ABSTRACT. Drift of aerially applied forest herbicides can result in chemical depositionrift of forest herbicides during aerial applications can result in chemical deposition to streams. It has long been assumed that vegetative barriers attenuate airborne drift. When airborne spray encounters a vegetative barrier, it is expected that some of the material will be captured, but data confirming this are sparse. Ucar and Hall (1999) conducted recent literature reviews of spray capture by vegetative barriers, and Wang and Takle (1995, 1997) and Wang et al. (2001) produced a detailed model of the airflow around vegetative barriers. Tuzet and Wilson (2007) largely confirmed the physical model proposed in the above work. Wilson (2005) indicated that capture by thin windbreaks is not sensitive to relatively small holes or gaps in the windbreak, although it is not clear whether this finding would apply to the thick riparian barriers discussed here (where the "gap" of interest is the low-density trunk space). Bouvet et al. (2006Bouvet et al. ( , 2007 tested low barriers of relatively simple geometries. They found significant correlation between data and a physically sophisticated model of deposition and trajectories of fine glass beads, building on

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