Flood Scale Research Articles

혁명 원조에서 특구 건설로 ―시아누크빌을 통해 본 아시아 냉전의 역설

Sihanoukville, a nucleus city of the “21st Maritime Silkroad” for the “Belt and Road Initiative”, exemplifies the strong cooperation between China and Cambodia. The formidable scale of Chinese capital flooding into Sihanoukville is reminiscent of the Cold War, as Sihanoukville was the principal port where Chinese aid for the Khmer Rouge arrived in the 1970s. The fact that China assisted the regime that carried out appalling genocide within its own borders remains problematic. Even more troublesome, the two countries have promoted a full-fledged partnership lacking a thorough examination of and reflection on the gruesome past. Notably, China’s aid for the Khmer Rouge echoed Mao’s “Three Worlds Theory” that highlighted Third World solidarity against imperial hegemony. The name of Sihanouk, once a symbol of the shared legacy of the Non-Alignment Movement between China and Cambodia, now returns as the “Sihanoukville Special Economic Zone” run by the Hun Sen regime that underwent the bloody refraction of the “Killing Fields”, which obliges us to summon and decipher the Asian Cold War map buried underneath the rosy blueprint of the “Maritime Silkroad”.

Effects of pore structure on surfactant/polymer flooding-based enhanced oil recovery in conglomerate reservoirs

To understand the displacement characteristics and remaining oil displacement process by the surfactant/polymer (SP) flooding in cores with different pore structures, the effects of pore structure on the enhanced oil recovery of SP flooding was investigated at the pore, core and field scales through conducting experiments on natural core samples with three typical types of pore structures. First, the in-situ nuclear magnetic resonance core flooding test was carried out to capture the remaining oil variation features in the water flooding and SP flooding through these three types of cores. Subsequently, at the core scale, displacement characteristics and performances of water flooding and SP flooding in these three types of cores were evaluated based on the full-size core flooding tests. Finally, at the field scale, production characteristics of SP flooding in the bimodal sandstone reservoir and multimodal conglomerate reservoir were compared using the actual field production data. The results show: as the pore structure gets more and more complex, the water flooding performance gets poorer, but the incremental recovery factor by SP flooding gets higher; the SP flooding can enhance the producing degree of oil in 1–3 μm pores in the unimodal and bimodal core samples, while it produces largely oil in medium and large pores more than 3 μm in pore radius in the multimodal core sample. The core flooding test using full-size core sample demonstrates that the injection of SP solution can significantly raise up the displacement pressure of the multimodal core sample, and greatly enhance recovery factor by emulsifying the remaining oil and enlarging swept volume. Compared with the sandstone reservoir, the multimodal conglomerate reservoir is more prone to channeling. With proper profile control treatments to efficiently enlarge the microscopic and macroscopic swept volumes, SP flooding in the conglomerate reservoir can contribute to lower water cuts and longer effective durations.

Ice jam flood risks on the rivers of the Baikal Basin

The article presents the results of analysis and assessment of risks related to ice jams on the rivers of the Baikal Lake Basin. It also proposes the recommendations for mitigation and rational development of coastal areas. Data on catastrophic ice jam floods for more than 100 years is presented, the factors of their formation and mechanism of their movement are considered. On the basis of official statistics from expedition surveys, potentially dangerous jamming areas have been identified, and the repeatability and extent of floods have been calculated. With the help of ArcGIS package the scale of possible flooding was determined, which allowed to reveal the list of economic objects within the damage area. Specific indicators have been used to calculate the expected damage to territories, facilities and population from the flood hazard. Analysis and assessment of economic risk from the floods on the Selenga River are given. Measures to minimize risks of negative impact of floods are proposed.

