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Lignumvitae / Indian Key waterway

Labor Day Hurricane 1935

Page 4:  Lignumvitae / Indian Key Waterway

To recap, a railroad was built across the Florida Keys mostly using dikes and viaducts, and the railroad was converted to a highway for trucks and automobiles. This infrastructure blocks tidal flow between Florida Bay and the Atlantic Ocean.


Figure 4.1:  Channel 5 viaduct and Craig fill, 1977.


Fig. 4.1 above shows a viaduct on the left connected to a dike on the right. The dike on the right blocks laminar flow of water over a shoal that may have had two navigable channels in it. A new bridge (not shown in this photo) has been built in front of the viaduct on the left, producing less turbulence than the viaduct, but the viaduct has not yet been torn down despite producing turbulent flow that retards water exchange between the gulf and ocean sides of the Keys.

On the other side of Lower Matecumbe, the waterway between Lower Matecumbe and Upper Matecumbe is spanned by long dikes with small bridge openings. The entire span could be a single bridge, or mostly bridges with small fills. Instead, mostly fills with small bridges are used, with the long fills perpendicular to tidal flow (providing storm surge blockage and turbulence).

Nautical charts from the 1860s show no land directly between Upper and Lower Matecumbe Keys.


Figure 4.2:  Nautical chart, 1861. [LOC]


Figure 4.3:  Nautical chart, 1864. [LOC]


A railroad dike was built directly between Upper and Lower Matecumbe Keys, along with a highway on wooden piers parallel to the railroad.

The 1935 Hurricane broke the highway off its piers and washed away parts of the railroad dike. Fig. 4.4 shows ebb current, after the 1935 Hurricane, draining water from Florida Bay in the background to the Atlantic Ocean in the foreground. Even though part of the dike is breached, it is still restricting ebb current, showing turbulence.

Restricting ebb current diverts water to surrounding areas that would otherwise drain to sea, draining Florida Bay more slowly causing damage to other Keys.


Figure 4.4:  Lignumvitae / Indian Key waterway after the 1935 Hurricane.


The dike has been mostly refilled, with gaps for small bridges. Fig. 4.5 below is part of a modern nautical chart showing the new dike across the Lignumvitae / Indian Key waterway.


Figure 4.5:  Modern nautical chart.


Opening up this waterway between Upper and Lower Matecumbe with mondern bridges would allow laminar flow of ebb current after a hurricane to ease pressure on neighboring Keys. Any fills should present minimal hydraulic cross section to water flow direction, not perpendicular to water flow.


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