| A Study of Hydrodynamics, Salinity, and Waves in the Acadiana Bay System |
PRESENTATION
William Miller Jr., Ph.D. bmiller@taylorengineering.com
Taylor Engineering, Inc., 9000 Cypress Green Drive, Suite 200, Jacksonville, FL 32256
Abstract
The Lower Atchafalaya River empties into Atchafalaya Bay and influences the Acadiana Bays system along the southwest coast of Louisiana. The system — Atchafalaya Bay and four bays to the west — receives most of its freshwater from the Atchafalaya River through the Wax Lake Outlet and Lower Atchafalaya River discharges.
Since the 1930s the system has changed from a brackish to a primarily freshwater environment and has experienced major waterway construction and mining of oyster reefs and shell deposits separating the western bays and the freshwater sources. Many attribute the freshening of the bays to the removal of this barrier. To understand the dynamics of the system, Taylor Engineering, Inc. developed two‐dimensional depth‐averaged numerical hydrodynamic and water quality models of the system. The models — calibrated for existing conditions using data from local sensor stations — examined seasonal variations of tide, river discharge, and wind as driving forces.
The models also simulated the restoration of oyster and shell reefs and pre‐1940 tributary configurations to examine their influence on the salinity of the system. The study results suggest that changing freshwater discharge rates, rather than oyster reef mining, caused most of the historical variations in salinity. A parallel study applied a two‐dimensional spectral wave model (STWAVE) and calibrated the model with site‐specific data. The study found that the muddy bottom dissipated the waves during normal conditions and high frequency storms. The addition of a bottom dissipation term to the STWAVE model simulated this effect.
The Louisiana Department of Natural Resources funded this study. |
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