|
|
|
|
|||||
|
||||||
From: George Huxtable (no email)
Date: Wed Dec 03 2003 - 18:45:24 EST
Frank Reed said-
>The Mississippi from Cairo north to St. Louis and beyond is entrenched.
>That means its course is stable on a time scale of centuries. South of Cairo,
>the river (before the USACE projects of the 20th century) used to whip back and
>forth cutting new channels and cutting off meander bends at an astounding
>rate. Similarly, there are stretches of the Missouri that are completely
>stable on
>a historical time scale and one large section (from Kansas City to the Dakota
>border, IIRC) that meandered significantly during the past 200 years.
That's useful information to me. It confirms my own findings that Lewis and
Clark's astronomical positions generally correspond well with their
descriptions of where they were, in relation to the settlements and
landmarks along their route, North from Cairo toward St Louis. Mark Twain
describes this section as rocky, and this is also clear from the L&C
journals. I would expect the unstable meanders to occur in the flatter
country.
However, there must have been at least one instability in the St
Louis-Cairo section. According to Gary Moulton, editor of the 13-vol L&C
journals, the Mississippi has, since L&C's time, captured and taken over
the lower stretch of the Kaskasia River, to form a large island. My Times
Atlas of 1957 shows at Kaskaskia a large chunk of Illinois territory on the
Missouri side of the river. I've seen a more recent map in which the river
seems to be back where it was: perhaps due to revetment work in the
interim.
=======================
>3) There is a mapping coverage available at various places on the net
>(including USGS) that shows details of most of the Missouri River in its
>meandering
>sections as of about 1890. There's next to nothing available before then.
=======================
There exists useful mapping from the University of Missouri which covers
all the campsites used by L&C, starting from Cairo, showing an
interpretation of L&Cs track and observation points. It provides "historic
hydrography" of the river, with a modern map superimposed (but not lat and
long). I haven't made a study of this mapping, yet. The first map, of the
Cairo junction, which is where they arrived on 14 Nov 1803, is at-
http://lewisclark.geog.missouri.edu/campsites/1804/nov14camp.shtml
(In that address, the "1804" looks wrong, but isn't. It's actually a
contraction for the navigation season that each map series covers, in this
case 1803-1804.)
Clark drew a map of the river junction at Cairo, which is given in Moulton
vol. 2 as fig.1, and I must say it differs significantly from the "historic
hydrography" of that website map.
=======================
Thanks to list members for useful pointers to web mapping. However, I'm one
of those old-fashioned souls who greatly enjoys reading a well-printed map
on a nice big fold-up sheet of paper. It's nearly as good as actually being
there. I wonder how many others feel the same way.
George.
================================================================
contact George Huxtable by email at , by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
================================================================
|