Supplementary Files
Keywords
Spillway Capacity
Dam Safety
How to Cite
Abstract
Probable Maximum Precipitations and Floods (PMPs/PMFs) are the hydrological loading criteria for contemporary dam/reservoir design and operation and maintenance (O&M) inspection programs. These parameters are dynamic and strictly desirable for safety of high hazardous infrastructure. The spillway safety rule and protocol are being tightened over the years. This study evaluates the overtopping hazards/potentials of both Air Itam (1962, 5.6 km2) and Teluk Bahang (1999, 10 km2) dams using three sets of PMP series (1) coastal PMP set (SMHB 1992,1994) adopted mainly in the past design studies, (2) current update and results of a nationwide PMP study by NAHRIM in 2008, and (3) PMPs with incorporation of an adjustment factor to account for climate change scenario by NAHRIM in 2013. This study has demonstrated primarily inadequate spillway capacity for Air Itam dam which was designed in the 1960’s without the benefit of adequate spillway sizing based on recent PMP/PMF methodology. Under both recent PMP/PMF loadings derived from a nationwide study (NAHRIM 2008) and climate change (NAHRIM 2013) scenarios, the existing morning glory spillway is inadequate for safe passage of PMP/PMF. It is recommended that retrofitting the existing spillway capacity should be considered as an urgent matter. Teluk Bahang dam designed and built in the late 1990’s was deemed adequate in its spillway capacity conforming to the contemporary PMP/PMF foresight. The dam is equipped with provision of ample headroom and anti-cavitation measures as additional margin of safety.
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