overnight.
Today's (Monday 01/08) 10am NOAA / National Weather Service forecast maps are predicting a total of 7 inches of rain along the SB/Ventura County line in the period ending 4pm tomorrow. That's a lot of rain on scorched earth. The rain area is of course much larger than just the area burned along the county line going North from Carp, and some of the strongest rain is exactly on the largest burned areas. I've sometimes used these maps for planning long flights, and have found them generally pretty accurate this close (~24 hours) to the forecast date. Here are the maps of total rainfall expected in six hour periods, adjusted to make some landmarks more visible. The colors aren't terrain, they depict the amount of rain with lighter green indicating smaller amounts. First the map for the 6 hours between 10am this morning and 4pm this afternoon, with the darkest green areas expecting about 0.8" of rain.
Things start getting scary after dark, with another two inches or so expected by 10pm.
Almost three inches of rain in 12 hours (probably 8, since most of it is likely to start in the afternoon) on scorched soil would be likely to create high risks to life and property. But look at what's next. Here's the forecast map for the next six hours until 4am when few people would likely be awake.
Those red areas are expected to get 4 inches more rain in six hours. Since the heaviest rain may come in the wee hours, it could easily be an inch per hour on the Thomas Fire area. Not good for anyone or anything in or below those watersheds. Unlike the fire, things could change far too quickly to get out of the way.
By tomorrow morning we'll start to find out if the forecasts are accurate, as rainfall diminishes to another inch by 10am Tuesday.
Again, most of that will probably happen before sunrise just after 4am. After 10am Tuesday the longer range prediction (more than 24 hours from this Monday 10am forecast) calls for only a quarter of an inch more rain as we find out what happened overnight.
SBitz
Jan 8, 2018, 5:10:22 PM1/8/18
to Santa Barbara CitiZen Network
Here are excerpts of a report by the City of Camarillo about a housing development's debris flow event mentioned on Edhat today by "CivilEngineer" regarding tonight's risks (links at the bottom).
Links:
City of Camarillo search about the event - Source of text quoted above: PDF - Web Browser version
The tributary areas of Barrancas [canyons or ravines] 2 & 3 and the young erosion area were severely burned in the Spring Fire which burned over 24,000 acres in May of 2013. ... Significant storm events occurred on October 31 and December 11 of 2014. ... Many homes were affected, including the structure at 6446 San Como Lane which was inundated with mud (Photo 6). The December 11 event generated substantially more flow and carried coarser debris further into the development causing extensive damage (Photo 7).
...
The link between burned watersheds and debris flows is well-established. Severe fires change the watershed in several important ways including:
1) The amount of readily eroded material in the watershed is increased both as a result of the burned debris left behind by the fire and through a process of “dry raveling” that tends to occur following a fire;
2) protections against mechanical slope erosion provided by the root structure, the vegetative canopy, and the ground litter are significantly reduced;
3) vegetative resistance to flow in main channels and tributaries is reduced, and perhaps most significantly;
4) the nature of the soil is changed.
Native soil typically is characterized by a fair degree of porosity and permeability that allows a certain amount of infiltration to the subsurface soils. Infiltration tends to dampen the effects of intense precipitation both by reducing the amount of water available for runoff (through absorption) and by slowing the runoff both on the surface and in the immediate subsurface. When a watershed is subjected to the intense heat associated with California wildfires, organic materials volatilized from the burning vegetation and litter tend to migrate downward and solidify into a subtle waxy, repellent substance in cooler soils a few inches below the surface. If the watershed is subsequently subjected to localized, intense precipitation, this waxy layer impedes infiltration. Rainfall rapidly saturates the upper few inches of soil, after which flow begins to move parallel to the slope face in the shallow subsurface above the waxy layer. The blockage to vertical infiltration and subsequent downslope movement results in very rapid runoff accompanied by significant removal of the uppermost surface soils. Where the rapid runoff is concentrated by subtle depressions in local topography, deep rills and even incised channels can form and contribute additional debris.
