Winter 2018-2019 Observations

[nrgjeff]

Chattanooga did it! 80 degree high earlier than last year. Might be earliest on record. 80 degree highs in the winter thread is LOL!

[Carvers Gap]

I took this photo yesterday.  The raised walking areas is a birding path through a wetland.  So, this ares is supposed to be a wetland.  That said, the area to the the right of the boardwalk is actually the paved greenbelt which is underwater and not the stream channel.  The stream itself is normally within its banks between the trees to the far right of the photo.  The bottom of the boardwalk to the right(as it curves through the trees and out of sight...not the walk closest to the front) is normal about 3' above the the paved greenbelt with some variation throughout its length.  That gives you and idea of how much water is flowing through there.  Should be a total mess for a few days.  Mud gets about 2-3" deep on the greenbelt after these events and is like ice, very fine and slick.  I almost ditched a bike one year on a thin film of that mud(maybe 2 millimeters thick at the time).  Also, there is a great photo on Facebook of the flooding along the South Fork of the Holston in front of Netherland Inn.  Just search for Kingsport Greenbelt on Facebook.  Finally, I heard on the radio that one(maybe two) swift water rescue had been made in Hawkins Co during the event.  

[Holston_River_Rambler]

Weather for the ducks!

 Landslide on Hawkins/ Hancock county line on highway 66:

 

[Carvers Gap]

BTW, kudos to the guys taking care of the Greenbelt in Kingsport.  They are already out clearing the mud.  They use a sweeper attachment(the kind that you see used to clear areas just before paving) to move the mud to the side.  Pretty nice day out there right now w sun and 46 here currently.  Going to take plenty of sun to dry things out.  Should be a great water year for tailerwater fisheries and mountain streams provided the flooding in the mountains is not severe(wipes out reds).  The first hatches will happen later this month or early March.  I bet when it hit 80 in the mountains that there were some hatches in the lower elevations of GSMNP.

[Carvers Gap]

Here is some drone footage of the Horse Creek area of Sullivan County(WCYB incorrectly labeled it as Hawkins Co).  This is around Sullivan Gardens.  Just follow the link.  Pretty impressive flooding.  This area is known for flooding, but it does give an idea of how much rainfall that we have had.  Right now, I am concerned that this might be a reoccurring theme as we sit under this SER.  Plenty of moisture available and easy transport into our region.

https://wcyb.com/news/sky5/sky-5-horse-creek-flooding

[Carvers Gap]

To couple with the the high rainfall...TRI had a +30 temperature departure yesterday.  That is just incredible.  

[Holston_River_Rambler]

Precip. moving in quick this morning. Redo of last month's unexpected snow incoming for NE areas? 850s look bad on SPC mesoscale analysis, but they looked worse for that one. 

 

 

[Holston_River_Rambler]

Had a little sleet here near downtown Knoxville.

[BlunderStorm]

hmm... close but no dice. It warmed too quickly.

[Holston_River_Rambler]

We tried  

[Holston_River_Rambler]

One last umph before the front passes:

 

That last band is a gully warsher. Had to stop complaining about ENSO states and go look outside it was so loud. 

Also of interest a little enhanced band aimed up 11W at Kingsport. Got some Cherokee lake enhancement, lol/

[Blue Ridge]

Almost looks like a mesovort just south of Maryville. 

In other news, 52 dbz over Johnson City...

[Carvers Gap]

8 minutes ago, Blue Ridge said:

Almost looks like a mesovort just south of Maryville. 

In other news, 52 dbz over Johnson City...

Yeah, that line did us no favors over here.  I have to go out in a bit and will see how the urban creeks look.  The one behind my house(which stays damp and barely runs)...I can hear it from the top of the hill.  It has a lot of water(relative to that creek) in it.

[Carvers Gap]

As long as I can remember we have had droughts and excessive rainfall years.  (Before system of TVA dams, flooding was a major problem in the Tennessee Valley. Obviously, I am too young to remember those years!)  And just remember it was a couple of falls ago that Gatlinburg nearly burned to the ground in an a crazy wind event that coincided with extreme drought.  And then currently...incredible amounts of rain for weeks on end.  Wild how things change. 

[Holston_River_Rambler]

I went to ETSU at Kingsport for a couple of years or so (maybe 01 -03 or so) and remember one year that I came over that hill that runs down by (now a Walgreens, but used to be a Pizza hut I think....ahh the good old days...) and hits 11W. 

