LANDSLIDE SUSCEPTIBILITY MAP OF KAVAJA, ALBANIA Mediterranean Meeting on ″Monitoring, modelling and early warning of extreme events triggered by heavy rainfalls″ University of Calabria, Soil Protection Dept., Cosenza (Italy), Jun 26–28, 2014 LANDSLIDE SUSCEPTIBILITY MAP OF KAVAJA, ALBANIA Olgert JAUPAJ Albanian Geological Survey

Introduction Landslide susceptibility is useful tool in urban planning, specifically for the definition of the land use zones and for the design of future construction projects and is is very necessary due to the strong impact of landslide processes on people and their goods

Abstract The Kavaja area is prone to landslides due to geological features, diverse terrain topography, high intensity spring-autumn rainfall, deep weathering associated with the humid climate and man-modified slopes In the study area 89 landslides are described and the bivariate statistical approach is used to obtain the Landslide Susceptibility Map. On the basis of these results, recommendations about landslide risk are given to take into account landslides in the land-use planning

GEOGRAPHY OF STUDY AREA Geographically, the study area is located in central-western part of Albania between latitudes 41° 12' 56" to 41° 1' 16"North, and longitudes 19° 26' 17 " to 19° 36' 34”East. This area represents anticline structures. The elevation ranges from 0 to 190,4 m above sea level, while the annual rainfall is around 1000 mm/Year. The study area is about 155 km2 and belongs to Kavaja district. An estimated 15 000 people live and work in this area.

GEOLOGY OF STUDY AREA This area, which belongs to pre-Adriatic depression of Albania geological terrains, consists entirely of molassic formations of Pliocene which lie transgressively on underlying formations of the Ionian and Kruja zones. The main geological formations that crop out in the Kavaja region are represented by: Quaternary deposits colluvial, deluvial, proluvial, alluvial, lagoon, marshland and maritime genesis (thickness 10m-30m) Pliocene molasses which consist of two formations: Helmasi formation Rrogozhina formation

Rrogozhina formation (N2R): HELMASI FORMATION (N2H) The molasses of this formation are represented by massive clay with very rare sandstone layers and constitute the core of the anticlines. Their thickness is over 1 000 m Rrogozhina formation (N2R): Molasses of this formation constitute the syncline structures. This formation is divided into three layers from the bottom to the top: N2R (a) - clays, siltstone. Thickness 250m. N2R (b) – siltstone - sandstone, Thickness 50 to 100 m. N2R (c) - mostly conglomerate and sandstone. Thickness 300m .

MATERIALS AND METHODOLOGY Data collection. Selection of the landslide causative factors on the basis of previous fieldwork survey and landslide inventory analysis in the study area. Evaluation of the role of landslide causative factors in the study area and preparation of the input factor maps for landslide susceptibility mapping. Apply Bivariate approach for deriving landslide susceptibility map of the study area. Based on the final map of the study area, recommendations are given on the landslide hazard prevention measures in order to help the local community to be prepared and to respond adequately to disasters.

DATA COLLECTION Archive data: Gathering all information from Central Archive of Albanian Geological Survey Field surveys: Looking new landslides,evaluate the landslide evolution, present state and activity Interpretation of landslide occurrences from aerial photographs according with field verification.

LANDSLIDE INVENTORY Based on the database of Albanian Geological Survey, around 73 landslides are observed in this area. This study was carried out for emergency, with the request of Municipality, in order to asses the risks and to give the recommendations to decrease them.

BIVARIATE APPROACH For this study the Bivariate approach was used, the principle of the analysis is to determine the densities of landslide occurrences within each parameter map and its parameter map classes, and to calculate weights based on the class distribution and the landslide density. With these weights parameter maps can be combined in Arc_GIS to obtain a Landslide susceptibility Map Six factors are more relevant than others so weighting values were generated for each parameter map in based of as the natural logarithm of the landslide density in the class divided by the landslide density in the entire map. This method is based upon the by equation of Van Westen

Bivariate statistical analysis Factor maps Cross tables Weight maps Landslides Geology WGeology Combination of weights . Map overlaying procedure Slopes WSlope . . Land use Wlanduse Validation Susceptibility map Introduction to GIS

LANDSLIDE INFLUENCING DATA LAYERS

GEOLOGICAL FACTOR

SLOPE FACTOR

ASPECT FACTOR

LAND-USE FACTOR

DISTANCE FROM STREAM FACTOR

Landslides Susceptibility Map All Wij layers for all the causative factors created in Arc_GIS are summed in raster calculator in Arc_GIS in order to obtain landslides susceptibility index map. The LSI values vary within the range of -2.2 to 0.89. For simplification the map interpretation the LSI values are divided into three different susceptibility classes, which are Low landslide susceptibility LSI <0.25 Moderate susceptibility 0.25>LSI>0.5 High susceptibility LSI>0.5

According to the susceptibility map the local government should: Not allowed new construction in high susceptibility (red) zone which is substantial danger for constructions and people inside houses in this area is. If they are existing the buildings cannot be enlarged or reconstructed. Transformations in existing buildings are only allowed if the risk is decreased. Allowed buildings in moderate susceptibility (blue) zone only under certain conditions depending on the type of hazard these conditions may include the requirement of additional studies, special construction techniques and a particular planning measures. Object like hospitals or schools should not be authorized in such zones. Allowed to build in (yellow) zone, but land-owners should be informed of the existing hazard. In these cases, adequate prevention measures should be taken because excavation of slopes for house building, agricultural terraces can generate instability problems

CONCLUSIONS (Wij =1.23) and formation (Wij=0.67) are more favorable for land sliding compared to the other geological formations. Analysis shows that slopes from 10°-25° are prone to landsliding. It is a fact that fewer landslides occur on mild and steep slope angles West facing slope (Wij=0.63) and Northeast facing slope (Wij =0.54) are more favorable for landsliding compared to the other slope aspect. Urban area (Wij=1.52) and shrubs (Wij =0.81) are more prone to landsliding compared to the other landuse because human activities and modification of the landscape play an important roles in triggering landslides. Analysis shows that distance from stream 0m-25m (Wij=0.71) and 25 - 50m (Wij =0.44) are more prone to landsliding compared to other distances.

FUTURE WORKS Extend the susceptibility map of Kavaja to all the territory of Albania with similar geological conditions as Kavaja which can provide useful information for government in order to develop policies for landslide reduction, buildings codes and land-use planning From susceptibility to hazards Vulnerability assessment of elements at risk in this study area as a pilot-project in order to extend the experience for the Tirana region Risk assessment under changing climate as a pilot-project of this area

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