Examining Observed Rainfall, Soil Moisture, and River Network Variabilities on Peak Flow Scaling of Rainfall‐Runoff Events with Implications on Regionalization of Peak Flow Quantiles

AbstractThe scaling of peak flows associated with a probability of exceedance (Qp) or a specific rainfall‐runoff event (QR) with respect to drainage area (A) is known as flood scaling and it has been widely used in peak flow regionalization. The attenuation and aggregation processes within the hillslopes and river network in a rainfall‐runoff event, provide a framework to test the scaling of QR. Although scaling of Qp has been reported in empirical studies, its physical interpretation is compromised, since Qp at each site could come from different rainfall‐runoff events. To address this problem, the authors explored the effect of actual variabilities of rainfall and soil moisture fields, and the effect of the river network structure, in the scaling of peak flows of 85 rainfall‐runoff events and peak flow quantiles that were observed in the Iowa River Basin at 43 streamflow gauges. The authors established empirical evidence that addresses two questions: (1) What does control the performance of the scaling of observed QR? (2) What is the interplay between sampling errors and the selection of explanatory variables in the construction of regional regression models for QR and Qp? For the first question, the authors found that the slope magnitude in the scaling of the rainfall intensity fields with respect to A controls the scaling' performance of QR. Regarding the second question, the authors demonstrate that the inclusion of river network descriptors should improve the regional equations to estimate peak flow quantiles unless stream gauging sampling errors affect the analysis.

Urban Flood Scaling Using Hydrologic and Hydraulic Models with Inception for Early Warning

Urban Flood Scaling Using Hydrologic and Hydraulic Models with Inception for Early Warning

Analysis of flood peak scaling in mesoscale non-nested basin

Abstract The study of flood scaling is an important means to solve the problem of flood prediction in ungauged and poorly gauged basins. With the impact of climate change and human activities, the mechanism and process of floods are constantly changing. However, in many areas, there are only simple scaling results that can be used to guide daily work. Taking the Daqinghe River basin as an example, a fixed flood scaling exponent determined in 1974 (before the change point of 1979) is still used all over the basin, which is apparently no longer appropriate. Therefore, in this paper, we aim to explore: (1) the scale relationship between the peak flows and the basin area under changing environments; (2) the validation of the scale invariance theory; (3) the physical relationship between the event-based scaling theory and the annual flood quantile-based scaling theory in the mesoscale non-nested and partly nested basins; and (4) the modification of the existing uniform flood scaling exponent in the study area. To achieve these objectives, eight simultaneous observed flood events in seven non-nested and partly nested mesoscale sub-basins of the Daqinghe River basin were selected to analyze the flood scaling theory. The results showed that there was a scaling relationship between the flood peaks and watershed area for the flood events, and the scale invariance theory was also supported herein. To analyze the effect of the environmental conditions on flood scaling in the Daqinghe River basin, the flood events were reconstructed after the change point (the year 1979). It was found that the flood scaling exponents of the reconstructed flood events are larger than those of the observed events after the change point. The flood scaling exponent changed with flood events, varying from 0.65 to 1.26 when considering the basin area as the independent variable, and decreasing with a minimum of 0.36 when taking the rainfall characteristics into consideration. It was also found that the mean of the event-based scaling exponents is larger than the annual flood quantile-based scaling exponents.

Study on hazard assessment of mountainous flood in riverside country- a case study in Xinshan, Hubei, China

Mountainous riverside countries have already become the weaknesses of flood disaster control infrastructure in China, so flood calculation based on hydraulics models plays a key role in urban flood monitoring, warning and prevention. In order to validate the availability of a proposed one-dimension hydraulics flood model, the paper selects Xinshan County, Hubei Province, China as a typical study area. Considering the river distribution system and flood source analysis in Xinshan County, its flood scale and calculation scheme are then proposed. On the basis of HEC-RAS software, the one-dimension hydraulics model is constructed, which is applied to calculating the river flood evolutions and diffusing embankment processes with the designed flood probability of 0.01, 0.02, 0.05, 0.10, and 0.20 respectively. The comprehensive flood process information (such as diffuse area, diffuse duration and water depth) is also retrieved, which is used to calculate flood hazard and map flood hazard distribution. Calculation results reveal that the main parts of Gufu River basically meet the flood prevention standard of 0.05 (probability) in Xinshan County, while the intersection of Gufu River and Wangjia River has lower flood prevention ability than its flood prevention standard, which are basically consistent with local reality and flood estimation. Moreover, this fact proves that the proposed one-dimension hydraulics flood model is effective.

