Posted on 10/18/2018 7:15:41 AM PDT by janetjanet998
Background: Over the past 3 days widespread rains of 6-10 have fallen on the Colorado river watershed above Austin. You may have seen amazing video of the Llano River wiping out homes and bridges. The llano river hit its highest level since 1935 with 300,000 cfs of water flowing into the CO River above Lake Travis at one point, This combined with other runoff caused Lake Travis to rise over 30 feet in 2 days!!
The current level at Lake Travis is over 701 feet with many homes flooded already...5th highest of all time
Llona river has receded with only 15,000 CFs now. Above the mouth of the LLona river is lake Manfield which was holding back water until after the rivers feeding in Lake Travis recede
They opened a record 8 floodgates on that Dam and 60,000 cfs is now flowing out,,this combined with other runoff means 90,000 cfs is still flowing into Lake Travis
Lake Travis now has 4 floodgates opened with outflow of 28,000 cfs. The record number is 6 gates in 1957. They are planning to open up to another 4 gates today which will cause flooding problems downstream for a record of 8 gates opened!!
with 90,000 inflow in and only 28,000 out Lake Travis is still rising about a foot every 6 hours 701.43 right now with a rise of about a foot every 6 hours
LCRA has been behind the curve.. first saying Lake travis will peak 690-695 then 695-700
now 705 to 710ft which will be around the record of just over 710 feet
The top of the spillway over on the Dam at lake Travis is about 714 feet,
Forecast is More heavy rains for the next week
NWS DISCUSSION
WITH THE SATURATED SOILS ACROSS PARTS OF SOUTH CENTRAL TEXAS AND THE CONTINUED WET FORECAST THIS REMAINS A DANGEROUS SITUATION AS RAINFALL FROM THE LAST FEW DAYS CONTINUES TO WORK ITS WAY THROUGH AREA RIVERS. THE LOWER COLORADO RIVER AUTHORITY ANNOUNCED THAT BY MID-DAY THURSDAY UP TO 8 FLOOD GATES AT MANSFIELD DAM COULD BE OPENED (4 ARE CURRENTLY RELEASING ABOUT 25,000 CFS DOWN THE COLORADO) TO MOVE SOME OF THE WATER FROM LAKE TRAVIS DOWN THE COLORADO. LAKE TRAVIS, AS OF 3AM IS AT JUST OVER 700 FEET MSL, THE 6TH HIGHEST THE LAKE HAS EVER BEEN (VISIT THE NWS AHPS PAGE AND SEARCH FOR MSDT2 TO VIEW THE OTHER PAST CRESTS). THE DEVILS RIVER IN VAL VERDE COUNTY, THE NUECES RIVER IN DIMMIT COUNTY, AND THE FRIO RIVER IN FRIO COUNTY ALL CONTINUE TO BE IN FLOOD THIS MORNING AS WELL.
WE URGE RESIDENTS AND VISITORS TO SOUTH CENTRAL TEXAS TO MONITOR CLOSELY THE WEATHER CONDITIONS FOR THE NEXT SEVERAL DAYS AS ANY RAINFALL AMOUNTS COULD LEAD TO ADDITIONAL FLASH FLOODING OR RIVER FLOODING. ALSO, THOSE ALONG THE COLORADO RIVER SHOULD MONITOR INFORMATION COMING FROM THE LOWER COLORADO RIVER AUTHORITY CONCERNING RELEASES FROM AREA LAKES AND TAKE NEEDED ACTIONS TO PROTECT LIVES AND PROPERTY ALONG THE COLORADO.
updated info https://floodstatus.lcra.org/#llevels
Two Main Road Could Close Due To Flooding Austin Officials Say
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I think that was when they were planning to open 4 more gates today..that has been put in hold for now..
The LCRA is currently weighing the consequences of opening additional floodgates at Mansfield Dam, following rising water levels at Lake Travis. If eight are opened, it would be the most opened in recorded historyhttps://www.kvue.com/article/weather/lake-travis-reaches-5th-highest-crest-more-floodgate-openings-on-hold/269-605581150.
