Eastern Japan Research Articles

Evolution of Sex Chromosome Heteromorphy in Geographic Populations of the Japanese Tago’s Brown Frog Complex

The sex chromosomes of most anuran amphibians are characterized by homomorphy in both sexes, and evolution to heteromorphy rarely occurs at the species or geographic population level. Here, we report sex chromosome heteromorphy in geographic populations of the Japanese Tago’s brown frog complex (2n = 26), comprising Rana sakuraii and R. tagoi. The sex chromosomes of R. sakuraii from the populations in western Japan were homomorphic in both sexes, whereas chromosome 7 from the populations in eastern Japan were heteromorphic in males. Chromosome 7 of R. tagoi, which is distributed close to R. sakuraii in eastern Japan, was highly similar in morphology to the Y chromosome of R. sakuraii. Based on this and on mitochondrial gene sequence analysis, we hypothesize that in the R. sakuraii populations from eastern Japan the XY heteromorphic sex chromosome system was established by the introduction of chromosome 7 from R. tagoi via interspecies hybridization. In contrast, chromosome 13 of R. tagoi from the 2 large islands in western Japan, Shikoku and Kyushu, showed a heteromorphic pattern of constitutive heterochromatin distribution in males, while this pattern was homomorphic in females. Our study reveals that sex chromosome heteromorphy evolved independently at the geographic lineage level in this species complex.

The Destructive Tree Pathogen Phytophthora ramorum Originates from the Laurosilva Forests of East Asia.

As global plant trade expands, tree disease epidemics caused by pathogen introductions are increasing. Since ca 2000, the introduced oomycete Phytophthora ramorum has caused devastating epidemics in Europe and North America, spreading as four ancient clonal lineages, each of a single mating type, suggesting different geographical origins. We surveyed laurosilva forests for P. ramorum around Fansipan mountain on the Vietnam-China border and on Shikoku and Kyushu islands, southwest Japan. The surveys yielded 71 P. ramorum isolates which we assigned to eight new lineages, IC1 to IC5 from Vietnam and NP1 to NP3 from Japan, based on differences in colony characteristics, gene x environment responses and multigene phylogeny. Molecular phylogenetic trees and networks revealed the eight Asian lineages were dispersed across the topology of the introduced European and North American lineages. The deepest node within P. ramorum, the divergence of lineages NP1 and NP2, was estimated at 0.5 to 1.6 Myr. The Asian lineages were each of a single mating type, and at some locations, lineages of “opposite” mating type were present, suggesting opportunities for inter-lineage recombination. Based on the high level of phenotypic and phylogenetic diversity in the sample populations, the coalescence results and the absence of overt host symptoms, we conclude that P. ramorum comprises many anciently divergent lineages native to the laurosilva forests between eastern Indochina and Japan.

Effect of population inflow and outflow between rural and urban areas on regional antimicrobial use surveillance.

Regional-level measures can complement national antimicrobial stewardship programs. In Japan, sub-prefectural regions called secondary medical areas (SMAs) provide general inpatient care within their borders, and regional antimicrobial stewardship measures are frequently implemented at this level. There is therefore a need to conduct antimicrobial use (AMU) surveillance at this level to ascertain antimicrobial consumption. However, AMU estimates are generally standardized to residence-based nighttime populations, which do not account for population mobility across regional borders. We examined the impact of population in/outflow on SMA-level AMU estimates by comparing the differences between standardization using daytime and nighttime populations. We obtained AMU information from the National Database of Health Insurance Claims and Specific Health Checkups of Japan. AMU was quantified at the prefectural and SMA levels using the number of defined daily doses (DDDs) divided by (a) 1,000 nighttime population per day or (b) 1,000 daytime population per day. We identified and characterized the discrepancies between the two types of estimates at the prefectural and SMA levels. The national AMU was 17.21 DDDs per 1,000 population per day. The mean (95% confidence interval) prefectural-level DDDs per 1,000 nighttime and daytime population per day were 17.27 (14.10, 20.44) and 17.41 (14.30, 20.53), respectively. The mean (95% confidence interval) SMA-level DDDs per 1,000 nighttime and daytime population per day were 16.12 (9.84, 22.41) and 16.41 (10.57, 22.26), respectively. The nighttime population-standardized estimates were generally higher than the daytime population-standardized estimates in urban areas, but lower in the adjacent suburbs. Large differences were observed in the main metropolitan hubs in eastern and western Japan. Regional-level AMU estimates, especially of smaller regions such as SMAs, are susceptible to the use of different populations for standardization. This finding indicates that AMU standardization based on population values is not suitable for AMU estimates in small regions.