Anyway, I saw tropical like waterfalls running down Bays Mountain one spring, maybe Feb since there were no leaves on the trees in my memory.  Don't remember the year for sure. 

I grew up on Kingsbay Drive at the very back end of Ridgefields and would often just go hike up Bays mountain or out, along the foot of it by the Holston River. The land is now owned (it was then, but hardly ever used) and occupied, but there was a time you could walk back to the Holston Defense/ BAE fence and follow a creek up the slope of Bays Mt. where it became a 100 ft waterfall. After seeing the creek from 11W (normally a tiny trickle) I decided to go back there and look at it. It was like a western flash flood had hit. It had literally carved out a 12 - 15 foot deep gouge near the bottom of the mountain. I know such floods must happen every once and while there because there is a shoal of large rocks immediately out in the Holston from that creek. 

Will never forget that gouge in the earth though and if any of you remember the year, let me know so I can try to dig up the radar imagery. 

[janetjanet998]

24 minutes ago, Carvers Gap said:

As long as I can remember we have had droughts and excessive rainfall years.  (Before system of TVA dams, flooding was a major problem in the Tennessee Valley. Obviously, I am too young to remember those years!)  And just remember it was a couple of falls ago that Gatlinburg nearly burned to the ground in an a crazy wind event that coincided with extreme drought.  And then currently...incredible amounts of rain for weeks on end.  Wild how things change. 

2018 was the wettest year on record for the TVA watersheds....BNA so far over 6 inches this month

lake Cumberland, the start of the flood control for the Cumberland river,  super high... approaching 734 feet..normal feb pool 700 feet..earlysummer pool peak 723 feet..record 751 feet

in 2010 floods, under minor drought,  it started at 675ish feet and rose to 703 as they cut all overflow to help down stream......I think you see my point 

 

PS at least the upgraded Wolf Creek DAM a few years ago to stop the seepage and leaks

[Carvers Gap]

16 hours ago, janetjanet998 said:

2018 was the wettest year on record for the TVA watersheds....BNA so far over 6 inches this month

lake Cumberland, the start of the flood control for the Cumberland river,  super high... approaching 734 feet..normal feb pool 700 feet..earlysummer pool peak 723 feet..record 751 feet

in 2010 floods, under minor drought,  it started at 675ish feet and rose to 703 as they cut all overflow to help down stream......I think you see my point 

 

PS at least the upgraded Wolf Creek DAM a few years ago to stop the seepage and leaks

Great information and thanks for sharing it.  Yeah, glad Wolf Creek was repaired.  I know trout fishermen are glad to have it back on line.  My region within the forum, Kingsport/Bristol/JC, is certainly sending its fair share of water into the Tennessee River system.  My primary and backup jogging routes are again flooded this AM.  Feeder streams and the main stem of the Holston are full or out of their banks.  Right now, I don't see any change during the next 10-14 days in what has become a very wet pattern up here.  Normally, we can manage a little bit of rain shadow due to the Cumberlands and/or Apps due to downslope winds.   Right now, it seems that rainfall is being accentuated west of I-81.  I know you all are well downstream.  Do you have a link to your flooding thread?

[janetjanet998]

3 hours ago, Carvers Gap said:

Great information and thanks for sharing it.  Yeah, glad Wolf Creek was repaired.  I know trout fishermen are glad to have it back on line.  My region within the forum, Kingsport/Bristol/JC, is certainly sending its fair share of water into the Tennessee River system.  My primary and backup jogging routes are again flooded this AM.  Feeder streams and the main stem of the Holston are full or out of their banks.  Right now, I don't see any change during the next 10-14 days in what has become a very wet pattern up here.  Normally, we can manage a little bit of rain shadow due to the Cumberlands and/or Apps due to downslope winds.   Right now, it seems that rainfall is being accentuated west of I-81.  I know you all are well downstream.  Do you have a link to your flooding thread?

here is the link to the general OH river flooding thread

they have increased outflow form Wolf creek dam to 28,000 cfs..it was 17.000 until yesterday..record outflow 40,000

lake level continues to rise 735.41 feet

https://www.tva.gov/Environment/Lake-Levels/Wolf-Creek

last year when they increased to these levels it made local news

after a minor system this weekend the ffirehose is aimed right for the TN valley and northern gulf coast states...model trends continue to inch more NW which would mean more the OH valley gets into it...NWS Nashville
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So far in 2019 Nashville has had 10.72" of rain- or 5.29" above normal. Clarksville has had 8.68" or 3.41" above normal. Crossville has had 9.00" or 2.34 above normal. Enjoy some dry weather today- while you can!

