OCR Text |
Show Avalanche zoning maps that are mapped according to communities will later become an addition to community building regulations. Avalanche zone mapping ideally should include the total area of a community. However, little would be accomplished by including the large barren and uninhabited terrain. Mapping can then be limited to settled areas, potential building sites and regions with existing or potential commercial links. Border areas with uniform topography separating two communities should be dealt with according to principles that apply to planning in general; such areas should be considered as a unit. Mapping should not stop where the areas of two communities meet, despite a political division of uniform topography. Sources of information available to researchers compiling avalanche zoning maps are: - Topography and forested areas - Avalanche scars in the terrain - An eventual avalanche register ( cadaster) - An eventual avalanche chronicle - Statements of local people Practice has shown that the general plan for the register of land property at a scale of 1: 10,000 can be used as an excellent foundation for studying the topography. Another valuable perspective can be gained by using the National Map with a smaller scale of 1: 25,000, which is not yet obtainable for all mountain areas. At a contour interval of 20m, this map does not show detailed land forms; however, it can be used as a stop- gap if the general plan is missing. Large maps have the disadvantage of being hard to handle, especially if large areas must be worked. They lose a great deal of clarity, which should not be sacrificed for exaggerated details. It is easier to record on larger scales, as for example 1: 5,000 or 1: 2,000. Yet such maps with altitude contours exist only for small areas. It is advantageous to inspect survey maps for possible avalanche areas, record them approximately, and then verify their existence in the field. Under these circumstances, mapping can be done confidently and efficiently. The study of topography is the most important undertaking since all other sources of information can give only data on avalanches that actually have occurred. Topography shows all the potential avalanche areas, as well as those of avalanches which seldom occur whose scars have disappeared and which have not been recorded in a chronicle or avalanche register. The forest is important for avalanche defense, especially at the starting zone. Its effect and importance with respect to the slide path and outrun area is often misunderstood. Forest growing in the slide path can divert small avalanches and if conditions are favorable, stop them. Recording small avalanches however for mapping purpose is useless. We need to know the area of the large ones. These will sweep the forest away, and much damage can be 11 |