Canyon Lake has the expensive homes and docks... you can bet they will keep that level while the rest of the state struggles...
((((ping)))) to 36.
LOL
Yes, Canyon Lake has SOME very nice, expensive homes. So does Lake Travis....so, that sort of disputes your statement.
Most homes on Canyon Lake are built up above the Army Corp of Engineers required build line.
Even when water levels have reached the spillway, most homes on the lake didn’t flood.
Oh , and docks are not permitted, on Canyon Lake.
Some have built stone landings, as “docks”, but the Corp is VERY strict about permitting even those.
No wood or permanent docks permitted. It is NOT a constant level lake.
at 130pm lake is now 702 feet..
current radar: moderate-heavy rain developing from San Antonio SW...this is moving WNN and may clip the SW portions of the water shed later
THe main watershead is precip free right now
also models seem to have backed off a notch on precip amounts ..will see what the NWS says
Everyone downstream to the ocean.
Rain hasn’t just fallen in the central basin. River and stream are running high downstream also. There’s no way the LCRA can please everyone. People were informed that Travis and Buchanan were built for flood control and that the constant level lakes were there to pass that water thru also at what level the water might rise to. If they built within any of those flood plains, it’s their problem.
Other than that, this is an historic flood with historic results.
Travis and Buchanan were built for flood control
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you are correct ..here is a video about the 1991 floods..and how they had to hold back and let Travis flood before they opened 4 gates because of massive rain/flooding downstream...but it’s not as near bad now dowstream...and opening another gate or to now would reduce the risk of overtopping the spillway and/or 8 or more gates open later
another 1 or 2 gates would only cause relatively few problems compared to the risk they are taking IMO
LCRA video “The Flood of 1991”https://www.youtube.com/watch?v=oJWmkbH-nOQ
We lived in Volente on Travis in ‘91. Ask those people downstream [in Lake Austin, along Lady Bird and the communities beyond] if they want more flow at this time.
I am thinking they cant open another gate until Mansfield dam reaches 710.
Bc the current CFS ourflow is approx 28K....they aren’t allowed to exceed 30k CFS and/nor if the Austin flood gauge exceeds 33ft. With 4 gates open..that is a CFS of approximately 7k...so if then ope another ir would push them above the 30K cfs.
Make sense?
Or I am looking at this all the wrong way.
Yes that is “protocol” ..nothing above 30Kcfs until above 710 feet...
but the lake wasn’t forecast to be that high for a couple more days but they almost did it anyway.if fact that was the plan until midday today to open 8 gates
the question is what were they worried about that made them almost release 50,000 cfs today with the lake ‘only” at 702 feet? And why did they change it?
If they wait till the lake is 710 feet and open 8 gates..(i.e. 50K).and inflow into the lake is above 50,000 cfs. then they lake would still rise
if another heavy rain storm hits during that time and inflow is much higher (i.e. over 100cfs ) then it would rise high enough to overflow the spillway at 714 feet
then there would be 8 gates open plus whatever is flowing over the spillway out of control
I should add this is going to be long battle. in all of Texas as the rivers and lakes in Texas are full and a wet pattern in place
check out the GEM from the Dallas NWS discussion about next week after the break Monday and Tuesday
. WHILE CONFIDENCE IS HIGH IN THE CHANCE OF RAINFALL
WEDNESDAY, WHAT IS STILL IN QUESTION ARE THE AMOUNTS. THAT’S
BECAUSE RAINFALL AMOUNTS ARE CONTINGENT ON WHETHER A TROPICAL
SYSTEM WILL DEVELOP IN THE EASTERN PACIFIC OCEAN AND GETS DRAWN
NORTHWARD BY THE UPPER TROUGH INTO MEXICO. SHOULD THIS OCCUR IT
WOULD PROVIDE STRONG UPPER LEVEL DYNAMICS FOR LIFT AND RESULT IN A
SWATH OF WIDESPREAD HEAVY RAINFALL ACROSS TEXAS. WE’VE SEEN BOTH
THE OPERATIONAL GFS AND ECMWF FLIRT WITH THIS SCENARIO ON
OCCASIONAL RUNS AND WE KNOW FROM CLIMATOLOGY THAT THIS IS A
PATTERN SETUP THAT HAS PRODUCED MANY INSTANCES OF 10+ INCHES OF
RAIN. AGAIN, WE WILL NOT START ADVERTISING OR ANTICIPATING THIS
UNTIL WE GET BETTER CONSISTENCY WITH THE POSSIBLE TROPICAL SYSTEM
(THAT HASN’T ORGANIZED YET), BUT WE’RE WATCHING THIS CLOSELY AS
IT’D BE A WORSE CASE SCENARIO AFTER ALL OF THE RAIN WE’VE ALREADY
SEEN.
