Monday, July 17, 2017

Flood 2017 - Creek Impacts

The July 6 flood certainly had an impact on the creek.  Some sections lost all lose material right down to the bedrock.

Other sections accumulated material brought down from upstream.

Deposition of stone in the creek channel was due to the formation of debris dams that temporarily slowed the speed of the water.  As the water slowed, it lost the energy necessary to carry heavy objects and the gravel dropped out into the creek bed.

Water diverted out of the creek channel carried its sediment load along with it.  A number of sand bars were formed well away from the creek. 

Where the creek left its bed with more momentum, gravel bars were left behind.

There were even a few large flat rocks left stranded far from the creek.

At one bend in the creek the flood water cleaned the face of this bedrock arch.  This feature has never been so easy to view.

Water was deep enough that the meanders in the creek had little effect on the direction of flow.  The current went straight down hill, passing cleanly over every bend and curve in the creek channel.

It was not hard to tell in what direction the water was flowing.  I don’t think a steam roller could have laid these plants down any more than this.  This particular area typically has a nice floral display in late July.  I don’t think that’s going to happen this year.

In the broad, flat areas, water depth peaked at between two and three feet.  It’s going to take a couple of years before the visual effects of this flood event begin to disappear.

Wednesday, July 12, 2017

Flood 2017 - The Storm

Last month I was describing the drought conditions currently being experienced at Blue Jay Barrens. I believe it’s safe to say that that particular period of drought has come to an end. On July 6, Blue Jay Barrens was the recipient of 6+ inches of rain in a period of less than 12 hours. The resulting flood conditions far surpassed anything we have ever experienced here in the past.

video
The rain began around 1:30 AM and continued until 8:30 AM. During that time approximately 3 ½ inches of rain fell. Our dry soils were able to accommodate most of that water and very little runoff occurred. The weather was clear for the next few hours, until a storm formed over the area around 12:20 PM. During the next hour, 2 ½ inches of rain was added atop soils which had nearly reached their saturation point. Runoff began immediately and the majority of that 2 ½ inches of water flowed overland across the landscape. The video above shows the runoff from a watershed only a few acres in size as it crosses the driveway in front of our house. The video begins during the most intense part of the storm and ends about five minutes after the rain stopped.

Even though I was dismayed at the magnitude of the disaster unfolding before me, I got some pleasure at viewing the scene shown in the photo above. The clear water coming in from the left is flowing from my field that has been managed for the past 30 years as tallgrass prairie. The muddy water to the right comes from neighboring properties and the Township road. When I first bought this property, all of that runoff water would’ve been muddy. It’s nice to see that my management efforts are having some positive effects.

The former access road, now grassed over, carries the excess floodwater past the prairie display garden and dumps it over the bank into the pond. Water from a more normal runoff event would all have gone through the shrubbery to the right.

With the pond’s primary spillway overloaded, water overtops the dam. This is something that has not occurred since I moved here.

During a year with more typical rainfall, the pond would currently be down to just a puddle and raccoons would be devouring the last of the tadpoles. Gray Treefrog tadpoles generally have a poor time of it in the pond. They breed later than most of the other frogs and the tadpoles generally don’t have time to fully develop before the water disappears. This flood event has been a boon to the Gray Treefrog population.

Thanks to all this water, I’ll be seeing many more of these newly morphed Gray Treefrogs during the next few weeks.