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.

Hurricane Ian and the Myakka

  Here's a link to my column as it ran in the Sarasota Herald Tribune. But, if you are not a subscriber, you probably can't get to it. 

Below is the column as I submitted it. 

The Myakka is not like many other Florida rivers – there is no persistent spring flow that keeps the river flowing all year. The closest thing to such a base flow is some mining and agricultural runoff. Yet, almost every year, the river shrinks to a point where there is not enough water to paddle downstream from Myakka River State Park. That’s what it was like for the first half of 2022.

 

And, virtually every year, usually during the late summer, rainfall fills the Myakka’s banks and the river expands into the adjacent hydric hammock – the oak and palm forest that somehow tolerates weeks of inundation.  Summer rains finally started spreading out into the hammock by mid-September. If it weren’t for these annual high-water events, pine flatwoods would probably line the river, but the high water creates conditions that disfavor the flatwoods species. So, if you perch in a wetland-fringing hammock, you’ll likely be standing in water at some point during the year.

 

Because our local thunderstorm-driven rains and the tropical storms and hurricanes occur at the same time of year, the two can coincide and create an inevitable, if unpredictable, situation. Thus Ian arrived while the Myakka watershed was already brim-full.  All of the Myakka’s impressive, extensive wetlands (Flatford Swamp, Tatum Sawgrass, Big Flats, the marshes associated with the Upper and Lower Lakes, and the hundreds of isolated ponds that speckle the pinelands and prairies) that normally have to be filled before any human-built structures are threatened, were already full. 

 

The first reports came from Myakka City, where residents were reporting record water levels. Bear in mind the water passing under the Highway 70 bridge represents only about a fifth of the watershed. Ian was pouring massive amounts of rain into the already saturated system. Then, south of Myakka City, reports came of devastating dairy cow losses at Dakin Dairy. 

 

Then the aging Hidden River dike was breached (again), flooding homes that had been built in the historic flood plain. Myakka River State Park was next, and after Ian passed, park officials took an airboat down the park drive to record unprecedented water levels. Even though park managers plan for high-water each year (they tie the picnic tables to trees so they don’t float away), most park facilities were not designed to handle this one-two punch. 

 

In addition to the rainfall impacts, many old pines and massive oaks in the region were lost due to high winds and those wind effects only increased to the south. 

 

As the bulge of river water worked its way downstream, in was inevitable that riverfront cabins and homes, Venice Myakka River Park, the River Palms subdivision, Sleeping Turtles Preserve, the Englewood Youth Foundation facility, Our Lady of Perpetual Help Retreat Center, Snook Haven, and Senator Bob Johnson Landing would all be dramatically impacted. 

 

Meanwhile, Myakka watershed ranches were contending with unusually high water, downed fences, and the likely loss of some of the only remaining productive citrus in the County. 

 

All that water had to go somewhere and I-75 was in the way. The internet provided alarming images that appeared to show I-75 completely submerged for long distances. It turned out those were photos of Highway 17 paralleling the Peace River, but the Interstate was closed for a period, necessitating a problematic detour.

 

The tributaries east of the Myakka River were experiencing the same overload as the main stem of the river. Big Slough (AKA Myakkahatchee Creek), Deer Prairie Slough, and Alderman Slough (running on the west side of Orange Hammock) were all funneling water towards North Port, which, like the State Park, was not designed to handle hurricane rain on top of a full system. Luckily, the vast majority of land above North Port has not been developed. Otherwise there would have been more water, faster. 

 

It may take a while to tease apart the hurricane surge effect from the river flow, but neighborhoods south of US 41 were inundated and Ian’s winds became more of a factor as evidenced by thousands of pieces of sheet metal, vinyl. insulation, and other debris stranded in Myakkan mangroves and embedded in the river bottom. 

 

This won’t be the last time we have copious tropical rainfall on top of an already-full Myakka system. No matter what we design for, there can always be a worse case event. What to do?  The goal is to keep people and their stuff out of areas destined to be inundated.

 

•One approach is to retain agricultural and park/preserve lands that can tolerate some inundation. Even temporarily accommodating a foot of water on a square mile of undeveloped land acre stores over 200 million gallons of water.

 

• Whenever possible, homes and other human structures need to be moved out of the flood plain. That could mean elevating, relocating, or paying people to relocate and removing the structures.

 

• Structures that can’t be moved, need to be prepared. Fuels, lubricants, biocides, etc. need to be stored (or moved) up, out of water’s reach. Governments could help residents with a variety of floodproofing strategies such as removable doorway dams that can block up to two feet of water and still allow access. And residents need accurate and timely information about when and how to evacuate.