The accumulation of beach material when there is an excess in the supply of sediment; see Goy et al. (2003) Geomorph. 50, 1–3. Progradation is a feature of, for example, delta and mangrove coasts; Hori et al. Geomorph. 41, 2 find that the average progradation rate of the Yangtze delta rose from 50 to 80 km/year about 2 000 years bp.