亚洲一区欧美在线,日韩欧美视频免费观看,色戒的三场床戏分别是在几段,欧美日韩国产在线人成

Ephemeral gully is a common erosion process and represents one of the significant watershed sediment resources in the hilly region on the Loess Plateau of China. A watershed with closure measures implement in Wuqi County, Shaanxi Province was taken as case study to quantify the relationship between the lengths of ephemeral gullies and eroded volume and assess the erosion rate in six years period. A total of 60 ephemeral gullies were surveyed under field conditions, and lengths of 245 ephemeral gullies were identified by two QuickBird images with the same time phase in years of 2007 and 2013. Results revealed that ephemeral gully density was 36.21km/km2 in 2013 and the total length of ephemeral gullies was changed from 13.74km in 2007 to 14.12km in 2013. Among 245 ephemeral gullies interpreted from images, the lengths of 46.94% gullies were decreased owing to connecting with gully heads with larger erosion rate or measurement error. Assuming that the cross section of an ephemeral gully is quadrangular frustum pyramid, the volume of 60 investigated ephemeral gullies was ranged from 0.4m3 to 15.43m3, which was 4.06m3 on average. Based on the built regression model, the volume change of 245 ephemeral gullies from 2007 to 2013 was 71.52m3. For 53.06% of ephemeral gullies with longer length than previous conditions, the average increasing rate was 0.2m3 per year for each growing ephemeral gully and the total increased volume was 157.51m3. The estimated erosion rate of ephemeral gullies was 67.31m3/(km2·a) on the 12 slope units with area of 0.39km2. The total eroded volume was about 100.97t/(km2·a) if the average soil bulk density was taken as 1.5g/cm3. Assuming that the average erosion rate of the other 46.94% ephemeral gullies was similar to those with increased length, the average erosion rate on the slope covered by herbal could be 215t/(km2·a). The results showed that ephemeral gully erosion rate could be estimated using very high resolution remote sensing such as QuickBird images, which could provide reference for the soil and water conservation on hilly Loess Plateau.