Wetland Development in Paddy Fields and Disaster Management

Description

This book proposes the use of green infrastructure to balance biodiversity conservation and disaster management. Paddy fields are one example of such infrastructure and are the focus of this book. In Japan, abandoned, once-cultivated land is increasing in the paddy fields due to the aging of society and recent depopulation. The author proposes to consolidate such lands and create wetlands because the paddy fields hold water during heavy rains, which prevents floods and protects cities. This is essential, considering that extreme weather conditions have increased the risk of flood damage in Japan. Not only do such wetlands hold water during the flood season, they also provide habitats for aquatic life and places for children to learn about the natural environment. In addition, fish farming in the wetlands will provide food for many people. The increase in water disasters associated with global warming is occurring not only in Japan but globally. The proposal presented in this book will help government officials around the world, especially those involved in urban and rural planning, to consider disaster management―an idea that will be welcomed by both engineers and biologists. Preface Acknowledgments Contents List of Boxes Part I Flood Control 1 Characteristics of Flood Disasters 1.1 Comparison of Rivers in Japan and the World 1.2 Impact of Urbanization 1.3 Global Warming and Flood-Related Disasters References 2 Flood Control Methods 2.1 Flood Control Methods 2.2 Open Levee 2.3 Paddy Field Dam 2.4 Watershed Control Appendix References 3 Significance of Flood Disturbance 3.1 What Does a Flood Carry? 3.2 Importance of Disturbance 3.3 Maintaining a River Ecosystem 3.4 Connection Among Mountains, Rivers, Villages and Seas Appendix References Part II Paddy Fields 4 Characteristics of Paddy Fields 4.1 Agriculture Across the World 4.2 Paddy Fields Throughout the World 4.3 Paddy Fields in Japan 4.4 Present State of Paddy Fields in Japan Appendix References 5 Multiple Functions of Paddy Fields 5.1 Introduction 5.2 Food Production 5.3 Flood Control 5.4 Sediment Collapse Prevention 5.5 Sediment Runoff Prevention 5.6 River Flow Stability and Groundwater Recharge 5.7 Water Purification 5.8 Atmosphere Control 5.9 Biodiversity Conservation 5.10 Land Conservation 5.11 Community Promotion 5.12 Preservation of Traditional Culture 5.13 Human Welfare 5.14 Environmental Education Appendix References Part III Case Study of a River 6 Flood Survey 6.1 Introduction 6.2 Methods 6.3 Results 6.3.1 Kochi River Flow and Water Quality 6.3.2 Water Quality of the Kochi River, Kita River and Obama Bay 6.4 Discussion 6.4.1 Relationship Between Discharge and Water Quality During Flooding and Normal Flows in the Kochi River 6.4.2 Relationship Among the Kochi River, Kita River and Obama Bay 6.4.3 Impact of Floods on Closed Waters Appendix References 7 Open Levee Survey 7.1 Introduction 7.2 Methods 7.3 Results 7.4 Discussion 7.4.1 Intensification of Flood Disasters 7.4.2 Agricultural Land Conversion 7.4.3 Declining and Aging of Agricultural Working Population 7.4.4 Restoration of Basin Residents’ Dependence on the River 7.4.5 Challenges to and Solutions for Open Levee Conservation Appendix References 8 Survey of the River Ecosystem Downstream of a Dam 8.1 Introduction 8.2 Methods 8.2.1 Survey Area 8.2.2 Water Quality, Stone Surface Deposits and Macroinvertebrate Assemblage Survey 8.3 Results 8.3.1 Water Quality and Stone Surface Deposits in the Ooishi River 8.3.2 Macroinvertebrate Assemblages in the Ooishi River 8.3.3 Site Comparison of Taxon Density of