Sheetflow season in review

Winter rains are vital for extending hydroperiod …

And therefore for also turning back the hands of the spring “wildfire severity” clock, but they are rarely enough to get sheetflow fully back up and flowing.

Tamiami sheetflow hasn’t had
a flood year since 2005

You can see that in the hydrograph above.

Most of the bridges along Tamiami Trail are still flowing to some extent (although some are only stationary), but the marl prairies that lie adjacent to the strands and sloughs are pretty much dry. By definition, you can’t have sheetflow if the “sheet” of shallow yet continuous expanse of water is gone.

A quick gander at the calendar graph below shows that once every few decades sheetflow persists through spring. It happened to some extent during the El Niños of 1983 and 1998 and in full during the dry season of 1995, but those cases are the rare exception not the rule.

More often, by March, the swamp is almost completely dry.

This historical calendar matches the color-coding
used in the hydrograph above.

The swamp needs a regular regime of summer rains to sustain sheetflow.

But in truth not even they along are often enough either. Case in point is what happened this past year. Sheetflow didn’t rise to its peak until after the summer rains were done and a trifecta of stalled fronts (or whatever they were) dumped in short order over 9 inches of October rain on the swamp.

Since then sheetflow has slowly and steadily declined.

Yes, most of the bridges along Tamiami Trail are still flowing, but the prairies that lie adjacent to where they flow are now mostly dry.

US Geological Survey at work measuring flows
at Turner River in Big Cypress Nat’l Preserve
February 2012

Special thanks to the US Geological Survey, Ft Myers and Ft Lauderdale offices, in coordination with Everglades National Park and the US Army Corps of Engineers for teaming up over the decades to measure flow across the Tamiami Trail.

It’s among the best and longest running data sets in the swamp.

Collecting all that data has involved lots of people over the years.

Most recently that includes Jaclyn and Craig.

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