Localized Downpours Research Articles

Radiocesium levels in contaminated forests has remained stable, even after heavy rains due to typhoons and localized downpours

In recent years, Japan has suffered serious damage due to natural disasters such as earthquakes, heavy rains due to tropical storms (typhoons) and localized downpours. To assess the chronological changes in the attenuation of external exposure doses and environmental radiation contamination due to the rainfall associated with typhoons and heavy rains during October to December 2019 in Fukushima, we measured environmental radiation levels in forest areas along the Mt Okura hiking trail in Tomioka Town, Fukushima Prefecture, near the Fukushima Daiichi Nuclear Power Station. We confirmed that (1) current ambient dose rates of 0.38–0.95 μSv/h in most forest areas were 79.9–84.7% higher than in residential areas; (2) the number of sites along the hiking trail where 137Cs was detected was limited (1.1–4.7%); and (3) individual dose rates of 0.21–0.34 μSv/h were lower than ambient dose rates. These findings suggest that radiocesium has remained stable in natural forests that have not been decontaminated even though current levels are low, despite the occurrence of heavy rainfall associated with Super Typhoon Hagibis in 2019 and localized downpours. Hiking while managing exposure to environmental contamination using a personal dosimeter may be the safest model for spending time of leisure activities.

English

Countries lack the infrastructure to deal with the drainage following flashfloods from localized downpours which may originate from localized evaporation or its combination with that from surroundings or from hurricanes. The natural distribution of water is the best and optimum for the globe. Among the world’s riparian countries, India makes her territory both the sources and the sinks of river discharges by constructions of dams, reservoirs, barrages, weirs, etc. on international rivers and diversion of their courses within herself. Water confinement constructions make rivers silted heavily reducing their discharge capacities all through but more so in the downstream. The two catastrophic incidences – 2013 Uttarakhand and 2014 Jammu-Kashmir - presented in this article vouch for the curses of water confinement. Theoretical treatments have been provided for studying the impacts on the climatic variables for pre- and post-dam periods. Against the backdrop of these incidences, India has threatened her western neighbor of cutting off water supply which she has already done to the eastern neighbor. She, however, opens the gates of all dams and barrages built upstream of the river-silted eastern neighbor Bangladesh and floods that country causing irreparable losses of lives and properties, and adding misery to millions of people when India fails to accommodate excess water. On top of this confinement of river discharges within India, she has been working on the master plan of river networking. It is imperative for judges of international arbitration court, donors, World Bank, policy makers, etc. etc. to take lessons out of this study.   Key words: Dams, reservoirs, evaporation, macrostate, microstate, extreme event, powerhouse, river basin, Ganges, Indus, Teesta, tributary, distributary, water piracy, upstream, downstream.

A Study on Evacuation Safety at Inundated Stairs by using Real-scale Hydraulic Model Experiment

In recent years, sudden and local downpours in Korea have become more frequent. These rainfall patterns increase load on drainage system and reduce ability to exclude inland water, leading to flooding. If such rainfall patterns lead to flash floods especially in dense urban areas, sudden submergence of underground spaces by floods can be a fatal threat to life. Therefore, it is very important to secure evacuation routes in case of inundated underground spaces. In this study, we tried to determine evacuation safety by understanding hydraulic characteristics of inundated stairs that could become evacuation routes in underground spaces. For this purpose, water depth and volume flow rate were measured at each point of inundated stairs, and data obtained from results were used to evaluate evacuation safety at each step.

