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Flood Stage

Posted on March 10th, 2013

Rain on snow, along with frozen soils, is a basic recipe for small stream flooding.  Given these ingredients, the result is that a high percentage of the precipitation becomes stream flow, with smaller amounts stored in surface depressional areas.

This weekend, I received my first gage alert from USGS Saturday afternoon, and another today.  In the end the Old Man’s Creek Gage (at Sharon Center Road) rose from 2.6 to 15.7 feet in about 24 hours, over 13 feet!  This is amazing, even to a professional hydraulic engineer, given that we have only received around 1.5 inches of rainfall.  As usual, I was excited to go for a walk at Old Man’s Timber to experience first-hand a USGS gage reading of 15.7 feet.

I started my walk on the North 40 acre parcel near Old Woman’s Creek.  As I approached the creek, I quickly realized that the water level was a combination of upstream water in the creek and backwater from Old Man’s Creek. The photo below is looking upstream along Old Woman’s Creek, the debris (ice, woody material and corn stalks) is accumulating at a bend in the creek.  The water level, is genuinely “bank-full”.

Debris Accumulating on Old Woman's Creek

Debris Accumulating on Old Woman’s Creek

 

I continued my walk along the floodplain south of Old Man’s Creek.  All throughout this area I found the depressional areas and remnant oxbows filled with standing water.  I noticed that these flooded areas had a wide variation in water clarity, those areas fed by overland flow from the Oak-Hickory ridges were very clear, whereas those areas that were filled with seepage flow from Old Man’s Creek were much more turbid.  I could not find any locations where Old Man’s Creek had a direct overland connection with the floodplain.  The standing water shown below is a blend of clear overland flow and seepage flow from the Creek.  This area is clearly a remnant channel that makes its way along side the active channel.  Interestingly, this area remained disconnected from direct overland connection to the creek, and I estimate that the water level was between 2 to 3 feet below the water level in the creek.  If Old Man’s Creek would rise another 18″, water would begin to actively flow through this area, resulting in all of the exposed land surface shown below to become inundated.

Floodplain South of Old Man's Creek

Floodplain South of Old Man’s Creek

 

Although perhaps a little difficult to see the in photo below, it was clear to me that the water level in the remnant channel (foreground) is between 2 and 3 feet below the flowing water (background) in the creek.  I haven’t found any historical data regarding the channel invert elevation of Old Man’s Creek, but it is most likely a receding creek bed, as a result of channel controls limiting its lateral movement, along with increased run off resulting from a conversion of the upstream landscape from deep rooted perennial prairie plants to row crop agriculture.  Falling stream channel elevations have clearly disrupted the flood frequency of many floodplains, whereas increased stream flows resulting from land conversion have had the opposite affect.  It will be interesting to monitor the plant and tree species on this parcel to see if they continue to be wet-soil adapted species or become a dry-soils community.

Oxbow Near Actively Flowing Creek

Oxbow Near Actively Flowing Creek

 

A walk over to Old Man’s Creek, showed it to be at bank full, with swift turbid water quickly flowing downstream.  I stood for a few minutes to observe the flowing water, and was interested to listen to the whirls and swirls of water interacting with the bankline and exposed trees.  Given that bank full flows are considered to be the “channel forming” flows, it will be interesting to see the formative processes that were at work, once the water levels return to normal levels.

Old Man's Creek at Bank Full

Old Man’s Creek at Bank Full

 

Alas, as I was walking out, I carefully walked past the owl’s nest and could see the top of the nesting mother.  Fortunately the noise of the river helped me to pass the nest unnoticed by its occupant.  I suspect the mother will welcome a break from the slow and steady rain that we have seen over the past day or so.

Mother Owl in Nest

Mother Owl in Nest

 

Although my walk today was cold and wet, it was nice to see the floodplain functioning as it should, holding and clarifying water, especially given the drought conditions we experienced last year.  The rains remind me that spring is just around the corner, and will continue to nourish the wet-soils woodland wildflowers that Miechelle and I enjoyed last spring!

 

 

2 Responses

  1. Tony says:

    This reminds me of the back country creeks and floodplains when I lived in upstate New York, with the rains flooding the creeks and the bitter cold but nice to enjoy non the less for a winter walk.

  2. Larry Weber says:

    Thanks Tony, I hope my post brought back fond memories for you!

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