An analytic investigation of the effect of surface seal mechanical properties, overland flow, and subsurface hydrology was performed on headcut development. Headcut growth rates on upland areas have been observed to be quite small (less than 0.00015 meter per second) and that they occur in increments in which chips break off at points where cracks have developed in surface seals. The substrate soil under the seal collapses and is removed by the flow. This mode of headcut development is the result of a strong interaction between the surface and the subsurface processes. The surface process is energetically controlled by the mechanical features of the seal whereas the subsurface process is hydrologically controlled. The analysis yields estimates of the temporal scale of headcut velocities. In cases of infiltration from the vertical gully wall into the substrate, the flexural wave velocity (seismic sound velocity) was found to inversely affect headcut velocity.