Landslides in West Coast metropolitan areas: The role of extreme weather events

Abstract Rainfall-induced landslides represent a pervasive issue in areas where extreme rainfall intersects complex terrain. A farsighted management of landslide risk requires assessing how landslide hazard will change in coming decades and thus requires, inter alia, that we understand what rainfall events are most likely to trigger landslides and how global warming will affect the frequency of such weather events. We take advantage of 9 years of landslide occurrence data compiled by collating Google news reports and of a high-resolution satellite-based daily rainfall data to investigate what weather triggers landslide along the West Coast US. We show that, while this landslide compilation cannot provide consistent and widespread monitoring everywhere, it captures enough of the events in the major urban areas that it can be used to identify the relevant relationships between landslides and rainfall events in Puget Sound, the Bay Area, and greater Los Angeles. In all these regions, days that recorded landslides have rainfall distributions that are skewed away from dry and low-rainfall accumulations and towards heavy intensities. However, large daily accumulation is the main driver of enhanced hazard of landslides only in Puget Sound. There, landslide are often clustered in space and time and major events are primarily driven by synoptic scale variability, namely “atmospheric rivers” of high humidity air hitting anywhere along the West Coast, and the interaction of frontal system with the coastal orography. The relationship between landslide occurrences and daily rainfall is less robust in California, where antecedent precipitation (in the case of the Bay area) and the peak intensity of localized downpours at sub-daily time scales (in the case of Los Angeles) are key factors not captured by the same-day accumulations. Accordingly, we suggest that the assessment of future changes in landslide hazard for the entire the West Coast requires consideration of future changes in the occurrence and intensity of atmospheric rivers, in their duration and clustering, and in the occurrence of short-duration (sub-daily) extreme rainfall as well. Major regional landslide events, in which multiple occurrences are recorded in the catalog for the same day, are too rare to allow a statistical characterization of their triggering events, but a case study analysis indicates that a variety of synoptic-scale events can be involved, including not only atmospheric rivers but also broader cold- and warm-front precipitation. That a news-based catalog of landslides is accurate enough to allow the identification of different landslide/rainfall relationships in the major urban areas along the US West Coast suggests that this technology can potentially be used for other English-language cities and could become an even more powerful tool if expanded to other languages and non-traditional news sources, such as social media.

The Impacts of Debris Torrents in Caribbean Coast of Honduras, Central America

ABSTRACT Kim, S.;Lee, H., and Jun, K.W., 2016. The impacts of debris torrents in Caribbean coast of Honduras, Central America. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1347–1351. Coconut Creek (Florida), ISSN 0749-0208. One of the main contributing factors in creating debris torrents is heavy rainfall. Global climate changes have led to an increase in localized downpours, causing an increase in torrent occurrences as well. The purpose of this experiment is to utilize numerical simulation for the analysis of debris torrents in their behaviour and mechanism. The numerical simulation is comprised of equations calculating mass continuity and momentum in order to consider erosion, deposition, and the combination of them both. The Finite Difference Method is applied to analyze the debris torrents. The numerical model of present study was applied ...

Flood Events in Gangapur Village, Banke District: An Example of Climate Change-induced Disaster in Nepal

Climate change impacts in Nepal have resulted, among others, localized downpour which may trigger severe flooding and associated disasters in some parts of the country, particularly in the southern slope of the Siwalik. The purpose of this investigation was to evaluate the consequences of climate change impacts in the Dhondra River watershed that covers southern slope of the Siwalik and northern part of the Terai plane in Banke district, western Nepal. For the purpose, a field investigation was carried out and it indicated that Ward Nos. 5 and 6 of Gangapur Village Development Committee (VDC) were inundated in 2000 due to the blockade of the Singhya River by the deposition of flood-driven sediments brought by the Dhondra River. Consequently, about 305 families were completely displaced due to the inundation in and around their home and farmlands. The flood was resulted due to a localized torrential rainfall in Dhondra River's upper reaches in the Siwalik area. Following the year 2000, the Dhondra River started depositing sandy sediments in and around the confluence point with the Singhya River during each monsoon seasons. This paper briefly summarizes the causes of the disaster and its consequences to the displaced people, and surrounding geo-environment.Journal of Institute of Science and Technology, 2014, 19(1): 79-85

Estimation of Real-Time Flood Risk on Roads Based on Rainfall Calculated by the Revised Method of Missing Rainfall

Recently, flood damage by frequent localized downpours in cities is on the increase on account of abnormal climate phenomena and the growth of impermeable areas due to urbanization. This study suggests a method to estimate real-time flood risk on roads for drivers based on the accumulated rainfall. The amount of rainfall of a road link, which is an intensive type, is calculated by using the revised method of missing rainfall in meteorology, because the rainfall is not measured on roads directly. To process in real time with a computer, we use the inverse distance weighting (IDW) method, which is a suitable method in the computing system and is commonly used in relation to precipitation due to its simplicity. With real-time accumulated rainfall, the flooding history, rainfall range causing flooding from previous rainfall information and frequency probability of precipitation are used to determine the flood risk on roads. The result of simulation using the suggested algorithms shows the high concordance rate between actual flooded areas in the past and flooded areas derived from the simulation for the research region in Busan, Korea.

