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ARS Home » Research » Publications at this Location » Publication #112553
Title: USING SPATIAL INFORMATION TECHNOLOGIES FOR DETECTING AND MAPPING THREE AQUATIC WEEDS IN TEXAS WATERWAYS

Author
item Everitt, James
item YANG, CHENGHAI - TX A&M RES & EXT SERV
item Escobar, David
item HELTON, R - TX PARK & WILDLIFE-JASPER
item HARTMANN, L - TX PARK & WILDLIFE-JASPER
item Davis, Michael

Submitted to: Forest Service Remote Sensing Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/18/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The inaccessibility and often large expanses of many wetlands make ground inventory and assessment difficult, time consuming, and often inaccurate. Improved techniques are needed to manage these areas. Remote sensing techniques offer rapid acquisition of data with generally short turnaround time at costs lower than ground surveys. A study was conducted to determine the light reflectance characteristics of three aquatic weeds (waterhyacinth, hydrilla, and giant salvinia) found in Texas waterways. Color-infrared aerial photography and videography were also evaluated for their detection. Reflectance measurements showed that these weeds had unique spectral characteristics. Color-infrared videography integrated with GPS and GIS technologies was used for distinguishing and mapping waterhyacinth and hydrilla infestations in the Rio Grande River of south Texas. Color-infrared photography was used successfully to detect giant salvinia in various waterways in east and southeast Texas. These findings should be of interest to wetland resource managers.

Technical Abstract: The invasion and spread of exotic aquatic weeds in waterways pose a major problem for wetland resource managers. Three aquatic weeds of major concern to Texas wetland resource managers are waterhyacinth [Eichhornia crassipes (Mort.) Solms.] hydrilla [Hydrilla verticillata (L.F.) Royle], and giant salvinia (Salvinia molesta Mitchell). Waterhyacinth and hydrilla ahave been in Texas waterways for some time, but giant salvinia has only recently been discovered. This paper presents data on the light reflectance characteristics of these weeds and the application of aerial color-infrared (CIR) photography and videography for their detection. CIR videography integrated with GPS and GIS technologies was used for distinguishing and mapping the distribution of waterhyacinth and hydrilla. Only CIR photography was used for detecting giant salvinia infestations. Reflectance measurements made on these weeds showed that they had unique spectral characteristics that facilitated their detection on aerial imagery. Waterhyacinth and hydrilla could be readily distinguished on CIR video imagery where they had bright orange-red and reddish-brown image responses, respectively. Healthy, green giant salvinia had a distinct pink image on CIR photographs. Dense populations of giant salvinia with mixtures of green and brown foliage had an olive-green image on CIR photographs. Integration of the GPS with the video imagery permitted latitude/longitude coordinates of waterhyacinth and hydrilla infestations to be recorded on each image. A portion of the Rio Grande River in southern Texas was flown with the video system to detect waterhyacinth and hydrilla infestations.