Flood of 2013 is Happening, Part 1

The Flood of 2013 is happening as I write to you.   The clock on my computer says 12:30 PM on Thursday.  It has rained for 3 days and it is continuing to rain, with a good chance that it will turn to snow later today.

My purpose in writing is to give you the links so you can see rainfall rates, river flows, and flood levels.  You can even get predictions from the National Weather Service.   If you are not a “numbers person” you might get value from the graphs or the map that shows the buildings and streets that flood as the river rises.   The map is only available for Bryson City, unless you can find something on the Web that I have not seen.

Most important is safety – safety for you, your family, and your neighbors.  Playing with computers is fine, but WATR wants to know that you are safe.  If you have flood damage or you face risk from flooding, sliding rocks, failing mountain roads – be careful, be wise, and stay safe!   When the river goes down, the sun comes out, send us pictures, and tell us about your experience of the Flood of 2013.

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We want your pictures!

Have pictures of flood creeks, trailers calf-deep in water, rock slides, collapsed roads?  Send them onto WATR’s facebook page.  Include an informative caption.  When and where was the picture taken?  Please include your name – you deserve the credit!

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There are four gage stations maintained by the U.S. Geological Survey (USGS) in the Tucksegee River watershed.  The names and links are shown here.

LinkLocationData starts:
Tuck. River at Bryson City Bryson City.  Flow, stage, and rainfallOctober 1897
Ocon River at BirdtownNext to bridge at Jenkins Store on Rt 19August 1945
Tuck. River at Barkers CreekBarkers Creek, where the Tuckasegee raft trips end.October 2007
Tuck. River at CullowheeCullowhee, up river from WCUOctober 2007
Rainfall in SylvaAt TWSAOctober 2008

Let’s look at some of the data.  This is “old hat” to kayakers.  They routinely go to the internet to see the discharge of their favorite river.  Too low, you scrape bottom; too high, it could be foolhardy.

USGS gage station on the Tuckesegee

Discharge is the flow measured in cubic feet per second.  During a prolonged storm it can get very high (compared to usual flows) so the graph uses log values.  (Remember logarithms from high school math, or am I spoiling your fun?)

 Go up and click on Tuck. River at Bryson City.   Questions for you:  Why are there “humps” in the flow starting on January 10?  Answer: this is not “natural flow” rather it shows the results of water releases to generate electricity high in the watershed.  Watersheds without dam releases do not show these pulses.

Notice the two peaks in flow (one on 1/14 and the next one right after midnight at the beginning of 1/15)?  If you follow the links for the other gage stations, you will see that the two peaks come from the Oconaluftee River where rainfall concentrated into two separate, intense storms.  Looking at flow on the Tuckasegee River at Cullowhee, there is only one peak or spike in flow (so far).

If you are interested in flooding, then you want to know the river stage, the technical term for the height of the water in the river.  The plot uses the term “gage height.”

Notice that the stage data also show a double peak.  At the moment, data from the rain gages show that precipitation is increasing so we expect the stage to start increasing again, to form a third peak.  Indeed, a prediction graph shown in Part 2 will show this third peak.

At gage stations with long records, USGS hydrologists have identified levels for different degrees of flooding.  For Bryson City

Flood Condition

Stage above: (ft)

 

Flood Event

Stage (ft)

Discharge (cfs)

Action

8

Minor

10

Flood of 2013

12.67

2,760

Moderate

13.5

Ivan peak (2004)

13.87

31,800

Major

15.5

Max in record: (1940)

15.95

61,600

The next blog will describe the data from the Automated Flood Warning System, and the cool and colorful websites showing the predicted flood for next few hours and super maps showing the inundation – who’s first floor is gonna get wet!

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What were the floods like in the olden days?

The Annual Peak Flow Data for the Tuckasegee gaging station in Bryson City provides a list of historical floods including three observations from the 19th Century.  Consider these:

Date

River Depth (ft)

5/1/184022
3/6/186719
6/1/187619

Wow!  Imagine a flooded Tuckasegee River that was 22 ft deep!  And no Fontana Lake to slow the water down!

Go to  Annual Peak Flows Tuck. at Bryson  to see the peak flows in the past century.  The big action happened in 1940 with its colossal and devastating flood.  Shortly after that, in late 1940 or early 1941, engineers closed the gates on the new Thorpe Dam that forms Lake Glenville.  That control of discharge in the (relatively) small southwestern corner of the watershed has made a big difference in flood frequency.  It has allowed many structures, mostly cabins and trailers, to be built close to the river.  Is this justifiable?  Is it wise?

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