Tropical Storm Debby: What the Lowcountry Learned About Stormwater Preparedness

Tropical Storm Debby made landfall near Steinhatchee, Florida on August 5, 2024 as a Category 1 hurricane with maximum sustained winds of 80 mph. After crossing Florida, the storm moved northeast across the Southeast, stalling over coastal South Carolina and Georgia for days. The slow movement was the problem. Debby wasn’t a powerful wind event for the Lowcountry. It was a rain event. And the rain was relentless.

Coastal South Carolina received 5 to 10 inches of rainfall across inland areas, with 10 to 15+ inches falling between I-95 and the coast. The highest recorded total in South Carolina was 19.03 inches along the Waccamaw River in Horry County. Flash flooding hit communities across the SC Lowcountry and Isle of Palms. Heavy rainfall caused significant flooding in parts of Charleston and North Myrtle Beach. On August 9, the National Weather Service issued a flash flood emergency for Moncks Corner, a designation reserved for the most dangerous flooding situations.

Seven confirmed tornadoes, ranging from EF-0 to EF-1, touched down during the event. One tornado destroyed businesses in Moncks Corner, adding wind damage on top of the flooding.

For property managers across the Lowcountry, Debby was a test. And many stormwater systems failed it.

What Failed and Why

The stormwater failures during Debby weren’t random. They followed a pattern that repeats with every major rain event in the Lowcountry. Systems that had been neglected failed first. Systems that were maintained held up better, even under extreme conditions.

Detention and retention ponds across Beaufort County, Charleston County, and Horry County overtopped because they’d lost storage capacity to years of sediment accumulation. Outlet structures that hadn’t been inspected since installation clogged with debris during the heaviest rainfall. Pipes that had partial blockages before the storm became completely blocked during it.

Properties near Charleston saw a compounding effect. The city’s low elevation and aging drainage infrastructure meant that even well-maintained private systems couldn’t discharge because the municipal systems they connected to were already at capacity. When the downstream system backs up, your upstream system can’t do its job regardless of its condition.

The takeaway isn’t that maintenance would have prevented all damage. Debby dropped extreme rainfall. Some flooding was unavoidable. But the difference between “our pond overtopped by two inches and drained within a day” and “our pond overtopped by two feet, eroded the banks, destroyed the outlet structure, and flooded three buildings” comes down to whether the system was functioning at full capacity when the storm arrived.

The Contamination Problem

Floodwater from stormwater systems isn’t clean water. After a storm like Debby, the water moving through streets, parking lots, and overwhelmed stormwater infrastructure contains harmful bacteria from septic systems and sanitary sewer overflows, oil and fuel from roads and parking areas, pesticides and fertilizers from lawns and agricultural areas, sediment carrying heavy metals, and in severe flooding, hazardous materials from flooded commercial and industrial sites.

This is why every public health agency warns people not to walk, swim, or drive through floodwater. It’s also why post-storm cleanup of stormwater infrastructure matters. The contaminants that Debby deposited in ponds, pipes, and basins don’t disappear when the water recedes. They settle into sediment, accumulate on structures, and affect water quality for months until they’re removed.

Property managers who waited to clean their systems after Debby found that the contaminated sediment was harder and more expensive to remove the longer it sat. Organic material decomposed, creating odor problems. Bacteria concentrations in ponds stayed elevated well into the fall.

Lessons for Property Managers

Debby reinforced several lessons that apply to every property with stormwater infrastructure in the Lowcountry.

Deferred Maintenance Compounds During Storms

A pond that’s lost 20% of its storage capacity to sediment during normal weather loses 20% of its flood protection during a storm. That’s not a minor issue when the storm drops 15 inches of rain. Every inch of capacity matters during extreme events. Pond dredging that seems like a “next year” budget item becomes an emergency expense when the deferred sediment causes the pond to overtop and damage adjacent property.

Outlet Structures Are the Weakest Link

Across the properties we saw after Debby, outlet structure failures were the most common cause of system-level problems. Clogged trash racks, corroded riser pipes, and displaced orifice plates prevented ponds from draining as designed. Our guide to outlet structure failures and their warning signs covers how to catch each of those before the next storm does. When the outlet can’t discharge, the water has to go somewhere else. That somewhere else is usually your parking lot, your building foundation, or your neighbor’s property.

