Powderhorn Ranch Geoenvironmental Atlas

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Powderhorn Ranch, situated along Matagorda Bay and Powderhorn Lake in Calhoun County, Texas, spans a vast 7,022 hectares. It was acquired for the state of Texas through a collaborative effort involving the Texas Parks and Wildlife Foundation, The Nature Conservancy (TNC), Texas Parks and Wildlife Department (TPWD), and The Conservation Fund.

The significance of Powderhorn Ranch from an environmental and conservation perspective is profound. It stands as one of the largest remaining expanses of native coastal prairie and is slated to be developed into a state park and wildlife management area. The ranch encompasses a diverse range of coastal ecosystems, including 18 kilometers of bay frontage, tallgrass prairies, freshwater and saltwater wetlands, and live oak woodlands that have evolved on a Pleistocene barrier island complex known as the Ingleside barrier system. According to TNC, Powderhorn Ranch provides year-round habitat for a variety of bird species, including shorebirds, wading birds, waterfowl, and serves as critical fall-out areas for migrating birds.

This geoenvironmental atlas serves as a comprehensive compilation of various datasets related to geology, topography, hydrology, geophysics, and biology. It aims to provide planners, managers, conservationists, and visitors with valuable information regarding the geologic, geomorphic, coastal habitat, and coastal hazard characteristics of Powderhorn Ranch.

The data compiled for this atlas includes high-resolution topographic information obtained from an airborne lidar survey conducted in July 2016, geologic mapping at a 7.5-minute quadrangle scale spanning from 2015 to 2018, wetland status and trends mapping based on aerial photographs dating from 1956 to 2008, historical shoreline movement data from the 1930s to 2015, interpretations of shoreline susceptibility to wave action, storm surge, and relative sea-level rise, inundation depths observed during historic hurricanes Carla (1961) and Beulah (1967), as well as near-surface geophysical measurements such as logs of 19 water wells and 8 time-domain electromagnetic induction soundings conducted on or adjacent to the ranch.

The primary objective of this atlas is to disseminate the current knowledge of the surface and near-surface environment at Powderhorn Ranch to the public. This information is intended to guide development and management decisions that prioritize responsible stewardship and the sustainable future use of the ranch.


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