Effects of Landscape Patterns on Runoff and Sediment in Danjiang River Basin

Abstract

The Danjiang River being the main tributary of the Hanjiang river, is the main water source of the south-to-north water diversion project in China, which is benefit from the protection of ecological environment. As the main reasons for ecological degradation, the land use changing and severe soil erosion attacted considerable attention in recent years. Based on the land use data and measured runoff and sediment data, the landscape pattern index analysis method and statistical analysis method were employed to explore the relationship between landscape pattern indexes and runoff and sediment in Danjiang River Basin (DRB). The results show that the runoff and sediment of the river present a downward trend from 1985 to 2018. The forestland was the dominant type of land use, and the growth rate of grassland was the highest. Results also show that the patch density (PD), the interspersion and juxtaposition (IJI), the edge density (ED), CONTAG, DIVISION and the largest patches index (LPI) have the same trend, indicating that the fragmentation degree of landscape, the connectivity between landscapes, and the richness of landscape increased. In addition, the shannon’s diversity index (SHDI) and IJI were positively associated with the runoff at landscape level, number of patches (NP), PD, ED, and CONTAG were negatively associated with sediment, and CONTAG was positively correlated with sediment. At class level, the NP, PD, LSI, and IJI of forestland, the NP, PD, and DIVISION of cropland, the LPI of grassland, and the NP, PD, and LSI of construction land were negatively correlation with runoff. The LSI and ED of grassland and the LPI of construction land were positively correlation with runoff. And the LSI, IJI, and ED of forestland and the LSI, IJI, and ED were negatively correlation with sediment.