Flood scaling under nonstationarity in Daqinghe River basin, China

Flood scaling issue is usually studied under stationary conditions. However, in recent decades, climate change and anthropogenic activities have changed hydrological processes, and stationary assumption has been questioned. To test the flood scaling invariance (simple scaling or multiscaling) and analyze the influence of environmental change on flood scaling parameter, in this study, eight mesoscale sub-watersheds in Daqinghe River basin were selected as the study area, and the trend and change point of annual maximum flood peak (AMFP) series were detected, respectively. All the AMFP series had downward trend, and the change point was around 1979. Therefore, the AMFP series are nonstationary. To analyze the flood scaling issue in the Daqinghe River basin, the AMFP series were reconstructed under the environmental conditions before and after the change point, respectively. Then, flood quantiles were calculated using the reconstructed stationary series. We also used GAMLSS (Generalized Additive Model in Location, Scale and Shape) to calculate flood quantiles based on the observed nonstationary AMFP series. According to the flood quantiles calculated by the above methods, the relationship of the drainage areas of the sub-watersheds and the flood quantiles was fitted with power function. Flood quantiles of the reconstructed stationary and observed nonstationary series showed obvious flood multiscaling. The increase in rainfall depth causes the increase in flood scaling exponents with the increase in return period, and different change ratios of land use before and after change point resulted in the flood scaling exponents of reconstructed series before 1979 were smaller than those after the change point at same return period.

Urban flood susceptibility analysis using a GIS-based multi-criteria analysis framework

Pluvial flooding is a common type of natural hazard caused by rainfall events with high intensity and short duration, which may lead to substantial property damages, transportation interruptions, and casualties. Modern cities are susceptible to pluvial flooding due to dense population and advanced economic development. To facilitate the development of better flood control and risk mitigation strategies, this study presents a new quantitative flood susceptibility analysis framework to estimate the potential flood extents and scale. The framework is based on the multi-criteria decision-making methods within a platform of the geographic information system (GIS). A composite urban flood risk index (FRI) is derived from various flood conditioning factors. The FRI consists of flood vulnerability index, hazard factors, and resilience capacity indicators. The flood-susceptible map is generated using the GIS spatial analysis tools and the analytic hierarchy process method. Zhengzhou city, China, is selected as the case study area. The result map shows that the highly susceptible areas are mainly located in Jinshui District, accounting for 64% of the total area of the risk zone. To further validate this framework, a flood inventory map is produced by mapping 74 test locations identified through survey data in this area, followed by plotting a receiver operating characteristic (ROC) curve. The ROC shows an area under the curve of 74.27%, which validates the proposed framework. Compared with other methods, the proposed framework is particularly suitable for application in data-scarce cases.

Influence of inflow discharge and bed erodibility on outburst flood of landslide dam

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.

A new method to estimate the total drainage area of soil-water conservation projects on the upstream of Wangkuai watershed in Daqinghe River basin, China

Abstract A new approach was presented to calculate the total drainage area (TDA) of many small hydraulic engineering projects on the upstream Wangkuai reservoir watershed considering flood scaling. By establishing the correlation of flood peak between Wangkuai and Fuping hydrological station, the event-based flood scaling in Wangkuai reservoir watershed was analyzed and the scaling exponent θ was 0.5688. Relations between flood peak and maximum 3 h rainfall amount were fitted for the undisturbed and disturbed periods to analyze the effect of small reservoirs on the flood peak. The average change ratio of flood peak was 15.05% and the TDA of small hydraulic structures was 939.88 km2.

