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Title: Using aerial photography for mapping giant reed infestations along the Texas-Mexico portion of the Rio Grande.

Author
item Yang, Chenghai
item Everitt, James
item Goolsby, John

Submitted to: American Society for Photogrammetry and Remote Sensing Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/10/2010
Publication Date: 6/10/2010
Citation: Yang, C., Everitt, J.H., Goolsby, J. 2010. Using aerial photography for mapping giant reed infestations along the Texas-Mexico portion of the Rio Grande. American Society for Photogrammetry and Remote Sensing Proceedings. CDROM.

Interpretive Summary: Giant reed is an invasive weed throughout the southern half of the United States with the densest stands growing along the coastal rivers of southern California and the Rio Grande in Texas. This study used aerial photography to map giant reed infestations and estimate infested areas along the Texas-Mexico portion of the Rio Grande. The total giant reed area along the Rio Grande between Lajitas and San Ygnacio was estimated to be 5985 ha with 3670 ha or 61% on the U.S. side and 2315 or 39% on the Mexican side. This study provides the first accurate estimates of giant reed infestations along the Texas-Mexico portion of the Rio Grande and this information will be useful for both land owners and government agencies for the management and control of giant reed.

Technical Abstract: Giant reed (Arundo donax L.) is an invasive weed throughout the southern half of the United States with the densest stands growing along the coastal rivers of southern California and the Rio Grande in Texas. The objective of this study was to use aerial photography to map giant reed infestations and estimate infested areas along the Texas-Mexico portion of the Rio Grande. Aerial color-infrared (CIR) photographs (each covering approximately a 2.4 km by 2.4 km area with 20-30% overlaps) were taken along the Rio Grande between Brownsville and El Paso, Texas in June and July 2002. Based on the aerial photographs and ground surveys, the portion of the river from San Ygnacio to Lajitas that has a river length of 898 km was found to be infested with giant reed with the densest populations located between Laredo and Del Rio. To estimate infested areas along both the U.S. and Mexican sides of the river, 65 out of the 480 aerial photographs taken between Lajitas and San Ygnacio were randomly selected. The aerial photographs were digitized, rectified to Google Earth imagery, and then classified using maximum likelihood classification techniques. The infested areas on both sides of the river as well as water area and river length from each photographic image were determined. Based on the estimates from the 65 aerial photos, the ratio of giant reed area to water area and the ratio of giant reed area to river length were calculated. The total giant reed area along the Rio Grande between Lajitas and San Ygnacio was estimated to be 5985 ha with 3670 ha or 61% on the U.S. side and 2315 or 39% on the Mexican side. This study provides the first accurate estimates of giant reed infestations along the Texas-Mexico portion of the Rio Grande and this information will be useful for both land owners and government agencies for the management and control of giant reed.