Docks on the St. Johns River

A slow river with small tides

The St. Johns flows north for 310 miles and drops less than 30 feet over that whole distance, about an inch a mile. The ocean tide reaches far upriver and reverses the flow twice a day.

The tide gets smaller as you go south. The average range is about 1.8 feet at downtown Jacksonville, about 0.9 feet at the Buckman Bridge and about 1.3 feet at Palatka. A fixed dock is often the simple choice on these stretches, because the water does not rise and fall far.

Wide water and wind

In Clay and St. Johns counties the river is more than two miles across in places. Wind blowing over that much open water builds waves that hit docks on the exposed shore, from Mandarin and Fleming Island down to Green Cove Springs.

Ask how the platform and the lift are set up for waves from the open side, and how high the deck sits above normal water.

Shallow shores

Much of the river shore slopes gently, so the walkway may have to run a long way out to reach water deep enough for a boat at low water. A longer walkway uses more of the area allowed over the water, which leaves less for the platform and a roof.

Creeks and side waters

Julington Creek, Doctors Lake and the creeks off the river are more sheltered than the open river. The builder still checks the depth at the spot where the boat will sit.

Questions to ask

• How long does the walkway need to be to reach usable depth?
• How is the dock set up for waves from the open river?
• Is a fixed dock enough for my tide range, or is a floating section worth it?
• Which county building department handles my address?