Application of GIS to Hydrology: Arc Hydro Data Model and Toolbar Extension
The Arc Hydro data model was developed to transition hydrologic modeling from an inventory-based data model to a behavioral model, established on the relationship between various hydrologic data sets. Arc Hydro has been adopted as the water resources industry standard geodatabase structure or “schema” and is comprised of five major data types: drainage features, geometric flow network, hydrography, channel description and time series. The relationships between the layers are determined by tracing the flow path of water through any given region. One benefit of using the Arc Hydro data model is that the connections between features are stored in the geodatabase using unique identifiers in the attribute table, relationship classes and a geometric network. The database can then be easily queried and more readily integrated into external hydrologic modeling software.
The Arc Hydro toolbar extension is designed to build and manage the Arc Hydro geodatabase model. This free extension can be used to pre-process a raster digital elevation model into the vector layers that are the core of the hydro data model, as well as delineate and characterize watersheds. The toolbar can then be used to: manage the attribute tables for the resulting feature classes (these identify hydrologic relationships and are used to calculate several parameters needed for modeling); generate a node/link geometric network (useful for “on the fly” flow path tracing through the watershed based on flow direction and up/down ID); and facilitate incorporation of NEXRAD or rain guage precipitation data for historic storm modeling.