NANFA-L-- Todd's Floodplain Physics Lesson

Gerald Pottern (
Fri, 14 Jul 2006 13:40:04 -0700 (PDT)

Hi Todd -- can you please explain further the physics
behind your statement below, why pools on a floodplain
drain away SLOWER after a channel has become incised ?
I dont understand how/why this would occur, unless
there's also some soil compaction going on as a result
of channel incision. The capillary action/ water
continuum thing is especially mystifying. Does
channel incision cause air voids in the soil that
inhibit water percolation or something like that ?

--Gerald, hangin on the Neuse

>> Todd Crail wrote:

What it sounds like (if it were here in OH, MI, IN) is
that you had hydrologically connected wetland features
on the historic floodplain, but the high to peak
discharge of the stream has downcut material from the
river channel so that the base flow channel of the
stream is _far_ below the watertable. This forces the
water to drip off the old floodplain (and sit fetid
with'skeeters that everyone whines about), rather than
pull via capillary action through the soils back into
the river (water is a continuum when connected, and
this water would "disappear" much more quickly if the
channel wasn't whacked, ...
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