5. Conclusions
In this study, the alluvial fan is confirmed further to be an important land resource and still has utilization potential in RRB. The main conclusions are as follows:
(1) There are 826 alluvial fans with 1166.03 km²in LRB. The quantity of all alluvial fans is dominated by the ones with area not more than 1 km², but the area of alluvial fans is dominated by the ones with area more than 10 km2.
(2) The distribution of alluvial fans is uniformed in LRB. The quantity of alluvial fans is concentratedly distributed in the center and east in LRB, and the area distribution trend is opposite with quantity. Especially in Damshung county in the west of LRB, the area of alluvial fans is 485.20 km2.
(3) Alluvial fans provide materials and places for local human and livestock to exist and settlement. The area of grassland is the most in all land-use types. The area ratio of cropland and imperious area in alluvial fans are just 2.16% and 4.52%, but which in LRB are 18.98% and 9.18%.
(4) The two types of alluvial fans have the more utilization potential in the future due to their considerable area and low land-use degree. The first one is alluvial fans which is occupied by grassland no less than 50%. And second one is alluvial fans which is occupied by grassland and bare land not less than 50% and 30%. Meanwhile, considering the accessibility of alluvial fan, the majority of alluvial fans are located within 5 km to road, village and river. The quantity ratio of alluvial fans distance to tertiary road, village and village within 5km are 93.70%, 53.63% and 61.86% respectively, and area ratio are 97.50%, 46.14% and 77.38%, respectively. Therefore, alluvial fan has the utilization potential in LRB where the suitable land for human is shortage.
Acknowledgments : This research was supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No. XDA20040202)and the second Tibetan Plateau Scientific Expedition and Research Program (STEP) (No. 2019QZKK0603)