Relationship between the accumulation of sediment storage and debris-flow characteristics in a debris-flow initiation zone, Ohya landslide body, Japan
Debris flows usually occur in steep mountain channels and can be extremely hazardous as a result of their destructive power, long travel distance, and high velocity. However, their characteristics in the initiation zones, which could possibly be affected by temporal changes in the accumulation co...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
|
| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://www.nat-hazards-earth-syst-sci.net/17/1923/2017/nhess-17-1923-2017.pdf |
| Summary: | Debris flows usually occur in steep mountain channels and can be extremely
hazardous as a result of their destructive power, long travel distance, and
high velocity. However, their characteristics in the initiation zones, which
could possibly be affected by temporal changes in the accumulation conditions
of the storage (i.e., channel gradient and volume of storage) associated with
sediment supply from hillslopes and the evacuation of sediment by debris
flows, are poorly understood. Thus, we studied the relationship between the
flow characteristics and the accumulation conditions of the storage in an
initiation zone of debris flow at the Ohya landslide body in Japan using a
variety of methods, including a physical analysis, a periodical terrestrial
laser scanning (TLS) survey, and field monitoring. Our study clarified that
both partly and fully saturated debris flows are important hydrogeomorphic
processes in the initiation zones of debris flow because of the steep
terrain. The predominant type of flow varied temporally and was affected by
the volume of storage and rainfall patterns. Fully saturated flow dominated
when the total volume of storage was < 10 000 m<sup>3</sup>, while partly saturated
flow dominated when the total volume of the storage was > 15 000 m<sup>3</sup>. Debris
flows form channel topography which reflects the predominant flow types
during debris-flow events. Partly saturated debris flow tended to form
steeper channel sections (22.2–37.3°), while fully saturated
debris flow tended to form gentler channel sections ( < 22.2°).
Such relationship between the flow type and the channel gradient could be
explained by a simple analysis of the static force at the bottom of the
sediment mass. |
|---|---|
| ISSN: | 1561-8633 1684-9981 |