SCOUR AT DAHSHOOR BRIDGE USING NUMERICAL MODELING AND NOVEL PIER SCOUR EQUATION

In Egypt, concerns about bridge pier scour is one of the important reasons for limiting the increase of the current flow releases from High Aswan Dam (HAD) above the current maximum of 270 Million m 3 /day. Higher flows might induce general scour at a bridge section if the bridge section is located in a scouring reach. In order to release higher flows than the current maximum, knowledge is required about how much total scour is expected around bridges built across the Nile River. Due to the importance of bridge pier scour, many investigators have worked on this critical subject but most of them have built their analysis on laboratory flume data that suffer from having simplified conditions and scale effects. When applying the existing empirical equations for predicting bridge pier scour to field cases, the scour depths are overpredicted which means increased construction costs. A new analytical equation for predicting pier scour is developed, Hafez 2004a, which are based on an energy balance theory. The developed equation expresses equilibrium bridge pier scour depth in terms of flow velocity, flow depth, bed sediment specific gravity, porosity and angle of