The catastrophic flood in Transbaikalia (Central Asia) in 1897: case study

The territory of Transbaikalia (Russia) is subject to occasional large-scale flooding. One of the most significant events in terms of scale and consequences is the historical flood that occurred in August 1897. In this article, we have tried to reconstruct the flood event. For this purpose, we have used all available historical sources (official statistical data, newspaper publications). The flood was observed almost simultaneously in two river basins (the Selenga and Shilka rivers). The main cause of the catastrophic flood was the abnormally intensive rainfall in the Hentey Mountains (Mongolia) and in Chikokonsky Ridge (southern Transbaikalia) in summer 1897. We have singled out four flood stages on the basis of the dates of flooding in different settlements. The flooding was accompanied by silting of considerable areas, and formation of new channels in local places. The flood in August 1897 in Transbaikalia, Russia, clearly demonstrated the vulnerability of both the environment and society to such catastrophic events.     

An integrated web framework for HAZUS-MH flood loss estimation analysis

Natural Hazards - Flood emergency management practices cover various aspects of flooding, such as demography, infrastructure, economy, transportation, and agriculture. Emergency managers and local...     

基于RS/GIS的城市财产保险洪灾损失评估研究

如何快速,有效地进行投保户洪涝灾害损失评估是保险行业急需解决的一个重要课题.从洪涝灾害的成灾机理出发,针对保险公司对具体受灾体理赔需求,提出了计算每个投保户洪灾损失率方法,建立基于遥感(RS)和地理信息系统(GIS)的城市财产保险洪涝灾害损失评估模型.建模时较全面地考虑了与投保物性质有关的承灾体易损度和与投保物所处环境有关的地基承载力等因素,并使用RS/GIS将其定量化提取.最后使用广东省深圳市洪灾数据进行模型检验.验证结果表明,模型对于各个投保户均能得到较好的精度.     

Developing an overall assessment map for flood hazard on large area watershed using multi-method approach: case study of Wadi Qena watershed,Egypt

Natural Hazards - Many parts of Upper Egypt as Sinai and Red Sea areas were hit by severe flash floods since 1976. Wadi Qena is considered one of the most watersheds that suffers from floods in Red...     

Engineering-geological model of the Segura River flood plain (SE Spain): a case study for engineering planning

This article presents a sedimentological and geotechnical study of the surficial sediments in the Segura River valley (SE Spain). We formulate an engineering-geological model consisting of four zones, each characterized by its geotechnical properties and by various geotechnical problems (namely low bearing capacity, significant ground settlement and liquefaction of sandy sediments). The model quantifies the geotechnical properties and potential problems in each zone. It serves as a useful tool for preliminary geotechnical investigations. The model also enables a better design of field surveys as well as optimal selection of geotechnical investigation techniques for future civil engineering works.     

Integrating risk perceptions into flood risk management: Trinidad case study

Natural Hazards - Flooding disasters are frequent and devastating events in Trinidad. Moderate amounts of precipitation burst riverbanks in central business districts, cities, and towns within the...     

Investigating the effects of land use change on flood hydrograph using HEC-HMS hydrologic model (case study: Ekbatan Dam)

Natural Hazards - Hydrological modeling academic studies have focused on the response to human-caused land use changes. The effects of land use change on flood degree in the catchment basin of...     

Seismic loss estimation tool as rapid survey for prioritizing buildings for disaster preparedness: case study to hospital buildings

Natural Hazards - Hospital buildings must be fully operational after the earthquake to protect the lives of patients as well as to provide emergency care and medical treatment to the victims....     

Nitrate and heavy metal pollution resulting from agricultural activity: a case study from Eskipazar (Karabuk,Turkey)

In most countries of the world, groundwater and surface water are at a serious risk of pollution due to chemicals used in agricultural activities. The present study examined whether such a risk exists in Eskipazar, Turkey and the surrounding area, which covers a surface area of 696 km². Nitrate pollution (NO₃) was observed in waters discharging from the Örencik Formation, consisting of loose conglomerate, sandstone, mudstone, siltstone, and claystone levels; from the Yörük member of the Örencik Formation consisting of limestone, from areas where the Örencik Formation and Yörük member are located together, and from alluvium. Agricultural is practiced in these areas, and the waters discharging from these formations are used as drinking water and for domestic purposes. In particular, periodically varying levels of pollutants, such as B, Pb, Hg, Se were detected in wells drilled in Örencik Formation featuring a high NO₃ concentration. The concentrations of S, Cr, Mn, Fe, Cu, Zn, Ga, Br, Sr, Y, I, Ba, and U in these waters are also slightly higher than other cold waters in the study area. In addition to the NO₃ pollution, high levels of Ca and SO₄ pollution was observed at a well drilled in alluvium. In addition, some trace element concentrations identified in the wells drilled in the Örencik Formation were higher than the average values at geothermal and/or mineral springs in the study area. The study area has an adequate sewage system and has no sources of pollution, such as mineralization, industrial center, waste disposal area, etc. Therefore, it is believed that the main causes of NO₃ and trace element pollution are fertilizers and pesticides used in agricultural activities. Water–rock interaction, usage period of fertilizers and pesticides, amount of precipitation, groundwater level, usage of elements by plants, mobility of elements, pH value of the environment, redox potential, adsorption/desorption, biochemical processes, etc. are thought to be the causes of the periodical variation of some trace element concentrations observed in these waters.     

