An increase in natural hazards due to global warming has broadened the gap between natural hazards and disaster prevention. This gap has raised the possibility that unexpected major disasters occur. As chances of a natural hazard grow, appropriate and efficient adaptation is considered as a last resort for lessening disaster. In water-related disasters such as floods and debris flows, individual disaster sites have specific thresholds (limits). When a natural hazard exceeds this threshold, a serious disaster strikes us. On the contrary when it is under the limit, disaster damage is kept to be small. Flood disasters and landslides have the side of “all or nothing.” This is a characteristic of water-related disasters. Climate change is causing natural hazards to exceed this threshold easily. This makes resilient proactive adaptation very important in disaster prevention. Specific adaptation measures developed hereafter must cope with serious water and sediment disasters throughout mountainous regions, rivers, urban areas, and coastal areas that are assumed to be influenced by global warming.
The Journal of Disaster Research has planned a special issue on the adaptation measures for disasters due to climate change. Having taken part in field surveys, computer simulations, and laboratory experiments and finding adaptation measures worth studying more deeply, I decided to contribute to this special issue as a Guest Editor. All of its 11 papers have been peer-reviewed. The broad topics covered range from floods, landslides, and storm surges to adaptation to the human being society.
I would like to extend my sincere thanks to the contributors and reviewers involved in producing these articles, especially to Dr. Hideo Oshikawa, Assistant Professor of the Department of Urban and Environment Engineering, Kyushu University, Japan, for his great support. I look forward with great anticipation to feedback from readers regarding these articles.
Local governments are expected to play a significant role in making cities resilient, especially in reducing disaster risks and adapting to climate change. To obtain the relevant actors’ understanding and cooperation in implementing adaptation measures, it is essential that the potential framing gaps which may arise between them in terms of the impacts and risks of climate change be filled in. In this study, we have identified the framing gaps between stakeholders and the general public. We analyzed the questionnaire data obtained from the general public and the stakeholder data obtained by means of a case study carried out in Tokyo. We then integrated the results and derived three implications: i) it is effective to implement climate change adaptation policy that local governments obtain an understanding of multi-benefit of the the policy as well as climate change risk from the public through community-based groups, avocational groups and other organizations in the local community. ii) as for a firmly locked-in view of climate change policy that the policy means just reducing greenhouse-gas emissions, communication strategies for accurately explaining the relationship between adaptation measures and mitigation measures is required, and iii) as for the challenges of agenda setting for incorporating climate change risk into administrative plans, the department of the environment who is in charge of climate change policy is required to take a leadership in a coordinating function, for example, raising the awareness of other departments in terms of adaptation measures and providing them with scientific knowledge of climate change risk.
Additional adaptation measures such as “basic improvement of sensitivity” and “adaptive governance against mid and long term impacts” are set as ideal directions for local governments. The study of the situations for implementing additional adaptation measures by local governments were determined by using checklists. It is clarified as a result that additional adaptation measures have not been considered enough.
The following problems in implementing measures from the “Japan local Forum for Climate Change Adaptation Society” were found:
(1) Prediction and evaluation of climate change impacts, (2) Concretization and evaluation of adaptation measures, (3) Communication and subject formation and (4) Implementation of the measures and preparation of conditions.
In the future, it is necessary to concretize additional adaptation measures at the research level, to share these additional adaptation measures with concerned parties and to promote the exchange of opinions.
Heavy local rainfall has been increasingly observed in urban Fukuoka on fine summer afternoons in recent years. Such rainfall tends to occur suddenly on calm afternoons and is considered to be caused by local wind conditions influenced by local topography rather than by weather fronts or typhoons. This local rainfall is considered to be caused by a mechanism different from similar rainfalls occurring on fine Kanto plain afternoons. We set up 14 rain gauges in urban Fukuoka in this study to clarify and confirm actual local rainfall conditions there. Maximum local rain is about 64 km2 lasting 10 to 30 minutes. The maximum 10-minute rainfall was 13.8 mm. The average surface air temperature on days with local rainfall differs 2◦–3◦C from that on fine days. Upper atmosphere humidity distribution differs greatly between fine days and those with heavy local rain. Accordingly, heavy local rain is more likely to occur if surface air temperature and humidity in upper atmosphere rise above a certain level. Some difference is seen between days of heavy local rainfall and fine day in terms of the K index (KI), a measure of atmospheric stability. We confirmed that the atmospheric state becomes more unstable on days with heavy local rainfall than on fine days. Heavy local rainfall often begins in either the eastern or western inland Fukuoka plain and moves toward the coast. That is, based on numerical simulation using the meteorological mesoscale weather research and forecasting (WRF) model, wind blowing opposite to the sea wind blows in the upper atmosphere, moving cumulonimbus clouds causing heavy local rainfall toward the coast. We also confirmed that heavy local rainfall tends to occur in eastern inland areas with wind from the west, but tends to occur in western areas with wind from the east. We therefore assumed that heavy local rainfall in urban Fukuoka was triggered by updrafts generated when wind struck the inland Fukuoka plain mountain system.
