LAND USE AND MANAGEMENT MAP PREPARATION PROCEDURE FOR THE LANDSLIDE HAZARD ZONATION MAPPING PROJECT IN SRI LANKA

Abstract

Seven districts out of 25 in Sri Lanka are prone to landslide. National Building ResearchOrganization (NBRO) is being carried out Landslide Hazard Zonation Mapping Project (LHMP)for these districts from 1990. For the purpose of this six maps i.e. Land form map, Slopecategory map, Bedrock geology, Hydrology, Landslide & Colluvium and Land use &Management maps were used

In the case of the land use and management legend development all national and internationalstandards and norms were evaluated and those applicable for the hazard zonation exercise wereadopted.

The legends used by various organizations connected with land use planning, such as forest landuse mapping project, Land use Policy Planning Division of the Survey Department, Land useDivision of the Irrigation Department and the Integrated Rural Development Project werescrutinized and evaluated as to their applicability for use in the legend development process.It was observed, after the above exercise was completed, that the existing legends used by theseorganizations lacked the required details and direction to accommodate the depth and emphasisto be placed on the management related stability parameters of land use categories that areimportant in state of nature criteria to be mapped for landslide hazard assessment. Therefore, aspecial purpose stability oriented land use & management legend should be evolved for this kindof special exercise

In order to develop the land use & management legend for LHMP, different managementcategories prevalent within the project area that could be identified to the scale of I: 10,000 anddemarcated though systematic air photo interpretations were identified.

The different management based land use categories and land use map units of the evolvedlegend were demarcated on transparent overlays affixed to the Air Photos (APs) beinginterpreted. Areas with doubtful land uses were marked with question marks for verification inthe field. APs to the scale of 1:10,000 in semi gloss papers were used for interpretations.

Four different stages an be involved in the map preparation which are transfer of land useboundaries to 1:10,000 ABMP maps, intermediate base overlay maps, updating using existingmaps and field checking & finalisation.