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This article focuses on how ecosystem-based approaches could be mainstreamed in recovery and reconstruction after large scale, rare and infrequent coastal hazards. In doing so, this study reviews historical practices of disaster management in rivers and coasts as well as reconstruction process after the Great East Japan Earthquake (GEJE). It reveals how ecosystem approaches are integrated in river and coast works and highlights some of the relevant policies, technical guidance and guidelines and good practices on the ground. This study also documents how Eco-DRR policy evolved and implemented after the GEJE and addresses some of the challenges in its implementation. In order to draw additional insights, the reconstruction processes of Hurricane Sandy in the United States (US) was also reviewed as GEJE and Sandy shares some common features. Experience from Sandy suggests the importance of the participatory planning process rather than technical guidance or guidelines. Although it is too early to judge whether either reconstruction process was better or not, nor difficult to generalize the conclusion from only two samples, these two experiences suggest only technical guidance and guidelines is not sufficient to mainstream Eco-DRR/CCA in the reconstruction from large scale, rare and infrequent disasters. It is also suggested that the critical role of participatory planning process with cross-sector, cross-professional and interactive design approach may lead more innovative solutions.

Ensuring access to affordable, reliable, sustainable modern energy is a key challenge in reducing poverty in developing countries. Off-grid rural electrification based on decentralized renewable energy has been recognized as an effective way to increase access to energy in remote areas. However, there is some doubt about its long-term sustainability. Previous studies have indicated that once renewable energy generation facilities are installed, the responsibility for operation and maintenance is often handed over to the local community, and, eventually, the project fails because of a lack of maintenance budget. This paper discusses issues related to the sustainability of MHP-based rural electrification as a case study in a remote village in West Java, Indonesia, that is deeply steeped local traditions. A complementary approach between the community and a private company was introduced to improve the economic sustainability of MHPPs while simultaneously conserving local traditions and livelihoods.

Study region Japan Study focus In Japan, floods exceeding the flood control plan by dams have become more frequent in recent years. When such a flood occurs, the reservoir is operated to discharge the same amount of flood as the inflow, which is called "Extreme Flood Control Operations". Therefore, knowing the implementation of Extreme Flood Control Operations is equivalent to knowing the scale and frequency of extreme flood events in Japan. The number of Extreme Flood Control Operations is expected to increase due to climate change, which provides a current assessment of the impacts of climate change. New hydrological insights for the region In Japan, the number of Extreme Flood Control Operations has been increasing between 1960 and 2019. However, the number of dams being built is increasing, and the number of Extreme Flood Control Operations per dam construction is decreasing. In more than one case (41 %) of the floods that were operated to prevent extreme floods, the capacity of the dam (the sum of the flood control capacity and the diversion capacity) was required to exceed the storage capacity of the dam. This means that there are some floods that cannot be handled by pre-flooding to ensure flood control capacity. Therefore, it is suggested that dams alone cannot cope with increasingly severe floods in the future.

Frequent inundation has become a serious problem in urban areas. It is necessary to improve rainwater retention/infiltration in the urban watershed. The purpose of this study is to report how private rainwater-retention/harvesting facilities can be spread gradually but steadily in the city by citizen-initiated activities. Rainwater harvesting tanks were installed intensively and a rainwater harvesting house was constructed in the city of Fukuoka, Japan after the city experienced a flood disaster. The former enhanced users’ daily preparedness for emergency, and the latter inspired construction of a rainwater-harvesting housing complex. A public elementary school is in use from April 2016, which is inspired by these facilities. The school premises are located on the land reclaimed from an old irrigation pond. Thus the school needs to be adapted to this condition. 3000 m 3 of rainwater can be retained within the premises. The amounts of retention and discharge are monitored, and the data is utilized for science education. In big cities, people tend to depend too much on the top-down, mega-system, which invites more impervious surfaces in urban areas. Bottom-up, individual/collaborative approaches should be adopted in order to achieve multiple purposes of preventing/mitigating disasters, preserving/conserving ecosystems and nurturing/rebuilding communities in the city.

