The Rio Grande River is located on the United States border with Mexico. In 1978 Congress designated a 196-mile (315 kilometer) segment of this river on the U.S. side as a national wild and scenic river under the Wild and Scenic Rivers Act. With an authorized boundary of 0.25 miles from the center of the river, the resulting Rio Grande Wild and Scenic River (RIGR) unit covers approximately 35,000 acres (14,000 hectares) of both private and public lands in southwest Texas. The Rio Grande River flows through RIGR in an easterly direction starting above Mariscal Canyon in Big Bend National Park (BIBE) at river mile 853.2 and continues to the boundary of Terrell and Val Verde counties in Texas (river mile 657.5).
As the Rio Grande River flows through the surrounding desert lands, it has dramatically sculpted the topology at RIGR creating rugged canyons, scenic rapids, dynamic shorelines, and small alluvial islands. The river is also the primary source of water in these arid lands where it creates many unique upland and riparian environments. To better understand and document the vegetation diversity occurring on these formidable, yet fragile RIGR habitats, the National Park Service (NPS), the NPS National Vegetation Inventory Program (NVIP) and the NPS Chihuahuan Desert Inventory and Monitoring Network (CHDN) started a RIGR vegetation inventory effort in 2010.
An eight-year, six-phase project was begun in 2010 to complete the inventorying and mapping of the vegetation at RIGR. 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 collected vegetation data at 77 classification plot and 81 observation point locations. Field data was then entered into the NVIP-specific PLOTS database and reviewed by CHDN staff. In phase three, CTI analyzed the digital PLOTS data to classify 35 RIGR plant associations using the revised U.S. National Vegetation Classification (rUSNVC) standard. During phase four, CTI created the digital vegetation map layer. In the accuracy assessment (AA) phase, contracted field crews collected data at 169 AA point locations that were randomly placed throughout RIGR. In 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 RIGR was created from high-resolution 2015 Texas Orthoimagery Program (TOP) imagery and ancillary data. By comparing the signatures on the imagery to field data, 47 map units (40 vegetated and 7 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 RIGR vegetation map was assessed for overall thematic accuracy at 93.1% (88.9% raw accuracy) with a Kappa value of 89.0%.
Products developed for RIGR are described and presented in this report and stored in the accompanying project digital files. Project deliverables include the final RIGR Vegetation Inventory Report, the RIGR Spatial GIS Geodatabase, Digital Field Photos, Metadata, Vegetation Descriptions, and the Field Key to the Vegetation Associations. For a full listing of the RIGR products available to download please visit the National Park Vegetation Inventory Product website.
