<p>The presence of methane hydrate reduces the permeability of sediment to both water and gas. Current models of relative permeability, based on heuristic concepts like pore filling or grain coating, do not accurately represent the complex nature of geologic media and often overlook three-phase scenarios involving gas, water, and hydrate. Here, we use a thermodynamic argument to determine the pore-scale positioning of hydrate and from this predict gas and water flow properties of methane hydrate-bearing sediments. We conduct gas and water flow experiments with and without hydrate, comparing the results to both our physical model and existing models. We show that the flow properties of gas and water in the presence of hydrate can be determined using measurements from sediment without hydrate. In lieu of two-phase experimental measurements, we give functional forms of the relative permeability that are based in measurements of sandy sediments.</p>