Spatial and seasonal impacts of submerged aquatic vegetation (SAV) drag force on hydrodynamics in shallow waters

Abstract Submerged aquatic vegetation (SAV) such as seagrass alters hydrodynamics as a drag force. Many studies have investigated the SAV drag force, but the time scales studied have been short (several days to a few weeks), ignoring seasonal variation, and the spatial scales have been small (several meters). Here, we performed field research and developed a new physical model incorporating seasonally varying SAV morphology (leaf length, leaf width, and shoot density) to investigate the effects of SAV drag force on the current field. We found that SAV attenuated the current velocity 50–70% during the 5-month computational period. Furthermore, the model showed a clear negative relationship between the leaf area index calculated from SAV morphology and current velocity. The physical model developed in this study can facilitate more accurate quantification of organic matter burial rates and the estimation of blue carbon sequestration by considering the SAV drag force.