THE REPUBLIC OF MAURITIUS MINISTRY OF ENVIRONMENT, SUSTANAIBLE DEVELOPMENT, DISASTER AND BEACH MANAGEMENT (MOESDDBM) THE PROJECT FOR CAPACITY DEVELOPMENT ON COASTAL PROTECTION AND REHABILITATION IN THE REPUBLIC OF MAURITIUS FINAL REPORT TECHNICAL GUIDELINE (Volume 3) June 2015 JAPAN INTERNATIONAL COOPERATION AGENCY KOKUSAI KOGYO CO., LTD. NIPPON KOEI CO., LTD. GE CENTRAL CONSULTANT INC. JR FUTABA INC. 15-112 THE REPUBLIC OF MAURITIUS MINISTRY OF ENVIRONMENT, SUSTANAIBLE DEVELOPMENT, DISASTER AND BEACH MANAGEMENT (MOESDDBM) THE PROJECT FOR CAPACITY DEVELOPMENT ON COASTAL PROTECTION AND REHABILITATION IN THE REPUBLIC OF MAURITIUS FINAL REPORT TECHNICAL GUIDELINE (Volume 3) June 2015 JAPAN INTERNATIONAL COOPERATION AGENCY KOKUSAI KOGYO CO., LTD. NIPPON KOEI CO., LTD. CENTRAL CONSULTANT INC. FUTABA INC. 㻸㼛㼏㼍㼠㼕㼛㼚㻌㼛㼒㻌㻿㼠㼡㼐㼥㻌㻭㼞㼑㼍 㻸㼛㼏㼍㼠㼕㼛㼚㻌㼛㼒㻌㻿㼠㼡㼐㼥㻌㻭㼞㼑㼍 20°0'0"E 30°0'0"E 40°0'0"E 50°0'0"E 60°0'0"E 70°0'0"E 80°0'0"E 20°0'0"N 20°0'0"N 10°0'0"N 10°0'0"N 0°0'0" 0°0'0" Republic of Mauritius 10°0'0"S 10°0'0"S 20°0'0"S 20°0'0"S 0500 1,000 2,000 km 20°0'0"E 30°0'0"E 40°0'0"E 50°0'0"E 60°0'0"E 70°0'0"E 80°0'0"E 㻰㼑㼠㼍㼕㼘㻌㻹㼍㼜㻌 㻰㼑㼠㼍㼕㼘㻌㻹㼍㼜㻌 57°30'0"E 20°0'0"S 20°0'0"S Rivie du Rempart Pamplemousses Port Louis Flacq Moka Plaines Wilhems Black River Grand Port Savanne 20°30'0"S Roads 20°30'0"S 0105 National border km Administrative border 57°30'0"E Location Map Rate of Currency Translation 1 USD = 35.230 Rs = 124.11 JPY 100 Rs = 2.760 USD = 342.56 JPY Rs: Mauritius Rupee As of June 1st, 2015 Table of Contents 㻌 Page I. Technical Guideline for Coastal Conservation 1 Objective and Outline .................................................................... I-1 2 Natural and Design Conditions .................................................... I-3 2.1 Natural Conditions in Mauritius .................................................................. I-3 2.1.1 Wind Conditions ............................................................................................. I-3 2.1.2 Wave ............................................................................................................... I-7 2.1.3 Water Level ................................................................................................... I-18 2.1.4 Geology and Geography of the coastal area ................................................. I-21 2.2 Design Condition ...................................................................................... I-27 2.2.1 Design Offshore Wave .................................................................................. I-27 2.2.2 Design Wave Heights within Reef ................................................................ I-29 2.2.3 Design Water Level within a Reef ................................................................ I-31 3 Coastal Conservation Measures ................................................ I-32 3.1 Introduction .............................................................................................. I-32 3.2 Nourishment ............................................................................................. I-35 3.2.1 Categorizing of Existing Coasts and Principle Method of Nourishment ...... I-35 3.2.2 Planning and Design ..................................................................................... I-37 3.2.3 Sand procurement Site for Beach Nourishment ............................................ I-43 3.2.4 Construction Stage ........................................................................................ I-51 3.2.5 After Construction ........................................................................................ I-54 3.3 Flexible Revetment .................................................................................. I-55 3.3.1 Introduction ................................................................................................... I-55 3.3.2 Planning ........................................................................................................ I-56 3.3.3 Construction .................................................................................................. I-58 3.3.4 Others ............................................................................................................ I-59 4 Examples ...................................................................................... I-60 4.1 Bali Beach Conservation Project in Indonesia ......................................... I-60 4.2 Sand Nourishment in Seychelles ............................................................. I-88 4.2.1 Introduction ................................................................................................... I-88 4.2.2 Design of Nourishment ................................................................................. I-89 4.2.3 Evaluation of Project ..................................................................................... I-91 4.2.4 Summary ....................................................................................................... I-93 4.3 Akiya beach .............................................................................................. I-94 4.3.1 Background of Beach Nourishment with Gravel .......................................... I-94 4.3.2 Study ............................................................................................................. I-94 4.3.3 Plan ............................................................................................................... I-95 4.3.4 Design ........................................................................................................... I-97 4.3.5 Construction .................................................................................................. I-98 4.3.6 Management .................................................................................................. I-99 4.3.7 Subjects and solutions ................................................................................. I-100 i II. Technical Guideline for Beach Monitoring 1 Field Investigation ........................................................................ II-1 1.1 Field Observation ...................................................................................... II-1 1.1.1 Beach Profile across the Structure (Groyne) .................................................. II-1 1.1.2 Beach Slope and Grain Size ........................................................................... II-2 1.1.3 Beach Scarp ................................................................................................... II-3 1.1.4 Vegetation ...................................................................................................... II-3 1.2 Beach Profile Monitoring ........................................................................... II-4 1.2.1 Cross-section Survey ..................................................................................... II-5 1.2.2 Building Database ........................................................................................ II-10 1.2.3 Other Monitoring Items ............................................................................... II-15 2 Wave and Current Measurement ............................................... II-17 2.1 Wave Measurement ................................................................................ II-17 2.1.1 Overview ...................................................................................................... II-17 2.1.2 How to Use the Equipment .......................................................................... II-18 2.2 Current Measurement ............................................................................. II-24 2.2.1 How to Use the Equipment .......................................................................... II-24 2.3 Installation and Removal ......................................................................... II-27 2.4 Examples of Data Analysis ..................................................................... II-28 2.4.1 Comparison of Wave Heights at Outer and Inner Reefs .............................. II-28 2.4.2 Comparison with Beach Profile Monitoring Data and Wave Height at Inner Reef .............................................................................................................. II-29 2.4.3 Comparison of Wave Height at the Outer Reef and the Current at the Inner Reef .............................................................................................................. II-30 3 Modification Analysis of Shoreline by Topographic Interpretation of Aerial Photos .................................................. II-33 3.1 Outline ..................................................................................................... II-33 3.1.1 Objective ...................................................................................................... II-33 3.1.2 Work Flow ................................................................................................... II-33 3.2 Collecting Aerial Photos .......................................................................... II-34 3.2.1 Variety of Aerial Photos .............................................................................. II-34 3.2.2 Photographing from Aircraft and Index Map ............................................... II-34 3.2.3 Examination of Scale and Photography Date ............................................... II-35 3.2.4 Scanning ....................................................................................................... II-35 3.3 Geometric