Analysis of water quality and circulation of four recreational Miami beaches through the use of Lagrangian Coherent Structures

- Four beaches in Miami, FL are analyzed using Lagrangian Coherent Structures.
- The LCSs are computed from a hydrodynamic model using the geodesic theory of transport barriers.
- Two of the beaches have a history of poor water quality.
- The LCSs are used to explain how circulation and mixing influence the water quality at each beach.

Four popular, recreational beaches in Miami, FL are Hobie Beach, Virginia Key Beach, Crandon Park Beach, and Bill Baggs Cape Florida State Park. While all of the beaches are within a few miles of each other in Biscayne Bay, they have greatly differing water qualities, as determined by the testing for fecal indicator bacteria performed by the Florida Department of Health. Using the geodesic theory of transport barriers, we identify Lagrangian Coherent Structures (LCSs) in each area. We show how these material curves, which shape circulation and mixing patterns, can be used to explain the incongruous states of the water at beaches that should be comparable. The LCSs are computed using a hydrodynamic model and verified through field experimentation at each beach.