Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

Here's something to think about - and I hope someone has some good
answers or can point me to a good source of info...

We have been doing some canoeing trips as a part of a summer orientation
program here at the University of Virginia. This year we have had to be
very conscious of river levels due to an unusually wet spring and early
summer around here. (Oddly enough, we had a record drought last year -
oh well.) I have found myself spending a lot of time explaining river
gauges and river levels to a variety of people in our organization so
they have some idea about risk management.

So now I have come up with a pretty standard speech explaining classes
of whitewater, river levels and water volume. Classes of whitewater
somewhat equates to classes of rock climbs - that seems to go over well
with most folks. However, people have a difficult time with
understanding river levels (what does 5 feet on this gauge mean?). They
also seem to understand the concept of CFS but it takes a little time
for them to grasp that just because CFS doubles, level does not
necessarily double and that 3000 CFS on the Maury River in Virginia is a
good bit different than, say, 3000 CFS on the Colorado :)

First question - does anyone have a good explanation for what river
level is supposed to represent and a good way to explain some of the
things above without degenerating into a technical hydrodynamic discussion?

Second (and partially related question) - I'm probably missing
something obvious here but I can't see the forest for the trees. I'll
use a specific example and we can generalize from there.

Looking at the James River (VA) gauge at Buchanan, you see that the
river is at a particular level and CFS - let's say, for example, 4.75
feet and around 3800 CFS, give or take. Looking downstream, we see that
the Maury River flows into the James at Glasgow, adding its flow to the
James at that point. We see that the Maury River at Buena Vista (a ways
upstream from the confluence) is running at 4.5 and around 2800 CFS.
Now moving downstream on the James, we look at the James River at
Holcomb Rock and the gauge reads about 7.25 feet and about 6000 CFS and
change. Common sense would say (river features like dams excepted) that
part of the extra CFS would be from the water coming from the Maury.
However, the ratio of level / CFS from Buchanan to Holcomb Rock seems
to be pretty continuous, regardless of the level / CFS being added by
the Maury.

So what gives? Is this a situation that is particular to this area or
am I missing something here that is true across the board? How does the
Mississippi change when the Ohio flows in?

What do you all think?

Eric

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

Eric-

A good point to make to beginners about river levels is to recall that
introductory physics lesson about speed and energy. As you recall the
energy of an object is the square of a speed - double the speed and
quadruple the energy. This is the most crucial element of understanding
different water levels for a beginner paddler - or a beginning driver.

Beyond that I think that CFS is best understood by experience. What is
considered a high level of CFS is a case by case, river by river, thing.
Probably the best you can do is mention the water level of the runs you are
doing and try and build the beginnings of comparative awareness - and
respect - for your class. Doing the same run twice at different levels
would also be wise- especially if you have a full semester.

If you can find a damn release run and figure out how to be at one of the
major rapids when they turn the water on that too can be quite instructive.

BTW - excellent question.

-Douglas Tooley

"Eric" wrote in message
...
Here's something to think about - and I hope someone has some good
answers or can point me to a good source of info...

We have been doing some canoeing trips as a part of a summer orientation
program here at the University of Virginia. This year we have had to be
very conscious of river levels due to an unusually wet spring and early
summer around here. (Oddly enough, we had a record drought last year -
oh well.) I have found myself spending a lot of time explaining river
gauges and river levels to a variety of people in our organization so
they have some idea about risk management.

So now I have come up with a pretty standard speech explaining classes
of whitewater, river levels and water volume. Classes of whitewater
somewhat equates to classes of rock climbs - that seems to go over well
with most folks. However, people have a difficult time with
understanding river levels (what does 5 feet on this gauge mean?). They
also seem to understand the concept of CFS but it takes a little time
for them to grasp that just because CFS doubles, level does not
necessarily double and that 3000 CFS on the Maury River in Virginia is a
good bit different than, say, 3000 CFS on the Colorado :)

First question - does anyone have a good explanation for what river
level is supposed to represent and a good way to explain some of the
things above without degenerating into a technical hydrodynamic
discussion?

Second (and partially related question) - I'm probably missing
something obvious here but I can't see the forest for the trees. I'll
use a specific example and we can generalize from there.

