The paper introduces a new measure for the integration of design and control. The measure is termed as a Disturbance Resiliency Index and reflects on the ability of the process to reject disturbances and prevent saturation in the manipulated variables. The paper presents the mathematical formulation for general nonlinear systems. The measure is defined mathemtatically and a set of properties and theorems are proved to enable its use. It is applicable both for steady state and dynamic systems. For a large number of systems and networks the application of the theory yields analytical expressions that one can study and analyze. In other cases, it yields bounding expressions that one can embed in optimization formulations and mathematical models. The paper contains several illustrations on the application of the measure on reaction systems, separation problems and heat exchanger networks.