hydrology parameters

San Juan Creek Hydrologic Parameters

PACE utilized the latest GIS technology to delineate 73 regional watersheds, 1,270 subwatersheds, over 1,000 miles of flow paths and over 1,000 hydrologic nodes for the San Juan Creek watershed.  The hydrologic information from the GIS was inputted into a modeling program called AES that computes the Orange County Rational Method, a model that generates runoff rates and time of concentration (Tc) for an Orange County unit hydrograph.  PACE generated a tool to automate the input sequence of the modeling software.  The AES software requires hydrologic parameters for each individual node to be manually inputted using an archaic DOS-type input form.  Over a half dozen parameters are inputted per node such as length of path, node elevations, land-use, channel type, and more.  This software developed in Vb.Net saved over 6,000 inputs resulting in 100’s of hours of man hours.  The output from the model and GIS data helped generate hydrologic statistics such as maximum loss rates, sub-area loss rates, pervious ratios, initial area land use, curve numbers (CN), concentrated flow, and an Orange County unit hydrograph.


  • ArcGIS
  • Spatial Analyst           
  • ArcHydro
  • AES
  • vb.Net
  • Python