Upstream and Downstream Systems Are Connected

Your stormwater system doesn’t exist in isolation. It receives flow from upstream and discharges to a downstream system. If the downstream system is overwhelmed, your system backs up regardless of its condition. If your system fails, the downstream system receives uncontrolled discharge. This is why municipal stormwater programs require private systems to be maintained. The whole network depends on each component functioning.

Documentation Matters

Property managers who documented the condition of their stormwater systems before hurricane season had a significant advantage in the insurance claims process after Debby. Photos showing the system was maintained and functional before the storm made it much easier to demonstrate that the damage was storm-related rather than the result of neglect.

Those who didn’t have pre-storm documentation faced harder conversations with adjusters. It’s difficult to prove a storm broke something when the insurer suspects it was already broken.

What to Do After a Major Storm

If your property experienced flooding or stormwater system damage during a storm like Debby, here’s what to prioritize.

Don’t Enter Floodwater

This bears repeating. Stormwater that’s mixed with sewage, chemicals, and debris is a health hazard. Keep residents, employees, and maintenance staff out of standing floodwater until it recedes naturally or is pumped by professionals with appropriate equipment.

Document Everything

Take photos and video of all damage as soon as it’s safe to access the area. Photograph water levels in ponds, damage to outlet structures, erosion, sediment deposits, and any structural damage to buildings, parking areas, or landscaping. Include wide shots that show context and close-ups that show detail. Date-stamp everything. This documentation supports insurance claims, regulatory responses, and repair planning.

Report the Damage

If your property is within an MS4 jurisdiction (most of Beaufort County, Charleston County, and coastal Georgia municipalities), report significant stormwater system damage to the local stormwater utility. Some jurisdictions require reporting within a specific timeframe. Failure to report can result in separate violations.

Schedule a Professional Assessment

Have a stormwater professional inspect the entire system, not just the obvious damage. Storms like Debby can cause underground pipe damage, embankment saturation, and structural shifts that aren’t visible from the surface. A post-storm assessment identifies everything that needs repair and helps you prioritize based on urgency.

Separate Emergency Repairs from Planned Repairs

Some damage needs immediate attention: active sinkholes, failed embankments, completely blocked outlets, or ongoing erosion that threatens structures. Other damage, like cosmetic bank erosion, minor sediment accumulation, or surface-level concrete cracks, can be scheduled for repair over the following weeks or months. Prioritizing correctly keeps costs down and addresses the most dangerous issues first.

Start Preparing for the Next One

Debby hit in early August. Hurricane season runs through November. If your system took damage in Debby, getting it repaired before the next storm is not optional. The Lowcountry averages one to two significant tropical events per year. The question isn’t whether another storm will test your system. It’s when.

That warning proved out fast. Seven weeks after Debby, Hurricane Helene carved a 500-mile path through the Southeast and put 28 South Carolina counties under FEMA disaster declarations. Our writeup of Hurricane Helene’s impact on South Carolina stormwater systems covers the recovery sequence for properties hit by both.

Building a Maintenance-First Approach

The properties that came through Debby in the best shape weren’t lucky. They were prepared. Their ponds had been dredged on schedule. Their outlet structures had been inspected and repaired. Their erosion control measures were intact. Their pipes were clear.

This isn’t a complicated formula. Regular inspections, timely repairs, and scheduled maintenance. The cost of staying ahead of problems is a fraction of the cost of reacting to failures during or after a major storm. Our hurricane season stormwater prep checklist lays the whole cycle out in a form you can hand to a maintenance crew.

For HOA communities in particular, stormwater maintenance belongs in the annual budget as a planned expense, not a contingency. Debby proved, again, that “we’ll deal with it when something breaks” is the most expensive maintenance strategy there’s.

AUE Land Can Help

Whether you’re still dealing with damage from Debby or getting ahead of the next storm season, AUE Land provides stormwater inspections, repairs, and maintenance across the Lowcountry. We work with HOAs, commercial properties, developers, and municipalities from Hilton Head to Myrtle Beach. Schedule a site assessment to find out exactly where your system stands.