Some areas of the incised channels were observed to be scoured to bedrock; others are filled with colluvium [rocks & sediment] and rock debris to estimated depths of about eight to ten feet. Where observed in isolated exposures, colluvial channel fill was observed to consist of an overall mix of pebble to cobble sized rock in a matrix of silty sand commonly supporting large-boulder-size clasts. Locally, channel walls in colluvium were observed to extend to heights of about 15 feet and to be vertical to overhanging where they appear to have been undercut by the recent erosion.
...
The link between burned watersheds and debris flows is well-established. Severe fires change the watershed in several important ways including:
1) The amount of readily eroded material in the watershed is increased both as a result of the burned debris left behind by the fire and through a process of “dry raveling” that tends to occur following a fire;
2) protections against mechanical slope erosion provided by the root structure, the vegetative canopy, and the ground litter are significantly reduced;
3) vegetative resistance to flow in main channels and tributaries is reduced, and perhaps most significantly;
4) the nature of the soil is changed.
Native soil typically is characterized by a fair degree of porosity and permeability that allows a certain amount of infiltration to the subsurface soils. Infiltration tends to dampen the effects of intense precipitation both by reducing the amount of water available for runoff (through absorption) and by slowing the runoff both on the surface and in the immediate subsurface. When a watershed is subjected to the intense heat associated with California wildfires, organic materials volatilized from the burning vegetation and litter tend to migrate downward and solidify into a subtle waxy, repellent substance in cooler soils a few inches below the surface. If the watershed is subsequently subjected to localized, intense precipitation, this waxy layer impedes infiltration. Rainfall rapidly saturates the upper few inches of soil, after which flow begins to move parallel to the slope face in the shallow subsurface above the waxy layer. The blockage to vertical infiltration and subsequent downslope movement results in very rapid runoff accompanied by significant removal of the uppermost surface soils. Where the rapid runoff is concentrated by subtle depressions in local topography, deep rills and even incised channels can form and contribute additional debris.
Some areas of the incised channels were observed to be scoured to bedrock; others are filled with colluvium [rocks & sediment] and rock debris to estimated depths of about eight to ten feet. Where observed in isolated exposures, colluvial channel fill was observed to consist of an overall mix of pebble to cobble sized rock in a matrix of silty sand commonly supporting large-boulder-size clasts. Locally, channel walls in colluvium were observed to extend to heights of about 15 feet and to be vertical to overhanging where they appear to have been undercut by the recent erosion.
Links:
City of Camarillo search about the event - Source of text quoted above: PDF - Web Browser version
SBitz
Jan 8, 2018, 5:25:12 PM1/8/18
to Santa Barbara CitiZen Network
Rainfall between 8am and 2pm today is already starting over the Thomas Fire area. Approaching half an inch in V.County's Lk.Casitas watershed, but a quarter inch already in SB County's Jameson & Gibraltar watersheds as you can see in this screencap of the SB County site:
Section Make8R
Jan 9, 2018, 12:20:45 AM1/9/18
to Santa Barbara CitiZen Network
heres a bit of weather discussion regarding the mechanics. Hope everyone has a good safe evening.