Looking at the James River (VA) gauge at Buchanan, you see that the
river is at a particular level and CFS - let's say, for example, 4.75
feet and around 3800 CFS, give or take. Looking downstream, we see that
the Maury River flows into the James at Glasgow, adding its flow to the
James at that point. We see that the Maury River at Buena Vista (a ways
upstream from the confluence) is running at 4.5 and around 2800 CFS.
Now moving downstream on the James, we look at the James River at
Holcomb Rock and the gauge reads about 7.25 feet and about 6000 CFS and
change. Common sense would say (river features like dams excepted) that
part of the extra CFS would be from the water coming from the Maury.
However, the ratio of level / CFS from Buchanan to Holcomb Rock seems
to be pretty continuous, regardless of the level / CFS being added by
the Maury.

So what gives? Is this a situation that is particular to this area or
am I missing something here that is true across the board? How does the
Mississippi change when the Ohio flows in?

What do you all think?

Eric

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

Eric wrote:
Here's something to think about - and I hope someone has some good
answers or can point me to a good source of info...

I think that local and overall gradient and the kind of soil or rock
through which the river cuts its way also plays a major role in
determining the difficulty level of the river/rapids.

--
Wilko van den Bergh
Eindhoven The Netherlands Europe
Look at the possibilities, don't worry about the limitations.
http://wilko.webzone.ru/

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

"Eric" wrote in message
...
Here's something to think about - and I hope someone has some good
answers or can point me to a good source of info...
. . .
First question - does anyone have a good explanation for what river
level is supposed to represent and a good way to explain some of the
things above without degenerating into a technical hydrodynamic
discussion?

"Degenerate?" It's for explaining relationships like you describe that
"technical hydrodynamic discussions" were invented. The hydrodynamic
relationship you're looking for relates the 'stage' (which, with the profile
of the stream bed, determines the cross sectional flow area) with the flow
velocity or the total volumetric flow rate. Without going into all of the
hand waving, the velocity will vary roughly as the square root of the depth
in a broad shallow stream. You can degenerate as far as you'd you like if
you feed 'streamflow' or 'Manning equation' into Google.

Better than that, you can construct the relationship directly from the real
world flow data on a particular stream you're interested in.

Second (and partially related question) - I'm probably missing
something obvious here but I can't see the forest for the trees. I'll
use a specific example and we can generalize from there.

Looking at the James River (VA) gauge at Buchanan, you see that the
river is at a particular level and CFS - let's say, for example, 4.75
feet and around 3800 CFS, give or take. Looking downstream, we see that
the Maury River flows into the James at Glasgow, adding its flow to the
James at that point. We see that the Maury River at Buena Vista (a ways
upstream from the confluence) is running at 4.5 and around 2800 CFS.
Now moving downstream on the James, we look at the James River at
Holcomb Rock and the gauge reads about 7.25 feet and about 6000 CFS and
change. Common sense would say (river features like dams excepted) that
part of the extra CFS would be from the water coming from the Maury.
However, the ratio of level / CFS from Buchanan to Holcomb Rock seems
to be pretty continuous, regardless of the level / CFS being added by
the Maury.

Forget trying to work with stages. First, their zeros are completely
arbitrary. Second, the relationship between stage and CFS can be minutely
dependent on the particular transverse profile and bottom characteristics of
the stream on which they're reported.

So what gives? Is this a situation that is particular to this area or
am I missing something here that is true across the board? How does the
Mississippi change when the Ohio flows in?

Combining stages would be meaningless. The CFSs, though, had better add up,
unless it's raining or it's VERY, VERY dry.

hth,
Fred Klingener

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

To further clarify the example about the Gauley you must look at a
couple of other things.

1) The distance between the gauges and the time when the flows (cfs)
were taken. The Belva gauge is about 27 miles downstream from
Summersville Dam. It's flow is based on what was being released at
Summersville Dam several hours earlier.

2) There are several small creeks that flow into the Gauley. These can
all add to the flow that is measured at Belva. Normally these creeks
add very little to the flow but they can make a significant difference
if their watersheds received a large amount if rainfall in a short
period of time.

