The Feasibility Study of the Flood Control Project for the Lower Cagayan River in the Republic of the Philippines Final Report Supporting Report ANNEX VI : FLOOD CONTROL THE FEASIBILITY STUDY OF THE FLOOD CONTROL PROJECT FOR THE LOWER CAGAYAN RIVER IN THE REPUBLIC OF THE PHILIPPINES FINAL REPORT Volume VI-1 SUPPORTING REPORT ANNEX VI FLOOD CONTROL Table of Contents Page CHAPTER 1 PRESENT RIVER CONDITION......................................................... VI-1 1.1 Present River Condition..................................................................................... VI-1 1.1.1 River System ....................................................................................... VI-1 1.1.2 General Features of Present River Channel .......................................... VI-2 1.1.3 River Morphology ............................................................................... VI-3 1.2 Flood Damages.................................................................................................. VI-14 1.2.1 Bank Erosion and Sedimentation ......................................................... VI-15 1.2.2 Flood Inundation ................................................................................. VI-18 1.2.3 Flood Damages.................................................................................... VI-19 1.3 Existing Flood Control Projects (Structural Measures)....................................... VI-20 1.4 Flood Disaster Prevention System (Non-structural Measures)............................ VI-21 1.4.1 Existing Disaster Management Plans and Activities ............................. VI-21 1.4.2 Existing Flood Forecasting and Warning System.................................. VI-23 1.4.3 Existing Evacuation Center.................................................................. VI-24 1.5 Existing Flood Control Facilities and River Related Structures.......................... VI-25 1.5.1 Flood Control Facilities ....................................................................... VI-25 1.5.2 River Related Structures ...................................................................... VI-25 CHAPTER 2 LONG TERM FLOOD CONTROL PLAN .......................................... VI-28 2.1 Basic Concept of Flood Control......................................................................... VI-28 2.1.1 Target Area .......................................................................................... VI-28 2.1.2 Basic Concept...................................................................................... VI-28 2.1.3 Conditions for Formulating Flood Control Plan ................................... VI-29 2.1.4 Upper Cagayan .................................................................................... VI-31 2.1.5 Middle Cagayan................................................................................... VI-32 2.1.6 Lower Cagayan.................................................................................... VI-32 2.2 Alternative Study of Flood Control Long Term Plans (from Magapit to Tuguegarao) ...................................................................................................... VI-36 2.2.1 Objective Reaches of Alternative Study ............................................... VI-36 2.2.2 Flood Control Plan in the Magapit Narrows (Magapit to Alcala)................................................................................................. VI-36 2.2.3 Flood Control Plan in the Reach from Alcala to Buntun Bridge.................................................................................................. VI-38 2.2.4 Flood Control Plan in the Reach from Buntun Bridge to Tuguegarao.......................................................................................... VI-41 2.3 Structural Measures of Flood Control Long Term Plan in the Middle Lower Cagayan ................................................................................................. VI-43 VI - i 2.3.1 Selection of Optimum Plan .................................................................. VI-43 2.3.2 Reviewed Flood Control Long Term Plan ............................................ VI-45 2.3.3 Cost Estimate....................................................................................... VI-47 2.4 Non-structural Measures.................................................................................... VI-48 2.4.1 Evacuation System .............................................................................. VI-48 2.4.2 Resettlement ........................................................................................ VI-50 2.4.3 Hazard Map......................................................................................... VI-50 CHAPTER 3 FLOOD CONTROL PRIORITY PROJECTS ...................................... VI-52 3.1 Structural Measures ........................................................................................... VI-52 3.1.1 General................................................................................................ VI-52 3.1.2 Objective Priority Projects subject to Feasibility Study ........................ VI-52 3.1.3 Project Formulation Criteria ................................................................ VI-52 3.1.4 Structural Measures of Priority Projects for the Lower Cagayan River ..................................................................................... VI-55 3.1.5 Urgent Works of Bank Protection for the Lower Cagayan River.................................................................................................... VI-58 3.2 Non-structural Measures.................................................................................... VI-59 3.2.1 Evacuation System Improvement......................................................... VI-59 3.2.2 Resettlement Area Development .......................................................... VI-61 CHAPTER 4 PRELIMINARY DESIGN OF FLOOD CONTROL PRIORITY PROJECTS ....................................................................... VI-62 4.1 General.............................................................................................................. VI-62 4.1.1 Design Criteria .................................................................................... VI-62 4.1.2 River Channel Improvement ................................................................ VI-62 4.1.3 River and Related Structures................................................................ VI-68 4.1.4 Estimation of Bill of Quantities............................................................ VI-71 4.2 Non-structural Measures.................................................................................... VI-72 4.2.1 Flood Forecasting and Warning System Strengthening Project ............. VI-72 4.2.2 Evacuation Center Strengthening Project ............................................. VI-75 4.2.3 Resettlement Site Development Project................................................ VI-76 VI - ii List of Tables Page Table 1.2.1 Critical Bank Erosion Sites in Cagayan River and Tributaries............VI-T1 Table 1.2.2 Recorded Major Disasters from 1987 to 1999 in the Republic of the Philippines...............................................................................VI- T2 Table 1.2.3 Summary on the Effects of the Destructive Tropical Cyclones in the Republic of the Philippines (1990-1999)..................................VI- T3 Table 1.2.4 Flood Damages due to Typhoon in Region II/CAR ..........................VI- T12 Table 1.3.1 Ongoing Flood Control Projects in Region 2 Office (for the year 2000) .........................................................................................VI- T15 Table 1.3.2 Proposed Flood Control Projects in Region 2 Office (for the year 2001) .........................................................................................VI- T16 Table 1.3.3 Ongoing and Proposed Flood Control Projects by LGUs (Pesos million) ..................................................................................VI- T17 Table 1.4.1 Existing Evacuation Centers ............................................................VI- T18 Table 1.5.1 Existing Flood Control Structures in Cagayan River Basin ................VI- T27 Table 1.5.2 Principal Features of Magat Dam and Major Intake Weirs .................VI- T28 Table 1.5.3 Principal Features of Irrigation Pump Stations along Cagayan River .................................................................................................VI- T29 Table 1.5.4 Principal Features of Major Bridges ..................................................VI- T30 Table 2.2.1 Cost Estimate of Preliminary Study (Alcala to Buntun Bridge) ..............................................................................................VI- T31 Table 2.2.2 Cost Estimate of Preliminary Study (Buntun Bridge to Upstream of Tuguegarao) ..................................................................VI- T33 Table 2.3.1 Cost Estimate of Alternative Plans for Flood Control Long Term Plan..........................................................................................VI- T35 Table 2.3.2 Bank Protection Works in the Reviewed Flood Control Long Term Plan..........................................................................................VI- T39 Table 2.3.3 Quantities of Major Works of Other Schemes in the Reviewed Flood Control Long Term Plan (lowermost, middle and upper reaches).............................................................................VI-