If this forecast is correct then the water is going over the spillway for sure even if 8 gates are open IMO
just out
..FLASH FLOOD WATCH NOW IN EFFECT THROUGH FRIDAY EVENING
THE FLASH FLOOD WATCH IS NOW IN EFFECT FOR
* A PORTION OF SOUTH CENTRAL TEXAS, INCLUDING THE FOLLOWING
AREAS, BANDERA, BEXAR, BLANCO, BURNET, COMAL, EDWARDS,
GILLESPIE, HAYS, KENDALL, KERR, KINNEY, LLANO, MAVERICK,
MEDINA, REAL, TRAVIS, UVALDE, VAL VERDE, WILLIAMSON, AND
ZAVALA.
* THROUGH FRIDAY EVENING
* ADDITIONAL NEW RAINFALL AMOUNTS OF 1 TO 2 INCHES WITH ISOLATED
SPOTS RECEIVING UP TO 5 INCHES MAINLY ACROSS THE NORTHERN HILL
COUNTRY. THE TIMING FOR THE HEAVIEST RAINFALL IS EXPECTED TO BE
LATE FRIDAY MORNING THROUGH THE AFTERNOON PERIOD.
This is why I think the situation will reach critical mass soon
1) Lake Buchanan was at 1013 feet before the deluge......they were holding back water at ZERO cfs as it was filling up to the 1018 flood level until the LLANO river crest eased(300,000 cfs peak)....the lake peaked at 1019.2 feet and is 1018.25 feet now with 60,000 bfs outflow and out 30,000 in) they can allow the lake to get much higher in fear of other issues
in other words no more or Little storage from Buchanan
2) The Pedernales river is the west arm of lake travis and extends west..no Dams on this river so it all flows into the Lake..at peak vales the other day it was probably dumping 20-30,000 Cfs into the lake
3) according to data the peak inflow from the dams above was 315,000 now lets add the 30,000 from the west river and another 15,000 for the shoreline area and lets say a total of 360,000 total inflow to the lake at peak flow.....
so last storm was 360,000 inflow to the lake from the lower watershed and ZERO from the upper upper from Rainfall runoff with ZERO outflow from travis
net inflow to travis and amazing 360,000 bfs at peak
now lets assume this Rainfall event is only 1/3 that as the last say 100,000 cfs max inflow from the rain.....there is 30,000 out flow now but that is being canceled out by the now Buchanan dam releases
Now I under that inflows at certain spots won’t peak out at the same time and will have peaks and valleys and I also understand it takes more water raise the lake at a foot at higher levels then at lower levels but I think you all see my concern
8pm update
another LSRA forecast failure: it has been obvious since last night and especially today that the lake is NOT going to be In the 705-710 ft level by Friday (tomorrow) the media of course has been using the doom and gloom 710 ft Friday since then
another LCRA issue is Lake Buchanan is still falling almost down to the 1018 level with LCRA previuosly implied where releases will stop. well its 1018.22 down a foot and falling rather fast since outflows are still 60K inflow no w only 32 or so
yet it still says thisLast Update: Oct 18 2018 4:38PM
also light to moderate rain now covers the west central portion of the basin
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