Rea Road Gillespie Property Flooding Concerns

Anyone living is South Charlotte knows we have a flooding problem. The question is do we allow developers to make it worse or do we step back and say lets' make sure we do this right?

The Gillespie Property Developer RK Investments Charlotte LLC was asked about flooding concerns voiced by dozens of property owners in the Piper Glen area.

The response by developer Russell Ranson was that flooding exists in Piper Glen under certain storm conditions and the Sutherland project is downhill from Piper Glen. 

According to the Charlotte Observer he said RK Investors will comply with all municipal rules by adding controls to mitigate storm water from its property. “It is important to understand that, currently, sections of a nearby golf course and other natural areas provide relief from excess stormwater and flood on occasion”.

Below are photos of what it looked like on January 9 and a normal September fall afternoon.

We need to be clear that the flooding of January 9th may or may not have been caused by the 485 expansion but it clearly contributed to it.

IN TO THE WEEDS

Yes, 1 inch of rain will create 27,000 gallons of stormwater runoff per acre of impervious surface. 

Based on NCDOT numbers and aerial photos the "estimated" additional impervious surface area added by the 485 expansion between the Elm Lane bridge and the Ballantyne Commons Parkway bridge (1.42 miles) at Tom Short Road is 35 acres. What they didn't pave over in this area they removed nearly all of the vegetation. 

On January 9th the 35 additional acres of impervious surface likey sent an "estimated" additional 3,000,000 gallons of stormwater runoff into Piper Glen via 3 creeks (Stuart's, Schitt's and Shepherd's) and eventually into Four Mile Creek which "added to the flooding" that we have seen in the photos shared by local news and social media. 

Fact - this is "additional" stormwater runoff we did not have 2 years ago.

It is important to recognize that flooding is often the cause of many factors.

Soil Saturation 

Temperature

Previous Rain Events (in this case rain on January 6th)

Precipitation Rate

However, NCDOT has been exploring the flooding and construction silt issues with the Mitchell Pond Number Six since the 485 expansion began. We now know and NCDOT confirms that this has been a problem that was not anticipated.

Furthermore, based on the USGS flood gauge located at Four Mile Creek and the USGS rain gauge located at St. Matthews we can see a solid correlation to the recent additional impervious surfaces created and the accompanying stormwater runoff to the increase in frequency of flooding.

Prior to the completion of the paving 485 express lanes Four Mile Creek would hit 10 feet about 3-4 times per year. Ten feet seems to be where the creek floods the TPC Piper Glen Fairways 1,2,10 and 11. Since late 2022 this has been happening about every 4-5 weeks or 10-12 times a year.  

The January 9th rain event pushed Four Mile Creek well past flood stage on a rather steady rain. Not a heavy rain not an isolation downpour just a steady soaking good for the crops rain.

Had the January 9th rain event occurred after the Gillespie project was completed (development of 70% of the 53 acres) totaling 37 acres of impervious surface would have created at least an additional 2,997,000 gallons of stormwater runoff adding to the 485 additional runoff.  

(The above is based on 3 inches of rain. We actually received 3.48 inches.)

So if we understand the variables and calculate the impervious surface area we can quickly determine the additional runoff created by the yet undeveloped projects like Gillespie.

Note NCDOT admits the water flowing into Schitt's Creek as well as Shepherds and Stuart's Creeks is coming from 485 and other sources. They haven't admitted to causing the flooding but, understand the concerns. 

Currently "Post Construction" stormwater plans need to be presented prior to issuing permits. But really should be a large part of the rezoning process.

Retention Ponds - only "slow down" the velocity of stormwater runoff; they don't limit the volume and the effect is only temporary.  

Also it's not just the water or volume but what is in it. Crazy amounts of pollutants.

The bottom line - Southern Mecklenburg County has a lot of FEMA flood zones. Most of our area in southern Mecklenburg County was farm "bottomland" prone to occasional flooding which was fine for cows and crops. 

Now the big issue, 3 inches of rain in 24 hours is not a rare event 100 year event. 

November 12, 2020 4.62

September 16, 2018 4.28

September 26, 2016 3.89

November 2, 2015 3.08

We even see records of 6.44 in 1997 and 13.11 in 1995 

We also had a 1.10 inch rain event on January 25th which pushed Four Mile Creek to over ten feet. 

We can clearly see how these last few rains have also overburdened the wetlands called Pooh's Corner (Property Owned by White Oak and Meck County) west of Elm Lane.

The bottom line is approval of the Gillespie Property Rezoning for an apartment complex would add another 1,000,000 gallons of stormwater to Four Mile Creek and Pooh's Corner every time it rains 1 inch.

Amateur sleuthing is fine but what do the experts say?

According to Don Ceccarelli, PE, CFM and Director of County Storm Water 

Charlotte-Mecklenburg Storm Water Services who reviewed the above information it all depends.

That is a lot of information and to be honest, without analyzing historic rainfall data, topographic maps and drainage features, I cannot really comment on most of the information.  However, I will add a few comments.

 

• Increased impervious / built-upon area does increase run-off to streams whether that built-upon area is driveways, rooftops, roads, parking lots, etc.
• Floodplain ordinances in Mecklenburg County regulate to a modeled “future” floodplain, assuming undeveloped properties are developed according to their zoning, to help account for the impacts of future development.
• There are development ordinances in place (i.e. post-construction ordinances) to reduce the impacts from increased run-off from development; both for water quality and flow.
• There were many places in Mecklenburg County that saw increased flooding during the run-off from the rain event on January 9 because of ground saturation (i.e. even pervious areas contributed additional flow more like impervious areas).

Look closely at what Don Ceccarelli says: "Floodplain ordinances in Mecklenburg County regulate to a modeled “future” floodplain, assuming undeveloped properties are developed according to their zoning, to help account for the impacts of future development."

In other words they are not considering zoning changes and density increases in their planning.

Given the dramatic change and increase in storm water runoff the Gillespie Project would create wouldn't it be better to have that information before giving a green light to increasing the density and therefor amount of storm water by 1000%? 

Unless we commit a massive amount of tax dollars to building man-made flood control we will need to be very careful what we approve for development. Density saturation is going to cause massive amounts of flooding. 

In the end it will cost us millions of dollars in damages, increased insurance premiums and even lives if we don't step back and think this through.