Debris-flows pose serious hazards to communities in mountainous regions of the world and are often responsible for loss of life and damages to infrastructure. Characterised by high flow velocity, large impact forces and long runout, debris-flows have potential discharges several times greater than clear water flood discharges and possess much greater erosive and destructive potential. In combination with poor temporal predictability, they present a significant hazard to settlements, transport routes and other infrastructure located at the drainage points (fan-heads) of watersheds. Thus, it is important that areas vulnerable to debris-flows are identified in order to aid decisions on appropriate land-uses for alluvial fans. This research has developed and tested a new GIS-based procedure for identifying areas prone to debris-flow hazards in the Coromandel/Kaimai region, North Island, New Zealand. The procedure was developed using ESRI Arc View software, utilising the NZ 25 x 25 m DEM as the primary input. When run, it enabled watersheds and their associated morphometric parameters to be derived for selected streams in the study area. Two specific parameters, Melton ratio (R) and watershed length were then correlated against field evidence for debris-flows, debris-floods and fluvial processes at stream watershed locations in the study area. Overall, strong relationships were observed to exist between the evidence observed for these phenomena and the parameters, thus confirming the utility of the GIS procedure for the preliminary identification of hydrogeomorphic hazards such as debris-flow in the Coromandel/Kaimai region study area. In consideration of the results, the procedure could prove a useful tool for regional councils and CDEM groups in regional debris-flow hazard assessment for the identification of existing developments at risk of debris-flow disaster. Furthermore, the procedure could be used to provide justification for subsequent, more intensive local investigations to fully quantify the risk to people and property at stream fan and watershed locations in such areas.
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机译：泥石流对世界山区的社区构成了严重危害，经常造成人员伤亡和基础设施损坏。泥石流具有高流速，大冲击力和长跳动的特点，其潜在排放量是清水洪水排放量的几倍，并且具有更大的侵蚀性和破坏性。加上时间上的可预测性差，它们对流域排水点（扇头）的定居点，运输路线和其他基础设施构成了重大危害。因此，重要的是确定易受泥石流侵害的区域，以帮助决定冲积扇的适当土地用途。这项研究开发并测试了一种新的基于GIS的程序，用于识别新西兰北岛Coromandel / Kaimai地区容易发生泥石流危害的区域。该程序是使用ESRI Arc View软件开发的，并使用NZ 25 x 25 m DEM作为主要输入。运行时，它可以为研究区域中选定的河流导出分水岭及其相关的形态计量参数。然后，将两个特定参数，梅尔顿比（R）和分水岭长度与研究区域溪流分水岭位置的泥石流，泥石流和河流过程的现场证据相关联。总体而言，观察到这些现象的证据与参数之间存在很强的关系，从而证实了GIS程序在科罗曼德/凯迈地区研究区初步识别水文地貌危害（如泥石流）的实用性。考虑到结果，该程序可以证明是区域理事会和CDEM小组进行区域泥石流危害评估的有用工具，可用于识别存在泥石流灾害风险的现有发展。此外，该程序可用于为随后的更深入的当地调查提供依据，以充分量化此类区域中溪流扇和集水区对人员和财产的风险。
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