Hurricane Ian and North Port

 You may have seen my column on Hurricane Ian and the Myakka (the blog entry below this one). Below are my thoughts regarding Hurricane Ian and North Port. There's some considerable overlap, which make some sense since it involves the same Hurricane and the same watershed. 

HURRICANE IAN AND NORTH PORT

We know one thing for certain about people still nursing the appealing idea that some Calusa blessing spares Sarasota from the worst effects of hurricanes – they live in north County. Folks in south county, and especially North Port, no longer harbor such illusions. They have been subjected to about the worst a hurricane can dish out. 

 

There are two main reasons Ian was so much more devastating in south Sarasota County. The first is the storm track. After landfall, the eyewall apparently clipped Englewood and passed over all of North Port. That subjected those areas to wind intensities far greater than what the City of Sarasota experienced.

 

Then there was the rain, measured between 15 and 20 inches during a 24-hour period. North Port is roughly 100 square miles in size, while the Myakka River Watershed is about 600 square miles. One way or another, every drop of rain that falls in the watershed that makes its way to Charlotte Harbor has to pass through North Port, either via the Myakka River, Big Slough (AKA Myakkahatchee Creek), Deer Prairie Slough, Alderman Slough, or overland. 

 

So, in addition to rain falling directly on North Port, the City frequently has to deal with additional runoff from the north.  Most of the time, rain falling further north in the watershed is absorbed into the soil and shallow aquifer, stored in wetlands, evaporates, or is transpired through plants. So, much of the rain that falls in the upper watershed never reaches North Port. That was the case for the first six droughty months of this year when the Myakka flow was quite low. People living along the River know it takes many weeks for the watershed sponge to fill and the river to rise significantly after summer rains start. That’s because the Myakka basin is blessed with extensive natural wetlands that include isolated ponds, Flatford Swamp, Tatum Sawgrass, Big Flats, and the marshes associated with the Upper and Lower Lakes that store and slow runoff. These wetlands are miniature, no-cost reservoirs that hold rainwater, resulting in a flow slowdown that explains why news media always cover Myakka high water situations several days after the actual rain events.

 

It took until Mid-September this year for the Myakka to become bank-full. But, unfortunately, the system was still quite full when Ian hit. That meant that much of the Ian event rainwater started making its way towards North Port more promptly than its typical slow motion, delayed-arrival fashion. 

 

When North Port was first incorporated it was roughly half the size it is today and consisted primarily of flat pineland and prairie dissected by numerous broad sloughs. Sloughs are natural, marshy watercourses that lack a defined water channel. When the sloughs filled, runoff would spread overland across the entire landscape. Early surveyors noted how wet the entire area was during the rainy season. Even a few inches of shallow inundation over many square miles stores and delays vast amounts of water. 

 

Eventually, agricultural interests farther north channelized the larger sloughs to drain their properties faster. GDC went further, using dredges to channelize the remaining sloughs. And, in many places, GDC graded the streets lower than the surrounding lots, predisposing the roads to flooding. The result, as the Governor noted, made North Port into Florida’s most inundated city following Ian.

 

Geography and meteorology conspire to make an Ian-type event inevitable, if not predictable. Higher ocean temperatures and GDC’s design decisions don’t help. For the people suffering in North Port, it is hard to see a bright spot in the reality of living at the downstream end of a large watershed. If there is one, it’s the fact that so little of the upstream watershed has been developed. The preserve lands and ranches above North Port can accommodate significant inundation without completely derailing lives. That’s millions of gallons. Because shallow flooding is not tolerated in residential developments, had those northern lands been developed, more of Ian’s rain would have been funneled downstream faster, making matters much worse. 

 

We can’t stop the rain – the challenge will be to provide North Port residents with better warning, facilitate the floodproofing of homes, and retain undeveloped lands that can accommodate shallow inundation without devastation. 

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The WUSF story about Hurricane Ian and North Port that accompanied the photo above may be heard here.