Project Number: 45206 May 2016
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Document Produced under Grant Project Number: 45206 May 2016 Grant 0299-NEP: Water Resources Project Preparatory Facility Final Report – Volume 5 Appendix J Mohana Prepared by Lahmeyer International in association with Total Management Services Pvt. Ltd. For Ministry of Irrigation, Government of Nepal Department of Irrigation, Government of Nepal This document does not necessarily reflect the views of ADB or the Government concerned, and ADB and the Government cannot be held liable for its contents. WRPPF-Package 3: Flood Hazard Mapping & Preliminary Preparation of Risk Management Projects i Final Report May 2016 APPENDIX J CONCEPT NOTES FOR MOHANA BASIN CONTENTS I. BACKGROUND ..................................................................................................................... 1 II. BASIN CHARACTERISTICS ................................................................................................. 3 III. HYDROLOGY ......................................................................................................................... 4 IV. FLOOD MAPPING ................................................................................................................. 5 V. IDENTIFICATION OF VULNERABLE AREAS .................................................................... 10 VI. PROPOSED INTERVENTION.............................................................................................. 11 VII. DESIGN OF PROPOSED WORKS ...................................................................................... 15 A. Design Discharge ........................................................................................................ 15 B. Spacing of the Embankment ....................................................................................... 15 C. Water Surface Profile .................................................................................................. 16 D. Longitudinal Ground profile ......................................................................................... 16 E. Typical Cross-Section of the embankment ................................................................. 17 F. Typical Drawing of Spurs ............................................................................................ 17 G. Typical Drawing of Check Dams ................................................................................. 17 H. Early Warning Systems and Training ......................................................................... 17 I. Quantity and Cost Estimate ........................................................................................ 18 1. Preliminary cost ................................................................................................. 18 2. Land Acquisition and Resettlement .................................................................. 18 3. Civil Works ........................................................................................................ 18 4. Quantity Estimate .............................................................................................. 18 5. Unit Rates .......................................................................................................... 18 6. Abstract of cost estimate ................................................................................... 18 VIII. COST BENEFIT ANALYSIS AND PROJECT IMPACT ...................................................... 20 A. Cost-Benefit Analysis .................................................................................................. 20 B. Impact on Poverty ....................................................................................................... 22 IX. CONCLUSIONS ................................................................................................................... 23 Volume 5: Appendix J Lahmeyer International in association with Total Management Services WRPPF-Package 3: Flood Hazard Mapping & Preliminary Preparation of Risk Management Projects ii Final Report May 2016 LIST OF ANNEXES ANNEX 1: RESULTS OF “WITH PROJECT” HYDRODYNAMIC MODELLING FOR 50 YEARS PLUS CLIMATE CHANGE SCENARIO ANNEX 2: DESIGN CRITERIA ANNEX 3: LONGITUDINAL PROFILE OF PROPOSED FLOOD EMBANKMENTS ANNEX 4: TYPICAL DRAWINGS ANNEX 5: PRE-FEASIBILITY DESIGNS, QUANTITIES AND UNIT RATES ANNEX 6: PRE-FEASIBILITY COST-BENEFIT ANALYSIS ANNEX 7: SOCIOECONOMIC SURVEY AND SOCIAL SAFEGUARDS ANNEX 8: ENVIRONMENTAL CONSIDERATIONS Volume 5: Appendix J Lahmeyer International in association with Total Management Services WRPPF-Package 3: Flood Hazard Mapping & Preliminary Preparation of Risk Management Projects iii Final Report May 2016 LIST OF FIGURES Figure 1: Location of Study Basins .................................................................................................. 2 Figure 2: Mohana Basin Modelled Reach ....................................................................................... 3 Figure 3: Maximum Flood Depth - 1 in 50 years plus Climate Change .......................................... 6 Figure 4: Maximum Flood Velocity – 1in 50 years plus Climate Change ........................................ 7 Figure 5: Maximum Flood Hazard – 1 in 50 years plus Climate Change ........................................ 8 Figure 6: Maximum Flood Risk – 1 in 50 years plus Climate Change ............................................ 9 Figure 7: Proposed Flood Mitigation Measures ............................................................................ 12 Figure 8: Maximum Flood Depth – 1 in 50 years plus Climate Change “with project” .................. 13 Volume 5: Appendix J Lahmeyer International in association with Total Management Services WRPPF-Package 3: Flood Hazard Mapping & Preliminary Preparation of Risk Management Projects iv Final Report May 2016 LIST OF TABLES Table 1: List of Priority Basins ......................................................................................................... 1 Table 2: Exceedance Probability of Maximum 24 hour Rainfall (mm) ............................................ 4 Table 3: Exceedance Probability of Peak Flow (m3/s) .................................................................... 4 Table 4: Areas Inundated at Various Exceedance Probabilities ..................................................... 5 Table 5: Flood Vulnerable VDC's .................................................................................................. 10 Table 6: Summary of Flood Mitigation Measures .......................................................................... 11 Table 7: Design discharge and spacing of embankment .............................................................. 15 Table 8: Results of Hydrodynamic “With Project” Modelling for 50 years plus Climate Change Scenario .......................................................................................................................... 16 Table 9: Summary of Costs ........................................................................................................... 19 Table 10: Estimates of NPV and IRR Mohana Basin Project ........................................................ 21 Volume 5: Appendix J Lahmeyer International in association with Total Management Services WRPPF-Package 3: Flood Hazard Mapping & Preliminary Preparation of Risk Management Projects 1 Final Report May 2016 I. BACKGROUND 1. The Asian Development Bank (ADB) and the Government of Nepal have tasked the “Water Resources Project Preparation Facility” (WRPPF) under the Ministry of Irrigation (MoI) to identify and prepare high priority water resources management projects for potential funding by the government, with assistance from ADB and/or other development partners. This initiative is consistent with the government’s and ADB’s priorities for enhancing climate resilience, ensuring food security and promoting inclusive economic growth. 2. As part of Package 3: Flood Hazard Mapping and Risk Management Project (FHRMP), flood hazard maps for twenty five river basins in the Terai region of Nepal as shown in Figure 1, were required to be prepared. Additionally, concept notes for interventions to pre-feasibility level were required to be prepared for six priority projects. 3. Six priority basins were selected from amongst the twenty five study basins in discussions with the Department of Water Induced Disaster Prevention (DWIDP) and WRPPF. The basins were screened using a number of criteria including, flooding vulnerability, flood damages and loss of human lives so that the priority basins could be identified. Flood mitigation measures were then identified in these priority basins. The priority basins selected are shown in Figure 1 and listed in Table 1. Table 1: List of Priority Basins S.N. River Basins Location 1 Biring New Province 1 2 Mawa Ratuwa New Province 1 3 Lakhandehi New Province 2 4 East Rapti New Province 3 5 West Rapti New Province 5 6 Mohana New Province 7 Volume 5: Appendix J Lahmeyer International in association with Total Management Services WRPPF-Package 3: Flood Hazard Mapping & Preliminary Preparation of Risk Management Projects 2 Final Report May 2016 Figure 1: Location of Study Basins 4. This concept note refers to the flood mitigation project in Mohana Basin. Mohana in New Province 7 has a history of moderate flood damage and loss of life in recent years. The river runs close to the regional centre of Dhangadi which is highly populated and has experienced rapid growth in recent years. 5. Mohana Basin has a Human Poverty Index (HPI)