With the melting of the record setting snow and the persistent rain that we are experiencing, flooding is occurring. The News and Tribune posted an article on Monday, March 9th about how flooding is slowing down work on the bridge projects. Since we can easily see some flooding right now, let’s quickly dissect the floodplain.

100-year floodplain = floodway + flood fringe

There are two parts of a floodplain:

  • The floodway is the part of the stream that is basically in the middle (where the water velocity is the highest).  This is where the channel of the river or stream exists.   The floodway also includes the area just prior to water moving into the flood fringe.  Check out the 23 second video I posted to YouTube that shows the Ohio River floodway.  The water is cruising!
  • The flood fringe is the area where the water is slowest, or even just standing (no movement at all). In the picture below, you can see that the water is not moving near the shore.  The water near the shore is in the flood fringe. Duffy's Landing Flooding

When you combine the floodway and the flood fringe, you get the 100-year floodplain.  The City of Ann Arbor, Michigan has a great illustration of the floodplain on their website.

High water marks

I was out today checking on the flooding along Riverside Drive and at Duffy’s Landing on Utica Pike in Jeffersonville.  I am keeping tabs on the water level and will be creating high water marks once the water recedes.  The goal is to collect flood height elevation data over time to compare with the data the Indiana Department of Natural Resources has gathered.  This will help us verify that the flood maps are accurate.

What about localized flooding?

If a single lot, several lots, or certain areas of a road have water ponding, it is probably experiencing a local flooding issue. This is something that the local Drainage or Street Department would typically work to resolve.  Sites with localized flooding may or not be part of the 100-year floodplain.  Flooding that occurs in a small area can happen at the top of a hill, perhaps in a subdivision, but will most likely not be in the floodplain.

To wrap up

The floodway is the risky part of the floodplain, where the water moves fast and can destroy structures and injure people (do not be the person that drives through the quickly moving water that is over the road because it is in the floodway)!  The flood fringe has the slowest water, but can still be dangerous.   Be safe, watch from a distance, and let the water move on through!