Wind-wave generation, affected by mud-induced wave dissipation in Deylam Bay

Considerable decay of wave energy along the wave trajectory over muddy beds makes a different wave generation/transformation in comparison with sandy/rocky environments. The role of soft mud to dissipate waves has been recently implemented to SWAN wave model. A new dispersion relation obtained from a two-layer viscous model is implemented in the wave-simulation model, SWAN-mud, to consider wave decay in coastal areas due to the presence of fluid mud deposits. Significant wave heights over gentle muddy slopes are usually overestimated using default SWAN model setup, while it is expected that using SWAN-mud setup, improves the correlation between model simulations and real field measurements. However, considering the viscous assumption of mud behavior in developing new dispersion relation, the model results are highly dependent on the assumed mud rheology and mud behavior in reality.The north-western part of the Persian Gulf is covered by mud deposits originated mainly from the Arvand River catchment area. Mud deposits up to 20 meters thickness are observed at the very shallow coast of Deylam Bay, which implies high rates of wave dissipation in the area; something which should be taken in to consideration for wave climate estimations. A set of 37-days field measurements in 2007 is available for model performance validation. This research aims to adopt various facilities implemented in SWAN wave model to regenerate the wave measurements at a mid-depth station in Deylam Bay, over the muddy bed of Northern Persian Gulf with acceptable accuracy. A number of about 30 model configurations are considered for wave generation over the mud coast of Deylam Bay. Input wind data are adopted from ERA5 product of ECMWF global model. WRF model is adopted to improve input wind data accuracy as well. The focus of this study is to develop a proper hindcast and forecast system for predicting wave characteristics in the north-western of Persian Gulf, including the mud induced wave dissipation in the areas covered with soft muddy deposits. The developed model considering mud-induced wave dissipation is validated against available field data. Based on the achieved results, the ordinary SWAN model setup is not capable to well estimate all the storm events in the period of measurements. However, considering the mud-induced dissipation, implemented in SWAN-mud model, the developed model is capable to capture all the events with different combinations of wave properties in the study area. The final model predictions favorably agree with the field survey data in the study area.