Why Belle Isle and South Beach flood without rain


West Avenue and Sixth Street on Friday morning.


By now, we’re all accustomed to the experience: Heading to work on a seemingly dry morning to find specific area ankle deep in water, no sign of rain but cars sloshing through a mini-flood.

The even-deeper water Thursday and Friday really begged the question: Why does South Beach flood when it’s dry?

We’ve heard it’s the high tide (and it is) and we think it’s worse now than it’s been in years past, though that’s debate-able. There was a similar spate of flooding just last fall (September, not October).

An unfortunate reality about South Beach: It’s just a bump above sea level. The lowest point is at Alton Road and 10th Street — less than three feet above sea level. You saw plenty of water there this week. Belle Isle is just a touch higher.

And facts about tidal forces: Every fall, the moon and earth align in a way that creates the highest tides of the year. It happens in the fall, but they call it a spring tide. A new moon, like we had this week, produces the highest flow, and a new moon at its closest pass of the earth only amplifies the effect.

So the tide is at its highest, and then goes even higher — maybe an extra foot because of the close pass of the earth. The canal on Dade Boulevard overflows it’s banks and seawall. Seawater pours out of the sewers, where rainwater is supposed to flow.

When you combine a full moon with a rain storm, you get what happened the last two Junes, when Belle Isle and the rest of South Beach flooded in about an hour of downpour.

The city hopes the solution to the problem will come from a $1 million engineering study it commissioned in June to devise a master plan to make the city’s stormwater system cleaner and less flood prone. Once that study is complete, Miami Beach will need to spend bigger bucks — and time — rebuilding the system.

Until that brings stronger pumps and new and bigger sewer pipes, we’ll continue to work a tough equation: Low land + high tides = flooding.


6 responses to “Why Belle Isle and South Beach flood without rain

  1. WOW. That was an explanation that even I can understand. Thanks, Belle Isle Blog Person !

  2. Very cool info. We have the same thing occur here in Southern California (Huntington Beach). The famous Pacific Coast Highway floods with seawater during the highest tides of the year.

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