It is my understanding that the level (feet) as measured by a USGS
gauge is not standardized (across many gauges). So the level on one
gauge on a river many not have anything to do with the level on
another gauge on the same river or a different river.

Flow, in almost all cases, is based on a calculation using the level
and a cross section of the riverbed at the location of the gauge.

Chuck

"EnzoM3" wrote in message .com...
Good example is the Gauley River. Gauley at Summersville is what's coming
out of the dam. Then the Meadow add it's flow, and downstream at Gauley at
Belva is pretty much the sum of the Meadow and Gauley at Summersville.

Jim

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

"ChuckB" wrote

It is my understanding that the level (feet) as measured by a USGS
gauge is not standardized (across many gauges). So the level on one
gauge on a river many not have anything to do with the level on
another gauge on the same river or a different river.

That's correct- the level is based on a somewhat arbitrary datum, thus "5
feet on the gauge" just means that the level is 5 ft. above the datum. The
datum is tied to sea level, so you might have a datum of 0 at 800 ft. above
sea level, so when the gage is at 5 ft., the water surface elevation is at
805 ft. MSL. 0 ft. does not equate to the stream bed either, in many (if
not most) cases.

Don't Post to This Thread
 

I've received a rather strange reply from the originator of this thread
which clarifies the real intent of the original, 'rambling' post. Although
the question is still good - the reason for it is intentionally misstated.

I've challenged the guy privately in response to his e-mail and I'll wait
for his response today before I post the rest.

But do take the warning that this guy is a risk to both his students and
perhaps even yourself.

-Douglas Tooley
"Felsenmeer" wrote in message
.. .

"ChuckB" wrote

It is my understanding that the level (feet) as measured by a USGS
gauge is not standardized (across many gauges). So the level on one
gauge on a river many not have anything to do with the level on
another gauge on the same river or a different river.

That's correct- the level is based on a somewhat arbitrary datum, thus "5
feet on the gauge" just means that the level is 5 ft. above the datum.
The
datum is tied to sea level, so you might have a datum of 0 at 800 ft.
above
sea level, so when the gage is at 5 ft., the water surface elevation is at
805 ft. MSL. 0 ft. does not equate to the stream bed either, in many (if
not most) cases.

Don't Post to This Thread
 

Mr. Tooley -

I'm not exactly sure what you are trying to say here. Are you implying
that I don't know what I'm talking about and I'm not in the position to
defend what goes on in my program? Because if that is the case, then
you are sadly mistaken. We have some very clear policies about how we
go about running our program that are firmly rooted in industry best
practice. Additionally, we spend an appropriate amount of time with our
staff training them to do the job we ask them to do.

My question was posted in good faith to gain some different perspectives
from the resources out there in the rec.boats.paddle newsgroup. I have
posted information in answer to questions there in the past and have
gained valuable information by posting questions to the newsgroup as well.

My question to you - What ARE you trying to suggest here?

Regards,

Eric Henkel

Mr. Henkel-

To be frank, given your non-ability to follow through on your original
question, I have to doubt your ability to accomplish your task. As far
as I can tell this post is nothing more than elaborate attempt to cover
your ass against educational administrators who have institutionalized
this trait.

You should either resign, or take responsibility for yourself, with all
the risks that entails.

You have today to try responding again. Elsewise I post your reply to
the newsgroup, with similar comments.

-Douglas Tooley

-----Original Message-----
From: Eric Henkel ]
Sent: Thursday, July 17, 2003 8:03 AM
To: D.L. Tooley
Subject: Thoughts on volume (CFS) and river levels and such (sort of
rambling)

Douglas -

Thanks for the answer. Unfortunately, it's the experiential thing
(learning by being on the river) that I can't use. I'm trying to
find a good explanation for folks in our administration and they
don't seem to want to take the time to go paddling (I don't know why
- doesn't make sense to me! :) )

Having been a raft guide on the Ocoee, I know that even 100 to 200
extra CFS can make a big difference in a river. However, I'm just
having a hard time translating to non-paddlers.

