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Followup submissions

Re: North Fork French Broad changes by Chris Bell (email)

Contributed 09/16/2004  Responses:  1

Harrison wrote:
The other change seems to be with the gauges, both the online USGS French Broad at Rosman and my hand-painted gauge on the US 64 bridge. Bob Fay ran the river Thursday and commented that even though my gauge read 2 feet, it felt a lot higher than the previous time he had run it at 2 feet. Several people who ran it Saturday at 8-9 inches, including Terry McGhee, said it felt like more than 1 foot. However when I ran it Sunday at 6 inches, it felt like 6 inches to me, maybe a couple of inches higher. However the Rosman gauge was reading under 500 cfs that day, which in the past would have equated to only 2 or 3 inches.

The most logical explanation seems to be that the flood scoured the river bottom at both my gauge and the Rosman gauge, making the gauge read lower than it did before. I would be interested to hear any opinions, especially from our resident stream gauge expert, Chris Bell.

Yes, I think a lot of gauge relationships changed last week and will change again this week. At some point the cfs's reported by the USGS gauges will become consistent with what they were in the past. The USGS spends a lot of time and money re-calibrating gauge "ratings curves" -- the graphs they use to translate stage heights (which change after floods) to river flows. The gauges themselves aren't all that expensive to install and maintain . . . the expense is in the re-calibration.

Once the Rosman USGS gauge is re-calibrated, the old relationship between Rosman flows and NFFB flows will re-assert itself. However . . . two things important to us may remain changed:
1. the relationship between NFFB flows and Harrison's painted gauge;
2. what any given flow of the NFFB means to us as paddlers.

The relationship between the NFFB flows and Harrison's painted gauge will almost certainly change for the reason Harrison identifies: scouring of the streambed around the gauge.

The relationship between NFFB flows (the water flowing down the gorge, not the height of the water on the bridge piling) and boatable levels may change due to changes in the streambed resulting from the flood(s). Specifically, some rocks no doubt got moved around and a lot of silt and gravel got washed out. The washing out of the silt and gravel may change the channels the water takes and change the depth of these channels. It may remove old hazards and create new ones (i.e., unplug some sieves). The nature of the Lower Rocky Broad changed significantly after the flood of '96 -- it actually became "rocky" again with all the silt and gravel gone!

On the plus side, the rivers may be a lot healthier for awhile with all the silt washed out. According to Leland Davis, the water in the Nolichucky clearer than he has ever seen it before. According to Phil Malatin, the same is true for Wilson Creek.

Bottom line: keep reporting what you learn regarding changes in your favorite runs, AND KEEP REPORTING THE LEVELS, THE TIMES THE LEVELS WERE READ, AND YOUR SUBJECTIVE EVALUATIONS OF THE LEVELS. Do it here or send them to me by email so that I can update the boating beta flows page.

-- Chris

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Re: North Fork French Broad changes by Kimberly Barbee (email)

Contributed 06/17/2005  Responses:  0

: I ran the North Fork on Wednesday and it was 800 cfs on the Rosman gauge and 6" at the bridge gauge. The hole at submarine is not too munchy at this level. What is the lowest level on the Rosman gauge that the North fork is runnable?

: Harrison wrote:
: The other change seems to be with the gauges, both the online USGS French Broad at Rosman and my hand-painted gauge on the US 64 bridge. Bob Fay ran the river Thursday and commented that even though my gauge read 2 feet, it felt a lot higher than the previous time he had run it at 2 feet. Several people who ran it Saturday at 8-9 inches, including Terry McGhee, said it felt like more than 1 foot. However when I ran it Sunday at 6 inches, it felt like 6 inches to me, maybe a couple of inches higher. However the Rosman gauge was reading under 500 cfs that day, which in the past would have equated to only 2 or 3 inches.
:
: The most logical explanation seems to be that the flood scoured the river bottom at both my gauge and the Rosman gauge, making the gauge read lower than it did before. I would be interested to hear any opinions, especially from our resident stream gauge expert, Chris Bell.
:
: Yes, I think a lot of gauge relationships changed last week and will change again this week. At some point the cfs's reported by the USGS gauges will become consistent with what they were in the past. The USGS spends a lot of time and money re-calibrating gauge "ratings curves" -- the graphs they use to translate stage heights (which change after floods) to river flows. The gauges themselves aren't all that expensive to install and maintain . . . the expense is in the re-calibration.
:
: Once the Rosman USGS gauge is re-calibrated, the old relationship between Rosman flows and NFFB flows will re-assert itself. However . . . two things important to us may remain changed:
: 1. the relationship between NFFB flows and Harrison's painted gauge;
: 2. what any given flow of the NFFB means to us as paddlers.
:
: The relationship between the NFFB flows and Harrison's painted gauge will almost certainly change for the reason Harrison identifies: scouring of the streambed around the gauge.
:
: The relationship between NFFB flows (the water flowing down the gorge, not the height of the water on the bridge piling) and boatable levels may change due to changes in the streambed resulting from the flood(s). Specifically, some rocks no doubt got moved around and a lot of silt and gravel got washed out. The washing out of the silt and gravel may change the channels the water takes and change the depth of these channels. It may remove old hazards and create new ones (i.e., unplug some sieves). The nature of the Lower Rocky Broad changed significantly after the flood of '96 -- it actually became "rocky" again with all the silt and gravel gone!
:
: On the plus side, the rivers may be a lot healthier for awhile with all the silt washed out. According to Leland Davis, the water in the Nolichucky clearer than he has ever seen it before. According to Phil Malatin, the same is true for Wilson Creek.
:
: Bottom line: keep reporting what you learn regarding changes in your favorite runs, AND KEEP REPORTING THE LEVELS, THE TIMES THE LEVELS WERE READ, AND YOUR SUBJECTIVE EVALUATIONS OF THE LEVELS. Do it here or send them to me by email so that I can update the boating beta flows page.
:
: -- Chris

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Re: North Fork French Broad changes by Harrison Metzger

Contributed 06/17/2005  Responses:  0

Regarding your question about what is the lowest flow on the Rosman gauge that the North Fork is runnable, that is a matter of preference, but I would say it hits zero on the red gauge I painted on the bridge somewhere between 300 and 350. A guy on Boatertalk however posted that it is "never too low" and apparently has done it down in the 180 range! Personally zero is my minimum and I usually carry Boxcar at that level.




: Thanks to Hurricane Frances, the giant log that has been wedged the last few years in the rapid on the right side of the island below Boxcar Falls has been washed out. It is now lodged on the undercut rock below Submarine Falls more than a mile downstream. If you have ever seen this log, it is wild to think about the force required to move it that far. When I ran the NFFB Sunday (9-12) at 6 inches, I was the only one my group to run Submarine, but the log was not really a factor. Unless it is really flooded you should be able to eddy out and paddle over the right side of it.
: The other change seems to be with the gauges, both the online USGS French Broad at Rosman and my hand-painted gauge on the US 64 bridge. Bob Fay ran the river Thursday and commented that even though my gauge read 2 feet, it felt a lot higher than the previous time he had run it at 2 feet. Several people who ran it Saturday at 8-9 inches, including Terry McGhee, said it felt like more than 1 foot. However when I ran it Sunday at 6 inches, it felt like 6 inches to me, maybe a couple of inches higher. However the Rosman gauge was reading under 500 cfs that day, which in the past would have equated to only 2 or 3 inches.
: The most logical explanation seems to be that the flood scoured the river bottom at both my gauge and the Rosman gauge, making the gauge read lower than it did before. I would be interested to hear any opinions, especially from our resident stream gauge expert, Chris Bell.
: Paddle safe,
: Canoeman

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