What Helene and Milton did in Tampa Bay: facts for builders

What did Helene do in Tampa Bay?

Helene pushed a large storm surge into the bay, even though it made landfall far to the north. The National Hurricane Center (NHC) final report says, “Within Tampa Bay, maximum storm surge inundation of 5 to 7 ft AGL occurred.” AGL means above ground level. Storm surge is seawater pushed onto land by a storm, and it is separate from rain flooding.

The report gives gauge readings too. The tide gauge at East Bay measured 7.2 feet above mean higher high water (MHHW), which is the average height of the higher of the two daily high tides. The gauge at Old Port Tampa read 6.83 feet, and the one at St. Petersburg read 6.31 feet.

The report also counts damage. It says Helene destroyed at least 419 homes in Pinellas and Hillsborough Counties combined. At least 18,512 structures suffered major damage in those two counties. Another 13,909 had minor or moderate damage.

These are NHC figures for the whole bay. Surge was not the same on every street, so they do not predict one address.

What did Milton do in Tampa Bay?

Milton flooded Tampa mostly through rain. The NHC says Milton made landfall as a category 3 hurricane on Siesta Key, and the winds near Tampa Bay were mostly offshore. As a result, the report says only 1 to 2 feet of surge occurred in Tampa Bay. The report notes a sharp surge gradient north of the landfall point.

Rain was the larger story here. The report says heavy rain caused “widespread river and urban flooding, particularly in the St. Petersburg-Tampa area where record-high crests were recorded on the Hillsborough River.” The highest storm total in the report was 20.40 inches near St. Petersburg.

How do the two storms compare?

The lesson is simple. One storm flooded from the bay side. The next flooded from the rain and river side. A home can face both kinds of risk. For the vocabulary, see storm surge and base flood elevation.

What do the 50 percent rule and permits mean after a storm?

Hillsborough County published a recovery page on the 50 percent rule after the storms. The page says the rule applies to people who live in a FEMA Special Flood Hazard Area in Hillsborough County. Under the County’s wording, if the cost of repair, reconstruction, rehabilitation or addition equals or exceeds 50 percent of a building’s market value, the entire structure must comply with current floodplain requirements.

Three details from the County page matter to builders:

• County costs include permits pulled in the prior 12 months from the date of your most recent permit application.
• You can use the Property Appraiser’s market value or a state-licensed appraiser’s value.
• Cosmetic repairs such as drywall do not need a permit, but they still require the Substantial Damage Packet to be submitted to the County for review.

The County page speaks for Hillsborough County. It does not say whether that process applies inside the City of Tampa. The City’s flood page has its own note: if improvements or repairs exceed 50 percent of a home’s value in an “A” or “V” zone, the house must meet current code, including elevation above the base flood elevation. Read both pages and ask which office handles your address. Our glossary explains the FEMA 50 percent rule, and substantial damage, which has its own entry.

What does a builder need to prove for a flood zone lot?

The City of Tampa asks for an elevation certificate. Its flood page says that to build in a FEMA special flood hazard area, you must provide an Elevation Certificate with your construction permit application. A Professional Engineer or Professional Land Surveyor must complete it. An elevation certificate records how high the lowest floor sits against the base flood elevation.

The City also offers a free flood zone check by phone. Call the Stormwater Department at (813) 274-3101 and give a street address. Read our page on building in a flood zone in Tampa for the full permit path.

What should owners do with this information?

Use these facts as a checklist, not a forecast:

1. Look up the flood zone for your address before you buy or plan work.
2. Ask the City or County whether the 50 percent rule could apply to a repair or remodel.
3. Get a market value from the Property Appraiser or an appraiser before you scope the work.
4. Plan elevation and drainage at the start of design, not at the end.
5. Keep records of the damage and each repair cost, since the rule counts them.

Storm design also covers wind, which these flood notes do not.

What is the next step?

If a storm affected your home or lot and you want to talk through a rebuild or a new custom home, call Halo Homes at (813) 956-1972 or write through the contact page. Bring your flood zone result and any damage records. You can also read about custom home construction.