To develop this design storm, the storm duration is first selected. Average intensities are then found by reading an IDF curve at selected duration shorter than the storm duration. The selected duration should be separated by a constant time step. Next, the accumulated storm volume is computed by multiplying each duration by the average intensity. The incremental rainfall volumes and intensities are computed and then arbitrarily rearranged to form a storm pattern. If the incremental intensities are not rearranged a front-end hyetograph, following the shape of the IDF curve, is obtained.