Multi-criteria analysis on Sedimentation Enhancing Strategies using a best-practice based decision support tool
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Many deltas around the world are confronted with subsiding land and reduced sediment inflow, a problematic scenario particularly when combined with a rising sea level. To prevent drowning and to maintain the morphological functioning of the delta, sufficient sediment and an effective sediment management are crucial. Sedimentation Enhancing Strategies (SESs) concern measures that enhance natural sedimentation processes in deltas in a suitable manner. Many SESs are designed for local use and are case specific. Best practices and guidelines that would help to use these designs in other deltas, are lacking. The main objective of this research is to determine the suitability of an existing SES as sediment management for any other delta. Therefore, I developed a decision supporting tool that scans the applicability, merits and risks of SESs. The criteria to assess the suitability were based on a literature research and an expert consultation on case-studies from the Danube, Ems-Dollard, Ganges-Brahmaputra, Mississippi and Rhine-Meuse deltas. Adding new data in future adds to the merits of the tool; the present version is a good proof of principle. Since the relevant aspects are multidisciplinary, the tool includes a multi-criteria analysis for an automated assessment of the applicability of existing SESs for other deltas. The criteria that determine the applicability of SESs are local biophysical settings, presence of a levee or polder system, restricting budget, available outfall area and the primary interests of the decision maker that uses the tool. These interests concern environmental impact and the necessary or desired land use/type change. Not all criteria could be quantified in the multi-criteria analysis, for example the rate of stakeholder involvement/participation and acceptance. The assessment by the tool can be considered indicative since all successful Sedimentation Enhancing Strategies require taking into account site-specific considerations. This emphasises the importance of more and improving designs, pilots and/or upscale modelling of implemented or planned SESs.