Risk Assessment of Mamak Dam Based on The ICOLD Modification Method and Risk Index Method

Abstract

The Mamak Dam has the risk of damage and the need for evacuation at an extreme downstream level. Risk considerations are based on the potential natural disasters of the dam, the impact of dam failure, design loads, and safety coefficients. The Risk Index method results in a score with parameters such as spillway capacity adequacy, safety factor adequacy against slopes, disaster factor (hazard), and all parameters analyzed to determine the Dam Safety Index (Idam). The drawback of the Risk Index method is neglecting downstream failure analysis. The ICOLD modification method for parameters is the same as the Risk Index method, but the ICOLD method considers downstream analysis. The modification involves adding parameters, such as the condition of the dam slope cover layer, based on the Mamak Dam Large Inspection results. In the Risk Index method, the Idam calculation value is 262.5. The total risk index value for Mamak Dam is 51.73, with a dam safety value of 92.337. In the ICOLD method, the Idam calculation value is 245, with a total risk index value for Mamak Dam of 48.28 and a Dam Safety value of 92.848. Meanwhile, using the Modified ICOLD method, the Idam calculation value is 245, with a total risk index value for Mamak Dam of 49.93 and a Dam Safety value of 92.603. Based on these results, the Dam Safety value with the Modified ICOLD method has decreased but still falls within the satisfactory classification (>75). Therefore, it can be concluded that Mamak Dam is currently at a safe level against normal loads and extraordinary loads (design floods and design earthquakes).