It is difficult to forecast hourly rainfall locally even using the latest meteorological models, although hourly rainfall averaged spatially to some extent can be used for calculating practical rainfall. This study conducts numerical experiments with triple nesting on the 2012 heavy rainfall event in northern Kyushu using the weather research and forecasting (WRF) model and examines the features of hourly rainfall averaged spatially. The dependence of rainfall is averaged spatially on a spatial averaging scale and clarified by comparing rainfall calculated by simulation using the WRF model with radar/AMeDAS precipitation analysis data. This study’s findings indicate the effective spatial averaging scale making relative error of calculated values to the observed ones minimum.
The typhoons that so often rage across Japan’s southwestern island, Kyushu, are expected to occur even oftener in the future due to global warming. Storm surge projections have been reported based on the super-high-resolution global climate model MRI-AGCM3.2S developed by Japan’s Meteorological Research Institute (MRI). AGCM3.2S overestimates typhoon strength around Japanese islands, however, and this could lead to exaggerated storm surge projection. We therefore evaluate a bias correction method of typhoon strength considering the typhoon characteristics of AGCM3.2 in estimating maximum storm surge anomaly on the Ariake Sea coast. Our results indicated the possibility of storm surge anomaly of 2.8 m, exceeding the current design storm surge anomaly of 2.36 m at the innermost Ariake Sea.
As the climate begins changing due to global warming, heavy rainfalls have become more frequent. These are, in turn, increasing the red soil runoff that has increasingly damaged the marine products and tourist industries. Over 85% of all such runoff is from farmland. Working with local farmers, we conducted field experiments in Ginoza Village in Okinawa’s Matsuda district to better understand the inhibitory effects on red soil runoff of different potential adaptation measures. Effectiveness of the adaptation methods conducted are discussed based on the obtained results. Further, a physical model is presented for simply estimating the sediment volume due to soil erosion by using the grain size distribution. The model can give a good agreement with the measured maximum particle sizes of the red soils discharged from farmland.
The new Cascade concept of flood control is demonstrated in laboratory experiments in which upstream dams in a series of dams constructed along a river overflow from emergency spillways while the final downstream dam is required only to use its normal spillway and never do its emergency spillway. Multiple small dry dams lacking a slide gate in a normal spillway should be constructed in a series rather than as a single large dam to prevent flood disasters and to preserve the natural environment. Dry dams for flood control have recently been reviewed, planned, and built at sites in Japan. In this paper, we compare the Cascade method to conventional flood control in laboratory experiments conducted based on the condition that dams all have the same reservoir capacity. Results have shown that the Cascade method using multiple dry dams was considerably more effective than conventional flood control. Furthermore, the additional flood control effect of a dry dam equipped with closable and openable gate in its regular spillway was experimentally confirmed although there is no such kind of the gate on an ordinary dry dam. This new dry dam should be constructed in the river’s upper reaches away from the existing downstream storage dam needing still more its capacity for water utilization, thus ensuring the amount of water available by closing the regular spillway after the dry dam is filled to capacity. The flood control capacity of dams including the new dry dam is stronger than that of an ordinary storage dam thanks to the dry dam’s storage function.
Using numerical simulation, we clarified the mechanism that the flood control capability is dramatically strengthened by using multiple serial dams efficiently, based on a new flood control concept that let dams overflow through emergency spillways. Numerical analysis results for a group of dry dams were used to quantitatively evaluate this effect and to derive an empirical formula. The conventional flood control approach sets the design high water discharge of individual dams, even when dams are constructed serially, ensuring that no overflows occurs in any of the dams, here called the “conventional” method. By comparing the group of dry dams based on the conventional method and a method on the same scale but set based on a new concept that we called Cascade method, we found that when the flood peak is cut in conventional control, the latter half of the cutoff flood peak must be cut again, making flood control redundant. The Cascade method avoids this redundancy in storage use and cuts the flood peak efficiently and linearly.
“Mangrove” is the generic name for plants growing on tropical and subtropical tidal flats. The mangrove is used for many things, including disaster protecting land from high waves and tides and tsunamis, cleaning rivers and drainage containing soil and sand, and providing a variety of organisms with living space. Climate change and rising sea levels are threatening the future of the mangrove. Developing effective ways to conserve mangroves is thus needed, but more must be known about how the mangrove’s ecology and how it develops. It has been pointed out, for example, that mangroves increased flooding by the Sumiyo River in Amami Oshima. We studied ways to develop the mangrove at the Sumiyo River mouth in Amami Oshima and its influence in local flooding, finding that the current mangrove forest had little influence on flooding and that sediment deposition accelerating in Sumiyo Bay due to a sea dike could enlarge the mangrove forest in future.
