Evaluation of Flushing Efficiency in an Embayment System Depending on Different Channel Configurations Using FVCOM: A Case Study in Abu Dhabi

In order to address water quality problems around the Corniche Island area in Abu Dhabi, the capital of the United Arab Emirates, a study was conducted to characterize existing conditions and investigate possible mitigation measures. The overall study includes field experiments to acquire hydrographic, water quality, habitat data, and hydrodynamic and water quality modeling to assess various alternatives. This paper focuses on the results of the hydrodynamic modeling done in support of the study. This study investigated the flow conditions in the New Corniche area of Abu Dhabi under three channel configurations. Configuration 1 represents existing conditions, Configuration 2 represents conditions prior to a resort development inside the bay, and Configuration 3 considers several new channels through the mangrove habitat. The FVCOM (Finite Volume Coastal Ocean Model) was used to generate spatially and time varying currents and water elevations. A comparison of the model-predicted currents for each of the three configurations indicates that Configuration 2 results in the strongest currents in the southern part of the bay and at the eastern end of the channel south of the mangrove habitat. There is very little difference in the currents at these locations for the other two configurations, although Configuration 3 does show a small increase in current speed over existing conditions at the eastern end of the channel. Currents in the mangrove habitat are weakest for Configuration 2, slightly stronger for Configuration 1, and markedly stronger during the flood cycle, but generally weaker during the ebb cycle for Configuration 3. These results indicate that Configuration 2 provides the strongest flows (and potentially the best flushing) in the channel located south of mangrove area while maintaining low flows in the mangrove habitat. A simple Lagrangian particle model was employed to provide a first-order estimate of the flushing characteristics to be expected from each of the three channel configurations. Using the model-predicted circulation for each configuration, particles were released at three locations around the New Corniche mangrove area: the eastern, middle, and western part along the channel south of the mangrove habitat. The particles were then tracked for 15 days as they moved in response to the model predicted currents for each channel configuration. A visual analysis of the particle distribution showed that in Configuration 1, particles released at the eastern location were quickly transported both into the mangrove area and out of the study area, while particles released in the middle section moved much more slowly through the system, and particles released at the western part moved very little. In Configurations 2 and 3 the particles released at all locations were distributed much more quickly and flushed out of the system. Considering the particle transport in terms of the percent of particles remaining within the New Corniche mangrove habitat area, Configuration 2 provides the greatest flushing (least retention) of particles released at all sites. Configuration 3 provides some improvement in flushing over that of Configuration 1, particularly for particles released at the Resort, but is not a significant improvement for particles released.