Bligh's creep theory ● According to Bligh's Theory, the percolating water follows the outline of the base of the foundation of the hydraulic structure. In other words, water creeps along the bottom contour of the structure. The length of the path thus traversed by water is called the length of the creep, L. L = LH + LV ● Further, it is assumed in this theory, that the loss of head is proportional to the length of the creep. ● If HL is the total head loss between the upstream and the downstream, and L is the length of creep, then the loss of head per unit of creep length (i.e. HL/L) is called the hydraulic gradient. ● Note, Bligh makes no distinction between horizontal and vertical creep.