Background Baisha River Basin is the main drinking water source in the main urban area of Chengdu. The "5·12" Wenchuan earthquake led to the accumulation of a large number of collapse and landslide debris on the steep slopes, resulting in serious soil and water loss during rainstorm, which has a serious impact on the water supply of the water source. The investigation and change trend analysis of loose material sources in the basin have important guiding significance for the comprehensive control of soil and water loss in the basin.

Methods Four periods of high-resolution remote sensing images one year before the earthquake and 10 years after the earthquake were selected. The loose material source was extracted by using object-oriented remote sensing automatic interpretation combined with human-computer interaction. The spatial distribution and dynamic change characteristics of material source were analyzed by GIS spatial analysis method.

Results Before the "5·12" Wenchuan earthquake in 2008, the loose material sources area of the basin was only 20.05 km², accounting for 5.57% of the total area of the basin. The "5·12" Wenchuan earthquake caused a large number of new loose material sources in the basin, with a total area of 106.31 km², accounting for 29.52% of the total area of the basin. At 10 years after the earthquake, the total material source area decreased by 66.95 km². There are still a few new sources in the basin after the earthquake, and the new sources in the 5 years after the earthquake are mainly distributed in the lower reaches of the basin due to human activities such as post disaster recovery and reconstruction, river dredging and mining. At 5-10 years after the earthquake, the newly added sources decreased, which was mainly caused by the expansion of the source range of some slopes in the upper reaches of the basin or the newly added collapse and landslide sources. The earthquake caused the average source center of the basin to move about 6.7 km downstream as a whole, and the average source center gradually moved back at 10 years after the earthquake.

Conclusions Although the ecological restoration of the basin is obvious, there is still a certain gap from that before the earthquake. The material sources in the three directions of southwest by west, northwest by west and northwest by north of the upstream are still in an unstable state, which is the area to be treated in the next step.