Transient early diagenetic processes in Rhône prodelta sediments revealed in contrasting flood events

Floods carry sediments to river deltas and the coastal zone, but little is known about the geochemical evolution of this particulate material deposited over a short period of time. Here, we studied two recent contrasting flood deposits in the Rhône River prodelta area (northwestern Mediterranean Sea). We monitored the porewater and solid-phase chemistry over periods ranging from a few days to 6 months after deposition. Non-steady state diagenetic processes associated with episodic deposition promote a wide spectrum of transient redox conditions in the shallow prodelta region of the Rhône. Specific attributes of diagenetic responses depend on the sources of flood material and scale (thickness) of deposition.The first flood unit of 20–30 cm was composed of light gray mud, poor in organic carbon and rich in reactive manganese oxides. The short-term responses of early diagenetic processes contrasted with a rapid consumption of O2 and NO3- over a few hours just after the deposition event, accompanied by a slower build-up of Mn2+ concentration, and a lagged response in Fe2+ concentration over a few days or weeks. This difference was due to the redox capacity of the sediment, evolving from oxidized, during the flood layer deposition, to more reducing conditions, after a few days or weeks, allowing Fe2+ to build up and remain in solution. Sulfate reduction may have started within a few days within the flood deposit and was greatly enhanced just below the former redox front due to a fresh input of organic matter (OM). This large production of H2S probably led to the precipitation of sulfide minerals in close vicinity to the former redox front, limiting the accumulation of Fe2+ and H2S. The unit was sampled repeatedly three times during the six months following the flood event, and showed that manganese oxides were reduced at a rate of 1.8 mmol m−2 d−1, whereas the iron oxide concentration did not vary substantially.The second flood unit was composed of darker sediment, rich in organic carbon and reactive manganese oxides. The first step of OM degradation was enhanced within this dark deposit with a high release of dissolved organic carbon (DOC). A peak in Mn2+ concentration was also measured in association with the peak in reactive manganese oxides, also showing the rapid reduction of manganese after an input of fresh reactive oxides, and its potential increased release into the water column. Finally, a peak in nitrate concentration appeared in the sediment porewater within this anoxic organic/manganese-rich layer, likely resulting from the anaerobic oxidation of ammonium by manganese oxides.

Sensitivity Analysis of the Surface Runoff Coefficient of HiPIMS in Simulating Flood Processes in a Large Basin

To simulate flood processes at the basin level, the GPU-based High-Performance Integrated Hydrodynamic Modelling System (HiPIMS) is gaining interest as computational capability increases. However, the difficulty of coping with rainfall input to HiPIMS reduces the possibility of acquiring a satisfactory simulation accuracy. The objective of this study is to test the sensitivity of the surface runoff coefficient in the HiPIMS source term in the Misai basin with an area of 797 km2 in south China. To achieve this, the basin was divided into 909,824 grid cells, to each of which a Manning coefficient was assigned based on its land use type interpreted from remote sensing data. A sensitivity analysis was conducted for three typical flood processes under four types of surface runoff coefficients, assumed a priori, upon three error functions. The results demonstrate the crucial role of the surface runoff coefficient in achieving better simulation accuracy and reveal that this coefficient varies with flood scale and is unevenly distributed over the basin.

Spatial-temporal variations of natural disasters during the Ming & Qing Dynasties (1368–1912AD) in Chaohu Lake Basin, East China

The Ming & Qing Dynasties experienced the Little Ice Age (LIA), a most abnormal climate event in nearly 2000 years’ of Chinese history, in which various natural disasters took place frequently. On the basis of systematically collecting and collating historical documents related to natural disasters, and by adopting mathematical statistics, geological succession, correlation and other methods, analysis and comparison were made on the spatial-temporal differentiation of disasters and correlation between various major natural disasters taking place in the Chaohu Lake Basin during the Ming & Qing Dynasties (1368–1912AD). The results show that 753 major disasters took place in the Chaohu Lake Basin during the Ming & Qing Dynasties. Among these, floods and droughts accounted for the largest percentage, while other disasters occurred occasionally. The Little Ice Age (1550–1850AD) was the period with a high incidence of natural disasters, and in the years from 1701 to 1750 natural disasters took place most frequently; between 1651–1700AD there was a declining period of flood frequency, though there were historically high occurrences of droughts and earthquakes. There were more floods than droughts suffered by Hefei, Shucheng, Chaohu, Wuwei and Hexian, while more droughts than floods suffered by Hanshan and Lujiang. Earthquakes in the basin mainly occurred in Chaohu, Shucheng, Hexian and Hefei, which are all near the Tan-Lu Fracture. The opposite is true for changes in the time scale of floods and droughts; this was probably caused by intra-seasonal oscillations of the subtropical high. The correlation between hails and wind disasters is significant, while other disasters are weakly correlated. There exists a certain association between spatial differentiation of occurrence frequency of natural disasters and landforms in the basin. The disaster-prone environment features landforms including plains, hills, low mountains, and these have a significant impact on the spatial distribution of five major natural disasters in the Chaohu Lake Basin.

