Michael,
The 1970 treaty provided for several artificial channel relocations and the
placement of the boundary into their specified middle lines upon their
completion. It also says that the boundary moves with the middle of the
accreting main channel in the natural segments, each state being entitled to
efforts to stabilize its banks. If the river moves by avulsion, the boundary
also moves, subject to a three-year delay for the losing state to exercise the
option or restoring the boundary to the original channel at its expense. If the
land lost is more than 250 hectares or has more than 100 residents, the boundary
stays put permanently, and it is the duty of both governments to restore the
river to the former channel at their joint expense. Prior to the 1970 treaty,
changes by accretion and avulsion were handled quite differently, although the
pertinent documents are not on-line.
Only the USGS can explain why it maps the way it maps. As to the map in
question, I suspect that they show the most recent river locations and have
applied the specified boundary in the new artificial channel. They appear not
to have revised the boundary shown in the neighboring natural channel, even on
the new portion of the map. Note that neither have they revised their contours.
In the natural channel just upstream from the large arc, they show the boundary
touching the Mexican bank and the 100-foot contour is in the middle of the
river! Apparently, they have revised the river throughout and the boundary in
the artificial channel, but not the boundary in the natural channels nor the
contours.
The IBWC makes a fresh map of the evolving boundary at least every ten years
(drawn onto aerial photos). I suspect that their schedule is out of sync with
the USGS's map revision schedule, and the USGS is loathe to move its depiction
of a boundary without authority on paper from the IBWC, even though their own
aerial photos show that the river has evolved.
Lowell G. McManus
Leesville, Louisiana, USA
----- Original Message -----
From: "Michael Kaufman" <mikekaufman79@...>
To: <BoundaryPoint@yahoogroups.com>
Sent: Friday, July 16, 2004 12:33 AM
Subject: Re: [BoundaryPoint] world class border arc census was Re: real bjneng
try afoot
> Ok thanks.
> In http://tinyurl.com/5ppgp how come the border hits
> both river banks? Isn't it supposed to be the median
> line in the river?
> Also in the same map, if you pan NE you can see an old
> map with the 2 meanders (and the border running
> through them). Here also the border is not in the
> middle of the river. In fact there it ran on land in
> one part. I CAN understand this (avulsions,
> accretions would NOT affect the border normally,
> right?).
> But this brings me back to my first question - where
> the current border hits the banks - didn't the 1970
> treaty make it so it was the median line even if the
> river moved? (Or am I not understanding this
> correctly?)
> -Mike
>
>
> --- "Lowell G. McManus" <mcmanus71496@...> wrote:
> > Michael,
> >
> > See my insertions below.
> >
> > Lowell G. McManus
> > Leesville, Louisiana, USA
> >
> >
> > ----- Original Message -----
> > From: "Michael Kaufman" <mikekaufman79@...>
> > To: <BoundaryPoint@yahoogroups.com>
> > Sent: Wednesday, July 14, 2004 10:55 PM
> > Subject: Re: [BoundaryPoint] world class border arc
> > census was Re: real bjneng
> > try afoot
> >
> >
> > > Thanks for these maps:
> > > For 1. Is the arc the one which faces north with
> > the
> > > "HUA" of CHIHUAHUA under it and the "S" of TEXAS
> > above
> > > it? Or the tighter one facing south just to the
> > right
> > > of it? Or the real wide one facing northeast to
> > the
> > > right of that?
> >
> > The arc in this map ( http://tinyurl.com/6msfp ) is
> > the really wide curve. The
> > others are bends in the natural channel above the
> > beginning of the artificial
> > channel. There is a short tangent stitch in the
> > artificial channel connecting
> > the natural channel to the beginning of the wide
> > arc. After making the arc, the
> > artificial channel enters a very long tangent for
> > over five miles. The former
> > natural channel is represented on this map by the
> > line that wanders away to the
> > lower left.
> >
> > > 2. Arc is the wide curve facing WSW where the
> > other
> > > stream comes in?
