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<br />Ou28Jl <br /> <br />Variations of the inventory map can include any combination of landslide <br />features and/or processes or the more detailed breakdown of anyone process or <br />type. <br /> <br />Because simple inventories are prepared mainly by interpreting aerial <br />photographs, they can be prepared in a short time by a few people at a <br />relatively low cost. <br /> <br />Simple inventories are used mainly to give an overview of the landslide hazard <br />in an area and to delineate areas where more detailed studies should be <br />conducted. Detailed inventories provide a better understanding of the <br />different landslide processes operating in an area and can be used to regulate <br />or prevent development in landslide areas and in the design of remedial <br />measures (USGS, 1981). They also provide a good basis for the preparation of <br />such derivative maps as "slope stability", "risk", and "land use". <br /> <br />These maps are limited by the fact that they show the distribution of past <br />landsliding, and don't necessarily indicate areas where future sliding may <br />occur. Also, as they become more complex, they require more field checking, <br />and more time and money to complete. <br /> <br />Landslide Susceptibility Maps <br /> <br />A landslide susceptibility map goes beyond the inventory map and depicts areas <br />that have the potential for 1andsliding in the future. These areas are <br />determined by correlating some of the principal factors that contribute to <br />lands1iding, such as steep slopes, weak geologic units, and poorly drained <br />rock or soil, with the past distribution of landslides. These maps usually <br />indicate only the relative stability of slopes rather than making absolute <br />predictions (USGS, 1981; Brabb, 1984). <br /> <br />Landslide susceptibility maps can be considered as derivatives of landslide <br />inventory maps since the inventory is a vital element of the preparation <br />process. Overlaying an inventory map, which shows existing slides, over a <br />geologic map can identify specific slide-prone geologic units. This <br />information can then be extrapolated to predict new areas of potential <br />sliding. In more complex maps more information, such as slope angle, aspect <br />and drainage, are considered. <br /> <br />- 15 - <br />