Analysis of impacts of polders on flood processes in Qinhuai River Basin, China, using the HEC-RAS model

Abstract Flood control with polders is prevalent in East China. Their impact on flood processes is critically important for flood control, but has not been well documented. The Qinhuai River Basin was selected as the study area. A Hydrologic Engineering Center – River Analysis System (HEC-RAS) hydraulic model was developed to simulate and predict storm flood processes and the associated impact of polders. The study shows that the HEC-RAS model is capable of simulating the impact of polders on flood processes in the Qinhuai River Basin. The polders increased the water level outside of the polders. The polders in upstream watersheds have a greater impact on the water level than polders close to basin outlets when individually distributed. The maximum water level at Dongshan section shows an increasing trend for different sized flood with the increasing number of polders in the basin, and a linear increasing trend associated with urbanization. The smaller the flood scale is, the greater the maximum water level changes.

Numerical Analysis of Effect of Bridge on Inundation Flow in the Kagetsu River on July 2017

The flood behavior often affected by bridges, due to the accumulation of debris around bridge piers or the reduction of flow late. On the other hand, the effect of a bridge on a flood was not well studied. In this research, the simulation of the flood in the Kagetsu River in July, 2017 was conducted using 2D flow model in order to evaluate the effect of a bridge on the flood capacity, water level and flood scale. The flood behavior in residential area was also simulated. As a result, the bridge increased inundation velocity and inundation area, especially in the area around the bridge. When water level exceeds the height of bridge, flow discharge was limited by the area of bridge opening, which caused flow capacity decreasing. The stream force of flood was relatively strong at the area around the bridge.

The influence of water disposal method on the property of chemical oil-displacement agent--taking Guan 109-1 area of Dagang oilfield as example

Abstract Aiming at the actual demand of Guan 109-1 block in Dagang oilfield, by means of instrumental analysis, chemical analysis, modern physical simulation, viewing polymer viscosity and seepage characteristic as evaluation index, the experimental research on the influence of water disposal method on the property of chemical oil-displacement agent was carried out. Results showed that through adding scaling agent, scale was formed because of the reaction between scaling agent and Ca2+, Mg2+ in the flooding water, which could enhance the viscosity of polymer solution. Through comparing the resistance factor and residual resistance factor of polymer solution which was respectively prepared with flooding water, softened water and scale, the resistance factor and residual resistance factor of polymer solution with scale was the largest, that of polymer solution prepared with softened water was second and that of polymer solution prepared with flooding water came last. Furthermore, scaling agent weakened the gelling effect between cross-linking agent Cr3+ and polymer molecule chains. The earlier the cross-linking agent Cr3+ was added, the larger the polymer viscosity, resistance factor and residual resistance factor of Cr3+ polymer were.

Livelihood resilience in the face of recurring floods: an empirical evidence from Northwest Ethiopia

BackgroundThe recent trend of increasing incidents of floods in Ethiopia is disrupting the livelihoods of a significant proportion of the country’s population. This study assesses the factors that shape the resilience and the vulnerability of rural households in the face of recurring floods by taking the case of Dembia district of Northwest Ethiopia as one of the flood-prone areas in the country.ResultsThe data for the study were collected through a survey of 284 households, two focus group discussions, and 12 key informant interviews. Principal Component Analysis and simple linear regression were used for the analysis. The former served both for data reduction and identification of the dominant factors that explain resilience to recurring flood hazards while the latter was used to check the relationship between resilience and vulnerability. Findings indicate that access and use of livelihood resources such as size of farmlands, availability of farm oxen, credit as well as ability to draw help from social networks were found to be the most important factors that determine the resilience of households to floods. Similarly, the coping strategies employed by households were found to be constrained mainly by the scale and impact of the recent floods and lack or shortage of basic infrastructural and social facilities.ConclusionsThe results confirmed that most of the traditional coping strategies employed by households failed to effectively help households offset the impacts of flooding. Given the livelihood context of smallholder farming system in the studied area, context specific institutional interventions such as the integrated use of both safety nets and cargo nets may help communities to overcome livelihood predicaments associated with the recurrent flood disasters. This implies that policy should focus more on addressing the factors that expose people to flood disasters and shape their resilience, rather than focusing on short-term emergency responses which seems to be the norm in much of the flood affected areas in the country.