Nurses Working in Nursing Homes: A Mediation Model for Work Engagement Based on Job Demands-Resources Theory.

This study examined the impact that the attractiveness of working in nursing homes and autonomous clinical judgment have on affective occupational commitment, and whether work engagement mediates these relationships. This analysis was based on the job demands-resources theory. The study setting was 1200 nursing homes (including long-term care welfare facilities and long-term care health facilities) in eastern Japan. An anonymous, self-report questionnaire survey was administered to two nurses from each facility, resulting in a prospective sample of 2400 participants. Overall, 552 questionnaires were analyzed, in which structural equation modeling and mediation analysis using the bootstrap method were performed. The results showed that the attractiveness of working in nursing homes does not directly affect affective occupational commitment; work engagement fully mediates the impact of attractiveness of working in nursing homes on affective occupational commitment. Additionally, autonomous clinical judgment showed a direct impact on both work engagement and affective occupational commitment, indicating that work engagement partially mediates the impact on affective occupational commitment. To increase the affective occupational commitment of nurses working in nursing homes, managers should help nurses recognize the attractiveness of working in nursing homes, and then provide appropriate support to help such nurses work in a motivated manner.

Increased frequency of participation in civic associations and reduced depressive symptoms: Prospective study of older Japanese survivors of the Great Eastern Japan Earthquake.

Few studies have examined whether changes in participation in civic associations can mitigate depressive symptoms among older disaster survivors. We examined prospectively the association between changes in participation in civic associations and changes in depressive symptoms among older survivors of the 2011 Great Eastern Japan Earthquake. We analyzed questionnaire-based survey data on pre- and post-disaster participation in civic associations and depressive symptoms compiled for 3567 respondents aged 65 years and above. Changes in these symptoms were assessed using a 15-item Geriatric Depression Scale (GDS) as a continuous variable for 2010 and 2013. We investigated four types of civic associations: sports, hobby, voluntary groups, and senior citizens' clubs. Changes in participation were calculated by subtracting the participation frequency measured in 2010 from that measured in 2013. Applying 95% confidence intervals, we used linear regression models with imputation to estimate the age- and sex-adjusted and multivariate-adjusted standardized coefficients. The survivors' GDS scores increased by 0.13 points on average between the pre-disaster and post-disaster periods. Average changes in the participation frequencies of respondents in each group were respectively +0.36 days/year, -5.63 days/year, +0.51 days/year, and -1.45 days/year. Increased frequencies of participation in the sports and hobby groups were inversely associated with changes in GDS scores (B=-0.003, Cohen's f2=0.10, P=0.01 and B=-0.002, Cohen's f2=0.08, P=0.04, respectively). The associations did not differ depending on the experience of housing damage caused by the disaster. In addition, we did not observe a significant association between changes in participation frequencies for voluntary groups or senior citizens' clubs and changes in GDS scores after multivariable adjustment. Depressive symptoms of older adults post-disaster may be mitigated through increased frequency of participation in sports and hobby groups; yet, civic participation did not mitigate the adverse impact of disaster experiences on mental health.

