Design hyetographs is online: the free geoapp that builds design hyetographs (constant, Chicago, triangular, alternating blocks) from the depth-duration curve h = a·tⁿ, compares them by return period, duration and shape, exports the series for SWMM / HEC-HMS and Excel, estimates a and n from observed depths and produces the PDF report. It is the design storm behind sewer, detention basin and hydraulic invariance checks.
