Hydrological Risk Valuation on The Design of Sukamahi Dry Dam, Bogor, West Java

The flooding risk has always been considered as an important factor ofthe risk safety management of dams. The extreme flooding in the downstream of a dam could be either due to dam failure or sometimes without failure. In both cases, they give serious risks to people and property in the downstream of the dam.Sukamahi dry dam at Cisukabirus River is a part of the upper Ciliwung Watershed, located in Bogor regency. Sukamahi dry dam was design for flood reduction purpose especially for the downstream regione.g. Bogor City, Bogor Regency, Depok City and Jakarta. Sukamahi dam has a capacity in flood reduction of 13.53 m3/s with probability exceeded 2 %, and time to concentration (tc) of peak discharge (Qp) at least 4 hours longer than the existing condition. Construction of dry dam might increase the magnitude of flood prone risk especially on the dam breach caused by spillway capacity failure case, although with lower probability. Simulation using HEC RAS 4.1 and an ex-antehydrological risk valuation Xrisk model wereperformed with three scenarios, i.e. normal risk, risk averse and risk takers, with simplified option value and option risk calculation. Risk valuation can be used by decision makers to evaluate the technical and risk feasibility of Sukamahi dry dam construction.