scholarly journals Distribution and Characteristics of Slope Movements in the Southern Part of Hiroshima Prefecture Caused by the Heavy Rain in Western Japan in July 2018

2019 ◽  
Vol 14 (6) ◽  
pp. 894-902
Author(s):  
Hideaki Goto ◽  
Yasuhiro Kumahara ◽  
Shoichiro Uchiyama ◽  
Yoshiya Iwasa ◽  
Tomoru Yamanaka ◽  
...  
Keyword(s):  
Heavy Rain ◽  
Slope Movement ◽  
Aerial Photographs ◽  
Large Area ◽  
Geospatial Information ◽  
Mountain Ranges ◽  
Slope Movements ◽  
Western Japan ◽  
Hiroshima Prefecture ◽  
Okayama Prefecture

Record-breaking heavy rainfall in July 2018 caused an extremely large number of slope movements over a broad area of western Japan. We mapped the distribution of slope movements in the southern part of Hiroshima Prefecture through an interpretation of aerial photographs that were acquired after the rainfall by the Geospatial Information Authority of Japan, and counted a total of 8,497 slope-movement starting points. The widespread distribution of slope movements – from Etajima City of Hiroshima Prefecture to Kasaoka City of Okayama Prefecture – suggests that the heavy rain affected a very large area. The starting points of debris flow during this disaster were commonly close to the crest of mountain ranges. We compared the distribution of slope movements to the 24-hr rainfall accumulation during the heaviest rainfall event to clarify the factors that caused regional difference in slope-movement distribution. We found the area of highest density of the slope movements was consistent with the area receiving a cumulative rainfall of >250 mm. This observation indicated that the position of slope-movement starting points was not related to differences in geology.

Extraction of Inundation Areas Due to the July 2018 Western Japan Torrential Rain Event Using Multi-Temporal ALOS-2 Images

2019 ◽  
Vol 14 (3) ◽  
pp. 445-455 ◽  
Author(s):  
Wen Liu ◽  
◽  
Fumio Yamazaki ◽  
Yoshihisa Maruyama
Keyword(s):  
Aerial Photographs ◽  
Rain Event ◽  
Visual Interpretation ◽  
Web Based ◽  
Inundation Area ◽  
Survey Report ◽  
Multi Temporal ◽  
Western Japan ◽  
Intensity Images ◽  
Okayama Prefecture

A series of heavy rainfalls hit the western half of Japan from June 28 to July 8, 2018. Increased river water overflowed and destroyed river banks, causing flooding over vast areas. In this study, two pre-event and one co-event ALOS-2 PALSAR-2 images were used to extract inundation areas in Kurashiki and Okayama Cities, Okayama Prefecture, Japan. First, water regions were extracted by threshold values from three-temporal intensity images. The increased water regions in July 2018 were obtained as inundation. Inundated built-up areas were identified by the increase of backscattering intensity. Differences between the pre-and co-event coherence values were calculated. The area with decreased coherence was extracted as a possible inundation area. The results of a field survey conducted on July 16, 2018 were used to estimate the optimal parameters for the extraction. Finally, the results from the intensity and coherence images were verified by making comparisons between a web-based questionnaire survey report and the visual interpretation of aerial photographs.

scholarly journals Flooding Along Oda River Due to the Western Japan Heavy Rain in 2018

2019 ◽  
Vol 14 (6) ◽  
pp. 874-885 ◽  
Author(s):  
Yasuo Nihei ◽  
Asataro Shinohara ◽  
Kaho Ohta ◽  
Shiro Maeno ◽  
Ryosuke Akoh ◽  
...  
Keyword(s):  
Large Scale ◽  
River System ◽  
Heavy Rain ◽  
High Rate ◽  
River Channels ◽  
Large Area ◽  
The North ◽  
Inundation Depth ◽  
Vertical Evacuation ◽  
Western Japan

The heavy rain that hit Western Japan in July 2018 triggered the worst rain-related disaster in the Heisei era, with the total of dead and missing persons exceeding 230, mainly in the Hiroshima and Okayama Prefectures. At several locations along Oda River (of the Takahashi river system) and its tributaries, dikes were breached due to large-scale flood, leaving 51 persons dead. This paper aims to shed light on the scale of inundation along Oda River and its tributaries and identify the characteristics of and critical factors for human damage. Field surveys were conducted to measure flood marks in flooded areas and river channels, and gauge the extent of damage to people and property. The surveys found that a large area was inundated on the north side of Oda River, with an inundation depth exceeding 5 m for 1 km in the south-north direction and 3.5 km in the east-west direction, which made vertical evacuation of residents difficult. The findings that about 80% of the dead were found on the first floor of their houses, with those who had lived in a one-story house and those who had lived in a two-story house accounting for 50% each of the deceased, indicate how difficult even vertical evacuation was. The findings appear to be related to the considerable inundation depth and high rate of water level increase, along with the fact that the majority of the deceased were elderly people.

