DOWNLOAD previous article 2. article - 2015/2next article Igor Ružić, Čedomir Benac,
Ivan Marović and Suzana Ilić

A stability assessment of coastal cliffs using digital imagery

Abstract

The investigated area around the Stara Baška settlement (the island of Krk, NE channel part of the Adriatic Sea) is in a delicate geodynamic balance. Marine erosion is quite prominent and the recorded cliff retreat between 1966 and 2004 was from 4 to 5 metres. The cliff slopes are formed in talus breccias. Strong waves and formations of wave-cut notches are the main causes of the cliff’s instability. The secondary causes are the weathering and erosion of the soil and rocks on the cliff. The slump of the cliff slope can occur in a rock mass with higher strength parameters, where the notches are cut a few metres inward into the toe of the cliff slope. A combined method for the stability analysis of the coastal cliffs was tested; this incorporates the cantilever-beam model and the structure-from-motion (SfM) photogrammetry. This method can provide highly detailed 3D geometrical data of the cliff, which can then be used in the calculations of the stability model. This is particularly important in a stability analysis of lithologically heterogeneous rocks such as breccias with varied geometry, which cannot be easily replaced by a rectangular surface. The simple and useful SfM method overcomes the limitations of traditional surveys in estimating the cliff overhang surface and the notch length.

Keywords

marine erosion, cliff stability, SfM photogrammetry, Krk island, Adriatic sea