Distribution feature and development characteristics of geohazards in Wudu district, Gansu province, Northwest China

Abstract

Background

The study area located at southeast Gansu, China, has long been afflicted by the intense occurrence of geohazards. The study area is characterized by interleaving terrain of precipitous mountains and valley basins, abundant precipitation, and complicated geological setting. In this work, 1144 geohazards including 759 landslides, 281 debris flows, and 104 collapse were presented and their types were categorized in detail. Then, the distribution of geohazards were analyzed and the controlling role of hazard-inducing environment and triggering factors on geohazards were preliminary presented.

Results

In this work, correlation analysis between geohazards and geological, topographical, and geomorphological context was conducted. Concave slopes with height smaller than 200 m and slope gradient between 21° and 40° is the favorable topographic feature for landslide occurrence and the predominant slope aspects of landslides are southwest, south, west, and southeast. Collapse generally occurs in slope with gradient larger than 45°. Valleys with valley gradient less than 400‰, valley height between 100 and 500 m, and watershed area of 1–10 km² register the largest percentage and the most favorable slope gradient for the supply of solid source at the debris flow source area is 25°–45°. The preferable strata for geohazards (landslide, collapse and debris flow) are Middle and upper Pleistocene loess, Holocene diluvium, Silurian phyllite and slate, Neogene mudstone, and Devonian schist and gneiss, and most geohazards occurred in tectonic erosional middle altitude mountain, tectonic erosional high-middle altitude mountain, tectonic erosional-diluvial planation surface. In addition, the controlling role of triggering factors, i.e., precipitation, earthquake, and human engineering activity was discussed and described in this work.

Conclusion

Geohazards in the study area are synthetically controlled by the hazard-inducing environment and triggering factors. The complicated sliding-prone strata and steep topography resulted from strong tectonic movement provides a favorable basis for the development and formation of geohazards. Heavy rainfall, strong seismic motion, and human engineering activity are the main triggering factors for geohazard occurrence.