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Extra Notes

Labor Day Hurricane 1935

Page 7:  Extra Notes
Hawk Channel

Hawk Channel is the long strip of Atlantic Ocean between the Florida Reefs and the Florida Keys. Hawk Channel may be deeper than the reefs, forming somewhat of an underwater bay between the reefs and the shore, or more precisely a wide channel.

Figure 7.1:  Indian Key to Alligator Reef ocean depths (feet).


Fig. 7.1 above shows ocean depths between Indian Key (upper-left) and Alligator Reef (lower-right). The reef is shallower than the ocean between the reef and the Keys (Hawk Channel). The ocean floor becomes much deeper past the reefs.

“Because reefs grow vertically to the low tide level, they provide very effective shelter to the coast… The more closely a reef is located to the coastline, the greater the shelter will be… Reef development may take place some distance offshore, in which case greater fetch and depth between reef and shore leads to higher energies impinging on the coast.”
— 
Charles R.C. Sheppard, “Coral Reef Coasts”, in Encyclopedia of Coastal Science p. 339

The Florida Reefs are not very close to shore, but not too far either, providing some coastal protection. For example, the storm surge of the 1935 Hurricane was recorded to be much higher at Alligator Reef than at shore.

Florida Bay is not deep, but is much wider than Hawk Channel, so it can hold much more water than Hawk Channel. The storm surge dumped a huge amount of ocean water into Florida Bay. Then the ocean level dropped suddenly, and Hawk Channel drained into the ocean (laminar flow) much faster than Florida Bay could drain into Hawk Channel (retarded flow), causing hydraulic head water pressure in the ebb current direction.

Technical Note: Coch, p. 222, Fig. 8.10a, refers to Hawk Channel as “Reef Back Bay”. The third word on p. 223 (“bay”) refers to Hawk Channel, not Florida Bay.


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