Effects of the Tibetan High and the North Pacific High on the Occurrence of Hot or Cool Summers in Japan

In this study, we investigated the effects of the Tibetan High near the tropopause and the North Pacific High in the troposphere on occurrences of hot or cool summers in Japan. We first classified Japan into six regions and identified hot and cool summer years in these regions from a 38-year sample (1980–2017) based on the monthly air temperature. To investigate the features of circulation fields over Asia during hot and cool summers in Japan, we calculated the composite differences (hot summer years minus cool summer years) of several variables such as geopotential height, which indicated significant high-pressure anomalies in the troposphere and lower stratosphere. These results suggest that both the North Pacific and the Tibetan Highs tend to extend to Japan during hot summer years, while cool summers seem to be associated with the weakening of these highs. We found that extension of the Tibetan High to the Japanese mainland can lead to hot summers in Northern, Eastern, and Western Japan. On the other hand, hot summers in the Southwestern Islands may be due to extension of the Tibetan High to the south. Similarly, the latitudinal direction of extension of the North Pacific High is profoundly connected with the summer climate in respective regions.

Genetic characteristics and phylogeography of the habitat generalist mayfly Ecdyonurus yoshidae (Ephemeroptera: Heptageniidae) in the Japanese archipelago

AbstractBecause of their early divergence in insect evolution, unique aquatic larval stage, and low dispersal ability, many mayfly species exhibit genetic structures that accurately reflect geological history and paleoclimatic changes. The present study investigated the genetic characteristics of Ecdyonurus yoshidae Takahashi (Ephemeroptera: Heptageniidae), a mayfly that inhabits a variety of freshwater habitats in Japan. Mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) gene sequences were generated from 209 mayfly specimens that were collected from 109 sites in Japan. A total of 145 haplotypes were detected, and nine of the lineages exhibited geographical regionality, with one lineage being endemic to Lake Biwa. The haplotype network was “bottleneck type” and included both star‐like structures and missing (or unobserved) haplotypes. Together, the haplotype network and FST values indicated that the Fukuejima Island group (Clade I) was genetically distinct from groups on the island of Kyushu, which is separated from Fukuejima Island by the Gotonada Sea. The common ancestor of E. yoshidae lineages in Japan was estimated to have diverged 1.14 mega‐annum (Ma) (95% highest posterior density interval, 0.55–1.78 Ma), and more regional genetic diversities were generated during the Middle to Late Pleistocene. Genetically distinct lineages of eastern and western Japan were separated by the Kinki Triangle region in central Japan. The genetic diversity of the habitat generalist E. yoshidae increased during the Middle and Late Pleistocene, when crustal movement and climate change in the Japanese archipelago occurred simultaneously.

Statistical framework for the evaluation of earthquake forecasting: A case study based on satellite surface temperature anomalies

Abstract There are growing observational evidences that various geophysical anomalies precede large earthquakes. However, the reliability of these anomalies for earthquake forecasting is controversial, and therefore more consistent assessment of forecasting ability is required. A framework for investigating pre-seismic anomaly detection using essential statistical indicators before global earthquakes is proposed. Surface temperature (ST) data from the Atmospheric Infrared Sounder (AIRS) sensor were used to realize this framework. First, seismic-related ST anomalies were identified, and then the statistical characteristics of forecasting ability for three indicators (accuracy, missed detection, and false alarm) were calculated in retrospective and prospective ways. The ST anomalies displayed some aggregation effects. Negative anomalies mainly concentrated on epicenters and to the north, while positive anomalies were found on the periphery; neither were strongly dependent on earthquake magnitude. The temporal evolution of forecasting metrics was relatively stable for the period 2010–2018. Mean accuracy, missed detection, and false alarm ratios were 6.01%, 1.60%, and 92.39%, respectively. Accuracy and missed detection ratios showed some spatial correlation and both peaked in the same area (e.g., eastern Japan); however, most areas showed very high false alarm ratios. Based on our findings, the combination of AIRS ST data and the Z-score anomaly detection algorithm to predict short-term earthquakes is currently not practical; the possibility of earthquake forecasting based on satellite thermal infrared measurements remains a huge challenge. However, our results confirmed the efficiency of this framework for quantitatively evaluating earthquake forecasting ability. This approach could be applied to various geophysical parameters and anomaly detection methods.

