"The One-Millionth Weihe River Map" compiled in 2005 reveals that the areas around bridges are the typical nodal points on the Weihe River.Using the measured data along with the map and other relevant information,this paper concludes that the main river channel becomes narrow as side shoals build up around the bridges.The main river channel leans toward one side of the bank,and curved waterway develops up and down the bridges,which imposes great eroding force to the bank.The maximum discharge by the bridges neither bears the flood with return period of 100 years or over if the roughness coefficient n=0.025 nor bears the flood with return period of 30 years if n=0.035.The gradient around the bridges becomes smaller than that of others on the river,generally leading to the turning of the river bed and the piling-up of sands,hence smaller gradient and lower water flow speed.The bridge areas in the urban quarter of Baoji City,especially the area around the Wolongsi bridge,become the greatest threat to the city when flood occurs.