Assessment of rice yield loss due to torrential rain: a case study of Yuhang County, Zhejiang Province, China

This study adopts a loss assessment and indemnity approach for rice crops at risk of flooding in Yuhang County, Zhejiang Province. Employing a hydrological model for simulating floods and a reduction model for predicting rice yield, the relationship between the rate of reduction in the rice yield and precipitation is discussed. We argue that the yield reduction rate can be assessed according to the amount of precipitation and designed a weather-based indemnity index for agricultural insurance purposes in Zhejiang Province. With geographic information system technology, the yield reduction rate and weather-based indemnity index were refined and found to effectively reduce the shortcomings of traditional agricultural insurance, i.e., moral hazard, large error in assessing disaster loss and high basis risk. The validity of the method was verified by the amount of rice lost due to No. 16 typhoon Krosa in 2007, and the results show that the proposed method can well simulate the reduction rate of rice yield according to precipitation data.     

Stream chloride concentrations as a function of land use: a comparison of an agricultural watershed to an urban agricultural watershed

The concentration of chloride (Cl^?) in streams in northern regions has increased as a result of applications of deicers. This study focused on quantifying the relationship between land use and stream Cl^? concentrations. The study area comprises two adjacent watersheds in central Illinois, with similar geology and climate but different land uses (agricultural and urban). GIS analysis delineated watershed land use and calculated road surface areas. Stream water samples were collected and analyzed for anionic composition. During the winter months, streams dominated with urban land use experienced a 20-fold increase in Cl^? concentrations (range between 36 and 1350 mg L^?1); Cl^? concentrations in agricultural dominated streams also increased, but the increase was smaller (3X) and concentrations remained low (between 11 and 58 mg L^?1). As road salts are not the sole source of Cl^? in a stream, Cl^? and bromide (Br^?) mass ratios (Cl/Br) and Cl^? and sodium (Na) molar ratios ([Cl]/[Na]) were used to identify potential sources of Cl^?. The ratios indicate urbanized watersheds were impacted by road salts; agricultural watersheds ratios indicate other anthropogenic sources. A nonlinear relationship between urban land use and stream Cl^? concentrations indicates urban land use as low as 23% results in elevated Cl^? concentrations (greater than 150 mg L^?1) in stream waters.     

Assessing flood hazard using flood marks and analytic hierarchy process approach: a case study for the 2013 flood event in Quang Nam,Vietnam

The production of flood hazard assessment maps is an important component of flood risk assessment. This study analyses flood hazard using flood mark data. The chosen case study is the 2013 flood event in Quang Nam, Vietnam. The impacts of this event included 17 deaths, 230 injuries, 91,739 flooded properties, 11,530 ha of submerged and damaged agricultural land, 85,080 animals killed and widespread damage to roads, canals, dykes and embankments. The flood mark data include flood depth and flood duration. Analytic hierarchy process method is used to assess the criteria and sub-criteria of the flood hazard. The weights of criteria and sub-criteria are generated based on the judgements of decision-makers using this method. This assessment is combined into a single map using weighted linear combination, integrated with GIS to produce a flood hazard map. Previous research has usually not considered flood duration in flood hazard assessment maps. This factor has a rather strong influence on the livelihood of local communities in Quang Nam, with most agricultural land within the floodplain. A more comprehensive flood hazard assessment mapping process, with the additional consideration of flood duration, can make a significant contribution to flood risk management activities in Vietnam.     

Geostatistical estimation of chemical contamination in stream sediments: The case study of Vale das Gatas mine (northern Portugal)

Based on an environmental geochemistry case study carried out in the neighbourhood of a W–Sn abandoned mine, the pollution in stream sediments was modelled through a Global Contamination Index. Such an index permits one to summarize the combination of deleterious elements in a single variable, obtained by the projection of samples onto the first axis of a PCASD (Principal Components Analysis of Standardized Data) applied to the entire n × p matrix containing the available concentrations of p = 16 elements in the set of n = 220 collected samples.In order to provide a sound basis for a coherent planning of the remediation process which will be put in operation in the affected area, it is necessary to balance the costs of reclaiming with the probabilities of exceeding the upper limits accepted for concentrations of environmentally harmful elements in sediments. Given these limits, they are back-transformed in the index values, providing a practical threshold between ‘clean’ and ‘contaminated’ samples. On the other hand, the minimum dimension of the cell to be reclaimed is restrained by the selected remediation process to be applied in the affected area. Hence, to meet the constraints of such a remediation process, it is required to estimate the probabilities of exceeding the index threshold in technologically meaningful sub-areas. For this end, the Indicator Block Kriging technique was applied, producing a series of maps where sub-areas to be reclaimed can be spotted for different probability levels. These maps, on which the decision making remediation agency can rely for its cost-benefit analysis, take into account both the spatial structure of ‘clean’ vs. ‘contaminated’ samples and the constraints of the reclaiming process.     

