Atlas 14 Temporals for XPSWMM

Back in January, we introduced the capabilities of XPSWMM that allows a modeler the ability to perform an ensemble-based critical duration analysis using the NOAA Atlas 14 Temporal Distributions. As the NRCS, formerly the Soil Conservation Service (SCS), retires the legacy rainfall distributions (Type I, IA, II, and Type III) and replaces with more location specific distributions, the question shifts toward is there a better distribution to consider over a standard nested intensity storm.

The NOAA Atlas 14 rainfall depths are pretty well known. The temporals that NOAA published are not as well known.  How might one incorporate the temporals into an analysis with XPSWMM? There are two methods and we explore these below.

The standard method to leverage the Atlas 14 temporal is the simplest yet time-consuming. It’s a copy and paste method between the application and the downloaded data from the NOAA Website. Download the Temporal distribution table data from the Temporals site for the Atlas 14 Volume, Region, and  Duration needed. The file (typically a CSV) is composed of four quartiles plus an all cases as a cumulative percent of depth.

Firstly, we need the convert to a decimal equivalent of the percentages provided, and then each set pasted into a Global Data Storm. From the Global Data Dialog box, add the storm with a name, and then edit the record. As this is a 24-hour storm, and Cumulative Depth, click the Constant Time Intervals and enter the data and paste the cumulative percentages. The Atlas 14, Volume 10, Region 1 24-hour, 90% exceedance, 1st Quartile storm would get pasted into the Global Storm as follows:

Repeat this for the exceedance and quartiles to get the full 24-hour storm ensemble set. With a pattern like this, one can simply edit the XPX file replacing the name and time series data for each set. The text below is the 80-percent exceedance for the 24-hour storm.

/* 80 PERCENT*/
GLDBITEM "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 
GLDBDATA W_DESCRIP "Rainfall" "AT14-V10R1-4Q-80P-24Hr" "Atlas 14 Vol 10 Region 1 4th Quartile 24 Hour storm 80 percent"
GLDBDATA R_REIN "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 48 0.0040 0.0107 0.0169 0.0220 0.0266 0.0313 0.0367 0.0428 0.0496 0.0567 0.0639 0.0708 0.0775 0.0839 0.0901 0.0965 0.1032 0.1105 0.1186 0.1275 0.1372 0.1478 0.1589 0.1705 0.1825 0.1948 0.2073 0.2202 0.2337 0.2480 0.2636 0.2809 0.3003 0.3224 0.3477 0.3766 0.4095 0.4469 0.4892 0.5367 0.5896 0.6478 0.7109 0.7777 0.8456 0.9105 0.9654 1.0000
GLDBDATA R_HOFF "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 1 
GLDBDATA R_KPREPC "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 2 
GLDBDATA R_RMULT "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 1.000 
GLDBDATA R_KTIMEC "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 1 
GLDBDATA R_THISTO "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 24.000 
GLDBDATA R_ROPT "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 0 
GLDBDATA R_RAINSMTH "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 1 
GLDBDATA R_RAINSYR "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 2018 
GLDBDATA R_RAINSHR "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 0 
GLDBDATA R_RAINSMIN "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 0 
GLDBDATA R_RAINSSEC "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 0 
GLDBDATA R_RAINSDAY "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 1 
GLDBDATA R_KTYPE "Rainfall" "AT14-V10R1-4Q-80P-24Hr" 1 0

I hope that helps:  Here are the Atlas 14 Volume 10 XPX Files zipped.



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