This paper describes some details and procedural steps in the equivalent resistance (E-R) method for simplifying the pier group of the Sutong Bridge,which is located on the tidal reach of the lower Yangtze River,in Jiangsu Province.Using a two-dimensional tidal current numerical model,three different models were established:the non-bridge pier model,original bridge pier model,and simplified bridge pier model.The difference in hydrodynamic parameters,including water level,velocity,and diversion ratio,as well as time efficiency between these three models is discussed in detail.The results show that simplifying the pier group using the E-R method influences the water level and velocity near the piers,but has no influence on the diversion ratio of each cross-section of the Xuliujing reach located in the lower Yangtze River.Furthermore,the simplified bridge pier model takes half the calculation time that the original bridge pier model needs.Thus,it is concluded that the E-R method can be use to simplify bridge piers in tidal river section modeling reasonably and efficiently.