YOUR OXBOW
INCIDENT
This earthcache will take you to a double
Oxbow, a type of Meander on the Eel River in Northeast Indiana. The
Eel's source is a bog southeast of Ft. Wayne and its mouth is at
the Wabash River at Logansport, Indiana.
The Eel River is a
meandering tributary of the Wabash, with Double Oxbow loops at S.
Whitley and N. Manchester, a triple oxbow at Liberty Mills, and
many greater or lesser single oxbows.
These bends in a river were popular spots for Indian
Villages, as they afforded protection from attack on three
sides.
A Meander is a bend in a river, also known as an oxbow loop.
A stream or river flowing through a wide valley or flat plain will
tend to form a meandering stream course as it alternatively erodes
and deposits sediments along its course. The result is a snaking
pattern as the stream meanders back and forth across its
floodplain.
Erosion is greater on the outside of the bend where water
velocity is greatest. Helicoidal (corkscrew like) swirls along the
outside of the bends increase the erosion effect. Sediment deposits
occur on the inside of the bend where flow rate is much slower.
This tends to increase the length of the bend.
Formation of
Meanders
Geographers have been unable to agree on the exact reason
that meanders form, however the formation of meanders is linked to
the existence of pool-riffle sequences where meanders form. The
existence of helicoidal flow in increasing the amount of erosion
occurring on the outside of a bend also plays a part in meander
formation.
One theory of meander development is that the formation of
sandbars causes the river to meander. Erosion is greater on the
outside of the bend where velocity is greatest. Deposition of
sediment occurs on the inner edge because the river, moving slowly,
cannot carry its sediment load, creating a slip-off slope. The
faster moving current on the outside bend has more erosive ability
and the meander tends to grow in the direction of the outside bend,
forming a river cliff.
The term Meander derives from the river known to the ancient
Greeks as the Maiandros, characterized by a very convoluted path.
As such, early usage of the term referred to convoluted and windy
speech and ideas, as well as the geomorphologic feature. The
Meander River is located in present-day Turkey, near the ancient
Greek town of Miletus. It is known in Turkey as the Menderes
River.
Meander ratio
Meander ratio is a means of quantifying how much a river or
stream meanders (how much its course deviates from the shortest
possible path). It is calculated as the length of the stream
divided by the length of the valley. A perfectly straight river
would have a meander ratio of 1 (it would be the same length as its
valley), while the higher this ratio is above 1, the more the river
meanders.
Sinuosity Index is the measure of meandering of a stream.
When the index is between 1 to 1.3 the river is Sinuous but if the
sinuosity index is greater than 1.3 then the river is said to be
Meandering.
In order to log this cache you
must:
1. Post a photo of your face at the
coordinates, with your GPSr, with the river in the background.
2. Email the owner with this information: What is your estimate of
the width of the river and the height of the nearside bank at this
location and did you detect any evidence of sandbars
present?
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