Association between acute myocardial infarction-to-cardiac rupture time and in-hospital mortality risk: a retrospective analysis of multicenter registry data from the Cardiovascular Research Consortium-8 Universities (CIRC-8U)

Despite the known association of cardiac rupture with acute myocardial infarction (AMI), it is still unclear whether the clinical characteristics are associated with the risk of in-hospital mortality in patients with AMI complicated by cardiac rupture. The purpose of this study was to investigate the association between the time of cardiac rupture occurrence and the risk of in-hospital mortality after AMI. We conducted a retrospective analysis of multicenter registry data from eight medical universities in Eastern Japan. From 10,278 consecutive patients with AMI, we included 183 patients who had cardiac rupture after AMI, and examined the incidence of in-hospital deaths during a median follow-up of 26 days. Patients were stratified into three groups according to the AMI-to-cardiac rupture time, namely the > 24-h group (n = 111), 24–48-h group (n = 20), and < 48-h group (n = 52). Cox proportional hazards regression analysis was used to estimate the hazard ratio (HR) and the confidence interval (CI) for in-hospital mortality. Around 87 (48%) patients experienced in-hospital death and 126 (67%) underwent a cardiac surgery. Multivariable Cox regression analysis revealed a non-linear association across the three groups for mortality (HR [CI]; < 24 h: 1.0, reference; 24–48 h: 0.73 [0.27–1.86]; > 48 h: 2.25 [1.22–4.15]) after adjustments for age, sex, Killip classification, percutaneous coronary intervention, blood pressure, creatinine, peak creatine kinase myocardial band fraction, left ventricular ejection fraction, and type of rupture. Cardiac surgery was independently associated with a reduction in the HR of mortality (HR [CI]: 0.27 [0.12–0.61]) and attenuated the association between the three AMI-to-cardiac rupture time categories and mortality (statistically non-significant) in the Cox model. These data suggest that the AMI-to-cardiac rupture time contributes significantly to the risk of in-hospital mortality; however, rapid diagnosis and prompt surgical interventions are crucial for improving outcomes in patients with cardiac rupture after AMI.

Food resource use by juveniles of the endangered sleeper Eleotris oxycephala in the Sagami River system, Japan

To ascertain the early food resource use of the endangered sleeper, Eleotris oxycephala, the food habits of juveniles were studied in a major stream (which received treated sewage discharge and had a low level of vegetation cover) and a tributary (which received little artificial inflow and had extensive vegetation cover) in the Sagami River system, eastern Japan in November 2015 (winter), May 2016 (spring), and August/September 2016 (summer). The stomach content compositions of 174 individuals and the stable isotope ratios of 30 individuals and their prey animals were investigated along with the species composition of prey animals in the environment. Various aquatic animals, including fish eggs, mollusks, crabs, palaemonid shrimps, atyid shrimps, isopods (asellids), chironomid larvae, and dragonfly larvae, were present in juvenile E. oxycephala stomach contents. In the tributary, they mainly preyed on atyid shrimps, which were abundant in the environment, with lower feeding intensity during winter season. In the major stream, throughout the year (including winter), they fed mainly on chironomid larvae, which were smaller and slower than atyid shrimps, and so easily caught, even by small recently recruited juveniles. There were abundant chironomid larvae in the major stream environment, where the water temperature seemed warmer and more eutrophic than in the tributary because of the treated sewage discharge, particularly in winter. These results indicated that feeding intensity differed between sites, particularly in winter, and this difference might be associated with differences in prey availability (i.e., chironomid larvae) or warm-water conditions. Moreover, juveniles could shift their use of food resources, in response to differences in prey availability. Thus, to conserve E. oxycephala in terms of early food resource use, it is necessary to conserve various aquatic prey animals such as atyid shrimps and chironomid larvae and their habitats.

