At optimal angle of attack, occurrence of destabilizing local scour phenomenon especially around the leading edge of the vane is formed and at this angle vane induced secondary circulation is also maximum. The maximum scour depth around the vane mainly depends on flow depth and flow Froude number. Flow Froude number is more important than Densimetric Froude number. This will presuppose checking the magnitude of local scour around the submerged vanes by a suitable local scour retarder method. © 2005 Taylor & Francis Group, LLC.