不同降雨特征条件下舟曲县地质灾害危险性区划

目的]合理区划甘肃省甘南藏族自治州舟曲县区域地质灾害危险性,为该区以及类似区域地质灾害危险性区划提供科学依据。方法]从舟曲县暴雨地质灾害触发因素入手,结合野外勘察,采用无限边坡稳定性SINMAP模型,开展不同降雨特征条件下区域地质灾害危险性区划研究,对不同级别下灾害区域面积和所占比例的迁移与转化规律进行定量评价。结果]地势低洼地区与地形湿度较高区域、灾害点分布规律一致,随着降雨量的逐渐增大,地表浅层土壤水分、土壤湿度区域面积逐渐增加,逐渐扩展到山脊和坡度较缓的斜坡单元;随着降雨预警级别的升高,1h雨量从10mm升至56mm,稳定性区域面积比例和所占滑坡比例分别减少22%和38%,不稳定性区域比例值分别增加121%和125%,潜在不稳定区域面积和所占滑坡比例始终最高,均值高达35%和39%;同时,基本稳定区、潜在不稳定区正逐渐向不稳定区及极不稳定区迁移与过渡,发生地质灾害的潜在性逐渐增大,危险程度日益加剧;预警级别升至蓝色Ⅳ级时,地质灾害即被触发,预警级别升至黄色Ⅲ级后,危害程度发生质变,地质灾害危险程度显著加剧。结论]降雨是舟曲地质灾害的诱发因素,如遇合适的强降雨条件,地质灾害危险程度依然严峻。

Risk Zoning of Regional Geo-hazards Under Different Rainfall Characteristics in Zhouqu County

Objective] We analyze the risk zoning of regional geo‐harzards in order to provide a scientific basis for regional geo‐hazards prevention and reduction in Zhouqu County ,Gansu Province and similar areas . Methods] We established regional risk assessment models for shallow geo‐harzards under different rainfall characteristics ,by using SINMAP model .Results] The distribution pattern of disaster spot in low ‐lying areas was consistent with high humidity area .With the increasing of rainfall ,the shallow soil moisture and area of wetness region increased gradually ,and extended to the ridge and gentler slopes .With the rise of rainfall warning level ,1 hour rainfall amount increased from 10 mm to 56 mm .The area proportion and land‐slide proportion in the stable region decreased by 22% and 38% ,respectively ,the related proportion in the unstable region increased by 121% and 125% ,respectively ,and the related proportion in the potentially unstable region was the highest ,and reached to 35% and 39% ,respectively .Meanwhile ,the basically stable and potential unstable region was gradually transferred into unstable and very unstable region .The potential of geological harzard occurrence in the study area was increasing gradually .The geo‐hazards such as land‐slides and debris flow could be triggered when the warning level was raised to the level Ⅳ blue warning , while when the warning level was raised to the level Ⅲ yellow warning ,the risk degree of geo‐hazards was increased significantly .Conclusion] Rainfall is a factor that induced geo‐hazards in Zhouqu County .In case of heavy rainfall suitable conditions ,the risk of geo‐hazards remains severe .