Shigeko Haruyama

Natural levees and human settlement in the Song Hong (Red River) delta, northern Vietnam

The Song Hong (Red River) delta, northern Vietnam, is characterized by huge natural levees in an area of the delta plain known as the West Floodplain where fluvial sedimentation predominates. The natural levees along the Day River, a major distributary of the Song Hong, are comparable in size with those of the main course of the Song Hong. The Day River levees are 3–8 km wide and rise 2–5 m above the adjacent backswamps and have played an important role in human settlements since the late Metal age. We discussed the relationships among the natural levees of the Day River, delta progradation and the distribution of archaeological sites on the delta plain. During the early Holocene, the accumulation of sediment discharged by the Song Hong enhanced both aggradation of the floodplain and river mouth progradation within the drowned valley of the Song Hong. Radiocarbon dates from cores, trench exposures, and archaeological sites record a dramatic slowing of aggradation when sea level stabilized during 6–4 cal. kyr BP (the Holocene sea-level highstand). As sea level fell to the present level during 4–0 cal. kyr BP, the river mouth prograded rapidly toward the Gulf of Bac Bo (Gulf of Tonkin) and the river channels extended seaward. In the West Floodplain, lateral accretion overtook vertical accretion to generate the present longitudinal profiles of the Song Hong and Day rivers. During this period, human settlements spread across the backswamp and Holocene terrace area, lagging around 2 kyr behind the shoreline migration.

Mapping Coastal Erosion Risk in the Southern Red River Delta, Vietnam

In recent years, the Red River Delta has suffered from coastal erosion due mainly to human activities. To determine the characteristics of coastal erosion, a coastal dynamic index was calculated by overlapping eight JERS-1 SAR (Synthetic Aperture Rader) images from 1994 to 1998. After combining the features of natural environment and land use, 74 meshes covering 500 m along the coastline were classified by cluster analysis of UPGMA (unweighted pair-group method using arithmetic averages) using the three major factors, i.e., costal dynamics index, banks, and land elevation. A coastal erosion risk map was produced by clustering 686 meshes, including the inland area. The coastline clusters and distance from the sea were used in the clustering. Finally, a vulnerability map of coastal erosion considering land use was constructed. The present land use was assessed by randomization of land use, and it became clear that the current land use was vulnerable to coastal erosion. This study indicates that when other information is not available, satellite data can be very useful for coastal erosion risk mapping.

Human Impacts on the Landcover Change of the Inle Watershed in Myanmar

The land cover of this basin showed the changes clearly. In 1990, closed forests were found in northern edge, eastern and southwestern part of the watershed area, near Pinlaung range, Kyauktalone range and Pindaya-Ywangan area, however, in 2000, these closed forests were changed to open forest, scrub grassland, and agriculture. In some part of the watershed area, near Taunggyi, scrub land was changed into open forest because of the reforestation program. Agriculture extension occurred in the lake watershed area especially in western and northwestern part of the lake, near Kalaw-Aung Ban, Heho Valley, and Thamakhan Plain. One of the unique characteristic of Inle Lake is hydroponic cultivation. Besides, tomato cultivation is an important economy of Inle Lake. This type of cultivation is practiced on the naturally floating island and it is effected the water surface area of the Inle Lake in the following ways such as after using the old floating garden islands, they are decomposed to the lake bottom and the lake will be shallower, and the extension of floating garden cultivation causes more shrinkage to the water surface area in the study area. The floating garden area was increased from 1990 to 2010 years. On the other side, water surface area is decreased from 1990 to 2010 year because it is influenced by climatic condition, extension of floating garden, and population growth of the study area.

Flood Risk and Mitigation Under Changing Land Use

In this study, we describe how flood hazard maps of the Kumozu fluvial plain were developed based on geomorphologic land classification maps and discuss the status of comprehensive disaster management with respect to flood mitigation in the lower reaches of the Kumozu River Basin in Mie Prefecture, Japan. Open levee-retarding basin systems are one of the traditional flood-mitigation strategies employed along the lower and middle reaches of river basins in Japan. Rapid changes in land cover and land use in the Kumozu River Basin have increased flood risk, and rapid urban expansion in the river basin has led to broad-scale encroachment of residential areas into agriculture land, reducing the area of flood buffer zones available for use as retarding basins. By assessing flood damage along the lower reaches of the Kumozu River Basin while taking into the consideration the role of traditional open levee-retarding basin systems, we clarify the utility of such systems in terms of flood mitigation and the importance of land use planning based on geomorphological land classification maps. Taken together, these results demonstrate the importance of incorporating nonstructural measures into river basin management.

Flood Risk Measuring under the Flood Protection Embankment Construction in Dhaka Metropolitan Zone

The flooding is a common feature for problem solution in rapidly urbanizing Dhaka city. In this research, evaluation of flood risk of Dhaka city in Bangladesh has been developed by using an integrated approach of GIS, remote sensing with socio-economic data. The purpose of the study is to evaluate the flooding risk concerning with the flood protection embankment in remarkable flooding events (1988, 1998 and 2004) and urbanization of Dhaka metropolitan zone. In this research, we considered the Dhaka city into two parts east Dhaka where is outside the flood protection embankment and west Dhaka where is inside the flood protection embankment. Using statistical data we explored the socio-economic status of the study area population by comparing density of population, land price and income level. We have drawn the cross section profile of the flood protection embankment into three different points for realizing the flooding risk in the study area, especially in the historical flooding year (1988, 1998 and 2004). According to the physical condition of the study area, the land use/land cover map has been classified into five classes. Comparing with each land cover unit, historical weather station data and the socio-economic data the flooding risk has been evaluated. Although various adaptation strategies for prevention infrastructure was developed on basis of 1988 memorial flood. As a result, urban area expansion has driven by infrastructure development by 10% and population growth by 5% inside the embankment area. The socio-economic development such as; the average total income inside of embankment has been increased 10 USD while the income outside the embankment remain same.