The continuous warming observed in recent decades as a result of climate change is posing significant threats to the environment, particularly for freshwater ecosystems. Therefore, it is highly important to predict the impact of this phenomenon on habitat suitability. However, such prediction requires the use of an integrated framework in which different parameters can be incorporated. While 1D modelling has been commonly used in river habit suitability simulations, most 1D mathematical models either do not provide enough information for the area along the rivers or do not consider the impact of river basin management on the river flow characteristics. This study seeks to develop such an integrated framework is in which water temperature and hydrologic-hydraulic parameters are jointly applied to simulate habitat suitability. The modeling setup is based on a combination of the Soil and Water Assessment Tool (SWAT) and international river interface cooperative (iRIC) models, and, due to the importance of the water temperature, the water temperature module in SWAT was modified. To examine the effectiveness of this method, Kikuchi basin is selected as the case study, and two different general circulation models, namely HadGEM2-ES and MICRO5, under two representative concentration pathways are applied to evaluate river habitat suitability under climate change conditions. The results showed a reduction in the river flows, water depths and velocities that have slightly positive effects on the habitat suitability of the Kikuchi river. However, this reduction causes some parts of the river to become dry, so that some of the habitats may disappear as a result of climate change. Moreover, it is shown that the downstream section of the Kikuchi river is more vulnerable to climate change. Therefore, migration of fishes to its upstream section is predicted. Finally, the proposed methodology is strongly recommended for use in modeling of other regions suffering water scarcity.

For the utilization of renewable energy from sources widely distributed in low-density non-urban areas the grid augmentation for its transmission to urban areas of high population density is often discussed under the premise that the present demand distribution remains invariant. Instead of grid augmentation, this study examined an alternative option of creating a power demand close to renewable sources and inducing population movements (i.e., Renewable Energy Exodus). First, the capacity of renewable energy to maintain populations in hilly and mountainous farming areas of Japan was evaluated from two perspectives: Task (1) a challenging nationwide balance based on possible energy demand saving scenario for the future, and Task (2) a conservative nationwide balance based on the current per capita energy demand and on the region-by-region generation–consumption matching concept. Because Task (2) indicated that Hokkaido, the northern-most island, has a huge capacity, Task (3) was conducted for Hokkaido by examining both energy balance and economic evaluation including job creation for the following two scenarios: (A) a supply to Tokyo scenario and (B) a local demand generation scenario, keeping the same conservativeness as Task (2) by using the current data for energy consumption per capita. The nationwide Renewable Energy Exodus estimates gave 48 million people for Task (1) (with the future per capita energy demand) and 10 million people for Task (2) (with the current per capita energy demand and region-by-region self-sustained balance), respectively. For Hokkaido Task (3) (with an additional economic assessment) gave 1 million people. The Renewable Energy Exodus concept combined with the green economy promotion was found to have a significant merit for a sustainable future of countries like Japan where economic and social disparities are serious between urban areas and non-urban areas.

Small scale hydropower energy goes a long way to fire up community development. Until 1920-30s, Japanese hydropower techniques had been established on a global level in each local area. However, after the second World War, the main energy resource was changed. This has resulted in a local decline in micro-hydro technical expertise and fewer waterwheel makers throughout Japan. At the present, we are going to work to re-make small scale hydropower technologies and markets. In this paper, we discuss and propose improvements to the “Japanese” small scale hydropower technology and production techniques, especially Pelton type wheel. The Pelton wheel technology of Nepal was freely available in the public domain so we decided to design a system based on that. We decided to designed by 3D-CAD and to make our Pelton buckets using a 3D printer. We compared the power generation capacity of our waterwheel with one purchased from New Zealand to investigate its effectiveness and efficiency. In our results of the experiment, the power generation curves for each turbine are approximately equal. The power increases continuously with increases in the flow rate. The maximum power generated by each turbine is approximately the same. This shows that it is possible to design a Pelton bucket that has a power generation efficiency comparable to a purchased bucket. The next step, the Pelton turbine designed in this study was chosen to be included in the Itoshima micro-hydro power generation system. So we scaled up and redesigned the Pelton turbine. In addition, we conducted a survey involving waterwheel makers regarding connecting to cost reduction. Using a 3D printer has the following advantages: 1.) Design deficiencies and failed designs can be identified at an early stage. 2.) Different forms of waterwheel can be made at low cost and in a short amount of time, which can then be used to run water experiments.