Monday, May 8, 2017

Flooding Risks Along Perkins Creek and Urban Areas

With an increase in heavy downpours across the Midwest and Southeast over the past 50 years it has become vital that we continue to look for advanced ways to track the threat of flooding events. The main goal is to give people as much advanced notice as possible so that they can prepare for rising water and be allowed time to get out of harms way.
In December of 2015, I wrote an article featuring the products shown here and how they may become part of our future for flash flood forecasting. The National Severe Storms Laboratory has been conducting research (FLASH) focused on using simulated water flow to help better predict the likelihood of water rises along rivers and associated tributaries. 
Below is an example of one of the products that the NSSL can display and it's archived data from the July 2015 flash flooding in the Paducah area. This particular product shows simulated surface water flow between 30 minutes before and 12 hours after a designated time. At the very start of the loop you'll notice a lot of yellow spread across the map and it's representative of the rain falling/coming to an end. The larger water channels are shaded in red, purple, and blue. By the end of the animation you can follow the access water and it's path downstream on many local rivers including those that empty into the Ohio. During the last few frames you can also see some of the northernmost creeks in McCracken County turning red (during flooding) before returning back down to yellow levels. 

Aside from the immediate preparedness angle, there has become a larger picture here on the local scale and for many of our communities that continue to grow. Urban sprawl means the local economy is trying to grow....a good thing! The other side of the coin is the drastic change in landscape and water run-off. The ability for storm water to drain efficiently can be changed just by paving a new parking lot or clearing land/altering the slope grading by small degrees. Those small changes can have a larger impact on if and how fast flash flooding can occur when heavy downpour events take place. We are seeing those types of economic development changes right here in our own back yard.

Photos taken by residents in the Paducah Area
People who live along and have businesses by Perkins Creek in Paducah have been dealing with this reality for several years now. While Perkins Creek has been known to flood for decades, the number of businesses that have changed drainage to that relief area has increased rapidly in the past 10-15 years. This makes it much more difficult to predict where and how the water is naturally managed.
The video below is from July 2015 when over 5" of rain fell in a short period of time just before sunrise. The runoff from this event inundated Perkins Creek and therefore dozens of homes and businesses. I don't have any personal investment in that particular area but I do feel it's my purpose to prepared people for future threats of weather related disasters. It's why I've been trying to educate people living in the MidSouth about the increase in heavy rainfall events expected in the future. While I understand both sides of the economic development issue with this particular area, I hope there will be serious consideration about how to manage or improve storm runoff for the people who have chosen to make this area home.

The increase in heavy downpours in the MidSouth ranges from 27-37% and the return of the top 1% events is also increasing. Here is a look at Kentucky itself. Rather than preparing for a single high impact heavy rain event, the trend suggests that we are now above that 1-year return frequency. To get the Downpour Index, here is how the data was calculated:

  • Calculate the inches of rainfall representing the top 1% of rainfall totals (from days with non-zero rainfall amounts) at each station.
  • Note: The vast majority of this heavy precipitation came as rain, although in a few rare instances, major snowfalls also count toward these large events.
  • Count the number of days per year exceeding this level at each station.
  • Average the number of events per year across climate division.
  • Weight the climate division total by its size as a proportion of the state.
  • Sum the weighted climate divisions total across each state per year.

1 comment:

  1. Its clear from the predictions and studies over the years that these heavy rainfalls can cause a flood on the mediocre level. But nothing can be said with surety but hope for best.