Table 1 Terrain attributes and their calculation methods

lnSLOPE

ln (SLOPE + 1)

SLOPE: slope gradient (degrees) calculated from the 90 m DEM interpolated by the bilinear option

SLOPE was calculated within 3 by 3 cells windows, using QGIS 3.14, by the Horns method

lnHAND

ln (HAND + 1)

HAND: Height Above the Nearest Drainage (m)

HAND was calculated by the method of Yamazaki et al. (2012) and Yamazaki et al. (2019)

TEXTURE

Density within a 10-cell radius of pits and peaks obtained by the difference between the Original DEM and the 3 × 3 median filtered DEM.

Original DEM: the 90-m DEM interpolated by the nearest neighbor option

The surface texture of Iwahashi and Pike (2007). TEXTURE was calculated by the “terrain surface texture” tool of SAGA (Conrad 2012a) in QGIS 3.4 (Threshold: 5-m, radius: 10 cells, no distance weighting)

CONVEXITY

Density within a 10-cell radius of convex points obtained by processing the DEM with a 3 × 3 Laplacian filter.

Original DEM: the 90 m DEM interpolated by the nearest neighbor option

The local convexity of Iwahashi and Pike (2007). CONVEXITY was calculated by the “terrain surface convexity” tool of SAGA (Conrad 2012b) in QGIS 3.4 (Threshold: 1-m, radius: 10 cells, no distance weighting)

Sinks

Sinks is the following region: ((Filled DEM)—(Original DEM)) > 0.

Original DEM: the 90-m DEM interpolated by the bilinear option. Filled DEM: DEM with the surface depressions (sinks) filled in

Filled DEM was calculated by the “Fill Sinks (Wang & Liu)” (Wang and Liu 2006) tool of SAGA in QGIS 3.4