Sustainable sediment management in ports
The development of a decision-making approach applied on a case study of Porto Amboim
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Abstract
Ports are located in deltas and dynamic coastal regions with large loads of fine sediment. Ports also enhance the import of marine sediment by channel and basin deepening. This results in the need for extensive maintenance and sediment management. Finding an effective and efficient sediment management strategy is difficult. This research dives into the current sediment management approaches and innovations to develop a decision-making approach to find the most suitable and sustainable sediment management strategy for a port.
There are several ways to optimize the sediment management in a port. With the principle to con sider sediment as a value resource to the port and the coastal system, rather than a waste, the sediment management hierarchy is obtained. This hierarchy consists of Prevent and Reduce, Recycle and Reuse and Disposal to find a sustainable sediment management strategy. Various Prevent and Reduce and Recycle and Reuse examples and methods are analysed in this research to identify their potential for sustainable sediment management. Furthermore, based on literature study, expert interviews and a workshop at Arcadis input is generated to propose a decision-making approach. This research develops an approach and a tool considering all the aspects of sediment management and for assessing potential strategies for sediment management in a port.
The decision-making approach considers four steps to find a sediment management strategy. The first step, sediment management objectives, defines the objectives of the stakeholders for the strategy. In the second step, fit to case, all the sediment management methods are considered and the potential strategies are defined. The third step, assessment of potential strategies, assesses the performance of each strategy with performance indicators in the decision-making tool. The performance indicators are selected based on the assessment categories and objectives. In the final step, meeting the objectives, the most suitable strategy is proposed and described for the long-term sediment management in the port. This approach supports the process to optimize sediment management in a port.
The proposed decision-making approach is applied and further developed with a case study on Porto Amboim. Porto Amboim is a port on the west coast of Angola. The port operates for the offshore industry and is currently experiencing sedimentation problems. The northward directed natural long shore sediment transport is interrupted by the port’s breakwater, resulting in sedimentation around the breakwater and at the lee side of the breakwater. This interruption disturbs the sediment balance in the region causing erosion problems at the down drift side of the port. The decisionmaking approach and tool are used to find a potential sediment management strategy for Porto Amboim. This potential strategy for Porto Amboim uses a sediment trap to manage the sediment in the region, ensuring sufficient port operations and restoring the sediment balance along the coast.
In order to use the approach in a generic way the results are reflected upon and a validation on the approach is performed. The reflection showed some uncertainties and limitations to the approach and tool because of the available information on the case. However, still two suitable strategies have been obtained for Porto Amboim. In the validation the approach has been applied on a second case study. This validation showed the potential for generic use of the decision-making approach and tool for sediment management. From the reflection and validation can be concluded that the available information determines the level of detail of the assessment of the potential strategies.
The main objective of this study was to explore the potential dredging and sediment management strategies to optimize sediment management in the port towards more sustainable methods, develop a decision-making tool and apply the tool in a specific case study. From this research the following can be concluded, the decision-making approach is considered a suitable approach to find a sediment management strategy for a port. All aspects of sediment management are considered and assessed. Therefore, further development of the tool and innovations in more aspects of sediment management are recommend. Yet, this research, the approach, and the innovative methods for sediment manage ment show a great potential for more sustainable maintenance strategies in the future.