Only Once Every 200 Years
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Through this Earthcache, you will investigate the South Fork Zumbro
River-Bear Creek Confluence occurring at Mayo Memorial Park just
North of the 4th Street SE Bridge in Rochester as well as learn
about Rochester’s Flood Control Project. This area is among one of
three confluences enhanced by the Flood Control Project within
Rochester City Limits.
First…a little basic background info about river
systems
Confluence:
-In geographical terms, this is used to describe the meeting of two
or more bodies of water. It commonly refers to the point where a
smaller body of water (called a tributary) joins with a more major
body of water (called a Main Stem). In this case, the confluence of
the South Fork Zumbro River and Bear Creek may not be a major
confluence of world-wide recognition…but, in my opinion, it is the
most impressive of the three in town (the other two confluences
with the South Fork Zumbro River include Silver Creek and Cascade
Creek). Though the confluence itself isn’t much to talk about on a
world scale…the surrounding Flood Control Project has been the
focus of Midwest Regional Interest for many communities along
similar river systems.
Tributary:
-As stated above, this term refers to a smaller body of water that
flows into a Main Stem (more major body of water). It is important
to note that tributaries do not flow directly into a sea…they serve
(along with the Main Stem) to drain the surrounding drainage basin
(the area of land where rain and melting snow drains into a body of
water).
River:
-Refers to the natural course of water, commonly freshwater,
flowing toward a lake, ocean, sea, or another river. As can be seen
on many maps, there are several other names commonly used; stream,
creek, brook…etc, but is important to note that there is no general
rule that defines what can or should be called a river. Use of
certain names varies from region to region and from one community
to the next.
River
Classifications:
Keep in mind, that though these classes are useful for visualizing
rivers, there are many other factors at work that effect rivers
(local climate, geology and surrounding communities).
Youthful River: A river with a steep
slope that has very few tributaries and flows relatively quickly.
Its channels tend to erode deeper rather than wider.
Mature River: A river with a slope
that is less steep than those of youthful rivers and flows more
slowly. A mature river is fed by many tributaries and has more
discharge than a youthful river. Its channels tend to erode wider
rather than deeper.
Old River: A river with a low slope
and low erosive capabilities. Old rivers are characterized by flood
plains.
Rejuvenated River: A river with a
slope that was raised by tectonic uplift.
Now…onto the subject matter
About these two bodies of
water:
Some of you may be wondering “Why does he keep referring to this as
the South Fork Zumbro River???” Well, the answer is… Though we
commonly refer to this part of the river in Rochester as the Zumbro
River…it is actually the South Fork Zumbro River (only a mere part
of the “actual” Zumbro River). As you may have guessed, though the
Zumbro River has its own tributaries, it is indeed a tributary of
the Mississippi River. The Zumbro River “technically” starts with
the confluence of its principle tributaries (near Zumbro Falls)
with a drainage basin of 1,428 square miles and a river length of
about 50 miles. As the South Fork Zumbro River flows North through
Rochester (and Olmsted County) it collects the Middle Fork Zumbro
River at Zumbro Lake. The river continues Northward into Wabasha
County collecting the North Fork Zumbro River about 3 and a half
miles out of Zumbro Falls (as the crow flies…not a the river
flows). From this point on, until it drains into the Mississippi
River, it is correctly called the Zumbro River. It is at this point
that it turns NorthEast and drains into the Mississippi River just
to the East of Kellogg.
But, enough about the Zumbro itself…this confluence (South Fork
Zumbro River & Bear Creek) lies among Rochester’s Flood Control
Project. The Flood Control Project focused on the South Fork Zumbro
River and two of its tributaries (Bear Creek and Cascade Creek).
The project was designed and constructed in partnership with the
Natural Resources Conservation Service. The project included 5.7
miles of riprap-lined channel (rock or other material used to
protect shoreline from erosion), .7 milies of architecturally
treated concrete channel, .5 miles of dredged channels, 3 drop
structures and 1.3 miles of levees as well as other recreational
use features.
One of the main, and most recognized recreational use features that
fewer and fewer Rochester residents know about (in regards to its
connection with the Flood Control Project) is Chester Woods Park
and its man-made lake. The man-made lake is what gives Bear Creek
much of its own life and personality. The Chester Woods Lake lies
at the headwaters of Bear Creek and serves as a water reservoir in
the area to help control seasonal flooding. Ironically enough, Bear
Creek was the focus of localized floods in August of 2007 when
areas of SE Minnesota received up to 17 inches of rain in a 24hr
period. With that being said, the Flood Control Project served its
purpose and helped protect much of Rochester, its Buildings and its
people.