Thanks again,

Eric
--
__________________________________________________ _________
Nothing is more terrible than activity without insight.
-Thomas Carlyle
__________________________________________________ _________
Eric Henkel
Director, Poplar Ridge Experiential Learning and Training
Assistant Director of Outdoor Recreation
"Soon-to-be Daddy-O"
University of Virginia -- Department of Intramural Recreational Sports
450 Whitehead Road; PO Box 400317
Charlottesville, VA 22904-4317
Ph: 434-924-3791
Fax: 434-924-3858
http://www.virginia.edu/ims



D.L. wrote:

I've received a rather strange reply from the originator of this thread
which clarifies the real intent of the original, 'rambling' post. Although
the question is still good - the reason for it is intentionally misstated.

I've challenged the guy privately in response to his e-mail and I'll wait
for his response today before I post the rest.

But do take the warning that this guy is a risk to both his students and
perhaps even yourself.

-Douglas Tooley
"Felsenmeer" wrote in message
. ..


"ChuckB" wrote


It is my understanding that the level (feet) as measured by a USGS
gauge is not standardized (across many gauges). So the level on one
gauge on a river many not have anything to do with the level on
another gauge on the same river or a different river.


That's correct- the level is based on a somewhat arbitrary datum, thus "5
feet on the gauge" just means that the level is 5 ft. above the datum.


The


datum is tied to sea level, so you might have a datum of 0 at 800 ft.


above


sea level, so when the gage is at 5 ft., the water surface elevation is at
805 ft. MSL. 0 ft. does not equate to the stream bed either, in many (if
not most) cases.

Don't Post to This Thread
 

Your original post stated you were looking to explain things to your students. In your private letter you belittled my freely given response and let slip at least some of your original intent in your vague and poorly worded original inquiry.

I am aware that Outdoor recreation leaders have an unclear status on campus - somewhere above many staff members, but below most faculty. My empathy for the politics you suffer on campus, but you should either confront those problems or leave, not foist them off on others, especially your students.

My original, private request still stands. Please make your intent with this post completely clear.

The only thing that is personally attacking you is yourself, and it appears quite rightly. I am explicitly challenging your professional qualifications as a river guide, as an educator, and as a public employee based on this thread.

Would you like me to explain that to you again?

-Douglas Tooley
"Eric" wrote in message ...
Since you don't know me as an individual, please take the time to clarify your questions before making an accusation such as this one.

You have never been on any sort of river with me or worked with me in any of the programs that I have spent time at in my 10+ years in outdoor education and recreation.

I asked for simple information. I received some good answers. However, I now find myself being attacked on a personal and professional level for reasons with which I am not entirely clear.

If you have questions, please contact me personally and do not attack me in a public forum unless you can be sure of what you are saying.

Eric Henkel

D.L. wrote:

I've received a rather strange reply from the originator of this thread
which clarifies the real intent of the original, 'rambling' post. Although
the question is still good - the reason for it is intentionally misstated.

I've challenged the guy privately in response to his e-mail and I'll wait
for his response today before I post the rest.

But do take the warning that this guy is a risk to both his students and
perhaps even yourself.

-Douglas Tooley
"Felsenmeer" wrote in message
.. .
"ChuckB" wrote
It is my understanding that the level (feet) as measured by a USGS
gauge is not standardized (across many gauges). So the level on one
gauge on a river many not have anything to do with the level on
another gauge on the same river or a different river.
That's correct- the level is based on a somewhat arbitrary datum, thus "5
feet on the gauge" just means that the level is 5 ft. above the datum.
The
datum is tied to sea level, so you might have a datum of 0 at 800 ft.
above
sea level, so when the gage is at 5 ft., the water surface elevation is at
805 ft. MSL. 0 ft. does not equate to the stream bed either, in many (if
not most) cases.

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

My reply contained herein (and earlier in the changed thread as well -

BTW - this is cut from my original post -

"I have found myself spending a lot of time explaining river gauges and
river levels to a variety of people in our organization so they have
some idea about risk management."

I did not say that I was teaching a class or specifically say that I was
talking about students when I was actually looking for information
specifically for administrators.

D.L. wrote:

"Eric" wrote in message
...
Maybe I should stop trying to explain things to risk managers /


administrators and just go paddling instead! Which is what I plan to do
this weekend.