상관계수가중치법을 적용한 실시간 강우량 추정에 따른 도로 침수위험지수 개발 방법에 대한 연구

Recently, flood damage by frequent localized downpours in cities are on the increase on account of abnormal climate phenomena and growth of impermeable area by urbanization. In this study, we are focused on flooding on roads which is the basis of all means of transportation. To calculate real-time accumulated rainfall on a road link, we use the Coefficient of Correlation Weighting method (CCW) which is one of the revised methods of missing rainfall as we consider a road link as a unobserved rainfall site. CCW and real-time accumulated rainfall entered through the Internet are used to estimate the real-time rainfall on a road link. Together with the real-time accumulated rainfall, flooding history, rainfall range causing flooding of a road link and frequency probability precipitation for road design are used as factors to determine the Flood Risk Index on roads. We simulated two cases in the past, July, 7th, 2009 and July, 15th, 2012 in Busan. As a result, all of road links included in the actual flooded roads at that time got the high level of flood risk index.

다양한 GIS 플랫폼을 위한 고해상도 기상레이더 정보 시각화 기법

기상레이더의 발전과 더불어 국내외적으로 정밀한 기상레이더를 이용한 토네이도, 돌발홍수 등의 돌발적인 기상현상에 대한 기상데이터 분석 및 기상현상 예측 기술 등의 연구가 활발히 이루어지고 있다. 그에 반해 레이더 자료에 대한 시각화 및 표출 방법에 대한 관심이 증가하고 있지만, 현재까지의 기상과 관련한 각 국가 기관 등에서는 단순히 표출된 레이더영상을 GIS 데이터에 사상하여 해석하는 데 급급한 실정이다. 본 논문은 저고도에서 일어나는 국지성, 기습성 기상변화를 관측하고 효과적으로 대응하기 위해, 시 공간적고해상도를 갖는 기상레이더로부터 관측된 데이터 자료를 효과적으로 표현하기 위해 다양한 GIS 플랫폼에서 서비스할 수 있는 고해상도 기상관측 데이터의 표현 기법을 제안한다. 제안 기법에서는 기상레이더로부터 획득된 데이터를 이용하여 래스터 및 벡터 형태의 고해상도 자료구조로 변환하여 GIS 플랫폼 상에서 정확한 좌표위치와 고도에 직관적으로 인지할 수 있도록 하기 위한 방법을 제시하였다. 실험결과 GIS 플랫폼과 융합된 고해상도 기상데이터를 이용함으로써 돌발성 기후변화, 국지성 폭우, 토네이도 등의 정확한 위치와 고도 등의 정보를 포함하여 기상상황을 직관적으로 인지하고, 상세히 분석할 수 있는 것을 확인하였다. According to development of weather radar, researches about observation, analysis or forecast of weather phenomena such as tornado, flash-flood etc. were encouraged by reducing frequency interferences, transmission noises, attenuations of radar signal. In contrast, there is a growing interest in the visualization and expression methods for weather radar data but weather radar manufacturers or the organs of government for weather are just busy interpreting expressed weather images projected on GIS. We propose an effective high definition weather radar information visualization method able to apply various GIS platforms to observe and take actions against rapid local weather changes effectively. In this paper, first we change information acquired from weather radar to raster or vector type high definition data structures using specific algorithms. And then, we quadrate our processed raster/vector type weather data with various GIS platforms accurately to make observers can recognize and check weather situations over exact geographical positions and elevations intuitively. Experimental results verify that our method make observers can recognize and analyze weather changes, tornados, local downpours or flash floods accurately by analyzing high definition weather radar data combined with GIS platform including detailed target locations and elevations.

Geomorphological records of human activity reflected in fluvial sediments in the Carpathians and their foreland

Records of human activity in valleys of the Upper Vistula River catchment and the Upper Dniester River catchment in the area of the Eastern Carpathian Foreland are synchronic and date back to the Neolithic Period. They include alluvia and colluvia in small valleys, linked with local downpours, as well as changes in large valleys, where flooding is reflected in modifications to river channels and an acceleration in the deposition of overbank facies. Among these periods are phases determined climatically (5th–7th centuries AD) and those reflecting human activity (1st–3rd centuries AD), as well as phases recording the coincidence of both factors (middle Neolithic, 10th–11th centuries AD and the Little Ice Age). The most distinct changes leading to transformation in valley slopes and bottoms are linked with the coincidence of humid climatic phases and periods of increased human impact.

