--- In
BoundaryPoint@yahoogroups.com, Michael Kaufman
<mikekaufman79@y...> wrote:
> From the specific to the general...
> Normally, when there is accretion, that deposited land
> becomes part of the territory to which it is
> deposited. If significant accretion causes a change
> in the riverbed, then the border will move, following
> either the median line or the thalweg.
it might also follow a high or low water line on a bank for example
it all depends of course on how the border has been defined
If there is an
> avulsion, the border will not change and remains where
> the old channel was.
we recently saw a surprising exception even to this eternal verity
in message 14510
but again of course only because it was specially defined that way
> I am getting this from:
> http://www.mhhe.com/earthsci/geology/mcconnell/streams/channel.htm
> http://www.nebraskasurveyor.com/rip-bnd.html
> So borders will generally move by accretion, but not
> by avulsion. Any other exceptions worldwide?
>
> --- "Lowell G. McManus" <mcmanus71496@m...> wrote:
> > 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@y...>
> > 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@m...>
> > wrote:
> > > > Michael,
> > > >
> > > > See my insertions below.
> > > >
> > > > Lowell G. McManus
> > > > Leesville, Louisiana, USA
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Michael Kaufman"
> > <mikekaufman79@y...>
> > > > 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@m...>
> > > > 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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