With the repeated heavy rains that we are experiencing during this wild summer, there are tons of questions from people on Facebook wanting to know why we (the City) are not stopping the flooding from occurring. This morning, the news was reporting that the Jeffersonville area was receiving rainfall at an approximate rate of 5 inches per hour. Recently, on June 26th, we received around 3 inches of rain in 45 minutes. The installed drainage infrastructure is not designed to handle this amount of water.
Since we can easily see some flooding right now, let’s quickly dissect the floodplain and learn some stuff.
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 (from earlier this spring). 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.
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.
Everyone lives in a floodplain
Now that you have a better understanding of what the 100-year floodplain means, you should recognize that structures can still take flood damage even if they are out of this magical zone. Many people do not realize that FEMA considers everyone to live in a floodplain, with a low, moderate, or high risk of flooding.
As you can see from the pictures, there were some upset homeowners (which I get). Unfortunately, there is little that the City can do for them, other than provide technical advice about how to flood proof, acquire insurance, and so forth. Most of them will probably purchase a Preferred Risk Flood Insurance Policy after this extreme rain event (estimated at approximately a 150-year event). As you can also see in the above picture of the cul-de-sac (with the truck), the water is not moving…it is in the flood fringe.
The flood finale
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 still or slow-moving water, but can still be dangerous. Be safe, watch from a distance, and let the water move on through.
As people are seeing from today and the other week, extreme flooding can result in numerous water rescues. Also, there are many homes and vehicles that were damaged over the weekend. Think ahead by purchasing a low-cost flood insurance policy and making emergency plans with your family…these types of rain events will most likely continue to occur.
If you experienced the heavy rains this weekend, let me know how you did in the comments section.