The efficiency of vegetative buffer strips in runoff quality and quantity control

In recent years, nonpoint source pollutions, caused mostly by surface runoff, have become a subject of interest. Vegetative buffer strips contain a special plant species being passed by the flow before getting into the water bodies. The main aim of the present study is to evaluate the impact of three different types of vegetative buffer strips to reduce the surface water pollutants including sediment, nitrate and phosphate. The experiments were carried out using the experimental plots with the dimension of 1 x 10 m(2) as well as the artificial runoff with a flow rate of 1.65 L s(-1) during a year. The results of this study showed that the vegetative buffer strips reduced the runoff volume by 35-90%, sediment concentration by 42-94%, nitrate concentration by 35-88% and phosphate concentration by 28-95%. According to the results, the vetiver grass has a high efficiency in runoff pollutants control; but, due to the probability of creating the concentrated flow among the bushes of vetiver grass, it is strongly recommended to use a resistant plant with a density and uniformity similar to the turf grass and consistent to climatic conditions of the study area along with the vetiver grass. Also, periodic cutting the plants is as an effective strategy to deal with the role of vegetative buffer strips as a source of nutrients and sediment.