MESOSCALE PRECIPITATION DISCUSSION 0001 NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1013 PM EST MON JAN 08 2018 AREAS AFFECTED...CENTRAL AND SOUTHERN CA COASTAL RANGES CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE VALID 090310Z - 090930Z SUMMARY...HEAVY RAINS WILL BECOME MORE WIDESPREAD OVERNIGHT WITH INCREASING CONCERNS FOR ENHANCED RUNOFF AND POSSIBLE FLASH FLOODING. BURN SCAR AREAS GENERATED FROM RECENT WILDFIRE ACTIVITY WILL BE PARTICULARLY SUSCEPTIBLE. DISCUSSION...GOES-16 1-MINUTE WV IMAGERY SUITE SHOWS IMPRESSIVE NORTHERN STREAM HEIGHT FALLS ADVANCING SOUTH DOWN OFFSHORE SOUTHERN CA AS MULTIPLE SHORTWAVE IMPULSES DIGGING DOWN THE WEST SIDE OF THE AMPLIFYING TROUGH DIG TOWARD THE BASE OF IT. GOES-16 RGB AIRMASS IMAGERY ALSO SHOWS A VERY IMPRESSIVE PV ANOMALY SIGNATURE ORIENTED NNW/SSE WITH AN ANOMALY CORE CENTERED NEAR 33.0N 127.7W. THIS STRONG VORT CENTER IS SEEN MOVING EAST AND WITH ADDITIONAL ENERGY DIGGING INTO THE BASE OF THE TROUGH...A WELL-DEFINED CLOSED MID LEVEL LOW CENTER WILL EVOLVE LATER THIS EVENING OFFSHORE SOUTHERN CA. VERY STRONG FORCING ALOFT WITH ENHANCED UPPER LEVEL DIVERGENCE AROUND THE EASTERN FLANK OF THIS MID LEVEL LOW WILL OVERSPREAD SOUTHERN CA THIS EVENING AND OVERNIGHT...AND WILL COUPLE WITH AN ANOMALOUS NORTHEASTWARD TRANSPORT OF SUBTROPICAL MOISTURE WEST OF THE BAJA PENINSULA FOR RATHER WIDESPREAD HEAVY RAINFALL AND ENHANCED RAINFALL RATES. MOISTURE FLUX ANOMALIES IN THE 850/700MB LAYER ARE FORECAST TO INCREASE TO NEAR 5 SIGMAS ABOVE NORMAL BY 06Z ACROSS THE TRANSVERSE RANGES OF SOUTHERN CA. THIS WILL BE AIDED BY A SOUTHWEST LOW LEVEL JET OF 40 TO 45 KTS WHICH WILL BE ORIENTED ORTHOGONAL TO THE COASTAL TERRAIN...AND WILL ALSO BE FACILITATING PRECIPITABLE WATER VALUES OF NEAR 1.1 TO 1.25 INCHES WHICH IS ABOUT 3 SIGMAS ABOVE NORMAL FOR THIS TIME OF YEAR. THIS WILL FAVOR RELATIVELY EFFICIENT RAINFALL PROCESSES WHICH WILL TEND TO ENHANCE THE RAINFALL RATES. HOWEVER...THE ORTHOGONAL NATURE OF THE LOW TO MID LEVEL WINDS RELATIVE TO THE COASTAL RANGES AHEAD OF THE OFFSHORE CLOSED LOW WILL FAVOR STRONG OROGRAPHIC ASCENT FOR NOTABLY HEAVIER RAINFALL RATES LATER TONIGHT. THE LAST COUPLE OF AVAILABLE AMSU PASSES SHOWED OFFSHORE RAINFALL RATES EXCEEDING A 0.50 INCH/HR IN SEVERAL LOCATIONS...AND THESE HEAVIER RATES SHOULD BEGIN TO ARRIVE IN EARNEST ACROSS THE CENTRAL AND SOUTHERN CA COASTAL RANGES BETWEEN 06Z AND 09Z. ALREADY THE 12Z ARW/NMMB SOLUTIONS AND TO AN EXTENT THE HRRR GUIDANCE HAS BEEN GENERALLY SLOW TO HANDLE THE INITIAL ARRIVAL OF MODERATE TO HEAVY RAIN THIS AFTERNOON ASSOCIATED WITH THE ARRIVAL OF SOUTHERN STREAM SHORTWAVE ENERGY WEST OF THE BAJA PENINSULA. THE LATEST GOES-16 IR/WV AND RGB IMAGERY CLEARLY DEPICTS THIS ENERGY AND A VORT CIRCULATION ADVANCING RAPIDLY INLAND OVER INTERIOR SOUTHERN CA. THE INITIAL WAVE OF HEAVIER RAINS HAVE HELPED TO PRIME THE SOIL CONDITIONS FOR THIS NEXT SURGE OF HEAVY RAIN AND ALREADY PARTS OF SANTA BARBARA...VENTURA AND LOS ANGELES COUNTIES HAVE SEEN OVER 1 INCH OF NEW RAIN. MOVING THROUGH ABOUT 09Z...EXPECT ADDITIONAL RAINFALL TOTALS OF AS MUCH AS 1.5 INCHES FOR THE CENTRAL AND SOUTHERN CA COASTAL RANGES...WITH ISOLATED HEAVIER TOTALS OVER THE TRANSVERSE RANGES GIVEN BETTER OROGRAPHIC FORCING HERE. THESE AMOUNTS IN CONJUNCTION WITH THE EARLIER RAINFALL WILL BEGIN TO CAUSE CONCERN FOR ENHANCED RUNOFF AND POSSIBLE FLASH FLOODING WITH THE DOMINANT CONCERN NOTED AROUND AREAS WHERE RECENT WILDFIRE ACTIVITY HAS GENERATED BURN SCARS. PERHAPS ONE OF THE MORE SUSCEPTIBLE AREAS WILL BE THE TERRAIN INVOLVING THE LARGE THOMAS BURN SCAR. THE THREAT OF DEBRIS FLOWS AND MUDSLIDES WILL BECOME ELEVATED...AND WITH ADDITIONAL HEAVY RAIN EXPECTED INTO TUESDAY MORNING...THIS THREAT WILL ONLY GROW FURTHER. EXPECT ADDITIONAL MPDS TO UPDATE THIS CONCERN AS THIS EVENT CONTINUES TO EVOLVE. ORRISON
