The Ishikari coast of Hokkaido, Japan is a wave-dominated semi-enclosed coast, the sediments of which are primarily sourced from a single river (the Ishikari River), forming a northeast deflected delta. Asymmetric and deflected deltas are generally considered to be formed under net longshore sediment transport downdriftward; however, through sedimentological and grain-size trend analysis (GSTA) of seafloor sediments, along with some other observational data, we recognised dominant updriftward sediment transport on the updrift-side of the deflected delta system. GSTA showed that the most important trend in the coast is coarser, better-sorted, and more positively skewed (CB+). CB+ trends around the river mouth converge from the lower shoreface zone to the river mouth spit on the updrift side. The trends reflect the combined effects of shore-normal wave action and river sediment discharge. Wave-driven surface currents crossing over the delta lobe converge at the southwestern side of the river mouth. In the deeper zone (lower shoreface), southwest (updriftward) oriented CB+ trends prevail. These trends reflect successive re-deposition of delta front sands, with progressive mud winnowing, driven by the strong south-westerly bottom currents observed in the bay during winter storms. Although GSTA did not show any apparent trend field in the nearshore zone, gradual fining of sand fractions to the southwest, along with the chronological transition of the coastline after the construction of a large port (trap of drifted sands on the downdriftside of the port and regression of coastline on the updriftside of the port), suggest a dominant longshore sediment transport updriftward on the updrift-side of the delta. Because the growth of deflected deltas depends on dominant sediment accretion on the updrift-side, these results can be rationalised in the case of internally sourced deflected deltas. Uncertainties remain regarding the net alongshore sediment transport of the entire Ishikari coast; however, the deflected planform is controlled by deflected mouth bars and river mouth jets due to the waves approaching the river mouth at slightly oblique angle in winter, and is likely independent on the direction of dominant sediment transport.

日本北海道的石狩海岸是波浪主导的半封闭海岸，其沉积物主要来自一条河流（石狩河），形成了东北偏斜的三角洲。通常认为非对称和偏转的三角洲是在净的近岸沉积物向下运移的情况下形成的; 然而，通过海底沉积物的沉积学和粒度趋势分析（GSTA），以及其他一些观测数据，我们认识到主要的向上漂移偏斜三角洲系统上流侧的泥沙输送。GSTA显示，沿海地区最重要的趋势是更粗糙，分类更好，更正偏斜（CB +）。河口周围的CB +趋势从下岸面区域汇聚到向上漂移的河口吐水处。这些趋势反映了海岸法向波浪作用和河流泥沙排放的综合影响。跨过三角波的波浪驱动的地表水汇聚在河口的西南侧。在较深的区域（较低的海面），以西南（向上漂移）为导向的CB +趋势占主导。这些趋势反映了三角洲前砂的连续沉积，以及逐步的泥沙淤积，这是在冬季暴风雨期间在海湾中观察到的强烈西南向洋流驱动的。尽管GSTA在近岸地区未显示任何明显的趋势场，但在建造大型港口之后，向西南方向逐渐细化了沙粒，并伴随着海岸线按时间顺序的过渡（在港口的下漂流处捕获了漂移的沙尘）。港口上游漂移的海岸线回归分析）表明，在三角洲上游漂移的主要近岸沉积物运移向上游漂移。由于偏转三角洲的增长取决于向上漂移侧的主要沉积物积聚，因此，对于内部来源的偏转三角洲，这些结果可以合理化。关于整个石狩海岸的净近海沉积物运输仍存在不确定性；然而，