# WMS:OC Rational Job Control

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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.

## Related Topics

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