Abstract: Reclamations in a hilly, fluvial and macrotidal estuary will narrow flood channels. Consequently, it may reduce the safety and stability of hydraulic structures downstream. For this, the paper calculated the maximum scour depth of piers of Yundan Bridge in Fujian province through a 2D numerical model, the semiempire and semitheory formulae about general scour and localized scour. The results indicate that, during flooding period, the scour depth of piers of Yudang Bridge is comparatively serious; so it is necessary to take protecting measures for piers. In addition, influence factors about the maximum scour depth of bridge piers are discussed, and then the conclusion is put forward that actual scour depth of piers hardly reach the calculated amount.

Key words: fluvial and macrotidal estuary, reclamation, general scour, localized scour, hilly, fluvial and macrotidal estuary, reclamation, general scour, localized scour