Hydrologist says systems must be better maintained, adapt to floodplain, changing climate.
By Ramon Lopez
Original Air Date: January 1, 2025
Johannes Werner: The hurricanes this season have produced big challenges and laid bare deficiencies of local stormwater management systems. Ramon Lopez interviewed an engineer with a big-picture view. Steve Suau has produced a study of Sarasota County’s stormwater management systems, and he will play a key role in an upcoming county commission meeting dealing with the fallout of the past storm season’s inland flooding.
The flooded Laurel Meadows subdivision.
Ramon Lopez: Floodwater management is a big local story, as the year 2024 should be remembered for Sarasota’s series of storms. It included a no-name tropical system in mid-June that dumped eight inches of rain in three hours, causing widespread flash flooding downtown and elsewhere in Sarasota County. It was followed by hurricane Debby, which brought a record one-day rainfall of 18 inches the first week in August. Debby flooded nearly all of the 86 homes in Laurel Meadows, unexpectedly.
To add insult to injury, Hurricane Helene in late September spawned a historic Gulf of Mexico storm surge that devastated the barrier islands. The repeated historic rainfall turned roads into rivers, caused hundreds of millions of dollars in property damage, and killed people.
None of this escaped the attention of stormwater engineer and hydrologist Steve Suau, who was asked by Spencer Anderson, Sarasota County’s Director of Public Works, to do an independent study to determine the cause of the unprecedented flooding from Hurricane Debby. Residents pointed to overdevelopment. Developers said the unprecedented volume of hurricane-produced rainfall was to blame. Local government officials point at the county’s current storm water regs and control systems, saying they were simply overwhelmed.
Currently, the county adheres to what is often referred to as a 100-year storm threshold — of 10 inches of rain in a 24-hour period — to determine acceptable flooding in certain areas. In the aftermath of the Debby deluge, Public Works Department staffers said there was simply too much rain, up to 18 inches in some areas of the county, for the infrastructure to handle. Given there were three punishing rain events this past summer in less than 100 days, much less 100 years apart, that met or exceeded that rain threshold, the guideline is set to be scrutinized on Jan. 21 in a special Sarasota County Commission workshop. Steve Suau will present the results of his independent study at the event.
At issue is whether the Public Works Department’s stormwater regulations are stringent enough to have prevented the severe flooding seen by Debby.
Based on good detective work, Suau figured out why the Laurel Meadows neighborhood was especially hard hit.
Steve Suau: As far as Laurel Meadows goes, in the Phillippi Creek basin, there’s an old dike out there, like a big berm, that was constructed between those watersheds of Phillippi Creek and Cow Pen Slough. Based on the nature of the flooding, you know that it occurred kind of after the rain had stopped from Debby, and it just overwhelmed Laurel Meadows. I got to thinking that there was something more than just a lot of rain that had contributed to that, and that that dike had breached. Somehow, water was getting through it, because the water levels, the flood levels on Cow Pen Slough on the east side of the dike, … were quite a bit higher than the water levels on the Phillippi Creek, the west side of the dike. So if that dike had in fact breached, that would explain to me why there was so much water coming in onto the Phillippi Creek area out there, in the Laurel Meadows in particular.
Suau
That dike is probably 50 years old or so, and I don’t know exactly what caused the breach. But after it was located, the county did find me when I alerted them to it, and they went out and they found it. We found on some old, on some LIDAR information mapping that was done, in I think in 2018 or 19, that indicated that that breach was there at that time. So it’s been there for several years, it was just the amount of rain that built water up so high that it did, all of a sudden, now create … it was like the perfect storm. The dike and the breach was there, had been there for a while, but nobody really knew until you got all that rain, and water started flowing through to get out, flow through it. The fact that the dike had not been … the breach was there contributed to it, in combination with the amount of rain.
RL: Based on his detailed study, Steve Suau developed recommendations that he believes will help prevent a similar occurrence from happening again.
They include:
- Identifying significant floodplain areas and protecting them from development.
- Stormwater streams must be cleaned on a regular basis.
- Dikes and levees must be inspected, and responsibility for their maintenance and upkeep must be established.
- Updating the stormwater criteria in the face of climate change.
SS: One of the recommendations is that that needs to be reconsidered, because the criteria that that’s used is based upon the Water Management District, and it’s based upon rainfall data through 1996. So the last 30-some years of rainfall has not been factored in, and the recommendation is that the Water Management District needs to consider what’s been happening in the last 30 years, and update the criteria based on what the science says.
RL: The former Sarasota County stormwater manager believes the county commissioners will back his recommendations.
SS: I’ve had the opportunity to meet with each of the commissioners individually, and my sense is they, every single one of them, is taking what happened this past summer pretty seriously. I would hope that they move forward with all the recommendations that I’ve made. They’re all constructive and intending to improve the county stormwater system, and move it forward in a positive direction.
RL: Stated Suau: “I wouldn’t have gone through all this on my own time when I could have been on the beach enjoying retirement.”
This is Ramon Lopez for WSLR News.
WSLR News aims to keep the local community informed with our 1/2 hour local news show, quarterly newspaper and social media feeds. The local news broadcast airs on Wednesdays and Fridays at 6pm.
