Field observations and grain-size analyses have been conducted on the formation and development of tidal couplets, as well as sedimentation before and after the storm surge of the Typhoon No. 11 of 1997 (Typhoon Winnie) on the tidal flats of central Jiangsu Province, China. The observations and measurements indicate that thin couplets (thickness 10⁻¹–10⁰ mm) form during normal flood–ebb cycles, whereas thick tidal couplets (thickness 10⁰–10¹ cm) form during spring–neap cycles. The results also suggest that, even during storm-surge conditions, sediment deposition still occurs on some high tidal flats. Compared with normal tidal-flat sedimentation, storm sedimentation is associated with coarser particle sizes, poorer sorting, more rounded particles, and clearly graded parallel- or cross-bedded sequences.