Net-spinning Caddisflies 8.4 Discussion Appendix References 9 Lake Biwa Survey 9.1 Introduction 9.2 Methods 9.3 Results 9.3.1 Submerged Macrophyte Survey 9.3.2 Bottom Sediment Survey 9.4 Discussion 9.4.1 Relationship Between Submerged Macrophytes and Bottom Sediment 9.4.2 Distribution Factor of Submerged Macrophytes 9.4.3 Influence of Artificial Reductions in Water Level on Submerged Macrophytes Appendix References Part IV Case Study of Paddy Fields 10 Drainage Canal System Survey 10.1 Introduction 10.2 Methods 10.2.1 Survey Areas 10.2.2 Survey Methods 10.2.3 Physical Environmental Survey 10.2.4 Aquatic Animal Survey 10.3 Results 10.3.1 Physical Environment in the Drainage Canal System 10.3.2 Total Numbers of Fish Caught at the Survey Sites 10.3.3 Total Numbers of Aquatic Insects Caught at the Survey Sites 10.4 Discussion 10.4.1 Physical Environment in the Drainage Canal System 10.4.2 Ecology of Opsariichthys Platypus 10.4.3 Ecology of Misgurnus Anguillicaudatus 10.4.4 Ecology of Calopteryx Atlata 10.4.5 Ecology of Orthetrum Albistyrum Speciosum 10.4.6 Effects of the Presence of Running Water in the Nonirrigation Season on Aquatic Animals in the Drainage Canal System 10.4.7 Proposals for Water Management in Consideration of Aquatic Animals 10.4.8 Proposals for Drainage Canal Maintenance Considering Aquatic Animals Appendix References 11 Irrigation Canal System Survey 11.1 Introduction 11.2 Methods 11.2.1 Survey Areas 11.2.2 Survey Methods 11.3 Results 11.3.1 Physical Environment in the Irrigation and Drainage Canal Systems 11.3.2 Biomass of Fish in the Irrigation and Drainage Canal Systems 11.4 Discussion 11.4.1 Physical Environment in the Irrigation and Drainage Canal Systems 11.4.2 Features of the Fish in the Irrigation and Drainage Canal Systems 11.4.3 Fishes at the Pools of the Irrigation Canal System 11.4.4 Issues with Conventional Irrigation and Drainage Canal Maintenance 11.4.5 Conservation Measures for Drainage–Paddy Field Fish 11.4.6 Conservation Measures for Irrigation–Drainage Fish 11.4.7 Step-By-Step Measures for Fish Conservation Appendix References 12 Fish-Retreat Ditch Survey 12.1 Introduction 12.2 Methods 12.2.1 Survey Areas 12.2.2 Survey Methods 12.3 Results 12.3.1 Aquatic Animal Biomass in the Fish-Retreat Ditch 12.3.2 Aquatic Animal Biomass Ascending to the Fish-Retreat Ditch 12.3.3 Aquatic Animal Biomass Descending from the Fish-Retreat Ditch 12.3.4 Water Depth, Water Temperature and Water Quality in the Fish-Retreat Ditch 12.4 Discussion 12.4.1 Characteristics of the Major Fish Species 12.4.2 Fish Types Occurring in the Fish-Retreat Ditch 12.4.3 Functional Significance of a Fish-Retreat Ditch 12.4.4 Management Issues Related to the Fish-Retreat Ditch 12.4.5 Future Outlook Appendix References Part V Wetland Development 13 Improvements to Enrich the Paddy Irrigation and Drainage Canal Systems 13.1 Introduction 13.2 Selective and Gradual Conservation Measures for Aquatic Animals 13.2.1 Conservation Measure A 13.2.2 Conservation Measure B 13.2.3 Conservation Measure C 13.2.4 Conservation Measure D 13.3 Water Flow Method in the Nonirrigation Season 13.4 Water Flow Plan for the Irrigation and Drainage Canal Systems 13.5 Paddy Fields as Social Assets Appendix References 14 Multiple Effects of Wetland Development 14.1 Introduction 14.2 Flood Control 14.3 Biodiversity Conservation 14.4 Environmental Education 14.5 Food Supply and Landscape Conservation 14.6 Recreation and Sports Appendix Reference 15 Wetland Management 15.1 Sizes and Sites of Wetlands 15.2 Importance of Regional Ecosystems 15.3 Importance of Basin Resident Dependence on Rivers 15.4 Wetland Management Appendix References