우리나라에 발생한 태풍의 시간 강우량 특성에 관한 연구

우리나라는 여름철의 큰 호우로 인해 주기적인 홍수피해가 발생하며, 이러한 호우의 원인은 태풍과 집중호우로 구분 할 수 있다 태풍은 열대 지방에서 발생하여 주기적으로 우리나라를 내습하여 극심한 강우와 강풍으로 인해 큰 피해를 발생시키고 있으며, 일반적으로 태풍에 의한 피해가 집중호우보다 큰 것으로 알려져 있다. 따라서 본 연구에서는 우리나라에 발생하는 강우 사상을 태풍과 집중호우로 구분하여 호우 원인별로 지속시간별 연 최대 강우량을 구축하였다. 따라서 발생 원인별로 구축된 시간강우자료의 통계분석을 통해 기본적인 특성을 파악하고 빈도해석을 통해 강우의 발생 원인별로 확률강우량을 산정하여 비교 분석하였다. 분석 결과에서 태풍에 의해 산정된 확률강우량은 지속시간과 재현기간이 커질수록 확률강우량의 증가가 전호우에 의한 확률강우량 보다 큰 지점이 있는 것으로 나타났다. The floods of Korea happens periodically during summer. The cause of heavy rain that provokes floods can be classified into typhoon and localized downpour. The typhoon happens in the tropical region. It causes one of the worst damage to Korea by extreme rainfall and strong wind. Usually, it is known that the flood damage by the typhoon is larger than that by the localized downpour. Therefore, this study classified rainfall events into typhoon events and localized downpour events based on the cause. Through statistical analyses of the rainfall data, this study investigated special quality of the rainfall during the time of typhoon. In analysis results, probability Precipitation calculated by the typhoon events were exposed bigger than that calculated by all rainfall events.

The response of slope and channel systems to various types of extreme rainfall: A comparison between the temperate zone and humid tropics

The mountain slopes and river channels of the temperate zone and of the humid tropics are modelled by various types of extreme rainfall. In the Flysch Carpathians the leading role is played by continuous rains causing floods and landslides, rainy seasons (wet years) mobilizing deep landslides and, to a smaller degree by local downpours. In the Darjeeling Himalaya with young relief and uplift tendency, the main influence on modelling the mountain slopes and river channels have been the extreme continuous rains separated by several decades of normal rainy season, playing the preparatory or relaxation role with simultaneous transformation of slopes and river channels. In both cases human impact has caused the acceleration of runoff and mobilization of sediment. The higher extremes of precipitation and steep slopes in the humid tropics are balanced (to some extent) in temperate zones by the lower infiltration rates and lower thresholds of mass mobility on the gentle slopes originated in the periglacial environment.

Rainfall in a ‘Cloudburst’

APART from an apocryphal record of 12.48 in. at Portree, Isle of Skye, on December 5, 1863, the largest amount of rain known to have been collected by a rain-gauge within a single day in the British Isles is 9.56 in. at Bruton, Somerset, on June 28, 1917. It has long been recognized, however, that the occurrence of far greater falls than this within much shorter periods than twenty-four hours must be invoked to account for the observed effects of those extremely heavy localized downpours which go by the name of ‘cloudbursts’. Raindrops cannot fall through air rising at a vertical velocity exceeding 8 m./s. Upward currents having a higher order of magnitude of ascent than that are often engendered during severe convectional storms, and thus it may happen that, under conditions of prolific condensation in a well-developed cumulo-nimbus cloud, large quantities of water are carried to an altitude far above their level of origin. If for any reason the convectional movement suddenly ceases or diminishes rapidly, as it may do when the storm system reaches an escarpment of hills, the water accumulated aloft descends more or less en masse. At such times the surface soil beneath may either be washed away to rock level or be deeply excavated and heaped as by a giant plough over areas ranging from a few thousand square yards to 100 acres or more in extent.