 

 

 

[Windspeed]

The flood control dam systems of the Middle and South Fork Rivers of the Holston, including the Watagua River was originally designed to handle a stalled-out tropical low. All of these dams acting as flood water holding reservoirs as the staging event might reach extreme levels off of all the feeder streams up the US HWY 11 corridor, including but not limited to Walker Mtn., Mt. Rogers, Holston Mtn., Iron, Roan, etc., and somewhere between the 72-96 hr range of a 10-15 inch deluge. However, with Boone Dam under repairs, I would imagine Boone Lake handicaps control storage right now, and in the event of similar rainfall amounts in a short period of time, stress would need to be held up rivers at S. Holston and Watauga Dams and strong release for downstream holding at Cherokee Lake. Unsure about Fort Patrick Henry Dam in Kingsport's purpose beyond hydroelectric for a high flood stage event. Someone with better knowledge might want to contribute here, but I've been led to believe its purpose is less than that of flood control than of hydroelectric generation for Eastman.

 

That all being said, while a student at ETSU several decades ago, the late Dr. Robert Peplies, a well-known geographer and remote sensing scientist in his own right, possessed some highly detailed TVA flood stage maps. Seeing a major spillway flood unfolding from Holston and Watagua Dams and what that would do to rivers downstream was quite eye-opening. We really don't ever want to see or witness a Camille-like deluge event rain itself out over the upper Tennessee Watershed in NE Tennessee / SWVA. I recall last year when there was uncertainty with Hurricane Florence's inland stall; catastrophic numbers were being modeled over some of those headwaters. The region lucked out again.

[janetjanet998]

24 minutes ago, Windspeed said:

The flood control dam systems of the Middle and South Forks Rivers of the Holston, including the Watagua River, was originally designed to handle a stalled-out tropical low. All of these dams acting as flood water holding reservoirs as staging might reach extreme levels off of feeder streams from Hwy 11 corridor and Walker Mtn., Mt. Rogers, Holston Mtn., Iron, Roan, etc., and somewhere between in the 72-96 hr range of a 10-15 inch deluge. However, with Boone Dam under repairs, I would imagine Boone Lake handicaps control storage right now, and in the event of similar rainfall amounts in a short period of time, stress would need be held up rivers at S. Holston and Watauga Dams and strong release for downstream holding at Cherokee Lake. Unsure about Fort Patrick Henry Dam in Kingsport's puropose beyond hydroelectric for a high flood stage event. Someone with better knowledge might want to contribute here, but I've been led to believe its purpose is less than that of flood control than of hydroelectric generation for Eastman.

That all being said, while a student at ETSU several decades ago, the late Dr. Robert Peplies, a well-known geographer and remote sensing scientist in his own right, possessed some highly detailed TVA flood stage maps. Seeing a major spillway flood unfolding from Holston and Watagua Dams and what that would do for rivers downstream was quite eye-opening. We really don't ever want to see / witness a Camille-like deluge event rain itself out over upper Tennessee Watershed in NE Tennessee / SWVA. I recall last year when there was uncertainty with Hurricane Florence's inland stall, catastrophic numbers were being modeled over some of those headwaters.

"and somewhere between in the 72-96 hr range of a 10-15 inch deluge"

this is what concerns me right now over the region including the OH valley..that happened in May of 2010 over TN but with  lake levels and streamflows below average..

the winter OH River river floods in 1937 saw a similar deluge..but again with below average rainfall preceding the event...which is the event that sounded the alarm for needed flood control

It seems to the models are delaying any pattern change again and again...with no more rain in the system (no/trace rain next 48 hours in the forecast)the OH river at Cairo IL, the "endpoint" for all the runoff, is now expected to reach 52 feet near major flood stage(53). feb 17 and hold at that stage for a week.. 20th highest on record..(record 61 and change in 2011)

 

[Carvers Gap]

