The majority of landslides in the Indian Himalayas are triggered by rainfall and earthquake.The geology and geomorphology also play an important role and constitute the major predisposing factor controlling landslides.Additionally,active tectonics modify the landscape,impacting the occurrence and distribution of landslides.The objective of this study is to investigate the role of some of the major predisposing factors to assess landslide patterns in the Yamuna River Basin as it is prone to recurrent landslide hazards.The approach mainly deals with the application of geographical information system-based statistical analysis and quantifying frequency-area distribution of rainfall-triggered landslides for the years 2015 to 2017.The analysis shows that the frequency of landslides is highest in the slope range 40°-70° and the mean landslide size is higher in the slope range 0°-20° and 300-40°,remaining constant on further increase in slope angle.The study shows that some critical slope range controls both the frequency and size of landslides.Landslides were mostly restricted to south facing slopes.About 91％of the landslide occur in the drainage density range of 1.2 to 2.1 km/km2 while landslides show very low occurrence in either lower(＜1.2)or higher(＞2.1)drainage density.Frequency-size distribution analysis of landslides depicts a distinct cutoff point but an indistinct rollover point.Under-sampling of small landslides can be a reasonable cause for this.Like other studies,the present data fits very well for medium and large landslides following an inverse power law with a scaling exponent of-2.16.Around 80％of landslides are smaller than the cutoff size and 20％larger than this value.The geology and tectonics of Lesser Himalayas and Sivaliks offer favorable conditions for frequent landslides.Areas such as Dehradun,Uttarkashi,Sirmaur,Shimla,and Solan are very prone to landslide activity owing to the presence of poorly consolidated sandstone,conglomerate,quartzites,phyllites,etc.Moreover,the majority of larger landslides are in the Dehradun district where precipitation,drainage density,and lithology are highly favorable to trigger large events.The present study has identified the critical range of predisposing factors responsible for landslides and presents the frequency-size distribution of landslides in the Yamuna River Basin.These are the key inputs in landslide susceptibility mapping and risk assessment.Therefore,the findings from the present analysis can be very helpful in landslide risk reduction and landslide hazard zonation and probably plan critical locations for installation of early warning signals.

Ravi SHANKAR;Gyan Prakash SATYAM;Prakash Kumar SINGH;Nilesh Kumar RAI;Ranjit Kumar PASWAN

REED,CSIR-Central Institute of Mining and Fuel Research,Dhanbad 826001,India;Department of Applied Geology,Indian Institute of Technology(ISM),Dhanbad 826004,India;Department of Earth and Planetary Sciences,University of Allahabad,Prayagraj 211002,Uttar Pradesh,India

山地科学学报（英文版）

[1]Ravi SHANKAR;Gyan Prakash SATYAM;Prakash Kumar SINGH;Nilesh Kumar RAI;Ranjit Kumar PASWAN-.Impact of geomorphometric parameters on the occurrence and distribution of landslides in Yamuna River Basin,North-Western Himalaya,India)[J].山地科学学报（英文版）,2022(08):2374-2396

geomorphometric,Yamuna,Sivaliks,Dehradun,Uttarkashi,Sirmaur,Shimla,Solan,conglomerate,phyllites

Impact,parameters,occurrence,distribution,landslides,River,Basin,North,majority,Indian,Himalayas,triggered,by,rainfall,earthquake,geology,geomorphology,also,play,important,role,constitute,predisposing,controlling,Additionally,active,tectonics,modify,landscape,impacting,objective,this,study,investigate,some,factors,patterns,prone,recurrent,hazards,approach,mainly,deals,application,geographical,information,system,statistical,analysis,quantifying,frequency,area,years,shows,that,highest,range,mean,size,higher,remaining,constant,further,increase,angle,critical,controls,both,Landslides,were,mostly,restricted,south,facing,slopes,About,drainage,density,km2,while,very,either,lower,Frequency,depicts,cutoff,point,indistinct,rollover,Under,sampling,can,be,reasonable,cause,Like,other,studies,data,fits,well,medium,following,inverse,power,law,scaling,exponent,Around,smaller,than,larger,value,Lesser,offer,favorable,conditions,frequent,Areas,such,activity,presence,poorly,consolidated,sandstone,quartzites,etc,Moreover,district,where,precipitation,lithology,highly,events,has,identified,responsible,presents,These,key,inputs,susceptibility,mapping,risk,assessment,Therefore,findings,from,helpful,reduction,zonation,probably,plan,locations,installation,early,warning,signals

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