Much of the South Fork Zumbro River through Rochester is lined with
concrete and steel to further protect the banks of the river as
well as the city of Rochester. The major changes of this part of
the river included widening and deepening the existing river
channel to further expand the River’s capacity to handle rising
waters. Though the project is considered complete, one area still
being worked on (in reference to bodies of water related to the
Flood Control Project) is Cascade Creek near the intersection of
Highway 52, Highway 14 & Civic Center Driver. This area was
effected by localized street flooding during the August 2007
Floods. Due to much of the work completed on the Flood Control
Project, much of the South Fork Zumbro River remained unchanged
with little to no effect on local neighborhoods. Any damage/bank
erosion on Bear Creek was limited to areas not improved by the
Project…but damage was fairly minimal when compared to other local
communities…thanks in part to the expanded capacity of the South
Fork Zumbro River and Bear Creek in the Rochester City
Limits.
Last, but certainly not least…since I do have an interest in
numbers…some of you may also find it interesting to know that due
to the Flood Control Project; there is a mere .5 percent chance of
flooding annually. For those that prefer the media catch
phrases…this translates to one of those possibilities of a 200-year
flood scenario!!!
Fiscal Cost:
Federal: $67,908,00
Non-Federal: $24,818,000
Total: $92,726,000
Why the worries about
flooding???
Simple answer: Most of Rochester finds itself at the lowest point
in the localized drainage system of creeks and rivers that have
eroded into the various bedrock formations to form the surrounding
basin. To help you understand the complexity of the drainage system
that surrounds Rochester…
The South Fork Zumbro River is the only major water feature in the
immediate area that eventually flows away from Rochester due, in
part, to the limestone plateau that surrounds Rochester on all but
its west, northwest and north sides. The creeks and their
tributaries that feed in the South Fork Zumbro all drain towards
Rochester and account for seven different watersheds that almost
all converge at or very near the center of Rochester. These various
creeks and streams have eroded into (and in some cases through) the
sedimentary rock connecting the upper limestone plateau to the
lower basin creating many of the hills and valleys seen in the
immediate area.
The watersheds feeding the South Fork Zumbro River in Rochester are
Bear Creek, Cascade Creek, King’s Run, Silver Creek, Mayo Run,
Hadley Creek and Willow Creek (many of which have city parks named
after them…which should give you a general idea of where these
watersheds are located). Ok, one may be asking themselves; “How bad
can it be, they are only creeks and streams?” Well, of the roughly
10 miles of the South Fork Zumbro River that runs through
Rochester, those 10 miles are fed by approximately 198 miles worth
of tributary creek flow…most of which occurs within a six miles
radius of Rochester!!! As more water flows into Rochester through
this tributary system, it only cuts deeper and further into the
local bedrock ensuring water will continually flow into
Rochester…and the only way out of Rochester is through the South
Fork Zumbro River.
Thus the need for Rochester to develop its Flood Control Plan to
deal with the surrounding landscape.
To receive credit for this Earthcache, you must
answer the following questions:
1) Determine the Flow Rate of Bear Creek and the South Fork
Zumbro River (in Feet per Second) near the coordinates listed
above.
-This can be done by measuring a distance along each of the
different bodies of water, then tossing a stick or twig upriver
from your starting point. With a stopwatch, time how long it takes
your stick or twig to complete the measured distance. Then use that
to calculate that into Feet per Second for each river (yes…you have
to do this twice…once for each body of water)
2) Measure the width of each river near the
confluence.
-This can be done by using your GPSr by marking coordinates on each
side of the rivers (yes…you have to do this twice…once for each
body of water)
3) Referring to the River Classifications above…decide if
the Zumbro River is a Youthful, Mature, Old or Rejuvenated River.
Please explain why you feel the way you do about your answer.
Please log your find as you email me the answers to the above
questions…I will contact you if there are any issues.
Note: The first question may be difficult when the rivers are
frozen over in the winter…so please complete only questions 2 and 3
during such times. Be aware…that I drive by this location each and
everyday…so, I will know when it is or isn’t possible to complete
question 1.
Of interesting note (something I learned while putting this
Earthcache together)…the straight-line distance from the beginning
to end of most rivers is only about one-third their actual
length!!!
Thank-you and enjoy this Earthcache!!! As always, pictures are
always welcome but are not required in order to log a find on this
Earthcache.
Additional Hints
(No hints available.)