scholarly journals Mortality by Age Group and Municipality in the July 2018 Torrential Rainfall

2019 ◽  
Vol 14 (6) ◽  
pp. 912-921
Author(s):  
Miho Ohara ◽  
◽  
Naoko Nagumo
Keyword(s):  
Mortality Rates ◽  
Age Group ◽  
Historical Records ◽  
Target Setting ◽  
Total Death ◽  
Western Japan ◽  
Hiroshima Prefecture ◽  
Torrential Rainfall ◽  
Okayama Prefecture ◽  
Nagasaki Prefecture

The July 2018 torrential rainfall caused tremendous damage to western Japan, claiming the lives of 237 people. This research analyzed the mortality due to the disaster by age group and municipality and compared it with historical records of past wind and flood disasters. The analysis confirmed that the total death toll of 237 including 115 deaths in Hiroshima Prefecture alone was the second highest in 41 years since 1978, following 427 deaths including 294 in Nagasaki Prefecture in the Nagasaki Great Flood in 1982. The analysis also found that the mortality rate in the age group 70 years and more was extremely high in Mabi Town of Kurashiki City, Okayama Prefecture and Saka Town, Hiroshima Prefecture, compared with that recorded in past disasters. Moreover, the paper discusses practical target setting for future mortality reduction by comparing the mortality rates in past disasters.

scholarly journals Special Issue on the Western Japan Heavy Rain

2019 ◽  
Vol 14 (6) ◽  
pp. 873-873
Author(s):  
Haruo Hayashi
Keyword(s):  
Disaster Response ◽  
Large Scale ◽  
Heavy Rain ◽  
The Elderly ◽  
Special Issue ◽  
Large Area ◽  
Floor Level ◽  
Problems And Solutions ◽  
Western Japan ◽  
Disaster Event

In 2018, Japan not only had an abnormally hot summer, but also experienced successive disasters, including the Northern Osaka Earthquake, the Western Japan Heavy Rain, Typhoon No. 21, the Hokkaido Mid Iburi Earthquake, and Typhoon No. 24. In particular, the record-breaking heavy rains continued in a large area of Western Japan from June 28 to July 4, due to the storm front and Typhoon No. 7. The amount of rainfall totaled over 1,800 mm in the Shikoku Region and 1,200 mm in the Tokai Region. The quantity of rain that fell within 48 and 72 hours in both the Chugoku and Kinki Regions, as well as many other areas, was the highest rainfall ever recorded. A special warning regarding heavy rain was issued in 10 prefectures and every kind of disaster that Japan had experienced recently occurred in various locations. As of August 21, a report from Disaster Management Section, Cabinet Office indicated 221 deaths, 9 missing persons, 68 severely injured persons, 319 slightly injured persons, 3 persons with an unknown level of injury, 6,206 destroyed homes, 9,764 severely-damaged homes, 3,765 partially-destroyed homes, 9,006 homes with flooding above the first-floor level, and 20,086 houses with flooding below the first-floor level. During this large-scale disaster, which was named the Western Japan Heavy Rain, the Disaster Relief Act was applied to 110 municipalities and JDR decided to issue a special edition to address issues pertinent to this specific disaster event. Paper submissions were requested that not only comprised demonstrative researches on hazard and damage characteristics, methods of evacuation, and features of disaster response, but also included introductions of best practices, which were conducted in various fields and prompted diverse collaboration to develop and establish measures to mediate the effect of the future Nankai Trough Earthquake, as well as problems and solutions to successfully realize diverse collaboration. In response to the call for papers for the special issue, nine researches were submitted and six were accepted following a strict review process. To address the category of hazard characteristics analyses, two papers analyzing the characteristics of the flooding resulting from the Western Japan Heavy Rain and one paper comprising an analysis of landslide disasters were accepted. In the category of disaster response, one paper focusing on the use of SNS and two papers regarding the elderly were accepted. It would be our sincere pleasure if this special issue could contribute to future reductions in damage resulting from natural disasters.