I thought you were asking us about your students. The answer for
bureaucrats in a legal/liability situation is adifferent kettle of fish.
Your attempt to hide your motivation only leads me to wonder what else you
are hiding. Did you have an injury on one of your trips?


No, there has not been an injury in our program. There has merely been
an ongoing effort within our organization to make sure that people on
all levels (participants, instructors, program directors,
administrators) have an understanding of what we do in our program and
why we make the decisions we do. This would prevent someone from making
a statement like "Oh, the river is only at 5 feet. That can't be too
deep - go ahead and paddle it." when they know nothing about
hydrodynamics. It's no different than me sitting in a weekly meeting
and asking questions about Automated External Defibrillators when it
does not have specific bearing on my program area.

It's basically a question about trying to find an easy way to explain
paddling issues to non-paddlers.

Combining stages would be meaningless. The CFSs, though, had better add
up,


unless it's raining or it's VERY, VERY dry.



Don't forget the groundwater part of the equation. Groundwater can either
add or subtract from flow levels and is a bigger factor than evaporation,
unless you have a major lake or reservoir. Groundwater tends to be a
seasonal factor. Here in the West where we receive most of our
precipitation in the Winter the cycle goes like this:

Fall Groundwater replenishes - decreased runoff
Winter Ground saturated - increased runoff - to snow level
Spring Ground saturated - increased runoff combined with snowmelt
Summer Groundwater runoff contribution gradually declines.

Groundwater is also affected by recent years precipitation and will be
decreased following a period of drought.

-Doug




Also makes sense here - although we had a drought last year, we have had
a much wetter spring than normal that has saturated the groundwater
table. Thus, when we have some of the violent thunderstorms or remnants
of tropical storms that roll through Virginia, water levels can elevate
rather quickly.

Eric

Thoughts on volume (CFS) and river levels and such (sort of rambling)
 

Thank you, Mr. Kanubic Travesty, this is the sort of answer that I was
looking for when I posed my "poorly-worded" question. Your reply was
certainly well put together and I hope other folks benefit as well. I
also appreciate the other replies that have been posted.

Oci-One Kanubi wrote:

Alright, Eric; here are some more monkey wrenches in yer werks, but
let me say the most important thing first: go out and buy Roger
Corbett's "Virginia Whitewater". Difficulty ratings, as you know, are
subjective (and I think Corbett overrates by about 1.5 classes) but
Roger's ratings are absolutely consistent. Roger was also an expert
amateur hydrologist, and I think you might find some good layman's
hydrology in his book, though I don't really remember for sure. Okay,
now:

You know that level (known to the USGS as "stage") is, for our
practical purposes, based upon an arbitrary zero, and that the river
can only be said to be "low" or "high" with reference to actual
experience. Over time, with experience on a given river at various
stages, a paddler can make his determination as to what stages are
"low" and what stages are "high". Of course, this is subjective and
will vary with the type of craft being paddled and with the skill of
the paddler. So, anyone you explain this to will need to understand
that difficulty as a function of stage is different for every river,
and can only be determined by direct experience (though, as we shall
see, there are some good predictive indicators).

Next, you know that volume, or "flow", is NOT arbitrary, and that
conclusions drawn from volume on one river may help you predict the
difficulty of another. But volume is only actually measured when it
originates with a dam release. On the James, for example, volume at
each gauging station is calculated as a function of the stage. The
parameters of this calculation are (1) stage, which is measured
directly, (2) cross-section, which was surveyed some time in the past,
and (3) velocity, which was measured at some time in the past at
different points on the cross-section. From cross-section at stage
(in square feet) and average velocity at stage (in feet per second) a
table was generated that shows cubic feet per second by stage.

UNFORTUNATELY (for gauging purposes) the river is not a static entity;
it changes. The cross section changes, bars (ephemeral natural dams)
build up and wash away, the bottom may change as sand, pebbles, or
cobbles are deposited or removed. A result of this is the phenomenon
of a paddler saying, "yuh know, I'm really getting better; this used
to be very difficult for me at 5.2'," or "geez, I'm getting old; this
used to be really easy at 2.8'." Well, maybe. But quite often, as
the riverbed changes, a given stage reflects a greater or lesser
volume than it once did, and difficulty is more rightly a function of
volume than of stage. Because flow is not measured, but calculated
from stage, these changes are not necessarily obvious to a paddler who
doesn't know the river intimately.

