Alluvial fans of Trans-Himalayan cold desert (Pin valley, India): quantitative morphology and controlling factors

ABSTRACT Pin valley is an ideal area for alluvial fans’ development. Being least disturbed and devoid of vegetation, fans of this area provide exquisite information and extraordinary opportunity to understand different factors that affect their morphology. Despite aforesaid advantages these fans are hitherto not studied. Thus, the present study is an attempt to understand the morphology of these fans and explore factors affecting fan morphology, primarily through morphometry. Data were derived from various satellite imageries, topographical sheets, DEM and field observations. Various parameters of 51 fans and of their basins were measured and relationships among different parameters were examined. The results of the study are generally comparable to literature though these fans are much steeper than their counterparts in similar environmental settings. Multi-proxy approach was used to explore controlling factors. Fan Conicality Index (FCI) and sweep angle of fan (SA ) suggest confinement imposed by surrounding environment has considerably reduced the size of these fans. Further, valley-floor width to height ratio (Vf ), feeder channel and geological group-wise analyses reveal that active tectonic attitude, order of feeder channel, lithology and characteristics of contributing basin along with associated depositional processes exercise significant control on morphology of these fans.