Residual Dose of K-Feldspar post-IR Irsl of Beach-Shoreface Sands at Kujukuri, Eastern Japan

We assessed the residual dose of K-feldspar grains from modern and Holocene beach–shoreface sands at Kujukuri, eastern Japan. Samples from the modern foreshore and shoreface (to 34 m depth) show residual doses &lt;0.2 Gy for infrared-stimulated luminescence (IR)&lt;sub&gt;50&lt;/sub&gt; measured during post-IR infrared-stimulated luminescence (pIRIR)&lt;sub&gt;50/150&lt;/sub&gt;, equivalent to potential burial age overestimation of only several decades for given dose rates. Residual doses of 1–3 Gy are retained by pIRIR&lt;sub&gt;50/150&lt;/sub&gt;, equivalent to 400–1,300 years; pIRIR&lt;sub&gt;50/290&lt;/sub&gt; residual doses are up to 30 Gy, suggesting possible overestimation by &gt;10,000 years. Residual doses of Holocene sands were also assessed by comparison with radiocarbon ages, revealing consistent results with modern sands. The pIRIR&lt;sub&gt;50/290&lt;/sub&gt; results show no pronounced correlation of residual dose with water depth, except for a few samples from &lt;5 m depth with residual doses several tens of per cent lower than those of deeper sands, suggesting that most samples were not fully bleached and that sustained subaerial sunlight bleaching diminishes the difficult-to-bleach component. Compared to the uncertainties associated with other factors, such as the fading correction, the residual doses of IR&lt;sub&gt;50&lt;/sub&gt; and pIRIR&lt;sub&gt;50/150&lt;/sub&gt; are negligible for samples older than late and early Holocene, respectively. In contrast, the residual dose of pIRIR&lt;sub&gt;50/290&lt;/sub&gt; may lead to critical age overestimation of Late Pleistocene deposits if the residual dose is not properly corrected.

Site conditions of herbaceous communities on the rocky coast of the Miura Peninsula, Kanagawa Prefecture, eastern Japan

Site conditions of herbaceous communities on the rocky coast of the Miura Peninsula, Kanagawa Prefecture, eastern Japan

The recent increase in central eastern China summer rainfall and its possible mechanism

This study investigated interdecadal variations in summer rainfall in central eastern China before and after the mid-1990s. The mean difference in rainfall between the two epochs (average rainfall in the 1981–1995 period: 5.0 mm day−1; average rainfall in the 1996–2010 period: 6.0 mm day−1) was significant at the 95% confidence level. This study explored the cause of the recent increase in summer rainfall in central eastern China by analyzing the difference in average rainfall between 1996–2010 (hereafter, Epoch II) and 1981–1995 (hereafter, Epoch I). Analysis of rainfall revealed that positive anomalies were observed in a southwest–northeast direction across the south-central region of eastern China, Korea, and Japan, while negative anomalies were observed at latitudes of 40–50°N and in most areas in the western North Pacific region. These findings suggest that summer rainfall in central eastern China is part of East Asian summer monsoons and have an out-of-phase relationship with western North Pacific monsoons. To identify the cause of the recent increase in summer rainfall in central eastern China, the difference in 850 hPa stream functions between Epoch II and Epoch I was analyzed. This study found that anomalous huge anticyclonic circulations were strengthened in the western North Pacific region and anomalous cyclonic circulations were strengthened in the south-central region of eastern China. As a result, anomalous northeasterlies originating from anomalous cyclones centered on Lake Baikal and anomalous southerlies originating from anomalous cyclones in the south-central area of eastern China joined in central eastern China. The typical anomalous atmospheric circulations in the negative Pacific Decadal Oscillation (PDO) phase and the average PDO index and summer rainfall in central eastern China from June to August exhibited a high negative correlation, which was presumed to have been present since the previous winter.

3.11 From One Disaster to Another: Japan’s Earthquake

This paper recounts the experience of the Great Eastern Japan Earthquake on 11th March 2011 and offers an assessment of reactions to it on personal, social and policy levels. Almost a decade after the event, it looks at traces of the disaster, discussing in particular the following questions. What were the consequences if any for Japan’s energy policy? What other consequences were there, for example, concerning crisis management? How did people integrate the earthquake into their view of history? How did the earthquake affect people’s life satisfaction? And how does it relate to current events? It argues that despite its for all concerned unprecedented severity the disaster led to gradual improvements, rather than fundamental change.

