A blog dealing with Sarasota County and the City of Sarasota.

Sunday, October 27, 2013

The Image that Inspired Jono's "Hole in the Shoal" Column

The Sarasota Herald Tribune was kind enough to run my guest column on October 27th, but it did not run with the Google Earth image that inspired the piece. reproduced below is my column with the Google Earth image. 


Watching the suspenseful lost-in-space movie, Gravity, I felt guilty at times -- abandoning the tense plot to stare at our wondrous planet. With borders erased and most human works minimized, it's so very easy to appreciate the sublime character of Earth. That got me wondering about what natural phenomena in Sarasota look spectacular from space, so I fired my laptop spaceship, Google Earth, and gazed down at Florida.  

The Gulf shoreline and darker “Myakka Island” area make Sarasota County easy to find. But being recognizable is not the same as being beautiful. I love the two Myakka lakes, but from space they are dark, potato-shaped blobs. Our beaches, which are so dramatic on the ground, are mostly fine white lines from space. The only naturally gorgeous natural phenomena I see are the two luminous, sinuous tongues of sand to the north and south of Lido Key. These are the so-called ebb tidal shoals of New Pass and Big Pass – glowing pale green flames flickering in a blue sea.

The Big Pass shoal is particularly striking. Two miles long, it departs from South Lido Park starting out wide and then turns and narrows in a reverse S curve, sheltering the north end of Siesta Key. Our other passes have been straitjacketed or bridged, but Big Pass remains wild and powerful  -- the juxtaposition of massive quantities of water and sand reshaping each other in a daily dance -- a place where the raw power of the Gulf can still be easily appreciated. Boaters and bathers need to be attentive and respectful.

These shoals are the result of two forces in dynamic tension. As the result of currents and winds, sand is generally moving from north to south along the Gulf shore. Meanwhile tides are surging in and out of the passes. The inhalation and exhalation of the bays sucks some sand into flood tidal shoals, and blows other sand out to ebb tidal shoals. Despite these distortions in flow, the sand keeps moving and the north-to-south trend is evident in the southward-bending shape of the shoals. While some of the sand lingers in the shoals, other sand continues on – so, metaphorically, some of Lido’s sand today was Longboat’s yesterday, and will be Siesta’s tomorrow.

The shallow shoals dissipate wave energy, which is why we see waves breaking on them. So in addition to passing some sand along to the next island, they shelter the shore in their lee, creating calmer areas that can lead to the accumulation of sand. In the passes this sheltering effect is contradicted by the force of water flowing in and out, but as the tidal flow is distributed, the wave shadow effect becomes more noticeable. So the shoals are doing at least three things: passing sand along, dissipating wave energy (sheltering areas of the shore), and thereby allowing for sand accumulation.

The competing forces that shape the shoals are so complicated (and so subject to random catastrophic events) that it requires extremely complicated and memory-intensive computer programs to even approximate pass behavior. There are very few people qualified to assess the predictive ability of these computer models. That doesn’t matter when the models are solely academic exercises meant to increase understanding of our barrier islands and passes.

But when people start using such models to make decisions about our beaches, then you want to make sure you understand the risks involved. Right now the City of Sarasota and the Army Corps of Engineers are proposing to remove more than 43 million cubic feet of sand from the Big Pass shoal. That’s going to create a big hole in the shoal. They want to put it on Lido Beach (and add three rock groins). The proponents have concluded, based on computer models, that the only noticeable effect of removing so much sand will be some “minor” increase in wave heights along the Siesta side of the pass.

But their model and conclusions have not been peer-reviewed. Local boaters, elected officials, homeowners, and other citizens do not have the training to assess how reliable these models are, so the only hope of objective interpretation of the risk to the shoal, and consequently the Siesta side of Big Pass, North Siesta Key and Siesta Beach lies in getting qualified experts to weigh in.

Did I mention Siesta Beach could be affected? The dramatically-wide Siesta Beach famed for its fine, blinding-white sand and gentle, family-friendly slope – our most popular park – the beach named the number one beach in the country in 2011.

Anyway, the City and the Corps are not currently planning on any peer-review (or any public hearings) on their hole-in-the-shoal proposal that will cost $23 million dollars and require a 50-year commitment with the Federal government. What could possibly go wrong with a plan like that?

1 comment:

  1. Mr. Miller raises fact filled concerns for a compelling need for peer review of the Corp's model. After all isn't that just using sound science before spending $23 million dollars and changing a shoreline that can be seen from space?


Please feel free to comment. Anonymous comments will not be posted. Others will be screened for appropriateness, but not position.