SURFICIAL GEOLOGIC MAP COMPILATION WITHIN THE DELAWARE RIVER BASIN IN SUPPORT OF THE U.S. GEOFRAMEWORK INITIATIVE

The Delaware River Basin (DRB) was chosen in 2019 as the first study area in the USGS Next Generation Water Observing System (NGWOS) initiative to assess low flows in large U.S. river basins. The DRB covers portions of five states (New York, Pennsylvania, New Jersey, Delaware, Maryland) and several geologic provinces, encompassing much of the complex geology of the Mid-Atlantic region. Groundwater storage is conceptualized to be greatest in the glacial surficial aquifers in the upper part of the basin, thus characterization of this critical zone is of primary importance for NGWOS modeling of baseflow to the upper Delaware River. In 2021 compilation of the best-available digital surficial geologic map data in the DRB was funded by the U.S. GeoFramework Initiative (USGI) to supply the USGI with data toward fulfilling the goal of complete digital surficial map coverage of the U.S., and to support the NGWOS baseflow modeling efforts in the DRB.

The work was divided into three main tasks: 1) compile existing digital surficial geologic map data at various scales (1:250,000 to 1:24,000) into the USGS Geologic Map Schema (GeMS) standard with the addition of estimated map unit thicknesses; 2) compile existing lidar-derived elevation data to create high-resolution base map imagery of the terrain; and 3) formulate a deep learning approach to automate the mapping of shallow bedrock and certain classes of surficial deposits from lidar-derived imagery where digital surficial geologic map data are lacking. Lidar-derived elevation models are being used for extraction of channel bank heights along streams that are incised through sediment to provide the minimum thickness of surficial materials in local areas. The geologic compilation work will also support intensive NGWOS monitoring studies at the sub-basin scale within the White Clay Creek watershed, Little Lehigh Creek watershed and the upper Neversink River watershed. An example of work in the upper Neversink River watershed will be highlighted to demonstrate how surficial geologic information can be used in conjunction with high-resolution terrain models to map hydrogeomorphic units for stream baseflow estimation.