Hydrodynamic and Sediment Transport Model Application for OSAT3 Guidance: Significant wave height

The U.S. Geological Survey has developed a method for estimating the mobility and potential alongshore transport of heavier-than-water sand and oil agglomerates (tarballs or surface residual balls, SRBs). During the Deepwater Horizon spill, some oil that reached the surf zone of the northern Gulf of Mexico mixed with suspended sediment and sank to form sub-tidal mats. If not removed, these mats can break apart to form SRBs and subsequently re-oil the beach. A method was developed for estimating SRB mobilization and alongshore movement. A representative suite of wave conditions was identified from buoy data for April, 2010, until August, 2012, and used to drive a numerical model of the spatially-variant alongshore currents. Potential mobilization of SRBs was estimated by comparing combined wave- and current-induced shear stress from the model to critical stress values for several sized SRBs. Potential alongshore flux of SRBs was also estimated to identify regions more or less likely to have SRBs deposited under each scenario. This methodology was developed to explain SRB movement and redistribution in the alongshore, interpret observed re-oiling events, and thus inform re-oiling mitigation efforts.

美国地质调查局（U.S. Geological Survey）开发了一种方法，用于估算比水密度更大的沙粒与油团聚体（油球或表面残留球（surface residual balls，SRBs））的迁移能力及沿岸输运潜力。在深水地平线（Deepwater Horizon）漏油事件期间，部分抵达墨西哥湾北部冲浪带的石油与悬浮泥沙混合并沉降，形成潮下垫席。若未被清除，这些垫席会碎裂形成SRBs，进而重新污染海滩。研究人员开发了一种用于估算SRBs迁移及沿岸运移的方法。研究团队从2010年4月至2012年8月的浮标数据中提取了一组代表性波浪条件，以此驱动空间变异的沿岸流数值模型。通过将模型输出的波浪与流共同诱导的剪切应力，与不同粒径SRBs的临界剪切应力值进行对比，估算了SRBs的潜在迁移能力。同时还估算了SRBs的潜在沿岸通量，以识别各情景下SRBs更易或更难沉积的区域。该方法旨在解释SRBs的沿岸运移与再分布过程，阐释已观测到的复油事件，从而为复油防控工作提供决策依据。