Design Storm Builder: Development of Representative Design Storms
Abstract:Design storms are used in hydrologic and hydraulic modeling for design and rehabilitation of sanitary sewer systems. Analysis of regional design storms relies on both rain gauge accumulations and archival radar data during the period of record. Hyetographs, which represent the temporal distribution of rainfall produced by a storm, can be developed from radar or rain gauge data. In the most basic form, hyetograph rainfall rates are applied uniformly over a sewer catchment or basin. Including radar data offers the advantage of determining storm movement and direction, as well as measuring area-intensity reduction factors. Design storms are static if the rainfall does not move over the catchment, and are dynamic when the hyetograph incorporates movement. A gridded dynamic design storm can be produced by specifying the trapezoidal cross-section and movement derived from radar, or by selecting a dimensionless hyetograph derived from rain gauges. This manuscript describes the data analysis and approach used to develop a local design hyetograph that is representative of local climatological conditions experienced by a collection system. A dynamic design storm, one that is gridded and moves across a basin or sewer catchment, achieves a more faithful representation of the input driving hydrologic/hydraulic response in terms of peak flow magnitude and timing. Because a dynamic design accounts for storm movement over the watershed, unrealistic assumptions of uniform rainfall can be avoided. By measuring rainfall intensity distribution with time, median hyetographs are developed that can be used both as static input and as the dynamic design storm that moves over the basin.
Document Type: Research Article
Publication date: January 1, 2011
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