A physically based model of soil surface sealing is proposed. The governing equations are formulated on the principle of conservation of mass assuming Darcy's law applies to a suspension lowing through the soil surface. The model incorporates the physics of surface sealing by mechanisms that capture suspended particles moving with infiltrating water. As a result of particle retention in the soil system, the intrinsic porosity is reduced and bulk density is increased, resulting in changes to soil hydraulic properties such as moisture retention and hydraulic conductivity. Empirical functions are developed to describe the changes of these properties as the seal develops. With this approach, the seal can be mathematically described by well defined initial and boundary conditions and transient seal properties can be simulated in a physically realistic manner.