The local scour at abutments, elliptical and straight guide banks in plain rivers was studied. The flow pattern and the scour hole parameters at abutments, elliptical and straight guide banks are different. Some researchers believe that the guide banks can be used to protect the abutments, namely to remove the scour hole from the abutment. But the scour hole does not disappear; it is developing at the head of a straight guide bank and is of a greater size than that at abutments. The scour near the straight guide banks has not yet been studied. A streamline concentration, a local increase in flow velocity, vortex and eddy structures, flow separation, an additional flow contraction by a separation zone, and a scour hole were observed at the head of the straight guide banks. The differential equation of equilibrium for the bed sediment movement in clear water is used, and a new method for computing the scour development in floods at straight guide banks is elaborated. The method is confirmed by experimental data. This method can be used for predicting in advance the scour development at straight guide banks with the flow and riverbed parameters varying during floods of different probability, sequence, frequency, and duration.