Abstract
Many of alien plant species effect on the functions of irrigation and drainage facilities, its maintenance, and ecosystem around these facilities. We developed a new method for impact assessment of alien plant species around the facilities in Japan. The method was composed to evaluate three items; distribution pattem, physiological or ecological characteristic, and adaptability to environment in the facilities. Each item was judged based on existing knowledge or field survey data. We applied this method to 50 major species. As the result, species which was reported as harmful had high score of impact, especially Altemanthera philoxeroides. Therefore it was suggested that this method could be used for impact assessment of alien plant species around the facilities.
