Scholarly record

ROCKFALL HAZARD MAPPING USING GIS SOFTWARE: AN APPLICATION IN A SELECTED AREA FROM SEBINKARAHISAR (GIRESUN-TURKEY)

I. Yilmaz, I. Keskin, M. Yildrim, B. Civelekoglu

Abstract

Rockfalls are natural process of cliff and hillside erosion, can be simulated by the computer programs. They consist of large rock fragments from a cliff, or boulders from a slope that bounce, roll, and slide down a hillside and come to rest in a “runout” zone at or near its base. Rockfalls are a major hazard in rock cuts for highways and railways, and in mountainous terrain. Rockfalls are generally initiated by some climatic or biological event that causes a change in the forces acting on a rock. These events may include pore pressure increases due to rainfall infiltration, erosion of surrounding material during heavy rain storms, freeze-thaw processes in cold climates, chemical degradation or weathering of the rock, root growth or leverage by roots moving in high winds. In an active construction environment, the potential for mechanical initiation of a rockfall will probably be one or two orders of magnitude higher than the climatic and biological initiating events described above. Rockfall simulation models are capable of producing reasonably accurate predictions of rockfall trajectories. Obviously more refined models will produce better results, provided that realistic input information is available. Most of the rockfall models include a Monte Carlo simulation technique to vary the parameters included in the analysis. This technique is similar to the random process of throwing dice - one for each parameter being considered. In a selected area from Sebinkarahisar (Giresun-Turkey) rockfall analysis was carried out along 32 profiles of the hillslopes. The program Rocfall 4.0 was used for rockfall analyses using a number of probabilistic options. The trajectories for 50 rockfalls using the Monte Carlo simulation process were obtained. Fall-out distance, bounce height, kinetic energy released during falling and velocity of the rocks along each profile were then investigated. The results of the analyses were evaluated, and the areas prone and susceptible to rockfall risk were established from contours obained by along 32 different profiles using the computer code in ArcGIS 9.1 software.

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