WMS:OC Rational Job Control

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OC Rational Method – Job Control dialog

The OC Rational Method – Job Control parameters include all of the universal data necessary to run an Orange County analysis that are not a part of a basin, reach, or reservoir. The following are the specific parameters defined as part of job control:

  • Units – By default Orange County performs computations in English units, however metric unit calculations can be specified.
  • Frequency – Select the return period of the design storm. Non-mountainous and mountainous IDF curve values are updated based on this selection. Enter IDF curve values for the 500-yr storm.
  • Expected Value – Toggle this check box on to do an expected value analysis. IDF curves and losses will be automatically updated for each sub-area if they have already been computed.

IDF Curves

IDF (intensity-duration-frquency) curves in Orange County are calculated differently depending on the location of the analysis. This section is subdivided into non-mountainous (areas below 2000 feet) and mountainous (areas above 2000 feet) regions.

  • Non-mountainous – The IDF curves are generated using a regression equation I = atb where:
    • I – Rainfall intensity (in/hr, mm/hr)
    • t – Duration (min)
    • a, b – Regression equation coefficients
  • Mountainous – The IDF curves are generated by interpolating between known intensities at specified time values.

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