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NetSTORM has been used by CDM and its clients since 1991 for rainfall analysis and planning-level rainfall-runoff storage-treatment analysis. This section introduces NetSTORM and describes its principal functions. NetSTORM adapts the concepts of the old HEC-STORM program into a modern interface, extends the STORM methodology to simulation of linked structures in a complex collection system, performs intensity  duration  frequency analysis (IDF) of precipitation data, and disaggregates hourly and daily precipitation data to higher resolutions for use in rainfall  runoff modeling.


NetSTORM has been developed at CDM over the last decade in response to evolving needs of urban hydrology engineering projects. The software is comprised of components for synthetic time series disaggregation, precipitation intensity  duration  frequency (IDF) analysis, and runoff storage  treatment  overflow analysis. The core functions of NetSTORM are its implementation of selected algorithms originally included in HEC-STORM (USACE, 1977) and its extension of the STORM methodology to simulate the multiple combined sewer overflow (CSO) regulator structures typical of urban collection systems. While these functions and others included in the program have been explored and improved upon by other researchers, NetSTORM possesses a unique collection of tools for rapid assessment of precipitation data and urban runoff assessment.


NetSTORM consists of the following principal features within a single graphical user interface:


Rainfall Disaggregation. NetSTORM adapts the time series disaggregation algorithms developed by Ormsbee (1989) for synthesizing sub-hourly data from hourly records, and from Socolofsky, Adams, and Entekhabi (2001) for synthesizing hourly data from daily data. While synthetic disaggregation of precipitation data is valuable for developing input data for long-term hydrologic simulations, the only off-the-shelf software the author is aware of for comparable purposes is StormPac  (Threlfall et al., 1999).


IDF Analysis. NetSTORMs IDF functions expand upon the abilities of programs such as the United States Environmental Protection Agencys (USEPA) SYNOP program that was later incorporated into USEPA SWMM4 (Huber and Dickinson, 1988). While much research has been done in the area of rainfall distribution analysis, such as Huff and Angels (1992) analysis of US Midwest rainfall frequencies, and various software packages can manipulate and summarize precipitation data (e.g. Hydrosphere Data Products Inc., EarthInfo Inc.), NetSTORM is unique in its specific design to aid the practicing engineer in developing custom IDF analyses.


STORM. The original STORM program (USACE, 1977) has been used in many engineering studies over the years. Others have developed similar programs, such as DHIs SAMBA (DHI, 2004). The STORM concept continues to be adapted into current studies. Results from analyses using STORM methodology have been incorporated into guidance documents such as the California Stormwater BMP Handbook (California Stormwater Quality Association, 2003), and into regulations such as Sacramentos drainage regulations (City and County of Sacramento, 1996). NetSTORM incorporates key components of the original storm program, adds many additional functions, and utilizes simple interface and output formats.