Rockfall hazard assessment of the slope of Mogao Grottoes, China based on AHP, F-AHP and AHP-TOPSIS

Hosting precious superb murals and painted sculptures from the fourth to the fourteenth century, the UNESCO word heritage site Mogao Grottoes are one of the most famous sites of Buddhist art. Although several reinforcement projects had been implemented, frequent rockfalls originated from the slope atop the cliff of Mogao Grottoes can be observed, representing a significant risk to both relics and tourists. Therefore, it is important to assess the rockfall hazard of the slope of Mogao Grottoes for the preventive protection as well as to inform future management decisions. In this study, rockfall hazard of the slope of Mogao Grottoes was assessed by using Analytic Hierarchy Process (AHP), Fuzzy-AHP (F-AHP) and AHP-TOPSIS methods and then the performances were evaluated by receiver operating characteristic curve (ROC) and area under curve (AUC). To execute these methods, a high-resolution digital surface model was first captured through UAV digital photogrammetry technology without contact. Belonging to four hazard levels (Very high, high, low and very low), the slope was divided into 10 units based on the slope topography. The hazard assessment result shows that 80% of the total slope units are at low rockfall hazard level and 20% slope units are at very high/high level, respectively. Moreover, loose debris and rainfall are confirmed as the most active causative factors. The result of AUC, ROC and recorded rockfall events reveal that the F-AHP is the most suitable method. Besides, this study also holds the potential applications of the F-AHP in the rockfall assessment for many other grottoes carved in conglomerate strata in Dunhuang.

Automated summary

In this study, the rockfall hazard of the slope of Mogao Grottoes was assessed using various methods, and it was found that the majority of slope units have low rockfall hazard. Loose debris and rainfall were identified as the most active causative factors. The F-AHP method was determined to be the most suitable, and it holds potential applications in the assessment of rockfall in other grottoes carved in conglomerate strata in Dunhuang.