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B. Geology
Formation of
Darby
Creeks
The Darby
Creeks
were formed by the melting of the glaciers.
The Creeks flowed as a braided stream from the large amount of glacial
melt water. Braided streams
typically transport a large amount of sediment and form shallow and wide stream
channels. During each of the three
glacial retreats the
Darby
Creeks
were actively transporting a large amount of debris.
The glacial debris was suspended in the stream as it flowed away from the
ice but the debris was dropped as the stream lost velocity.
This material, referred to as outwash, consists of poorly compacted sand
and gravel and forms the broad, flat plains adjacent to the streams.
As the melt water stopped, the
Darby
Creeks
became entrenched in single channels and began active erosion of the newly
deposited glacial material or outwash. The
erosion of the streams ultimately formed the high-level terraces that are
present along the creeks especially south of US Route 40.
The present day flood plains of the
Darby
Creeks
represent the former width of the braided streams during the melting of the
glaciers (Brockman, Personal Communication, 2003).
Big Darby
The
Big
Darby
Creek
was formed by the melting of the glacial retreats.
The final glacial retreat formed the Powell Moraine which directed the
flow of melt water along its front edge (See Map
3). The melt water
followed a path that forms the present day course of the
Big
Darby
Creek
through
Union
County
. The Big Darby Creek followed the
front edge of the Powell Moraine until it reached the present day area of Plain
City and ran into a slightly higher area which was enough to divert the stream
flow south (Brockman, Personal Communication, 2003).
Little
Darby
Creek
The headwaters of the Little Darby
Creek began within the Cable Moraine Complex.
As water was melting from the glacier, it was directed toward present day
Mechanicsburg but glacial ice forced the water to drain towards the
Miami
River Basin
. Once the ice melted the water was
then able to follow the present day topography and drain into the Darby
Watershed (Brockman, Personal Communication, 2003).
   
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