Landslide hazard and risk zoning for urban planning and development

Disasters caused by landslides have continued to increase during the last decades notwithstanding the significant efforts of the United Nations aimed to reduce their consequences. The reason for a risk increase is essentially related to demographic pressures and territory mismanagement. Fortunately, some countries and regions have already progressed in the development of procedures for managing urban and population growth as well as for minimizing the associated risks. The procedures are based on hazard and risk zoning which, however, can imply difficulties because of technical and socio-economic contributing factors. Starting from the valuable experience gained in several countries, the present paper discusses the improvement of urban planning and development by hazard and risk zoning, albeit recognizing the efforts still required for quantifying zoning criteria and adapting them to landslides risk management necessities. Risk mitigation strategies are therefore discussed, also considering the valuable contribution that can be furnished by the skilful use of new technologies and mathematical modeling. However, improvement of both remote sensing and data treatment techniques should not detract from field work and personal judgment since the current use of landslide inventories, which are the key input parameter for hazard assessment and validation, cannot be prepared in a reliable way with automatic data capture techniques exclusively. Uncertainties and errors in landslide zoning restrict the applicability of the hazard and risk maps for practical purposes and can generate conflicts. The validation of both procedures and maps is, therefore, a necessity especially in urban areas