Development of Regional Design Storms for Sewer System Modeling

Design storms that consider a range of durations and depths, and represent local rainfall climatology are required for hydrologic and hydraulic modeling of sewer projects. The time history of rainfall at a point is known as a hyetograph. Hyetographs are used to represent expected distribution of rainfall with time, at a point, or over an area for input to hydraulic models for design. Analysis of radar and rain gauge data for a particular municipality or region can be used to determine representative point-scale and areal rainfall distributions. Radar offers a unique opportunity to measure the movement of storms in terms of direction, velocity, and areaintensity reduction factors. From radar and rain gauge data, local model hyetographs can be derived that are both gridded and dynamic, and representative of the local climate.