Existing GIS data can be utilized to define hydrologic objects. The data may be created from DEM data using other hydrological analysis toolsets. These datasets usually have a catchment layer, a stream layer, and an outlet layer. They can be imported into VO and used to create NasHyds/StandHyds, RouteChannels and AddHyds.

To create hydrologic objects from existing GIS layers:

  1. Add existing GIS data using Add Feature Layer button in GIS tab. Move the layer on top of base map layer and zoom to it using the Zoom to Layer context menu.
  2. Select feature(s) in imported layers using the Select tool in GIS tab or the Map Context Menu.
  3. In Map Context Menu, select the desired type of hydrologic object in Generate Selected Geometry As menu. The new hydrologic object will be this type. Depending on the type of selected features (point, polyline or polygon), some menus may be disabled as there is no proper geometry for those hydrologic objects. In this case, no polyline feature is selected, so RouteChannel, MuskingumCunge and RoutePipe are disabled.

  1. A new hydrologic object will be created for each selected feature. The shape-based parameters (e.g. area for catchments and length for channels) are automatically calculated from the shape and all other parameters will use the default values.