No. MINISTRY OF DISASTER MANAGEMENT AND HUMAN RIGHTS DEPARTMENT OF IRRIGATION OF THE MINISTRY OF IRRIGATION AND WATER MANAGEMENT COMPREHENSIVE STUDY ON DISASTER MANAGEMENT IN SRI LANKA FINAL REPORT (SUPPORTING REPORT) MARCH 2009 JAPAN INTERNATIONAL COOPERATION AGENCY ORIENTAL CONSULTANTS CO., LTD. ASIAN DISASTER REDUCTION CENTER GED JR 09-042 MINISTRY OF DISASTER MANAGEMENT AND HUMAN RIGHTS DEPARTMENT OF IRRIGATION OF THE MINISTRY OF IRRIGATION AND WATER MANAGEMENT COMPREHENSIVE STUDY ON DISASTER MANAGEMENT IN SRI LANKA FINAL REPORT (SUPPORTING REPORT) MARCH 2009 JAPAN INTERNATIONAL COOPERATION AGENCY ORIENTAL CONSULTANTS CO., LTD. ASIAN DISASTER REDUCTION CENTER TABLE OF CONTENTS page Supporting Report A Current Condition and Master Plan Formulation A.1 Kelani River Basin......................................................................................................................A-1 A.1.1 Basin Overview ................................................................................................................A-1 A.1.2 Past Significant Floods.....................................................................................................A-2 A.1.3 Review of Previous Flood Management Studies..............................................................A-4 A.1.4 Basic Concept for Flood Management Planning..............................................................A-6 A.1.4.1 Planning Scale..................................................................................................A-6 A.1.4.2 Target Period for Implementation ....................................................................A-7 A.1.4.3 Basic Conditions for Formulation of Master Plan............................................A-7 A.1.4.4 Design Standards and Guidelines...................................................................A-15 A.1.5 Alternative Structural Measures.....................................................................................A-16 A.1.5.1 Alternative Plans ............................................................................................A-16 A.1.5.2 Distribution of Design Flood Discharge.........................................................A-17 A.1.5.3 Principal Feature of Structural Measures .......................................................A-17 A.1.6 Promising Non-Structural Measures ..............................................................................A-21 A.2 Kalu River Basin.......................................................................................................................A-25 A.2.1 Basin Overview ..............................................................................................................A-25 A.2.2 Past Significant Floods...................................................................................................A-26 A.2.3 Review of Previous Flood Management Studies............................................................A-29 A.2.4 Basic Concept for Flood Management Planning............................................................A-30 A.2.4.1 Planning Scale................................................................................................A-30 A 2.4.2 Target Period for Implementation ..................................................................A-31 A.2.4.3 Basic Conditions for Formulation of Master Planning...................................A-31 A.2.5 Alternative Structural Measures in Target River Basins.................................................A-37 A.2.5.1 Alternative Plans ............................................................................................A-37 A.2.5.2 Distribution of Design Flood Discharge.........................................................A-38 A.2.5.3 Principal Feature of Structural Measures .......................................................A-39 A.2.6 Promising Non-Structural Measures ..............................................................................A-41 A.3 Gin River Basin.........................................................................................................................A-42 A.3.1 Basin Overview ..............................................................................................................A-42 A.3.2 Past Significant Floods...................................................................................................A-43 A.3.3 Review of Previous Flood Management Studies............................................................A-45 A.3.4 Basic Concept for Flood Management Planning............................................................A-45 A.3.4.1 Planning Scale................................................................................................A-45 A.3.4.2 Target Period for Implementation ..................................................................A-46 A.3.4.3 Basic Conditions for Formulation of Master Plan..........................................A-46 A.3.5 Alternative Structural Measures in Target River Basins.................................................A-51 A.3.5.1 Alternative Plans ............................................................................................A-51 A.3.5.2 Distribution of Design Flood Discharge.........................................................A-52 i A.3.5.3 Principal Feature of Structural Measures .......................................................A-53 A.3.6 Promising Non-Structural Measures ..............................................................................A-55 A.4 Nilwala River Basin ..................................................................................................................A-57 A.4.1 Basin Overview ..............................................................................................................A-57 A.4.2 Past Significant Floods...................................................................................................A-59 A.4.3 Review of Previous Flood Management Studies............................................................A-60 A.4.4 Basic Concept for Flood Management Planning............................................................A-61 A.4.4.1 Planning Scale..............................................................................................A-61 A.4.4.2 Target Period for Implementation ..................................................................A-61 A.4.4.3 Basic Conditions for Formulation of Master Planning Scale.........................A-61 A.4.5 Alternative Structural Measures in Target River Basins.................................................A-66 A.4.5.1 Alternative Plans ............................................................................................A-66 A.4.5.2 Distribution of Design Flood Discharge.......................................................A-68 A.4.5.3 Principal Feature of Structural Measures .......................................................A-69 A.4.6 Promising Non-Structural Measures (Nilwala) ..............................................................A-71 Supporting Report B Hydrological and Hydraulic Model Studies B.1 Description of River Basins ........................................................................................................ B-1 B.1.1 Kelani River Basin ........................................................................................................... B-1 B.1.2 Kalu River Basin .............................................................................................................. B-3 B.1.3 Gin River Basin................................................................................................................ B-3 B.1.4 Nilwala River Basin......................................................................................................... B-4 B.2 Data Collection and Analysis ...................................................................................................... B-5 B.2.1 Topographical Data .......................................................................................................... B-5 B.2.2 River Cross Sections ........................................................................................................ B-6 B.2.3 Flood Protection Schemes and Flood Prone Areas........................................................... B-6 B.2.4 Hydrological Data............................................................................................................ B-7 B.2.5 Hydrometric Data............................................................................................................. B-9 B.3 Study Methodology................................................................................................................... B-11 B.3.1 MIKE 11 Modeling System............................................................................................ B-11 B.3.2 MIKE 11 HD Module..................................................................................................... B-11 B.3.3 NAM Module ................................................................................................................. B-12 B.4 Kelani River Basin Model......................................................................................................... B-12 B.4.1 Hydrological Modelling................................................................................................. B-12 B.4.2 Hydrodynamic Modelling .............................................................................................. B-15 B.5 Kalu River Basin Model...........................................................................................................