Hydrodynamic modelling of a sea-crossing bridge in the Maldives

Abstract

‘Gaadhoo Koa Channel’ is an atoll pass located in the southern tip of Male Atoll, Maldives, which separates the capital city, Male and the main international airport Hulhule island. The Gaadhoo Koa channel is known for its strong tidal flow and strong swell waves and is located in a strategic area which includes the main shipping lane for Male port and also marine traffic lanes connecting both Male and Hulhule with nearby inhibited islands and tourist resorts. Recently, a water crossing bridge has been constructed across the channel connecting these two islands. As a result, 21 bridge piers have been built across the channel which can result in potential changes of the flow regime in the vicinity of the bridge. This project report presents a numerical modelling study to investigate the hydrodynamic impact of the bridge piers in the Gaadhoo Koa channel. Various different software used for hydrodynamic modelling were explored and Delft3D-FLOW software was chosen. The model results were calibrated against water level data from Hulhule station and finally model simulations were run to assess the hydrodynamic impact of the bridge piers. The results indicated that the flows in the close vicinity of the bridge were reduced with the introduction of bridge piers. Also, the magnitude of flow velocity reduced around bridge piers and increased in between bridge piers. Furthermore, the overall velocity distribution in the northern region from the bridge axis showed a decreased pattern while the southern regions showed an increased pattern: peak velocity in the northern region decreased by 7.3 % 500 m from bridge axis while peak velocity in the southern region raised by 33% 500 m from bridge axis. Based on these findings, it can be considered that the introduction of bridge piers can have a considerable impact on the hydrodynamic conditions of Gaadhoo Koa atoll pass.