31 minutes ago, Windspeed said:

The flood control dam systems of the Middle and South Forks Rivers of the Holston, including the Watagua River, was originally designed to handle a stalled-out tropical low. All of these dams acting as flood water holding reservoirs as staging might reach extreme levels off of feeder streams from Hwy 11 corridor and Walker Mtn., Mt. Rogers, Holston Mtn., Iron, Roan, etc., and somewhere between in the 72-96 hr range of a 10-15 inch deluge. However, with Boone Dam under repairs, I would imagine Boone Lake handicaps control storage right now, and in the event of similar rainfall amounts in a short period of time, stress would need be held up rivers at S. Holston and Watauga Dams and strong release for downstream holding at Cherokee Lake. Unsure about Fort Patrick Henry Dam in Kingsport's puropose beyond hydroelectric for a high flood stage event. Someone with better knowledge might want to contribute here, but I've been led to believe its purpose is less than that of flood control than of hydroelectric generation for Eastman.

That all being said, while a student at ETSU several decades ago, the late Dr. Robert Peplies, a well-known geographer and remote sensing scientist in his own right, possessed some highly detailed TVA flood stage maps. Seeing a major spillway flood unfolding from Holston and Watagua Dams and what that would do for rivers downstream was quite eye-opening. We really don't ever want to see / witness a Camille-like deluge event rain itself out over upper Tennessee Watershed in NE Tennessee / SWVA. I recall last year when there was uncertainty with Hurricane Florence's inland stall, catastrophic numbers were being modeled over some of those headwaters.

Great info.  Boone/Patrick Henry is a similar setup to Watauga/Wilbur.  One dam's reservoir backs into the other dam's tailwater.  I think the Wilbur and FPH are basically hydroelectric with very little additional storage as those reservoirs remain basically filled year-round. The generations schedules of those tandems are often similar.  (I alway check the schedule before going out fishing on Watauga or S. Holston....the water comes up fast) Watauga, S Holston, and Boone are more flood control.  Obviously, Boone is out of commission right now a they augment the earthen area of the dam.  Cherokee is a huge catch basin when compared to the other two.  Interesting to know the system up here was built to withstand that big of a tropical event.  In those days engineers always built excellent redundancy into their systems.  At this time of year, there should be plenty of storage.  Where things get sketchy is if those fill early and the El Nino pattern continues.  I would suspect TVA is sending plenty of water down stream right now so as to leave room for additional storage due to the current pattern - hence the Ohio River concerns. MBY concern with flooding is more in line with feeder rivers and streams...such as in our area like Reedy and Horse Creeks or in the mountains along the many creek/small river systems(North Fork here in town or Little River in Townsend as examples) that will potentially see significant precip in the coming weeks.  I know some local school systems have been operating on delays so that the sun can come up and give bus drivers better visibility to see low/flood prone areas.  Of note, I have one little island that I keep an eye on just upstream of Netherland Inn(you might now it...about 20 yards below the RF bridge)....during low water years it barely goes under water and even has weeds/grasses growing on it, even during spring.  A couple of years ago, someone even stuck a metal chair on it.  That chair was there for months on end.  I don't think I have seen that island for a few months.  A lot of water is being moved this winter.  

As an aside....you mentioned flood plains.  Do you remember when FPH was testing their flood gates and a log became jammed in one of the gates and it wouldn't shut?  That was an eye opener for everyone downstream.  I bet some folks were sweating bullets.

[Windspeed]

Do you remember when FPH was testing their flood gates and a log became jammed in one of the gates and it wouldn't shut?  That was an eye opener for everyone downstream.  I bet some folks were sweating bullets.

I recall hearing about it but I cannot remember when that occurred. I can't find any news associated with it online.

 

While I'm at it, I've found little resources for the last time S. Holston and Watagua's spillways were even inundated / utilized. Certainly not in my lifetime. When Camille stalled in '69, it was further northeast of the New River and ECD; therefore, the Shenandoah River Valley and James River Watershed took the brunt of severe flooding. There were also some flooding events in the mid 70s that may have utilized the Holston and Watauga spillways. One of those floods severely impacted downtown Bristol from the Beaver and Clear Creek Reservoir storage facilities, though this is unrelated to Holston and Watauga Dams and their spillways, it may have been one of those events. The point is those lakes are designed hold a signficant amount of runoff. But it also goes to show just how rare a 10-15" or greater short term event is for our region.

