Abstract
Introduction: Active faults and accompanied tectonic activities are a key triggering factor for debris flows in mountainous region. In this paper, the spatial distribution of 19 debris flows along Ya-Lu highway in western China was analyzed. Method: We collected basic data of these 19 debris-flow gullies in the in-situ investigation work, and documented key parameters including watershed area, the averaged slope gradient, gully type, debris-flow magnitude, and developing stage of the gully. Based on the DTM data from SRTM database, the overall spatial distribution features of these debris flows are analyzed. Result and Conclusion: We used a polar coordinate system to illustrate the relationship between debris flow magnitude and the direct distance to the active fault. In this system, the spatial distribution of these debris flows is represented by the vertical distance to the fault and the angle between gullies to the fault. It is revealed that the debris-flow magnitude has a close positive relationship with the vertical distance to the active fault, that generally debris-flow magnitude increases as closing to the active fault.
Highlights
Active faults and accompanied tectonic activities are a key triggering factor for debris flows in mountainous region
For the gullies locate in Shimian to Lugu region, the space relationship between debris flow gully and active fault rupture are not evident, other phenomenon can be found that due to the influence by multiple active fault rupture, the scales of debris flow locate in Ya’an to Shimian region are more huge
In Fig. (6), the gullies of D01 to D06 are controlled by two faults, the distances from these gullies to either fault is much greater than D07~D19, the magnitude of these debris flows are comparable. it is shown that the number of the faults in the zone plays an important role to control the debris flow magnitude
Summary
Active faults and accompanied tectonic activities are a key triggering factor for debris flows in mountainous region. Debris flows are one of the most common geomorphic phenomena in mountainous areas. They have been defined as mass movements consisting of granular solids, water and air moving as a viscous flow [1]. Previous studies have indicated that debris flows are the result of a complex interaction between environmental and human factors under certain pluviometry conditions [6]. These factors often fall into a number of categories, such as geomorphic, geological, land use/land cover, and hydrological factors [7 - 9]. Active faults are important geological structure for triggering debris flows because it is a common wisdom that the generated tectonic activities in the fault zone directly increase the sediment in the debris-flow gully [12]
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