Landform and Vulnerability for Disaster in Land Use Changing

The fluvial and coastal landforms have important roles causing natural disaster and had influence on disaster-stricken area of liquefaction under the expansion of land use changing in the Tone River lowland. In this chapter, the disaster vulnerability, specific liquefaction, is designated upon several mesh maps of risk levels, landform, land use, and vulnerability transformation of liquefaction on land use changing in the case of the lower Tone River floodplain. The liquefaction vulnerability is brought by physical dimensions as the scale of earthquake, the distance from hypocentral region, landform and sedimentation, underground water table, etc., and the other hand, the human dimensions as recent rapid land use change and regional planning without knowledge of geomorphology are accelerating higher vulnerable level, low resilience, and longer period for resuscitation from disaster. The land use changing with urban sprawl on site has been inducing to be new and transforming vulnerability level. Geomorphology demonstrates landform process and explaining the former natural disaster occurrence history and vulnerability level of disaster; therefore, understanding disaster vulnerability on site in the fluvial and coastal plain would support future regional planning toward to secure from disaster mitigation and appropriate land use pattern planning should be discussed in future. The essential of risk reduction needs appropriate sustainable education, and the geomorphology should be core subject due to secure for lives.

Natural Disaster and Coastal Geomorphology

Asia and the Pacific regions are exposed to severe natural disasters because many densely populated cities are sited on coastal plains. The geomorphic features in coastal areas have a key role in defining the risk levels and the vulnerability to natural disasters of coastal regions. Rapid land-use changes in recent decades have forced a transformation in risk assessment to approaches that analyze and evaluate the relationship between social structures and natural disasters. Disaster resilience should incorporate more insight into social structures and more local community activities as the next advance in disaster mitigation. The 2011 East Japan (Tohoku Japan) earthquake has presented many lessons for consideration by regional land-use planners regarding the relationship between geomorphology and tsunami damage, and the appropriate activities of local communities. In this introduction chapter, the author illustrates the relationship between a natural disaster and coastal geomorphology by using the response of the lower Abukuma River basin to the tsunami that followed the 2011 East Japan earthquake. The damage caused by the earthquake and tsunami took different forms on each type of coastal landform and demanded specific responses from the relevant social structures, including evacuation activities. Future regional planning for disaster mitigation should incorporate scientific knowledge of coastal geomorphology.

Introduction—Overview of Natural Disasters and Coastal Landforms

Asia and the Pacific regions are exposed to severe natural disasters because many densely populated cities are sited on coastal plains. The geomorphic features in coastal areas have a key role in defining the risk levels and the vulnerability to natural disasters of coastal regions. Rapid land-use changes in recent decades have forced a transformation in risk assessment to approaches that analyze and evaluate the relationship between social structures and natural disasters. Disaster resilience should incorporate more insight into social structures and more local community activities as the next advance in disaster mitigation . The 2011 East Japan (Tohoku Japan) earthquake has presented many lessons for consideration by regional land-use planners regarding the relationship between geomorphology and tsunami damage , and the appropriate activities of local communities. In this introduction chapter, the author illustrates the relationship between a natural disaster and coastal geomorphology by using the response of the lower Abukuma River basin to the tsunami that followed the 2011 East Japan earthquake. The damage caused by the earthquake and tsunami took different forms on each type of coastal landform and demanded specific responses from the relevant social structures, including evacuation activities. Future regional planning for disaster mitigation should incorporate scientific knowledge of coastal geomorphology.

Land-Cover Change and Climate Change Analysis of the Amur River Basin Using Remote Sensing Data

We used remote sensing data to clarify recent climate changes and land-cover changes in the Amur River Basin. We also analyzed locations of remarkable land-cover and land-use changes that are of concern for their socioeconomic impacts on fluvial geomorphology. We focused especially on wetlands on the fluvial plain along the Amur River main stem. Land-cover changes in Northeast China are more extensive and rapid than those in Russia and related with land degradation in the north. Rapid land-cover changes have had notable effects on surface erosion and land degradation where is repeated flooding of branches of the Amur River in Northeast China.

Wetland and Flooding in the Amur River Basin

The Sanjiang Plain has been cultivated by the Chinese government since the 1950s. Change in its land cover has caused serious flooding. By contrast, the Kiya River Basin in Russia, on the opposite side of the Sanjiang Plain, has not experienced a change in land cover. In this study, a geomorphological map was made, and land cover change on the Sanjiang Plain is clarified using Shuttle Radar Topography Mission and Japanese Earth Resources Satellite 1 Synthetic Aperture Radar data. The wetland condition for the Kiya River Basin is also examined. Finally, human impacts on the Sanjiang Plain are analyzed. Land in the study area was significantly cultivated; one-third of the alluvial plain was cultivated from 1992 to 1996. The Kiya River Basin is always submerged and rarely suffers major floods. The history of land cover change corresponds to the time series of annual minimum discharge. The water holding capacity has been lost and floods occur more frequently because the wetland has disappeared.