[Windspeed]

I realize this is the OBS thread and we're getting way into historical territory here, but if folks don't mind the somewhat off topic with respect of future flooding events. Here is a PDF the '77 flooding event. This event was more severe on the Tug, Clinch and North Fork of the Holston than South Fork. This was a hyper active setup with southerly sub tropical jet. The pattern may've not even been that far off from what we're about to experience.

 

https://www.weather.gov/media/rlx/April1977FloodsinAppalachianRegion.pdf

 

Here is a brief summation of that event. I do not believe the spillways on the South Holston Dam and Watagua Dams were utilized as the high flow rate was far worse on North Fork, Clinch in SWVA and Tug in Kentucky where the 8-10" totals fell:

 

Intense rainfall caused record-breaking floods on April 2-7, 1977, in southwestern Virginia. The flooding was most severe in the Big Sandy and Tennessee River basins (both these rivers are outside of Virginia but their basins extend into the State); flooding was of less magnitude in the New River basin. Record peak stages were recorded at many gaging stations. For the Clinch River at Cleveland (fig. 3, site 6), the peak stage was 2.0 feet higher than the previously recorded maximum of 24.4 feet on January 30, 1957, and the highest recorded since the flood of 1862. The recurrence intervals of flood peaks at 18 gaging stations within the area were equal to or greater than 100 years. Damage to public and private property, roads, and bridges was extensive, and was estimated by the Virginia Department of Emergency Services to be about $243 million (Runner and Chin, 1980, p. 26). In Kentucky, Tennessee, Virginia, and West Virginia, 22 deaths were reported and estimated property damage totaled about $400 million (Runner and Chin, 1980, p. 1).

I'm still digging for other events but I'm starting to think those spillways have never had to be utilized, unless there was some event in the 50s.

 

 

[Holston_River_Rambler]

Here's a wild one from Knoxville's history:

 https://www.visitknoxville.com/blog/post/when-the-creeks-rose-floods-in-knoxville-history/ 

If you've ever been to market square in downtown Knoxville, well.....

apparently it was an island in early March 1867.

http://cmdc.knoxlib.org/cdm/singleitem/collection/p265301coll7/id/835/rec/1 

Contemporary account:

https://savingtnhistory.blogspot.com/2014/02/the-great-flood-of-1867.html 

 

[Carvers Gap]

1 hour ago, Windspeed said:

I recall hearing about it but I cannot remember when that occurred. I can't find any news associated with it online.

 

While I'm at it, I've found little resources for the last time S. Holston and Watagua's spillways were even inundated / utilized. Certainly not in my lifetime. When Camille stalled in '69, it was further northeast of the New River and ECD; therefore, the Shenandoah River Valley and James River Watershed took the brunt of severe flooding. There were also some flooding events in the mid 70s that may have utilized the Holston and Watauga spillways. One of those floods severely impacted downtown Bristol from the Beaver and Clear Creek Reservoir storage facilities, though this is unrelated to Holston and Watauga Dams and their spillways, it may have been one of those events. The point is those lakes are designed hold a signficant amount of runoff. But it also goes to show just how rare a 10-15" or greater short term event is for our region.

I think their spillways were utilized within the last 2-3 years.  Whichever year, the lakes(Watauga and S. Holston) filled up early and they had no room to store more water...so they dumped it.  It is not to uncommon I don't think(maybe a few times during a decade) South Holston dumps into the spillway sluice on one side of the dam.  I could be wrong though.  Usually a little yellow box appears on the app for a certain dam and notes that such-and-such dam will be spilling until further notice w very high cfs numbers. For example, right now Fort Loudon is spilling until further notice(could be that the generators are offline, but more likely they are dumping water as it is not a lake that really drops during winter).  I watch the generation schedules fairly regularly so I know when I can fish.  It is a "no go" when they are dumping water at those rates.  The rivers are basically blown out.  TVA has a great lake levels app.  Usually, it is not overly noticeable downstream when they open the gates.  The water will appear high, but they are super careful not to exceed certain cfs limits(not sure of the actual term) which will get into residences or overrun industrial intakes.  When they are sluicing(spilling) a little yellow box appears at the top.  Right now, for example, it appears that South Holston and Watauga are filling their reservoirs and holding back water.  It says they are sluicing right now at just about 200 cfs, but that is not true flood water being dumped.  When they are dumping water, it is more like 3,000-4,000 cfs or more on the upstream dams.  Fort Loudon is way more than that - 42,000 cfs roughly today.  The upstream dams are likely holding back water right now(as evidenced by Ft Loudon sluicing) which means the influx from feeder streams is pretty high due to rainfall OR they are both working on generators OR they are making sure not to send too much downstream as they try to clear as much water from the downstream system as possible - probably a combo of scenario 1 and 3.  And of course, all of that water is money in the bank for summer generation.  As a fishermen, I like when TVA is working on a generator...usually means consistent flows of 200-300 cfs out of the SoHo.  