SBitz
Jan 9, 2018, 3:58:28 AM1/9/18
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I've been looking at updated forecasts. The midnight aviation update for KSBA (SB Airport) is for thunderstorm potential and rain to start again at 1am with winds increasing from the ESE gusting up to 37mph by 3am when rain is forecast to be heavy until 6am when light rain returns and wind gusts drop to 23mph. About 7am wind shifts to come from the South and by early afternoon more from the West, with showers and periods of rain. About 5pm Tuesday the expectation is that wind gusts finally abate to a more steady WNW 14mph in light rain showers into the night.
The highest Thomas Fire area rainfall totals so far are 2" at the county line in the Jameson Reservoir watershed, and 0.86" on the ridge in the Gibraltar area. Those 6 hour rainfall accumulation maps I posted earlier now predict 6" on the Thomas Fire in the county line area between 10pm Monday and 10am Tuesday, tapering off to about 1/3" between then and 4pm. Clearly the conditions (wind, but especially rain) are and will be much different up in the mountains, especially in the Thomas Fire area on the county line.
The highest Thomas Fire area rainfall totals so far are 2" at the county line in the Jameson Reservoir watershed, and 0.86" on the ridge in the Gibraltar area. Those 6 hour rainfall accumulation maps I posted earlier now predict 6" on the Thomas Fire in the county line area between 10pm Monday and 10am Tuesday, tapering off to about 1/3" between then and 4pm. Clearly the conditions (wind, but especially rain) are and will be much different up in the mountains, especially in the Thomas Fire area on the county line.
SBitz
Jan 9, 2018, 12:33:18 PM1/9/18
to Santa Barbara CitiZen Network
Many reports of flooding, electrical outages and transformers exploding, people killed and injured, helicopter medivacs, and major property damage. Edhat has several articles and comments with some details. 101 and 166 both closed. Debris flow across Amtrak.
KEYT has been off air since last night, although it may be working on Cox cable. Live stream is working at this link.
Recent news article with description of local impacts:
http://www.sanluisobispo.com/news/local/article193693384.html
I'm going to start a new Topic in a few minutes for ongoing updates.
KEYT has been off air since last night, although it may be working on Cox cable. Live stream is working at this link.
Recent news article with description of local impacts:
http://www.sanluisobispo.com/news/local/article193693384.html
I'm going to start a new Topic in a few minutes for ongoing updates.
Message has been deleted
Jaz2
Jan 12, 2018, 1:46:58 AM1/12/18
to Santa Barbara CitiZen Network
I'm not sure if this informative WaPo article will post, but here it is with several explanatory maps and explanation of how the whole mess started:
https://www.washingtonpost.com/graphics/2018/national/california-mudslides/?hpid=hp_hp-visual-stories-desktop_no-name%3Ahomepage%2Fstory
https://www.washingtonpost.com/graphics/2018/national/california-mudslides/?hpid=hp_hp-visual-stories-desktop_no-name%3Ahomepage%2Fstory
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