Preprints
https://doi.org/10.5194/esurf-2022-67
https://doi.org/10.5194/esurf-2022-67
 
30 Nov 2022
30 Nov 2022
Status: this preprint is currently under review for the journal ESurf.

Reveal the relation between spatial patterns of rainfall return levels and landslide density

Slim Mtibaa and Haruka Tsunetaka Slim Mtibaa and Haruka Tsunetaka
  • Department of Disaster Prevention, Meteorology and Hydrology, Forestry and Forest Products Research Institute, Tsukuba city, 305-8687, Japan

Abstract. It is known that the spatial rainfall pattern can mark landslide distribution across the landscape during extreme triggering events. However, the current knowledge of rainfall controls on this distribution remains limited. Here, to reveal what rainfall characteristics control landslide spatial distribution, we explore the spatiotemporal pattern of a rainfall event that triggered over 7,500 landslides (area ≈ 100–104 m2) at a regional scale with an area of ≈ 400 km2 in Japan. Using a 5-km resolution radar-driven hourly precipitation dataset with 32 years of records, we compared rainfall return levels for various time range from 1 to 72 h and landslide density in each ≈ 25 km2 grid cell. The results show that, even if the surface slope distribution within grid cells is similar, the number of landslides in a ≈ 25 km2 grid cell was substantially high when the rainfall return levels exceeded the 100-year return period in all examined timespans (i.e., 1–72 h). In contrast, when only specific-duration rainfall intensities (e.g., 6–48 h) exceeded the 100-year return level, the landslide density in corresponding grid cells tended to be low. Consequently, the landslide density increased with the increase in the rainfall return level of various timespans rather than a specific rainfall intensity, such as downpours for a few hours or long-term cumulative rainfall for 48 h. Moreover, with the increase in the landslide density, the number of relatively large landslides exceeding ≈ 400 m2 increased. Therefore, the spatial differences in rainfall return levels potentially constrain the density of total landsliding and relatively large landslides. In this sense, whether rainfall intensities reach high return levels rarely experienced in a wide timespan ranging from a few hours to several days is one of the key determinants of the spatial distribution of landslides and the extent of related hazards.

Slim Mtibaa and Haruka Tsunetaka

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2022-67', Anonymous Referee #1, 14 Dec 2022
  • RC2: 'Comment on esurf-2022-67', Anonymous Referee #2, 03 Jan 2023
  • RC3: 'Comment on esurf-2022-67', Anonymous Referee #3, 05 Jan 2023
  • EC1: 'Comment on esurf-2022-67', Sagy Cohen, 11 Jan 2023

Slim Mtibaa and Haruka Tsunetaka

Slim Mtibaa and Haruka Tsunetaka

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Short summary
We explore the relation between the spatial patterns of rainfall return levels for various timespans (1–72 h) and landslide density during a rainfall event that triggered widespread landslides. We found that landslide density increases with increased rainfall return levels for the various examined timespans. Accordingly, we conclude that whether rainfall intensities reached exceptional return levels for a wide time range is a key determinant of the spatial distribution of landslides.