NEMADJI RIVER EarthCache
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Difficulty:
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Terrain:
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Size: 
(other)
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The Nemadji River and its tributaries flow through Minnesota and
Wisconsin, draining approximately 433 square miles. Approximately
40% of the drainage basin is in Wisconsin. According to the
Carlton, MN Soil and Water Conservation District (CSWCD),
approximately 192,000 acres of the land is forested, or 69% of the
watershed, with 53% of forested land consisting of deciduous trees
greater than 45 years old.
Approximately one third of the basin is comprised of glacial till
and glacial lake-laid clay soils. These soils are commonly referred
to as "red clay" and were formed during the last glaciation of the
area some 10,000 years ago. Red clay is considered highly erodible
and is prone to extensive mass wasting through "slumping" along
streams and tributaries. The upland two thirds of the basin is
sandy and loamy tills and glacial outwash. These soils are
generally sandier and much less erodible than red clay.
The Nemadji River is famous for its turbid, clay-filled water.
About 33% of the river’s basin is covered in red clay,
sometimes up to 200 feet thick; this layer was deposited during a
geologic period when glacial lakes covered the region (CSWCD).
Though red clay erosion is natural, human activities on the land in
the last century have accelerated the natural process, and the
river has cut deep valleys into the surrounding bluffs. According
to the Natural Resources Conservation Service (NRCS), movement of
soil material downhill due to gravity (slumping) is severe. Nearly
90% of the fine sediment in the river is due to bluff erosion and
slumping, and 74% of this sediment ultimately ends up in Lake
Superior (CSWCD).
The major human activities that have had a significant impact on
the hydrology of the Nemadji River basin are the early logging
practices dating back to the mid 1800s. Logging converted forest to
permanent agriculture, streams were cleared to efficiently
transport logs to the sawmills,, and roads and railroads cut
through the basin. This all led to efficient hydrologic pathways
for water to get to the river quickly (Nemadji River Basin
Project). While approximately 70% percent of the watershed is now
reforested, the deciduous trees adjacent to streams may not be an
effective sediment filter, or may not form a sturdy enough root
system to hold soils in place. Many red clay slumps in the
watershed move downhill despite tree cover, likely due to shallow
groundwater movement beneath the root zone. The riparian areas
along the stream vary dramatically in width and quality
(NRCS).
You must email me the answers to these questions to post a "FIND"
for this cache. You may also post a picture of yourself at the
posted coordinates with the Nemadjii River behind you.
1. At the posted coordinates, take a sample with your hands. What
do you have?
A. Clay
B. Sandy Loam
C. Sand
Hint: you can determine what you have in your hand by rolling
it.
2. After you complete question one, go to these coordinates:
N 46 41.612
W 092 02.247
Now, take another sample from this site and ask yourself, "What
type of soil is this?"
3. Which area, #1 or #2 has greater amount of slumping and
why?
4. [OPTIONAL] if you choose, you can take a picture of
yourself/team with the Nemadjii River in the background while
holding your GPSr in the picture.
Email me your answers here:
I am a proud member of:
Resources:
http://www.ci.superior.wi.us/index.aspx?NID=365
http://en.wikipedia.org/wiki/Nemadji_River
http://www.glc.org/tributary/models/nemadji.html
Additional Hints
(No hints available.)