Assessment of Slope Stability at Erbil Citadel, Kurdistan Region of Iraq Using Bejerman’s Method

Abstract

The Erbil Citadel is located in the center of Erbil City; the capital of the Kurdistan Region of Iraq. The shape of the citadel is a large, oval hill. The Citadel was inhabited more than 6,000 years ago and is thought to be one of the longest-continuously inhabited sites in the world. Therefore, the Citadel was announced in 2014 as a World Heritage by UNESCO. The height of the Citadel is not uniform; it ranges between (28–30) m, the top elevation is 429 m (a.s.l.), whereas the bottom elevation ranges between (407– 416) m (a.s.l). The Citadel has an oval shape with diameters between (350 – 420) m, the E–W being the longest. The slopes of the Citadel (Tell) display severe erosion and slope stability problems, the main types are creep, which can endanger the existing historical buildings, especially on the edges of the Citadel. Different data about the Citadel have been reviewed but couldn’t find special studies concerning the slope stability of the Citadel. Therefore, we have applied Bejerman’s method, which is a quick field method to assess the slope stability of the slopes of the Citadel to find the Landslide Possibility Index (LPI). Eleven stations were selected around the Citadel to apply Bejerman’s method, the stations were selected in the site; wherever clear indications were found for slope instability. The results of the assessment showed that the LPI ranges between 18–22, which means grade IV, and Failure possibility of Medium (2 stations), and High (9 stations). Recommendations are given to keep the slopes of the citadel as safe as possible.