The FLASH Project: Improving the Tools for Flash Flood Monitoring and Prediction across the United States

Abstract This study introduces the Flooded Locations and Simulated Hydrographs (FLASH) project. FLASH is the first system to generate a suite of hydrometeorological products at flash flood scale in real-time across the conterminous United States, including rainfall average recurrence intervals, ratios of rainfall to flash flood guidance, and distributed hydrologic model–based discharge forecasts. The key aspects of the system are 1) precipitation forcing from the National Severe Storms Laboratory (NSSL)’s Multi-Radar Multi-Sensor (MRMS) system, 2) a computationally efficient distributed hydrologic modeling framework with sufficient representation of physical processes for flood prediction, 3) capability to provide forecasts at all grid points covered by radars without the requirement of model calibration, and 4) an open-access development platform, product display, and verification system for testing new ideas in a real-time demonstration environment and for fostering collaborations. This study assesses the FLASH system’s ability to accurately simulate unit peak discharges over a 7-yr period in 1,643 unregulated gauged basins. The evaluation indicates that FLASH’s unit peak discharges had a linear and rank correlation of 0.64 and 0.79, respectively, and that the timing of the peak discharges has errors less than 2 h. The critical success index with FLASH was 0.38 for flood events that exceeded action stage. FLASH performance is demonstrated and evaluated for case studies, including the 2013 deadly flash flood case in Oklahoma City, Oklahoma, and the 2015 event in Houston, Texas—both of which occurred on Memorial Day weekends.

Adsorbed Organic Material and Its Control on Wettability

Laboratory core flood and field scale tests have demonstrated that 5–40% more oil can be released from sandstone reservoirs by injecting low salinity water, rather than high salinity fluids, such as seawater or formation water. The effect has been explained by a change in wettability of the minerals that form the pore surfaces, as a result of the decrease in divalent cation concentration. We have previously demonstrated that, even for solvent cleaned core samples, mineral surfaces retain a significant quantity of carbon containing material and this affects wettability and response to changed salinity. Here we quantified the response of sandstone core plug material in its preserved state (i.e., after storage in kerosene) and after the same core plug material was treated with ethanol and ozone to remove adsorbed organic compounds. We used the chemical force microscopy (CFM) mode of atomic force microscopy (AFM) to directly measure the adhesion force for two types of molecules on pore surfaces of individual sand grains that were plucked from an oil reservoir core plug. We functionalized AFM tips with alkane or carboxylate, so they resembled tiny oil droplets and measured adhesion to the sand grain surfaces in artificial seawater (ASW; 35,600 ppm) and in ASW diluted to ∼1,500 ppm (ASW-low). Both before and after the ethanol/ozone treatment, and for both the alkane and the carboxylate functionalized tips, the adhesion was lower in ASW diluted to ∼1,500 ppm than in ASW. For both alkane and carboxylate, the difference in adhesion between ASW and ASW-low was higher before the ethanol/ozone treatment. We attribute this change in response to the salinity dependent force caused mainly by the electric double layer (EDL) at the sand grain surfaces. We interpret the higher adhesion difference, before a very thorough ethanol/ozone treatment, to be a result of the loss of the organic material that was originally adsorbed on these surfaces, which adds to the charge density and thereby to the salinity dependent EDL force. Investigating the same area on the same pore surface, before and after removal of the organic material, demonstrates without doubt that it is organic material that causes the low salinity response, not the underlying mineral surface.