Hydrology

The Hydrology Section has responsibility for a number of activities, including the following:

  1. Perform modeling studies to provide the peak flows and hydrographs used in District facility design projects.
  2. Monitor storm rainfall and runoff, do forecast modeling, and advise the Sheriff's Office of Emergency Services on the potential for flood damages in the County.
  3. Install and maintain a hydrographic gage network to provide real-time data during storms and collect data for use in design studies. The data collected from our gages are made available to the public for their use through our website.
  4. Perform sediment yield calculations, especially after fires.
  5. Maintain and update manuals and reports describing our design procedures and hydrology programs.
  6. Review Hydrology Studies submitted with permit applications and CEQA review packages.

Hydrology Data Available to the Public

The Historical Rainfall and Streamflow Data site contains finalized reports and preliminary data for the rain and stream gages and evaporation stations operated by VCWPD or in conjunction with the USGS or other agencies. Please read our Frequently Asked Questions file included on the data home page for detailed information about the data website and what it provides. The Current Storm Information page provides snapshots of real-time data collected by our gage network. These data provide current rainfall totals, stream gage plots, and weather information.

Design Hydrology Methodology

Design hydrology Manual imagePlease see the 2010 update of the VCWPD Hydrology Manual and our design hydrology programs (downloadable on this site) to use our design hydrology methods.  In general, peak flows from urban and small undeveloped watersheds for use in channel design can be evaluated using our modified rational method and programs (VCRat2.6, TC Calculator). Peak flows and hydrographs for regional facility design can be evaluated using the calibrated S-Graph developed from 2005 storm data using HEC-HMS. Other peak flow design methods that have been used to evaluate floodplains include the results from flow frequency analyses and inserting design storm rainfall in continuous models such as HSPF. For information on these advanced methods, please contact the Hydrology Section at (805) 654-2069 or email your request to HydroData@ventura.org.

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 run it here at the District. 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.

The District has also developed Excel spreadsheets that will do Tc calculations and calculate a hydrograph for one subarea and route the hydrograph through a detention basin. These spreadsheets use iterative calculations and are still being tested to make them more reliable. Beta versions are provided as follows:

Questions about their use can be submitted to hydrodata@ventura.org

The District is currently updating the Visual Basic code used as the interface to the legacy FORTRAN VCRat program to work on Windows 10 and 64-bit machines. We expect to have the updated programs available by the end of 2017.

Debris and Detention Basin Information

Information about the District's Debris and Detention Basins can be obtained from the Manuals available on our Basin Manual Webpage.