This earthcache adventure will take you on a
journey along Duck Creek in Bettendorf, Iowa. On your travels I
will introduce you to a water feature called meandering. Duck Creek
travels through the city Bettendorf without much notice by the
general public on the path it follows and why.
A meander in general is a bend in a sinuous
watercourse, also known as an oxbow loop, or simply an oxbow. A
meander is formed when the moving water in a river erodes the outer
banks and widens its valley. A stream of any volume may assume a
meandering course, alternatively eroding sediments from the outside
of a bend and depositing them on the inside. The result is a
snaking pattern as the stream meanders back and forth across its
axis. Over time meanders migrate downstream, sometimes in such a
short time as to create civil engineering problems for local
municipalities attempting to maintain stable roads and bridges.
Heavy erosion of the banks can be seen along the path of Duck
Creek.
The meander ratio or sinuosity index 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.
The channel sinuosity index is the channel
length (displayed in red on the map) divided by the valley length
(displayed in yellow on the map) and are calculated from a map or
from an aerial as shown in the picture of Duck Creek. Sinuosity
Index has a non-mathematical utility were rivers and streams can be
placed in categories; for example, when the index displays a ratio
of 1 to 1.4 the river or stream is sinuous, but if the ratio is 1.5
and 4, then the river or stream is meandering.
As shown the aerial photograph below, the
straight line distance (in yellow) between points 1 & 2 is 0.32
miles, while the channel distance (in red) is 0.82 miles giving us
a ratio of 2.56 moving to the East. Also displayed in the aerial
photograph, the straight line distance (in yellow) between points 2
& 3 is 0.52 miles, while the channel distance (in red) is 0.88
miles giving us a ration of 1.69 moving to the West. Remember that
a ratio of only 1.5 is needed to be classified as meandering.
There is plenty of parking near point 1. You
may chose to walk the path that follows Duck Creek as it meanders
through town, or you may also access the points by driving. Either
way the distance is about 1.7 mile one way. All points are handicap
accessible
Please read these carefully:
To receive credit for this Earthcache, you
must complete the following requirements and e-mail me the answers
through my Geocaching profile.
Do not post your answers in your log entry. In
addition you must post the required pictures when you log you find
or your entry will be deleted.
Start at point 1 (N41 32.551 W90 30.070) - (1)
Post a photo with your log showing you and your GPSr with the mile
post and Duck Creek in the background (ensure the number on the
post is not visible in the picture). (2) What is the number on the
post at this location?
At point 2 (N41 32.606 W90 30.670) - (1) How
wide is Duck Creek at this location? (the measurement can be taken
easily from the bridge).
At point 3 (N41 32.714 W90 31.017) - (1) Post
a photo with your log showing you with the Duck Creek rapids in the
background. (2) Tell me the type of soil you are standing in at
this location. (3) What is the creek bed lined with at this
location.
FTF goes to S10, Congratulations ! ! !