In the design of flood levee systems there are many parameters and variables with associated uncertainties. This paper presents models which systematically analyze the various types of uncertainties in the hydrologic aspect as well as hydraulic aspect of design and analysis to define the risk and reliability of overtopping. Both static and time dependent risk models are developed. Results show that risk evaluated by the simple return period method can be underestimated by 10% to 50%, depending on the loading distribution model used. The risk‐safety factor relationships are shown to be very sensitive to the hydrologic loading probability model adopted, so that composite models are suggested for risk analysis.