Mountain hazards mapping in Nepal's middle mountains. Maps of land use and geomorphic damages (Kathmandu-Kakani area)

This paper discusses natural and cultural aspects of the Kathmandu-Kakani area. It is sixty square kilometres in extent and includes part of the Kolpu Khola watershed which flows into the Trisuli River, parts of the Kathmandu Valley, and surrounding forested hills. The Kolpu Khola watershed, with relatively dense population, intense agricultural use, and severe mountain hazards problems, is representative of many parts of the Nepalese Middle Mountain belt. The first part of the paper describes and comments upon a multi-coloured land-use map of the area (scale 1:10,000). About fifty percent of the area is cultivated either with rice and wheat on irrigated terraces, or with corn, millet, and buck-wheat on non-irrigated terraces. In many areas these terraces are situated on steep slopes. Forests, except in the northern part of the protected Royal Forest (Rani Ban), have been very extensively degraded and replaced by large areas of shrubland. Comparisons between the area in 1964 and in 1971, interpreted from air-photographs, and the actual state of present land use show an increase in cultivated land at the expense of pastures and forests. The second part includes an interpretation of a map of geomorphic damages (scale 1:10,000). For representative elements of the legend, formal, genetic, and dynamic aspects are examined. The distributions of destructive forms and processes are discussed and suggestions are made concerning practical measures for damage reduction. The most striking feature is the heavy concentration of geomorphic damages in the steep, cultivated Hill Zone of the field area. In comparison, the erosive processes in the forested areas and on the plain of the Kathmandu Basin are of minor importance. Gullies, badlands, and landslides account for more than 90 percent of the actual losses of cultural land. The two maps provide an important basis for hazards assessment and compilation of maps of mountain hazards and slope stability which are currently in preparation. They will also constitute a benchmark against which to assess future landscape changes.