A compilation of data on the effects of hydromorphological threats on Posidonia oceanica and Cymodocea nodosa seagrass species was conducted. A literature review was carried out to determine specific parameters for defining, on the one hand, the hydrodynamic impact and, on the other hand, the morphological impact. Regarding the hydrodynamic impact, the maximum hydrodynamic conditions that seagrasses can withstand in a given area are reflected in the position of the upper limit of these meadows. Data for defining this upper meadow limit were extracted from the literature. Velocities that favour seagrass growth and thresholds above which uprooting of plants may occur were also identified in the literature. Additionally, the importance of maintaining minimum velocities above a certain threshold to prevent a decrease in internal oxygen levels as the flow velocity decreases was highlighted. A literature review was also conducted on numerical models to estimate the hydrodynamics on the position of seagrass meadows. These models serve as valuable tools to enhance the understanding of hydrodynamic and morphological conditions affecting seagrasses in specific areas.
Regarding morphological impacts, damage functions for burial and erosion levels were developed for different seagrass species using data from laboratory experiments and field studies available in the literature. The search was extended to all seagrass species worldwide. The species included in the analysis were Cymodocea nodosa, Cymodocea serrulate, Posidonia oceanica, Zostera noltii, Zostera marina, Halophila ovalis, Halodule uninervis, and Syringodium isoetifolium. Burial and erosion thresholds for 50% and 100% mortality of shoots were extracted. At 50% mortality, some species showed the capacity to recover from these impacts, whereas at 100% mortality, shoot death was observed to be independent of the duration, frequency or timing of events. The results of this project can also be applied to the design of sand fills to conserve adjacent seagrasses by gradually distributing sand across the beach profile and avoiding burial levels that exceed the identified mortality thresholds.
Additionally, literature data on the design of breakwater armour units were compiled and analyzed to identify design criteria that optimize the ecological function of breakwaters and reduce the carbon footprint of concrete production. Implementation barriers that need to be addressed for effective implementation and broader adoption of more sustainable and multifunctional coastal defences were also proposed.
The participation in leading national and international coastal engineering conferences allowed for the dissemination of results and engagement with the scientific community interested in innovative advances related to Nature-based Solutions, and engineering consultancies as end-users of the project results to integrate them into their projects. The dissemination of results at conferences and during the secondment also facilitated collaborations with researchers working in the same field.
