University of TehranIranian Journal of Soil and Water Research2008-479X48520180121Effect of plot scale on runoff under natural rainfall (Case study; Saravan region, Rasht)Effect of plot scale on runoff under natural rainfall (Case study; Saravan region, Rasht)113311446476910.22059/ijswr.2017.219919.667569FAMisaghParhizgarUniversity of GuilanHosseinAsadiUniversity of Tehran0000-0003-2333-4938Sayed AliMoussaviLecturer, Department of Water Engineering, University of GuilanJournal Article20161210One of the challenges to progress in hydrology and soil science researches is that the theories are only applied to certain time-space scales. This study was carried out to find out the effect of plot size on runoff generation and to quantify it’s scale effects on runoff generation. For this purpose, 6 experimental plots with the length of 3 to 60 m and the width of 1 to 6 m were established on a hillside in the Saravan region of Rasht, Guilan province, Iran. The outflow runoff data was collected from October to May 2015, and then the data were analyzed. Also, the height of rainfall was measured for each plot using rain gauges. Results of the study showed that as the length of plots increase, the amount of runoff per unit area decrease with a non-linear pattern. The Comparison between the mean values of the plots confirmed that there are no significant differences among plots with lengths longer than 10 m in terms of runoff yield. However, there were significant differences among plots with a shorter or a longer size (P > 0/05). The research results verified the optimal length of 10 m for scaling proposes. A two-parameter model was used for scaling hillslope runoff ratio. Model parameters were determined by model calibration using 9 rain events. The evaluation of the model showed its appropriate efficiency for plots shorter than 30 m long. One of the challenges to progress in hydrology and soil science researches is that the theories are only applied to certain time-space scales. This study was carried out to find out the effect of plot size on runoff generation and to quantify it’s scale effects on runoff generation. For this purpose, 6 experimental plots with the length of 3 to 60 m and the width of 1 to 6 m were established on a hillside in the Saravan region of Rasht, Guilan province, Iran. The outflow runoff data was collected from October to May 2015, and then the data were analyzed. Also, the height of rainfall was measured for each plot using rain gauges. Results of the study showed that as the length of plots increase, the amount of runoff per unit area decrease with a non-linear pattern. The Comparison between the mean values of the plots confirmed that there are no significant differences among plots with lengths longer than 10 m in terms of runoff yield. However, there were significant differences among plots with a shorter or a longer size (P > 0/05). The research results verified the optimal length of 10 m for scaling proposes. A two-parameter model was used for scaling hillslope runoff ratio. Model parameters were determined by model calibration using 9 rain events. The evaluation of the model showed its appropriate efficiency for plots shorter than 30 m long. https://ijswr.ut.ac.ir/article_64769_dd83596a8d0fd44f7debe0bf5edc11e2.pdf