An interesting aside, South Holston actually has a third emergency spillway that empties into the woods.  That one I don't think has ever been used.  

[Carvers Gap]

1 hour ago, Windspeed said:

I realize this is the OBS thread and we're getting way into historical territory here, but if folks don't mind the somewhat off topic with respect of future flooding events. Here is a PDF the '77 flooding event. This event was more severe on the Tug, Clinch and North Fork of the Holston than South Fork. This was a hyper active setup with southerly sub tropical jet. The pattern may've not even been that far off from what we're about to experience.

 

https://www.weather.gov/media/rlx/April1977FloodsinAppalachianRegion.pdf

 

Here is a brief summation of that event. I do not believe the spillways on the South Holston Dam and Watagua Dams were utilized as the high flow rate was far worse on North Fork, Clinch in SWVA and Tug in Kentucky where the 8-10" totals fell:

I'm still digging for other events but I'm starting to think those spillways have never had to be utilized, unless there was some event in the 50s.

 

 

A good and maybe seemingly unlikely resource might be to look at local fishing reports for the Watauga or South Holston tailwaters. They might note if either dam is spilling water.  South Holston River Flyshop has a good archive.  I read a few from last year and didn't note anything unusual, but sometimes those places won't say anything as they are just not on the water.

[Windspeed]

I think their spillways were utilized within the last 2-3 years.  Whichever year, the lakes(Watauga and S. Holston) filled up early and they had no room to store more water...so they dumped it.  It is not to uncommon I don't think(maybe a few times during a decade) South Holston dumps into the spillway sluice on one side of the dam.  I could be wrong though.  Usually a little yellow box appears on the app for a certain dam and notes that such-and-such dam will be spilling until further notice w very high cfs numbers. For example, right now Fort Loudon is spilling until further notice(could be that the generators are offline, but more likely they are dumping water as it is not a lake that really drops during winter).  I watch the generation schedules fairly regularly so I know when I can fish.  It is a "no go" when they are dumping water at those rates.  The rivers are basically blown out.  TVA has a great lake levels app.  Usually, it is not overly noticeable downstream when they open the gates.  The water will appear high, but they are super careful not to exceed certain cfs limits(not sure of the actual term) which will get into residences or overrun industrial intakes.  When they are sluicing(spilling) a little yellow box appears at the top.  Right now, for example, it appears that South Holston and Watauga are filling their reservoirs and holding back water.  It says they are sluicing right now at just about 200 cfs, but that is not true flood water being dumped.  When they are dumping water, it is more like 3,000-4,000 cfs or more on the upstream dams.  Fort Loudon is way more than that - 42,000 cfs roughly today.  The upstream dams are likely holding back water right now(as evidenced by Ft Loudon sluicing) which means the influx from feeder streams is pretty high due to rainfall OR they are both working on generators OR they are making sure not to send too much downstream as they try to clear as much water from the downstream system as possible - probably a combo of scenario 1 and 3.  And of course, all of that water is money in the bank for summer generation.  As a fishermen, I like when TVA is working on a generator...usually means consistent flows of 200-300 cfs out of the SoHo.  

An interesting aside, South Holston actually has a third emergency spillway that empties into the woods.  That one I don't think has ever been used.  

A good and maybe seemingly unlikely resource might be to look at local fishing reports for the Watauga or South Holston tailwaters. They might note if either dam is spilling water.  South Holston River Flyshop has a good archive.  I read a few from last year and didn't note anything unusual, but sometimes those places won't say anything as they are just not on the water.