Another result of this is that, in yer case, for e.g., the Maury, or
the Buffalo, or the Tye may have changed its bed so that for a given
measured stage it is delivering a very different volume, whereas the
reverbed at the gauge below the confluence has NOT changed, so THAT
gauge continues to report flow very accurately. Hence (beyond the
water travel-time, groundwater seepage, ungauged tributary, etc.,
issues mentioned by others), there is oftentimes a disjunct between a
reported volume on the main stem and the sum of the reported volumes
on the tributaries.

Okay, so that is a major caveat wrt volume, or flow. Nevertheless, in
the short term, we as paddlers can use reported flow the same way we
use reported stage based upon an arbitrary datum. It doesn't really
matter (on a given river) if the USGS reports a flow of 700 cfs when
the actual flow is 1,000 and reports a flow of 1,000 when the actual
is 1,500, as long as we, from our experience, know that we can be
comfortable at (a reported) 700 but not at (a reported) 1,000.

But, beyond that, it is also fairly safe to say that the reported flow
is rarely GROSSLY misstated at the levels we normally boat -- i.e.,
above boating zero and below flood stage. If the reported volume is
approximately in the right ballpark, we can use our experience on one
river to make some reasonable assumptions about a river we have never
seen. But volume alone is never enough. The next most important
factor (in my personal view) is gradient. As volume goes up,
difficulty goes up, and as gradient goes up, difficulty goes up.
Thus, the Upper Yough at 600 cfs is approximately the difficulty of
the Upper Gauley at 2800 cfs, because the gradient of the Yough is so
much greater. The next most important factors in difficulty are
probably streambed width and morphology. The effects of streambed
width can be seen on various rivers with a rapid named "The Narrows".
Volume and gradient may be the same as the wider spots above and
below, but the difficulty increases in the narrows. Likewise is
morphology an issue: a river with constant gradient and few surface
rocks is usually a lot easier (though sometimes a more dangerous place
to swim) than a pool-drop river with complicated technical rapids,
other things (volume, gradient, width) being the same.

The upshot of this is, you can make some predictions about the
difficulty of an unfamiliar river based upon (reported approximate)
volume and measured gradient, compared to familiar rivers of similar
volume and gradient, and you can make even better predictions if you
have been able to learn something about the bed-width and morphology
ot the unfamiliar river. You also ought to look at Monte Smith's book
("Southeastern Whitewater", I think it is called, for an excellent
discussion of these four, and several other, factors that affect the
difficulty of a river.

Finally, however, there is the matter of more-or-less permanent
dangerous features; undercuts and boulder sieves, for e.g., which are
entirely independent of volume, gradient, or bed-width, though they
are obviously a function of morphology. These can sometimes be
discovered by low-water scouting, but are usually only known through
paddler lore - experience passed on from one boater to another.

The upshot is, you can explain it as well as you can to non-boaters,
but river difficulty- and danger-assessment is highly subjective,
dependant upon a number of inter-related attributes of the river, of
the boat, and of the boater, highly variable with weather, and has
never been subjected to rigorous analysis (I mean, 300 million
Americans are interested in the weather, and that has not yet yielded
to rigorous analysis, so who's gonna solve an equally difficult
problem for 15,000 whitewater boaters?) The judgment of a trusted
experienced paddler who knows yer skill level and that of yer group,
is still yer best tool for river safety.

Dunno if this is what you were looking for, exactly...

--
-Richard, His Kanubic Travesty

PS, ignore Tooley; he's cranky (i.e., he's not always a crank, but
sometimes...)

================================================= =====================
Richard Hopley, Winston-Salem, NC, USA
rhopley[at]earthlink[dot]net 1-301-775-0471
Nothing really matters except Boats, Sex, and Rock'n'Roll.
rhople[at]wfubmc[dot]edu 1-336-713-5077
OK, OK; computer programming for scientific research also matters.
================================================= =====================