Abstract: The impact of geological condition on dangerous segments of river was analyzed in this paper on the basis of previous research results of the impact of flow. Through investigation of historical dangerous segments under the administration of Guangdong Province, we acquired the proportions of dangerous segments caused by different factors. Hydrological measurement, bedload sampling, and indoor experiment demonstrates that besides unfavorable flow condition. Furthermore we selected three non-dangerous segments with unfavorable flow regime as comparison, and the result shows that despite unfavorable flow condition, good geological condition will not give rise to dangerous segments. In conclusion, dangerous river segments are closely related to both river regime and geological condition. In particular, in soft soil foundation area, the geological condition of dike should not be neglected.

Key words: soft soil foundation, dike, river regime, flow, geology, causes of dangerous segments