> >
> > Yes. In this map ( http://tinyurl.com/6u56h ), the
> > arc comes at the end of the
> > very long tangent mentioned above. The other stream
> > coming in is the old
> > channel. Notice how it formerly crossed the middle
> > of the arc. After the arc,
> > there is another short tangent before this segment
> > of the relocation ends as the
> > river resumes its natural channel.
> >
> > > 3. Arc faces NNE to the right of "CO" of PRESIDIO
> > CO?
> > > Or facing S/SSW just below BM 252?
> >
> > The former. Between arcs 2 and 3, the river has
> > occupied its natural channel
> > between the cities of Presidio and Ojinaga. Just
> > below the highway bridge, it
> > enters a tangent artificial channel of approximately
> > 1.25 miles without any
> > transitional arc. Then, in this map (
> > http://tinyurl.com/6qgrl ), that tangent
> > ends with a transitional arc back to the natural
> > channel just above the railroad
> > bridge. The curve near the benchmark is a natural
> > bend. There are two more
> > tangent artificial channels in the area below the
> > railroad bridge, but they are
> > without transitional arcs.
> >
> > > 4. I remember seeing this before - the 1/4 circle
> > > facing SE.
> >
> > Yes. At http://tinyurl.com/5ppgp , you can see the
> > natural channel making a
> > large meander off to the northwest of this arc. It
> > makes another large meander
> > to the north of the artificial tangent just below
> > the arc. The relocation here
> > eliminated both meanders in the river and boundary.
> >
> > > Also - Is Beaver Island somewhere in this
> > vicinity?
> > > Is this still an island (if it is in the area, did
> > > rechannelization have an effect?)?
> >
> > The "Beaver Island" tract that was transferred to
> > Mexico in the 1970 treaty was
> > located near Roma-Los Saenz, Texas (about 48 air
> > miles upriver from the fourth
> > arc above). It was where the word "Tamaulipas" now
> > appears on the map at
> > http://tinyurl.com/54zcp . It was a rather squarish
> > piece of the USA had been
> > been orphaned high-and-dry on the southern side of
> > the river by a much earlier
> > avulsion. This tract and the more contentious
> > Horcón tract, on which part of
> > the town of Río Rico had unwittingly developed
> > (about 26 air miles downriver
> > from the fourth arc above) were transferred to
> > Mexico in exchange for the two
> > meanders gained by the USA at the artificial fourth
> > arc. No channel relocations
> > were necessary for the transfer of the Beaver Island
> > and Horcón tracts because
> > both were already on the southern side of the
> > existing river. The island within
> > the river that is visible on the map belongs to the
> > USA.
> >
> > > -Mike
> > >
> > >
> > > --- "Lowell G. McManus" <mcmanus71496@...>
> > wrote:
> > > > The maps from the MXUS Treaty of 1970 showing
> > four
> > > > arcs are at a scale of
> > > > 1:20,000 on three long sheets, each about one
> > foot
> > > > by three feet. They are
> > > > black-and-white aerial photos with the
> > boundaries
> > > > through both the old channels
> > > > (shown by lines between numbered traverse
> > points)
> > > > and the projected relocated
> > > > channels plotted onto them.
> > > >
> > > > I can scan pertinent portions of these maps for
> > you
> > > > on request. Meanwhile, here
> > > > are links to view the arcs on USGS topo maps
> > showing
> > > > the arcs in the relocated
> > > > channels.
> > > >
> > > > There are three arcs in the Presidio/Ojinaga
> > area:
> > > > Curve No. 1: http://tinyurl.com/6msfp
> > > > Curve No. 2: http://tinyurl.com/6u56h
> > > > Curve No. 3: http://tinyurl.com/6qgrl
> > > >
> > > > The fourth is above Hidalgo/Reynosa:
> > > > http://tinyurl.com/5ppgp
> >
> > > >
> > > > Lowell G. McManus
> > > > Leesville, Louisiana, USA
> >
>
>
>
>
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