Torrential rain possibly due to climate change has begun causing disasters annually, with water and sediment resulting from heavy rainfall in relatively narrow upper basins often arising in short periods. Because most of these basins are traversed by class B rivers administered by local governments, data on disasters are not accumulated comprehensively. Targeting the Sumiyo River basin on Amami Oshima Island, this study involved field surveys and numerical simulations to clarify inundation features in areas short on data based on hearings from investigation results. Calculation results have reproduced water levels, together with hearing results, including the initial inundation process in which rain water flowed directly from mountain slopes and later inundation processes mainly caused by overtopping and dike breach on the Sumiyo River. (Note that river bed fluctuations and dike breach progress are to be addressed in the future.)
In 2009, the heavy rainfall induced by Typhoon Morakot hit Hsiaolin Village that caused catastrophic flooding, landslides, landslide dam breakages and debris flows. Such a called “compound disaster” is defined as a disaster in which extensive floods or sediment transports occur simultaneously or consecutively at the catchment area during an event. It challenges current warnings, forecasting and responses to sediment disasters. New concepts and procedure thus are needed to cope with such “compound disasters.” Rainfall hydrographs show downpours of long duration, high intensity, high accumulation and large extent. To better delineate these disasters and provide possible coping strategies, we rebuild the temporal order and spatial distribution of the disaster processes involved. The study suggest correlating individual disaster types with rainfall through simulation. This could clarify the causality between what happened in Hsiaolin Village and related disasters. Our results will strengthen disaster prevention in debris flows and shallow landslides using strateghies that could then be applied to warning systems for deep-seated landslide and landslide dams. The derivative issues and the approach to compound disaster prevention are suggested for future tasks.
Extreme typhoon precipitation events frequently have a socioeconomic impact and result in the loss of human life. Therefore, conducting thorough evaluations of the disaster scale before the occurrence of extreme typhoon precipitation events is beneficial to disaster reduction. This study selects the Tsengwen River basin, Taiwan, the area most severely impacted by typhoon Morakot, as a demonstration area, and adopts dynamical downscaling data to simulate the top ten extreme typhoon precipitation events of the future (from 2069 to 2099) under climate change. The SOBEK model (commercial software) and the Taiwan Typhoon Loss Assessment System (TLAS), established by the National Science and Technology Center of Disaster Reduction (NCDR), are used to evaluate the potential losses resulting from the ten extreme events. The results indicate that the average total loss caused by the ten simulated typhoon events amounts to US$439 million, with agriculture, followed by aquaculture and forestry, suffering the greatest damage. A correlation analysis is also employed to identify key factors that influence loss, including the maximum 6-hour cumulative precipitation, the maximum peak runoff, and the use of the land. Based on these analysis results, this study provides applicable coping strategies that will effectively reduce the impact of future extreme precipitation events in the Tsengwen River basin.
Containment vessels, which contain any radioactive materials that would be released from the primary system in an accident, are the last barrier between the environment and the nuclear steam supply system in nuclear power plants. Assessing the probability of failure for the containment building is essential to level 2 PSA studies of nuclear power plants. Degradation of containment vessels of some nuclear power plants has been observed in many countries, so it is important to study how the corrosion has adverse effects on the capacity of containment vessels. Conventionally, the reliability analysis of containment vessels can be conducted by using Monte Carlo Simulation (MCS) or Latin Hypercube Sampling (LHS) with the deterministic finite element analysis. In this paper, a 3D finite element model of an AP1000 steel containment vessel is constructed using the general-purpose nonlinear finite element analysis program ABAQUS. Then the finite element reliability method (FERM) based on the first order reliability method (FORM) is applied to analyze the reliability of the steel containment vessel, which is implemented by combining ABAQUS and MATLAB software platforms. The reliability and sensitivity indices of steel containment vessels under internal pressure with and without corrosion damage are obtained and compared. It is found that the FERM-based procedure is very efficient to analyze reliability and sensitivity of nuclear power plant structures.
Torrential rains have been increasing in frequency. There have been instances in which residents were caught up on their way to evacuation shelters. It is important to check on hazards caused by conditions, on the adequacy of evacuation facilities, and on water levels and weather advisories. When taking appropriate action in torrential rains, it is necessary to assess weather and water information based on the preliminary survey of evacuation. To improve the quality of decision making, a science-based procedure should utilized by public agencies to judge the situation. We propose a procedure manual and web-based system for take appropriate action as disaster response.
Millions of non-engineered constructions in Indonesia are vulnerable to earthquake. Therefore, a simple, affordable and replicable method to strengthen the existing non-engineered construction in Indonesia is introduced. The retrofitting method described in this report is based on the principle of sandwich structures, having a masonry wall as core and covered on both sides with ferrocement layers. Numerical analysis result and shaking table test is included in this paper.