I was actually referring to the concrete overflow spillways, not the flood gates. I know SoHo and Watagua do regular non-generating sluice releases for positive cfs oxygenating flow. But in reference to specific flood stage events, the reservoir overflowing into the concrete spillways is what I am referring to here. I'm not sure that has ever happened. I have hiked out to the wooded spillway many times. That particular one has a flows paths toward the River Bend area and I imagine such record levels would be quite destructive, beyond just the renowned trout fishing tourism located there. But I am trying to imagine a record 10-15" short term event off of Middle and South Forks and Watauga and what that would mean for reservoirs downstream. The runoff from Rogers-Holston Mtn for SoHo and Iron-Roan for Watagua probably would top those concrete emergency spillways with huge cfs rates.

[Carvers Gap]

28 minutes ago, Windspeed said:

 

I was actually referring to the concrete overflow spillways, not the flood gates. I know SoHo and Watagua do regular non-generating sluice releases for positive cfs oxygenating flow. But in reference to specific flood stage events, the reservoir overflowing into the concrete spillways is what I am referring to here. I'm not sure that has ever happened. I have hiked out to the wooded spillway many times. That particular one has a flows paths toward the River Bend area and I imagine such record levels would be quite destructive, beyond just the renowned trout fishing tourism located there. But I am trying to imagine a record 10-15" short term event off of Middle and South Forks and Watauga and what that would mean for reservoirs downstream. The runoff from Rogers-Holston Mtn for SoHo and Iron-Roan for Watagua probably would top those concrete emergency spillways with huge cfs rates.

Got ya.  Just a difference in definitions...The SoHo has the generation unit area on the left and then to the right a sluice for spilling excess water.  Yeah, I don't think the "wooded" emergency spillway(the third one) on the SoHo has ever been used.  I can't imagine what type of event would cause that.  Whew!  Usually if TVA sees a sizable event on the horizon, they push a bunch of water down stream of the area to be impacted and hold water upstream.  Wasn't there a dam out in California recently that had to use its overflow spillway and it almost destroyed the dam and blew out large portions of that overflow spill way?  I can't imagine what type of rainfall that would require.  

(And for those new to the conversation....I don't think anyone is talking about flooding of that magnitude.) 

As for oxygen...TVA has done a great job below Norris and South Holston with the weir dams which help with that in addition to keeping constant flows.  Night and day improvements over the past 30-40 years.

And as an observation of today's wx....a brisk wind has been blowing all day.  It has certainly been nice to see the sun!

[Windspeed]

Yeah, I don't think the "wooded" emergency spillway(the third one) on the SoHo has ever been used.  I can't imagine what type of event would cause that.  Whew!

Beyond the flood gate / sluice that feeds the right exit channel, there are two concrete spillways we are discussing. We mentioned the wooded one about a mile south on the shale ridge line, but I don't think the adjacent concrete spillway has ever been topped either. Same situation for Watauga, though it just has the single spillway.

Wasn't there a dam out in California recently that had to use its overflow spillway and it almost destroyed the dam and blew out large portions of that overflow spill way?

Yes, the Oroville Dam emergancy. As bad as that was, fortunately the rain subsided and they were eventually blessed with a cfs discharge that was manageable before the dam was compromised.

I can't imagine what type of rainfall that would require.   (And for those new to the conversation....I don't think anyone is talking about flooding of that magnitude.)

Well the '77 short term event dumped 8-10" on portions of the Clinch and Tug/Sand River Valleys. And certainly, no, we are not suggesting a similar event outcome anywhere in the same region over the next few weeks. But if modeling shifts a bit slightly north with some of those 6-9" outputs into the upper watershed, it could get sketchy. This whole off topic discussion by me was just born on the realization of what the upper Tennessee watershed can and cannot handle from a perspective record flood stage event. Again, that's why I mentioned Camille. Imagine it stalling out over SWVA instead of the Shenandoah Valley? Our region has never seen what is very possible given such a scenario.

 

Again, apologies if I derailed OBS. Enjoy the sunshine while it lasts tomorrow morning.

[Holston_River_Rambler]

https://wlos.com/news/local/blown-away-grandfather-mountain-sets-new-wind-speed-record?fbclid=IwAR2qGMiRrzlZmM50Y8U5ExOpXd0-WCc-3GGi4Z8BywtzsFVnkQbs0ElN3I8