Based on the mechanism of breach erosion observed in various tests in the laboratory and field, a mathematical model for breach growth simulation in noncohesive-dikes (sand-dikes) has been developed. The model has been calibrated with the data of a field experiment and verified with the data of a laboratory experiment, yielding good agreement. The model has also been used for simulation of the failure of a prototype dike, computed results are more or less in agreement with an eye-witness report.