scholarly journals Retracted: Pierced Salt Domes in the Persian Gulf and in the Zagros Mountain Ranges in Southern Iran and their Relationship to Hydrocarbon and Basement Tectonics

2013 ◽  
Vol 2 (10) ◽  
pp. 116-133
Author(s):  
Hamid Reza Samadi
Keyword(s):  
Persian Gulf ◽  
Field Work ◽  
Aerial Photographs ◽  
Zagros Mountain ◽  
Mountain Ranges ◽  
Salt Domes ◽  
Southern Iran ◽  
Geological Processes ◽  
Basement Faults ◽  
The Persian Gulf

The most enigmatic problems with the nearly 200 salt domes pierced in the Persian Gulf and in the Zagros Mountain Ranges (ZMR) in southern Iran, a unique morphology in the world, have been the matter of this study, which is based on a combination of field work, enhancement of satellite and aerial photographs etc. In the ZMR, structural anomalies are frequently associated with similar facies distribution patterns. In the eastern portion of the region, emergent salt plugs of Infra-Cambrian age exhibit the same alignment patterns. Such trends bear no apparent genetic relationship to the Tertiary folding responsible for the present Zagros fold belt, but rather indicate their affinity with linear basement features which are readily observable on Land sat imagery and aerial photographs. Bending of anticlines in the competent cover rock, combined with minor strike-slip faults and horizontal displacements of parts of folded structures, strongly point to the presence of these basement faults. The salt plugs, which have pierced cover rocks of up to 10000 m thick, are distributed on the Arabian Platform along regional basement faults. The area of diapir outcrops is bounded by the Oman Line to the east and by the Kazerun fault to the west. Pieces of the basement have been brought up to the surface on some of the salt domes. The fragments were transported by rotational ascent of the Hormuz Salt Formation to the present and former land surfaces. The recognition of features related to basement tectonics and realization of their implication in the control and modification of geological processes are important adjuncts to the search for hydrocarbon accumulations in this region. To our best knowledge, data of basement faults in the study area are scarce. Therefore, this study was carried out to determine basement faults and their relation to salt dome distribution. Considering the fold axes bending, the trend of the salt plugs and also the distribution of epicenters of the last century, n umerous new basement faults are introduced in this paper.

scholarly journals Improvement in WRF model prediction for heavy rain events over North Sumatra region using satellite data assimilation

2021 ◽  
Vol 893 (1) ◽  
pp. 012040
Author(s):  
Immanuel Jhonson Arizona Saragih ◽  
Huda Abshor Mukhsinin ◽  
Kerista Tarigan ◽  
Marzuki Sinambela ◽  
Marhaposan Situmorang ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Initial Data ◽  
Satellite Data ◽  
Wrf Model ◽  
Heavy Rain ◽  
Convective System ◽  
Large Area ◽  
Weather Forecasts ◽  
Rain Events ◽  
North Sumatra

Abstract Located adjacent to the Indian Ocean and the Malacca Strait as a source of water vapour, and traversed by the Barisan Mountains which raise the air orographically causing high diurnal convective activity over the North Sumatra region. The convective system that was formed can cause heavy rainfall over a large area. Weather Research and Forecasting (WRF) was a numerical weather model used to make objective weather forecasts. To improve the weather forecasts accuracy, especially for predict heavy rain events, needed to improve the output of the WRF model by the assimilation technique to correct the initial data. This research was conducted to compare the output of the WRF model with- and without assimilation on 17 June 2020 and 14 September 2020. Assimilation was carried out using the 3D-Var technique and warm starts mode on three assimilation schemes, i.e. DA-AMSU which used AMSU-A satellite data, DA-MHS which used MHS satellite data, and DA-BOTH which used both AMSU-A and MHS satellite data. Model output verification was carried out using the observational data (AWS, AAWS, and ARG) and GPM-IMERG data. The results showed that the satellite data assimilation corrects the WRF model initial data, so as increasing the accuracy of rainfall predictions. The DA-BOTH scheme provided the best improvement with a final weighted performance score of 0.64.

