HY_Features is the international standard conceptual data model for surface hydrologic features which will be used as the basis for the 3DHP data model – the planned successor to the NHD. HY_Features concepts have been used for design of the National Weather Service Next Generation National Water Model (known as the Next Generation Water Resources Modeling Framework) and a national river-identifier scheme known as “Mainstems”. HY_Features has not yet been used in a specific data model for hydrographic data. We hope to define a well-documented logical and physical data model for the 3DHP to carry forward key functionalities of NHDPlusHR into the 3DHP. The concepts described by HY_Features are key to understanding how hydrographic data are organized across scales and how we integrate landscape and river information in a cohesive and modular way. It’s important that everyone have some knowledge of this conceptual basis to ensure we are able to communicate across teams in an accurate and productive way.