Dam risk analysis for Bhadra dam and reservoir system July 2018 iPresas Risk Analysis Avda. del Puerto, 180, 1ºB 46023 – Valencia Tel.: (+34) 963 309 121 www.ipresas.com Dam risk analysis for Bhadra dam and reservoir system DAMSAFE Innovative technologies for enhancing dam safety and water management in India DAM RISK ANALYSIS FOR BHADRA DAM AND RESERVOIR SYSTEM D2.1 July 2018 iPresas Risk Analysis 3 Dam risk analysis for Bhadra dam and reservoir system DISCLAIMER Dam risk analysis for Bhadra dam and reservoir system is a report conducted within the framework of the DAMSAFE project (Deliverable D2.1), based on available information kindly provided by KaWRD and CWC. Conclusions and recommendations derived from the analysis described in this document in no way restrict neither reduce dam owner responsibilities concerning conducted and future dam safety actions for Bhadra dam reservoir system. ACKNOWLEDGMENTS The authors would like to thank the Netherlands Enterprise Agency for co-funding the DAMSAFE project through the Partners for Water programme. In addition, the following organizations have provided valuable information for conducting the presented risk assessment: Karnataka Water Resources Department (KaWRD). Central Water Commission of India (CWC). CONTACT INFORMATION For any information, please contact: Ton Peters, DAMSAFE coordinator Email: [email protected] Ignacio Escuder, DAMSAFE WP2 Coordinator. Email: [email protected] 4 Dam risk analysis for Bhadra dam and reservoir system Table of Contents List of tables .................................................................................................................................................. 7 List of figures ................................................................................................................................................. 9 Abbreviations ............................................................................................................................................... 11 1. Introduction ......................................................................................................................................... 13 1.1. Motivation ..................................................................................................................................... 13 1.2. Content and structure of the document ........................................................................................ 14 1.3. Communication and dissemination of results ............................................................................... 14 2. Dam description .................................................................................................................................. 15 2.1. Location ........................................................................................................................................ 15 2.2. Main dam characteristics .............................................................................................................. 17 2.3. Cross section drawings ................................................................................................................. 18 2.4. Description of outlet works and spillways ..................................................................................... 21 2.5. Brief description of major problems and rehabilitations in the past .............................................. 22 2.6. Potential Hazard Classification ...................................................................................................... 23 3. Risk Assessment and Management Framework .................................................................................. 24 4. Identification of Failure Modes ............................................................................................................ 27 4.1. Introduction ................................................................................................................................... 27 4.2. Information review ........................................................................................................................ 28 4.3. Technical site visit ......................................................................................................................... 30 4.4. Dam safety evaluation ................................................................................................................... 31 4.5. Failure Mode Identification ............................................................................................................ 43 4.6. Classification of Failure Modes ...................................................................................................... 54 4.7. Identification of investigation and surveillance needs ................................................................... 55 4.8. Proposal of risk reduction actions ................................................................................................. 56 5. Quantitative Risk Assessment ............................................................................................................. 57 5.1. Introduction ................................................................................................................................... 57 5.2. Risk model architecture ................................................................................................................ 57 5.3. Risk model input data.................................................................................................................... 59 5.4. Risk results for the current situation ............................................................................................. 83 5.5. Risk evaluation .............................................................................................................................. 87 5 Dam risk analysis for Bhadra dam and reservoir system 5.6. Uncertainty analysis ....................................................................................................................... 88 5.7. Prioritization of risk reduction actions ........................................................................................... 91 6. Semi-Quantitative Risk Analysis ......................................................................................................... 101 6.1. Introduction ................................................................................................................................. 101 6.2. Semi-Quantitative risk results ...................................................................................................... 102 6.3. Prioritization of new studies or instrumentation .......................................................................... 106 7. Conclusions ....................................................................................................................................... 108 8. References......................................................................................................................................... 111 6 Dam risk analysis for Bhadra dam and reservoir system List of tables Table 2.1. Bhadra Dam characteristics: crest levels. ........................................................................................ 17 Table 2.2. Bhadra Dam characteristics: key figures. ........................................................................................ 18 Table 4.1. Review of information for Bhadra dam. ........................................................................................... 29 Table 4.2. Summary of main urban areas located downstream of Bhadra Dam. ............................................. 40 Table 4.3. Breach parameters for overtopping failure mode in the main dam used in FIM2017 ...................... 41 Table 4.4. Results from dam safety evaluation assessment. ............................................................................ 42 Table 4.5. Classification of failure modes for Bhadra dam. .............................................................................. 54 Table 4.6. Identified investigation and surveillance needs for Bhadra dam. ..................................................... 55 Table 4.7. Proposed actions for Bhadra dam. .................................................................................................. 56 Table 5.1. Participants on Risk Assessment process for Bhadra Dam. ............................................................ 57 Table 5.2. Data of selected stations for the analysis. ....................................................................................... 59 Table 5.3. Rainfall rates at each selected station.............................................................................................. 60 Table 5.4. Rainfall rates estimated at each subcatchment. ............................................................................... 60 Table 5.5. Results from hydrologic modelling for different return periods. ...................................................... 60 Table 5.6.Intervals of previous water pool levels used for Bhadra Dam. .......................................................... 63 Table 5.7. Probabilities for each combination of gate availability. .................................................................... 64 Table 5.8. Key characteristics of variables for analyzing failure for FM4. ......................................................... 69 Table 5.9. Results from failure probability elicitation