PENNSYLVANIA HYDROGRAPHY DATASET (PAHD) DERIVATION AND COMPILATION METHODOLOGY

Currently, there are no publicly accessible hydrography datasets that are accurate to a local scale (approximately 1:5,000 as defined by the USGS), include elevation attributes (z-values), and provide statewide coverage for Pennsylvania. To address this need, the Pennsylvania Department of Conservation and Natural Resources, Bureau of Geological Survey (BGS) has created the Pennsylvania Hydrography Dataset (PAHD). PAHD consists of hydrography data generated from the most recent quality level 2 (QL2) light detection and ranging (lidar) elevation data, which means that PAHD geometries are as spatially and temporally accurate as this elevation data (2017-2020). The Geographic Information System (GIS) workflow developed by BGS for producing these geometries includes geomorphon analysis, masking techniques, and least-cost analysis. These methods, in addition to the utilization of QL2 lidar, result in geometries that are accurate to a 1:2,400 scale. While this is more accurate than the most recent iteration of the National Hydrography Dataset (NHD), there is inherent value in linking the two datasets to preserve the plethora of supplementary data and applications tied to the NHD series. Therefore, PAHD is linked to the most recent NHD version through manually transferred attribution. Because NHD conflation is a goal for PAHD, the USGS’s specifications and requirements for elevation-derived hydrography (EDH) are also being applied to PAHD geometries. By sharing its derivation workflow with local and regional groups, the BGS aims to promote collaboration in hydrography production. Organizations will be empowered to produce project-specific data which may then be incorporated into PAHD and, ultimately, be accepted into NHD. This presentation outlines the primary methods of hydrography derivation and compilation for PAHD.