FLOOD ANALYSIS IN THE NUTA RIVER BASIN DURING THE WESTERN JAPAN HEAVY RAIN IN JULY 2018

2019 ◽  
Author(s):  
RITSUKI SHIMIZU ◽  
TATSUHIKO UCHIDA ◽  
YOSHIHISA KAWAHARA
Keyword(s):  
River Basin ◽  
Heavy Rain ◽  
Western Japan ◽  
Flood Analysis

scholarly journals Design of a geodetic database and associated tools for monitoring rock-slope movements: the example of the top of Randa rockfall scar

2004 ◽  
Vol 4 (2) ◽  
pp. 187-196 ◽  
Author(s):  
M. Jaboyedoff ◽  
P. Ornstein ◽  
J.-D. Rouiller
Keyword(s):  
Land Management ◽  
Rock Slope ◽  
Slope Movement ◽  
Data Correction ◽  
Slope Movements ◽  
Spatial Changes ◽  
Critical Slope ◽  
Slope Monitoring

Abstract. The need for monitoring slope movements increases with the increasing need for new areas to inhabit and new land management requirements. Rock-slope monitoring implies the use of a database, but also the use of other tools to facilitate the analysis of movements. The experience and the philosophy of monitoring the top of the Randa rockfall scar which is sliding down into the valley near Randa village in Switzerland are presented. The database includes data correction tools, display facilities and information about benchmarks. Tools for analysing the movement acceleration and spatial changes and forecasting movement are also presented. Using the database and its tools it was possible to discriminate errors from critical slope movement. This demonstrates the efficiency of these tools in monitoring the Randa scar.

Analysis and assessment of ephemeral gully erosion in wide areas of Navarre (Spain) from routinely obtained ortophotographs

2020 ◽  
Author(s):  
Youssef Chahor ◽  
Javier Casalí ◽  
Rafae Giménez
Keyword(s):  
Management Practices ◽  
Sudden Change ◽  
Low Frequency ◽  
Direct Methods ◽  
Gully Erosion ◽  
Aerial Photographs ◽  
Large Area ◽  
Small Watersheds ◽  
Ephemeral Gully ◽  
Ephemeral Gullies

<p>Ephemeral gullies (EG) are linear erosion features located in swales where runoff concentrates during or immediately after rainfall events. EG are temporary because they are easily filled by conventional machinery and cause important soil losses in cultivated areas. Casalí et al. (1999) distinguished three types of EG: “classical”, formed by concentrated runoff flows within the same field where runoff started; “drainage”, created by concentrated flows draining areas upstream from the field; “discontinuity”, found in places where management practices create a sudden change in slope. There is still a great lack of knowledge about the true extent and importance of this EG. In this sense, the information obtained from aerial photographs can be of great value. The main objective of this work is to evaluate the possibility of making an exhaustive characterization of the space-time evolution of ephemeral gullies in a relatively large area from color aerial photographs. The effect of precipitation on the EG will be also analyzed.</p><p>The 570 ha study area is almost completely cultivated with winter cereals and located in the Pitillas district (Navarre). Climate is Continental Mediterranean (on average 550  mm yr<sup>-1</sup>). Soil (upper horizons) are loam–silty loam in texture.</p><p>EG within cultivated fields were located, classified and digitized using GIS interfaces over seven colour orthophotos (1:5000 with 0.5mx0.5m resolution) taken between 2003 and 2014. Gully length was determined after locating EG down and upstream ends. EG drainage areas and slopes were determined using a 2 m resolution DEM.</p><p>To determine EG volumes, an empirical power model for the study area defining the relationship between EG lengths and volumes was first obtained from previous field measurement, and then used for the EG lengths from this study. The corresponding erosion rates were also calculated.</p><p>57 small watersheds affected by EGs were identified, being 39 of them classified as drainage EGs, and the remaining 18 EGs as classic. 70% of the small watersheds were affected by EG only once. In remaining watersheds EG reappeared from twice to seven times. Therefore, it seems that the repeatability is not as high as thought.</p><p>The average erosion rate in classical EG is about 1.1 Kg m<sup>-2</sup> year<sup>-1</sup>. Previous assessments using accurate direct methods reported an average value of 0.8 Kg m<sup>-2</sup> year<sup>-1</sup> for very similar watersheds in the same area. Although it is not a conclusive proof, this findings indicate that both methods provide similar results.</p><p>A very high correlation (r<sup>2</sup>= 0.84) has been found between the length of the gullies formed in the study area and the total annual precipitation. It would follow that EG erosion would also be controlled by the overall amount of rainfall also in Mediterranean climates, and not only by high intensity-low frequency events.</p><p><strong>References</strong></p><ol><li>Casalí, J. J. López, J. V. Giráldez, 1999. Ephemeral gully erosion in Southern Navarra (Spain). CATENA 36: 65-84.</li> </ol>

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