Hard and soft measures for earthquake and tsunami disaster mitigation

A destructive earthquake struck the Kobe region on January 17, 1995, and a massive earthquake and tsunami struck eastern Japan on March 11, 2011. We present an overview of the casualty aspects of the 2011 Tohoku earthquake compared with those of the 1995 Kobe earthquake. In the Tohoku disaster, some water gates and seawalls saved some villages from the tsunami effects, though some did not. Based on these examples, we discuss the efficiency of soft and hard measures and consider their respective merits and demerits. The main causes of death in the Kobe and Tohoku EQs were, respectively, collapsing buildings and drowning in the tsunami. Although the time to death was very short in both cases, people often have more time to evacuate in the case of an interplate earthquake leading to a tsunami. Basic countermeasures against tsunamis include such hard measures as water gates, seawalls, and embankments. Soft measures need to be implemented in areas where hard measures are insufficient

Emergency flood detection using multiple information sources: Integrated analysis of natural hazard monitoring and social media data

Extreme weather events are occurring more frequently as a result of climate change. In October 2019, eastern Japan was hit by Hagibis, a large and high-speed typhoon. This unprecedented typhoon caused the evacuation of over 4000 people, injured more than 300 people, and damaged more than 98,000 dwellings throughout the affected area. Because floods are one of the most devastating natural disasters in Asia, providing an effective early warning system (EWS) is critical to reducing disaster impacts. However, warnings based only on natural hazard monitoring do not offer sufficient protection. Integrating natural hazard monitoring and social media data could improve warning systems to enhance the awareness of disaster managers and citizens about emergency events. We analyzed time-series data including rainfall intensity, 90-min-effective rainfall, and river water level as well as Twitter data related to disaster events during the 5-day period from 11 to 15 October, focusing on the most affected areas in Japan. The analysis included more than 60,000 tweets. Our analysis confirmed the utility of the statistical approach of outbreak detection with social media data in the early detection and local identification of multiple-flood events, and the results from the municipality-level analyses show that tweet frequencies related to the flood disaster ontological categories were significantly correlated to temporal variations in the hazard monitoring data. Thus, flood detection at the administrative level using social media data combined with current hazard monitoring data can enable a decision-driven EWS design. Interactive approaches for decision-making and knowledge production should continue to be considered in the face of climate-change-induced disasters.

The Manchurian Agricultural Society and Attempts to Establish a Colonization Bank in 1914-1915

Based on materials from the Russian State Historical Archive of the Far East and a number of other sources, the present article examines the activities of the Manchurian Agricultural Society (MAS). Founded in Harbin in 1912, MAS was actively involved in the developing of fertile land along the SinoEastern Railway (Kitaisko-vostochnaia zheleznaya doroga) strip. As the article points out, the leadership of the Company also came up with plans for the colonization of Northern Manchuria, the territory of which belonged to China. So far historians never considered the activities of MAS from this angle; MAS has so far been credited with the role of a conductor of Russian agricultural knowledge, through training specialists for agriculture in Manchuria and offering agro-technical education to the population living along the Sino-East Railway. Until Russia entered the First World War, MAS had some chances of obtaining support for its project in commercial and industrial circles, which were interested in strengthening Russian influence in northeast China. The author notes that serious adjustments in the activities of MAS were due to changes in the international political situation in 1914-1915. Circles in the Russian government were interested in maintaining friendly relations with their eastern neighbors, China and Japan. It is shown that in the changing political environment, without receiving support from the Russian government and the Governor-General of the Amur Province, the Company was able to redirect its activities. Its leadership concentrated on trying to create a special Colonization Society and a subsidizing Colonization Bank, whose funds were to be composed of shares, bonds, and treasury subsidies. The goal of this new Society and the Bank was to support Russia's economic undertakings in the Far East - the organization of agricultural and industrial enterprises, and the provision of financial and technical assistance to them. However, the First World War, which went very badly for Russia, did not allow for a realization of these plans. The problems of the colonization of the region were not resolved.

Global phylogeography and invasion history of the spotted lanternfly revealed by mitochondrial phylogenomics.

