Rainfall Tables
HydroCAD
provides several options for defining the rainfall distribution to be used with
the SCS or SBUH runoff procedures.
Most projects
will use one of the predefined rainfall tables listed below. The most
common are the SCS/NRCS rainfalls
listed at the top of the table.
With HydroCAD-10, you can also
generate a synthetic rainfall distribution based on local precipitation
frequency data. Details here.
For special applications, you
can create a custom
rainfall table by hand.
Predefined Rainfall Tables
The following predefined rainfall distributions are included with HydroCAD-10, or available for download from this page.
| Rainfall Name(s) | Comments |
| Type I 24-hr Type IA 24-hr Type II 6-hr Type II 12-hr Type II 24-hr Type III 6-hr Type III 12-hr Type III 24-hr |
Standard SCS/NRCS distributions used for most projects in the United States. Supplied as polynomial curves for optimum results over the widest range of Tc values. The 6 and 12 hour durations were added in HydroCAD-9.1 |
|
Type I 24-hr Tabular Type IA 24-hr Tabular Type II 6-hr Tabular Type II 12-hr Tabular Type II 24-hr Tabular Type II 48-hr Tabular Type III 24-hr Tabular |
Tabular versions of standard SCS/NRCS distributions. Recommended only for direct TR-20 comparisons. Available by download only. Right-click any item and save to your HydroCAD\Rainfall folder. |
| Type II FL 24-hr | Modified Type II storm used by Southwest Florida Water Management District and Saint Johns County, Florida. |
| Type IIA CS 24-hr | Modified Type IIA storm for Colorado Springs, Colorado. Added in HydroCAD 6.1 |
| Type B 6-hr | Same as the Emergency Spillway distribution (ESH), but preset to a duration of 6 hours. Added in HydroCAD-10 build-4. |
| "Chicago Storm" | This term refers to a technique for using IDF coefficients to define a mass curve. This is illustrated in the "Sample D" rainfall table and discussed in the rainfall.txt file. |
| SFWMD 24-hr SFWMD 72-hr) |
Southern Florida Water Management District |
| FDOT 1/2/4/8/24-hr FDOT 3/7/10-day |
Florida Department of Transportation |
| Orange County, Florida 6-hour 24-hour |
Use with 10, 25, or 100 year depth. Right-click any item and save to your HydroCAD\Rainfall folder. Added in HydroCAD-10 build-2. |
| SJRWMD 96-hr half-hour tenth-hour |
Saint John's River Water (Florida) management District 96-hour rainfall based on the SCS Type II 24-hour rainfall according to Section 14.2 of the MSSW Handbook. Available in half hour increments as described in MSSW, or tenth hour increments for greater accuracy and consistency with the Type II storm on which is based. Added in HydroCAD-10 build-2. |
| Spillway Emergency | SCS Emergency Spillway Hydrograph (ESH, a.k.a Type B). |
| Spillway 1-day 10-day | SCS Principal Spillway Hydrograph (PSH) |
| Constant Intensity | Usable at any duration. Added in HydroCAD 7.0. |
| Sample A (intensity curve) Sample B (smoothed curve) Sample C (mass curve) Sample D ("Chicago" storm) |
Fictional rainfall examples that may be used as the basis for custom storms. |
| Austin 3-hr | Design storms for Austin, Texas, for return periods of 2, 5, 10, 25, 50, & 100 years. |
| Charlotte 6-hr | 2-yr and 10-yr "Balanced Storms" for Charlotte, NC |
| E-WA Short E-WA Long Region 1-4 |
Eastern Washington State. Added in HydroCAD 7.1 |
| Fayette 5-hr 1995 Fayette 6-hr 10-yr Fayette 6-hr 100-yr Fayette 18-hr 1992 |
Lexington-Fayette, KY. Added in
HydroCAD 7.0. |
| Fayette05 6-hr 10-yr Fayette05 6-hr 100-yr Fayette05 24-hr 10-yr Fayette05 24-hr 100-yr |
Lexington-Fayette, KY - revised 2005 rainfalls. Added in HydroCAD 7.1. |
| Fayette09 1-hr 1-yr (Lexington- Fayette09 1-hr 10-yr Fayette09 1-hr 100-yr |
Lexington-Fayette, KY - new 2009 rainfalls. Added in HydroCAD-10. |
| Huff 0-10sm Huff 10-50sm Huff 50-400sm |
Illinois Huff distributions from ISWS Bulletin-71 & Circular-173. Supplied for 1st, 2nd, 3rd, and 4th quartiles. |
| Huff B70 0-10sm | Updated Illinois Huff distributions from ISWS Bulletin-70. Supplied for 1st, 2nd, 3rd, and 4th quartiles. Added in HydroCAD-10. |
| Indy Huff 24-hr | Variation of the Huff distributions from Indianapolis Stormwater Manual 5/10/95. |
| Indy Huff | Indianapolis SQU Guide 7/20/06. Supplied for 1st, 2nd, 3rd, and 4th quartiles. |
| LA County DPW 24-hour LA County DPW 96-hour |
Los Angeles County DPW 2006 Hydrology Manual, using 10%+40%+35%+100% depths. Added in HydroCAD-10. |
| NJ DEP 2-hr | New Jersey DEP Water Quality Storm. Added in HydroCAD 7.1 |
| RSA 24-hr (Type 1, 2, 3, 4) | "Chicago" style rainfalls for Republic of South Africa. Added in HydroCAD-10. Rainfall type and depth maps: 1MB PDF |
| San Diego 6-hr San Diego 24-hr |
San Diego Country, CA. Added in HydroCAD 6.1. |
| San Louis Obispo 24-hr Type U and D 2, 10, 25, 50, and 100 year |
San Louis Obispo, CA, upper and lower watersheds. Added in HydroCAD-10. |
| Seattle 24-hr | Seattle, Washington, Flow Control Technical Requirements Manual, November 2000. |
| SEWRPC-90 | SE Wisconsin 90th Percentile storm. Added in HydroCAD-7.0 |
| Shelbyville | Shelbyville, IN uses standard Huff distributions, above. |
| Thurston 24-hr (1/2 to 100-yr) Thurston 24-hr 1990 Thurston 7-day 100-yr |
Thurston County, Washington. |
If you need a rainfall that is not listed here, you can create a custom rainfall table or download local rainfall data.