Geomorphological development characteristics and spatial differentiation of alluvial fans in high mountain canyon areas:A case study in the Parlung Tsangpo Basin,southeast Tibet
Alluvial fans are common deposition landforms at the outlets of mountain streams(gullies).Maturely developed and stable alluvial fans are favorable sites for work and daily life in mountainous areas,but they are also potentially prone to debris flows and flash floods.The study of the geomorphic characteristics and development causes of alluvial fans can help to prevent and control geohazards and to rationally utilize soil and water resources,which has important scientific value and practical significance.Taking alluvial fans in the Parlung Tsangpo Basin,southeast Tibet as case samples and combining Google Earth,remote sensing images,and field surveys,we statistically analyzed the geomorphic characteristics,spatial differences,and main types of the regional alluvial fans,preliminarily examined the causes for their spatial diversity,and discussed the changes of the regional alluvial fans under the influence of climate change.The following conclusions were drawn:1)The alluvial fan area fluctuates sharply in comparison with the slope in the Parlung Tsangpo Basin,and the mainstem alluvial fans are in general smaller and steeper than those developed in major tributaries;the alluvial fans of the three tributaries show a trend of increasing in area(in median values)from the upstream to the downstream(that is,fan areas of Quzong＜Bodui＜Yigong),while the slope shows a tendency of decrease;the fan area is weakly correlated with the contribution basin area,the fan slope is negatively correlated with the basin area and positively correlated with the ruggedness of the basin,and there are obvious differences in the fitting relationships between the alluvial fans of the four analyzed areas and the morphometric parameters of the basins.Alluvial fan-basin morphology parameters in the four analyzed areas shows obvious differences in the fitting relationships.2)The morphological characteristics of the three types of fans in the basin,namely,fans formed by flood,debris flow,or colluvial processes,are quite different,and their links with the basins from which they originate are different,as shown by the fact that the correlation between the debris flow fans and the basin morphology parameters is the strongest,while that of the colluvial fans is very weak.3)Fan development is affected by factors such as precipitation,sediment supply,dominant dynamic processes and the role of the main river,among others.Under the influence of climate change(for example,warming,increased heavy rainfall events,and so on),new alluvial fans are constantly created in the basin and the size(or even type)of the original alluvial fans is changing.
NETL
NSTL
万方数据
维普
