[A-CG37] Water and Sediment Dynamics from Land to Oceans [En]

[ACG37-P05] Impact of Ebb-Delta Dynamics on Sediment Budget at Tidal Inlets

*Janaka Bamunawala¹、Shota Yamamoto¹、Keiko Udo¹ (1.Tohoku University)

キーワード：climate change impacts, reduced-complexity modelling, holistic modelling approach, catchment-estuary-coastal systems

Shoreline variation near tidal inlets can be assessed as a sediment budget-related issue and, therefore, depends on the sediment volume exchange between the inlet-estuary system and the coastal zone. Several factors contribute to this exchange of sediment volume at tidal inlets, including fluvial sediment supply from river catchment, sea-level-rise-driven estuarine sediment demand, longshore sediment transport, and ebb-delta systems in the vicinity. Understanding the holistic behaviour of these integrated systems (i.e., river catchment, inlet-estuary systems, and coastal zone) is important when projecting the future evolution of inlet-interrupted shorelines under climate change impacts and anthropogenic activities. Recently, researchers have investigated this holistic behaviour of catchment-estuary-coastal systems to project the future evolution of inlet-interrupted coasts while considering fluvial sediment supply (i.e., catchment contribution), estuarine sediment demands, and longshore sediment transport (i.e., coastal contribution). However, the role of ebb-delta dynamics and its impact on the sediment budget is yet to be investigated. Therefore, this research focuses on including ebb-delta sediment dynamics in the sediment budget calculations at tidal inlets by considering the Thu Bon estuary (Vietnam) as a case study. Here, the sediment reservoir concept for inlet sediment storage and transfer used in the CASCADE model was used to assess the contribution of ebb-delta sediment dynamics to the total sediment volume exchange between the inlet-estuary system and the coastal zone. The evolution of the selected inlet-estuary systems was assessed over the 21^st century under four of the IPCC’s sixth assessment report climate scenarios (viz., SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). The results indicate that including ebb-delta sediment dynamics significantly affects total sediment volume exchange, thus reducing coastal erosion along the up- and down-drift coasts at the tidal inlet. These results also highlight the importance of including ebb-delta dynamics in modelling efforts to assess the climate change responses of inlet-interrupted coasts worldwide.