Biological invasion has been a serious global threat due to increasing international trade and population movements. Tracking the source and route of invasive species and evaluating the genetic differences in their native regions have great significance for the effective monitoring and management, and further resolving the invasive mechanism. The spotted lanternfly Lycorma delicatula is native to China and invaded South Korea, Japan, and the United States during the last decade, causing severe damages to the fruits and timber industries. However, its global phylogeographic pattern and invasion history are not clearly understood. We applied high‐throughput sequencing to obtain 392 whole mitochondrial genome sequences from four countries to ascertain the origin, dispersal, and invasion history of the spotted lanternfly. Phylogenomic analyses revealed that the spotted lanternfly originated from southwestern China, diverged into six phylogeographic lineages, and experienced northward expansion across the Yangtze River in the late Pleistocene. South Korea populations were derived from multiple invasions from eastern China and Japan with two different genetic sources of northwestern (Loess Plateau) and eastern (East Plain) lineages in China, whereas the each of Japan and the United States had only one. The United States populations originated through single invasive event from South Korea, which served as a bridgehead of invasion. The environmental conditions, especially the distribution of host Ailanthus trees, and adaptability possibly account for the rapid spread of the spotted lanternfly in the native and introduced regions.

Ensemble flash flood predictions using a high-resolution nationwide distributed rainfall-runoff model: case study of the heavy rain event of July 2018 and Typhoon Hagibis in 2019

The heavy rain event of July 2018 and Typhoon Hagibis in October 2019 caused severe flash flood disasters in numerous parts of western and eastern Japan. Flash floods need to be predicted over a wide range with long forecasting lead time for effective evacuation. The predictability of flash floods caused by the two extreme events is investigated by using a high-resolution (~ 150 m) nationwide distributed rainfall-runoff model forced by ensemble precipitation forecasts with 39 h lead time. Results of the deterministic simulation at nowcasting mode with radar and gauge composite rainfall could reasonably simulate the storm runoff hydrographs at many dam reservoirs over western Japan for the case of heavy rainfall in 2018 (F18) with the default parameter setting. For the case of Typhoon Hagibis in 2019 (T19), a similar performance was obtained by incorporating unsaturated flow effect in the model applied to Kanto Region. The performance of the ensemble forecast was evaluated based on the bias ratios and the relative operating characteristic curves, which suggested the higher predictability in peak runoff for T19. For the F18, the uncertainty arises due to the difficulty in accurately forecasting the storm positions by the frontal zone; as a result, the actual distribution of the peak runoff could not be well forecasted. Overall, this study showed that the predictability of flash floods was different between the two extreme events. The ensemble spreads contain quantitative information of predictive uncertainty, which can be utilized for the decision making of emergency responses against flash floods.

Assessment of potentially reusable edible wild plant and mushroom gathering sites in eastern Fukushima based on external radiation dose

Edible wild plant/mushroom gathering, an essential food acquisition and outdoor recreation activity in rural areas, has declined in the area near the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in eastern Japan. The present study first evaluated the spatial distribution of potential gathering sites of various edible wild plant/mushroom species before the accident by administering a face-to-face questionnaire survey to local gatherers as well as utilizing the group analytical hierarchy process (AHP) and geographic information systems (GIS). Then, the damage to and future reusability of previous gathering sites were estimated from the perspective of the external radiation dose by overlaying maps of potential gathering sites and the time-series air dose rate (ADR) up to 2050 incorporating different gathering frequency scenarios. The study area is located in Kawauchi village in the eastern Fukushima prefecture, at 12–30 km southwest of FDNPP. The spatial distributions of gathering sites before the accident differed widely among species at the local scale because of their different environmental preferences. In contrast, the temporal variation in the reusability of the gathering sites was notably small among different species. The external radiation dose in the potential gathering sites declined sharply in the early post-accident years and gradually in the later years through the physical decay of radiocesium, i.e., 134Cs and 137Cs, with different half-lives. Moreover, the gathering frequency and heterogeneous distribution of radiocesium substantially affected the temporal variation in reusability for the gathering sites. These results indicate that an early resumption of gathering would be possible by reducing the gathering frequency and avoiding higher ADR areas, whereas it will take a much longer period to resume gathering in areas with higher ADR. Further research is required that considers both internal and external radiation doses in the geospatial context for the restoration and safer use of edible wild plants/mushrooms.