Big Bend National Park (BIBE) is located in south Texas on the Rio Grande River as it flows, or bends northeast on its path to the Gulf Mexico. The park covers approximately 801,163 acres (324,219 hectares) directly across the river from Mexico on the United States (U.S.) international boundary. In 1935, through an act of Congress, BIBE was established as the first National Park in Texas. BIBE is located in the Chihuahuan Desert ecoregion and has a rugged topography consisting of the Chisos, Rosillos, Deadhorse, and Mariscal Mountains, many foothills, mesas, river canyons, and broad desert plains dissected by an intricate network of washes, arroyos and drainages. To better understand and document the vegetation occurring on these formations, the National Park Service (NPS), the NPS National Vegetation Inventory Program (NVIP) and the NPS Chihuahuan Desert Inventory and Monitoring Network (CHDN) started a BIBE vegetation inventory effort.
An eight-year, six-phase project was begun in 2010 to complete the inventorying and mapping of the vegetation at BIBE. In phase one, Cogan Technology, Inc. (CTI) reviewed the existing vegetation data, summarized the previous classification efforts, and created a new sampling plan. In phase two, NPS, Rio Grande Institute (RGI), and Lady Bird Johnson Wildflower Center (LBJWC) ecologists used the sampling plan to collect 499 classification plots and one observation point across the landscape. Field data was then entered into the NVIP-specific PLOTS database and reviewed by CHDN staff. In phase three, CTI analyzed the PLOTS data to classify 55 plant associations using the revised U.S. National Vegetation Classification (rUSNVC) standard. During phase four, CTI created rUSNVC-type map units to produce a detailed digital vegetation map layer for the project area that included 810,482 acres (327.991 hectares) in and around BIBE. In the accuracy assessment (AA) phase, contracted field crews collected data at 1,113 AA point locations that were randomly placed by map class throughout the project area. The final phase, CTI finalized the classification, reported the AA results, revised the final vegetation map, and delivered the final products to the NVIP.
The resulting spatial database and vegetation map layer for BIBE was created from high-resolution 2015 Texas Orthoimagery Program (TOP) imagery and ancillary data. By comparing the signatures on the imagery to field data, 72 map units (62 vegetated and 10 land-use/land-cover) were developed and used to delineate the vegetation. The interpreted vegetation polygons were then digitized into a Geographic Information System (GIS) layer that was field-tested, reviewed, and revised. The final BIBE vegetation map was assessed for overall thematic accuracy at 81.8% (79.2% raw accuracy) with a Kappa value of 78.4%. Products developed for BIBE are described and presented in this report, as well as stored in the accompanying project digital files. Project deliverables include the final BIBE Vegetation Inventory Report, the BIBE Spatial GIS Geodatabase, Digital Field Photos, Metadata, Vegetation Descriptions, and Field Key to the Vegetation Associations.