Modelling coincidence and dependence of flood hazard phenomena in a Probabilistic Flood Hazard Assessment (PFHA) framework: case study in Le Havre

Many coastal urban areas and many coastal facilities must be protected against pluvial and marine floods, as their location near the sea is necessary. As part of the development of a Probabilistic Flood Hazard Approach (PFHA), several flood phenomena have to be modelled at the same time (or with an offset time) to estimate the contribution of each one. Modelling the combination and the dependence of several flooding sources is a key issue in the context of a PFHA. As coastal zones in France are densely populated, marine flooding represents a natural hazard threatening the coastal populations and facilities in several areas along the shore. Indeed, marine flooding is the most important source of coastal lowlands inundations. It is mainly generated by storm action that makes sea level rise above the tide. Furthermore, when combined with rainfall, coastal flooding can be more consequent. While there are several approaches to analyse and characterize marine flooding hazard with either extreme sea levels or intense rainfall, only few studies combine these two phenomena in a PFHA framework. Thus this study aims to develop a method for the analysis of a combined action of rainfall and sea level. This analysis is performed on the city of Le Havre, a French urban city on the English Channel coast, as a case study. In this work, we have used deterministic materials for rainfall and sea level modelling and proposed a new approach for estimating the probabilities of flooding.

     

Application of analytical hierarchy process (AHP) for flood risk assessment: a case study in Malda district of West Bengal,India

A field experiment was conducted from 2 May 2010 to 1 May 2012 in the Gurbantunggut Desert, the second largest desert in China, to investigate saltation activity and its threshold velocity, and their relations with atmospheric and soil conditions. The results showed that saltation activity occurred more frequently during 08:00–20:00 Local Standard Time in spring and summer, with air temperatures between 20.0 and 29.0 °C, water vapor pressures between 0.6 and 0.9 kPa, soil temperatures between 25.0 and 30.0 °C, and a soil moisture lower than 0.04 m³/m³. At 2 m height, the saltation threshold velocity varied between 11.1 and 13.9 m/s, with a mean of 12.5 m/s. Threshold velocity showed clear seasonal variations in the following sequence: spring (11.7 m/s) < autumn (12.7 m/s) < summer (13.6 m/s). Affected by soil conditions, aeolian sand transport was weak, with an average annual aeolian sand that transported across a section (1.0 m × 2.0 m) of less than 6.0 kg.     

Probability-weighted hazard maps for comparing different flood risk management strategies: a case study

The study proposes an original methodology for producing probability-weighted hazard maps based on an ensemble of numerical simulations. These maps enable one to compare different strategies for flood risk management. The methodology was applied over a 270-km² flood-prone area close to the left levee system of a 28-km reach of the river Reno (Northern Central Italy). This reach is characterised by the presence of a weir that allows controlled flooding of a large flood-prone area during major events. The proposed probability-weighted hazard maps can be used to evaluate how a structural measure such as the mentioned weir alters the spatial variability of flood hazard in the study area. This article shows an application by constructing two different flood hazard maps: a first one which neglects the presence of the weir using a regular levee system instead, and a second one that reflects the actual geometry with the weir. Flood hazard maps were generated by combining the results of several inundation scenarios, simulated by coupling 1D- and 2D-hydrodynamic models.     

Alpine overdeepenings and paleo-ice flow changes: an integrated geophysical-sedimentological case study from Tyrol (Austria)

We present a study of the inneralpine basin of Hopfgarten focused on the analysis of basin fill in order to reveal its formation in relation to paleo-ice flow and tectonics. The study is based on geological mapping as well as seismic (reflection and refraction) and geoelectrical surveys. The oldest sequence in the basin, identified by seismic stratigraphy at 400 m below surface, consists of coarse grained sediments of supposedly Oligocene to Miocene age, which subsided along faults linked to the Inn fault. Three superimposed sequences, each displaying baselaps in contact with a subglacially formed unconformity and sigmoid foresets, show pleniglacial conditions followed by a glaciolacustrine environment. The uppermost of these three sequences lies on top of last glacial maximum till (LGM; Würmian Pleniglacial; MIS 2) and represents Termination I. The middle sequence is classified as Termination II following the Rissian Pleniglacial (MIS 6). The oldest glacial sequence cannot be constrained chronostratigraphically but might correlate with Termination V following the major glaciation of MIS 12. Limited glacial erosion during the LGM occurred only during the ice build-up phase. Further overdeepening was impeded due to topographic barrier and mutual blockades of glaciers within this highly dissected landscape. The occurrence and relative timing of the impediment was controlled by the onset of transfluences and thus by the altitude of coles. The higher amount of overdeepening during older glacial periods is explained by longer phases of free ice advance in the ice build up phase due to higher transfluences routes at that time. Thus, the preservation of older Pleistocene sequences within the basin may be the result of the lowering of watersheds from one glaciation to the next. Our model of an inverse relationship between glacial shaping of the surface and the subsurface may apply to similar Alpine landscapes as well.