A first-order link between local separation of supersonic turbulent boundary layer flow and structural deformation is established. First, mathematical analysis of the Kármán-Pohlhausen momentum integral equation is carried out with the assumption of spatially varying surface topology in order to identify fluid-centric representations of structural deformation. Next, a data-driven approach is used to identify the dominant fluid-centric parameters.This ultimately yields a simple linear correlation between local skin friction coefficient and surface curvature, which is the unifying parameter relating deformation and separation. This link represents a key step towards deep understanding on the nuanced interplay between turbulent boundary layers and structural deformation; and significantly improves fundamental understanding of fluid-structure interaction problems with prominent turbulent boundary layer dynamics.