2017 Design Hydrology Manual and VCRat2.64 Now Available!


1) Some  64-bit Windows10 computers are preventing the VCRat2.64 Install Package from creating the required c:\VCRatWorkspace folder. If the install package does not create this folder, the program will not run. You have to create the folder (case sensitive) so that the program will run.

2) If you have tried to install the VCRat2.6 program on your 64-bit computer, you must uninstall that program before installing the 2.64 program.

3) Windows10 Computers require that you have Administrator privileges to change the options in the VCRat2.64 program to use J Zone rainfall or mix storm types in a single model run. The alternatives for providing this capability on your computer are provided in a memo (Download Memo).


Open 2017 Hydrology Manual (24 mb, pdf) (Appendix E files provided below)

Download 2017 Hydrology Manual (24 mb, zip)

Go To 2018 VCRat2.64 Download Page

Open Public Viewer for 2017 NOAA Rain Zone Map- 31 Zones, 10-, 25-, 50-, and 100-yr Rainfall Contours – and 2005 LiDAR Data

Open 2017 VCRat2.64 and Spreadsheet User Manual

Read How to Use Shapefiles in AutoCAD Civil 3D or Map 3D

Questions? Email: HydroData@ventura.org


Design hydrology Manual imageUpdated Manual Includes:

  • -Revised Rainfall Zones using NOAA 2011 Design Intensity Data
  • -Updated C Coefficients
  • -VCRat2.64 Program to run on 64-bit machines with Windows 7 and 10
  • -VCRat2.64 can use revised rainfall and C coefficients or legacy rainfall and C coefficients
  • -Tc Calculator Excel Spreadsheet (Appendix E-27)
  • -VCRat Single Subarea Runoff and Detention Basin Routing Excel Spreadsheet (Appendix E-28)



Coming Soon:

Updated Tc Calculator program to use revised NOAA rainfall zones.

2017 Hydrology Manual Appendix E Files

E-1       10-Yr Rainfall PDF Map (pdf 14mb,download)

E-2       25-Yr Rainfall PDF Map (pdf, 14mb,download)

E-3       50-Yr Rainfall PDF Map (pdf, 14mb,download)

E-4       100-Yr Rainfall PDF Map (pdf, 14mb,download)

E-5       10-Yr Rainfall Shapefiles NAD83 (zip,download)

E-6       25-Yr Rainfall Shapefiles NAD83 (zip,download)

E-7       50-Yr Rainfall Shapefiles NAD83 (zip,download)

E-8       100-Yr Rainfall Shapefiles NAD83 (zip,download)

E-9       NOAA Rain Zones Map and Shapefiles NAD83 (zip,download)

E-10     Updated Soils Map Shapefiles (zip,download)

E-11     Example VCRat2.64, 2.6, and 2.2 Files (zip,download)

E-12     Design Rainfall Frequency and Hyetograph Files (zip,download)

E-13     HEC-HMS Design Storm Model Input files (zip,download)

E-14     Hydrograph Transformation Spreadsheets (zip,download)

E-15     Permit Report Submittal Example (zip,download)

E-16     Tc Example Files (zip,download)

E-17     Flow-Through Basin Design Spreadsheet (zip,download)

E-18     Flow-Through Basin Model Files (zip,download)

E-19     Small Area Basin Design Spreadsheet (zip,download)

E-20     Example AR Files- VCRat2.2 and 2.64 (zip,download)

E-21     VCRAIN.DAT Files for VCRat (zip,download)

E-22     Yield Adjustment Example Files (zip,download)

E-23     Multiple Areal Reduction Factor Files for VCRat2.2 (zip,download)

E-24     Bypass Basin VCRat2.6 Files (zip,download)

E-25     Small Area Hydrograph files (zip,download)

E-26     VCRat 2.64V030 Programs (zip,download)

E-27     Tc Calculator Spreadsheet (xlsx,download)

E-28     VCRat and Basin Routing Spreadsheet (xlsx,download)

E-29     Bulked Flow Spreadsheet (xlsx,download)

NEW!   VCWPD Flood Zone Map (jpg,download)

Tc Calculator Training Materials

Download these updated Tc Calculator Spreadsheet and VCRat2.64 training materials for the updated 2017 Hydrology Manual.

Download these Tc Calculator and VCRat2.6 training materials from the 2009 training class (2010 Hydrology Manual).


2010 Design Hydrology Manual and VCRat2.6

The 2010 VCWPD Hydrology Manual and our design hydrology programs (downloadable on this site) for 32-bit machines are still available for use with the legacy rainfall mass curves and C coefficients.

Notice: VCRat 2.6 Program 64-bit Compatibility Warning!!!

VCRat2.6 was tested successfully on 32-bit PC computers with Windows Vista  and Windows 7 Operating Systems. It will not run on 64-bit machines without a workaround. If your 64-bit machine is using Windows 7 Pro, you can set up a Virtual PC with an XP Mode that will allow you to use our programs. This is how we ran it at the District on 64-bit machines. Download or view the Brochure and HowToGuide and download the MicroSoft applications at the following websites:

You may have trouble transfering data from network drives to your Virtual PC.  In that case, you may have better luck with a memory stick for data transfer.

A consultant reported that he was able to run our 32-bit programs using VMWARE.

Ask a Question, Report a Problem or Concern!