Hydrodynamic and dispersion modeling as a tool for restoration of coastal ecosystems. Application to a re-flooded lagoon

Abstract

Protection of endangered coastal ecosystems is today of great environmental interest and scientific value. Numerical models have been developed and applied to coastal areas, in order to simulate hydrodynamic and environmental processes. These models constitute an excellent tool in order to apply the right measures to restore the endangered environments. Drana lagoon is a recently re-flooded water priority ecosystem (Nature 2000 network). It was drained in 1987 and seventeen (17) years later it was restored (2004). The purpose of this study originated from the need to protect and manage Drana lagoon, an ecosystem with great environmental interest, scientific and economical value. In the first part of this paper, water circulation inside the lagoon was simulated, using a hydrodynamic model. Several cases were investigated based on different driving forces, such as tide, wind and fresh water inflows. The hydrodynamic model reproduced the water level measurements with great success as long as the RMS between measured and predicted water levels didn't exceed the 4% of the data range during validation (model skill = 0.98). In the second part, an advection/dispersion model was used for the spatial and temporal simulation of both temperature and salinity. Oceanographical and meteorological field measurements were used for the calibration and validation of both models. The computed daily water temperature variations were well correlated with the data gained during the field observations. The measured and the computed time series present a model skill equal to 0.90 for the station S879 and 0.93 for S892 during validation, while the RMS vary between the two stations from 14% to 10% of the temperature data range. The salinity variations in the first station are described adequately (skill = 0.83, RMS = 15% of the data range) by the model, however the measured salinity for the second station cannot be reproduced as well. Drana lagoon is a hypersaline water ecosystem. After its re-flooding, the fresh water discharge from two drainage channels and the way these discharges can affect the salinity distribution was investigated. The spatial salinity distribution inside the lagoon was simulated for three different scenarios. © 2007 Elsevier Ltd. All rights reserved.