Table 4 Summary of predictor variables for developing the classification models.

Variable	Acronym	Unit	Reference
Debris flow events	DF	—	⁶
Area	Area	m²	⁵⁴
Perimeter	PE	m	⁵⁴
Elevation difference	ED	m	⁵⁴
Channel gradient	CG	%	⁵⁴
Average slope	AS	°	⁵⁴
Average aspect	AA	°	⁵⁴
Channel length	CL	km	⁵⁴
Active fault	AF	m	⁵⁵
Seismic intensity	SI	—	⁵⁵
Rock hardness	RH	—	^{55, 56}
Aridity index	AI	—	⁵⁷
Moisture index	MI	—	⁵⁷
Annual accumulated temperature above 10 °C	ACT	°C	⁵⁷
Annual rainfall	AR	mm	⁵⁷
Annual temperature	AT	°C	⁵⁷
Maximum daily rainfall	MDR_1	mm	⁵⁸
Maximum 3-day rainfall	MDR_3	mm	⁵⁸
Normalized Difference Vegetation Index	NDVI	—	⁵⁹
Soil texture	ST	—	⁵⁷
Water erosion intensity	WaE	—	⁵⁷
Wind erosion intensity	WiE	—	⁵⁷
Freeze-thaw erosion intensity	FtE	—	⁵⁷
Land use	LU	—	⁵⁷
Settlement sites	RA	—	⁶¹
Population density	PD	persons/km²	⁵⁷
Road length	RL	km	⁶⁰

*Detailed classification of part indexes.
Seismic intensity: (1) < VI; (2) VI; (3) VII; (4) VIII; (5) ≥ IX.
Rock hardness: (1) Very strong; (2) Strong; (3) Medium; (4) Weak; (5) Very weak; (6) Solum.
Soil texture: (1) Sand; (2) Silt; (3) Clay.
Water erosion intensity: (1) Very low; (2) Low; (3) Moderate; (4) High; (5) Very high; (6) Extreme.
Wind erosion intensity: (1) Very low; (2) Low; (3) Moderate; (4) High; (5) Very high; (6) Extreme.
Freeze-thaw erosion intensity: (1) Very low; (2) Low; (3) Moderate; (4) High.
Land use: (1) Paddy field; (2) Dry farm; (3) Forest; (4) Shrubbery; (5) Open forest; (6) Other forest; (7) High coverage grassland; (8) Moderate coverage grassland; (9) Low coverage grassland; (10) River; (11) Lake; (12) Reservoir; (13) Permanent glacier; (14) Mudflat; (15) Bottomland; (16) Urban land; (17) Rural residential area; (18) Other construction land; (19) Sand; (20) Gobi; (21) Saline-alkali soil; (22) Wetland; (23) Bare; (24) Rock; (25) Others.
Road length: (1) Highway; (2) National road; (3) Provincial road; (4) County road; (5) Railway.

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