Abstract:
Abstract: In order to investigate the effects of different slope grass strips patterns on hydrological connectivity of the slope-gully system, we selected topographic convergence index and topographic wetness index as structural connectivity indicators, and the simplified hydrograph and derived relative surface connection function as functional connectivity indicators which were used to analyze the hydrological connectivity of groove system in different grass strip patterns (upper, middle, lower and foot slopes). In this paper, we used artificial simulated rainfall experiment which was conducted in the State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China at Xi'an University of Technology from July to August 2014. According to the loess plateau typical geomorphic features design indoor slope gully system model, the model for steel soil bin, groove width was 1 m, including Liang Mao slope gradient of 12°, slope 8 m long; groove was 25° slope degree, slope length 5 m. Liang Mao slope and gully slope ratio was roughly control in 1.6:1.0, representing the proportion of slope gully loess plateau region. The experimental rainfall intensity was set at 1.5 mm/min, and the rainfall space was evenly distributed to more than 80% before the experiment began. We started to count the time after the rainfall was produced. All the muddy water samples were collected in every minute to calculate the runoff volume per minute. After 30 minutes of runoff, the rainfall experiment stopped. The results showed that different grass strip patterns had different influence on the connection process of slope ditch system. The closer to gully the grass strip was located, the longer the initial runoff time was. The total runoff was small in the grass strip layout in the middle and lower slope position. The lower slope and the foot slope had great influence on the runoff collection. The structural connectivity of grass strip was arranged on the placement of the middle and upper slopes which were superior to that of other positions,and were more conducive to the connection of water system after rainfall. The distribution of topographic convergence index was similar to normal distribution, while the distribution of the terrain moisture index was in line with the positively skewed distribution. The topography of the grass strip position which was arranged on the placement of the middle and upper slope was more conducive to the confluence than other patterns. In the middle and upper slope, the average topoqraphic wetness index of the grass strips after rainfall decreased by 10.59% . The closer the grass strip was to the top of the slope, the better the functional connectivity was, but the saving capacity of precipitation was poor. Compared with other patterns, the grass strip in the upper slope needed less water to produce flow and the functional connectivity was the best. When the rainfall stopped, there were about 70% of the total rainfall was used for saving with the grass strip laid in the lower and foot slope, while the one located in the middle and upper parts were only 50%. This study can provide reference for the prevention and treatment of slope gully in the Loess Plateau, China.