Maximum Water Level Research Articles

Population dynamics of Capitella aff. teleta (Polychaeta, Capitellidae) in Gamo Lagoon, northeastern Japan, during a series of restoration works following the 2011 Great East Japan Earthquake and tsunami

The population dynamics of the capitellid polychaete Capitella aff. teleta were studied in Gamo Lagoon, located in northeast Japan, for the subsequent 2 years from 2016, when a series of restoration works was conducted following the 2011 Great East Japan Earthquake and tsunami. Capitella aff. teleta was found to be widely distributed from the estuary side, where the levee was located, to the innermost part but was more abundant in the innermost part, which is rich in organic matter. In the lagoon, the daily maximum water level dropped from 2017 to 2018 during the reconstruction of a flow-conducting levee, which blocked water flow and isolated the inner part of the lagoon. Although the density decreased drastically for approximately 11 months under diurnal hypoxia and strongly reducing conditions, small-sized new recruits were observed and the population recovered quickly after the daily maximum water level increased. In Gamo Lagoon, C. aff. teleta inhabiting the innermost part and estuary side of the lagoon contributed to maintaining the population by dispersing planktonic larvae between them. Thus, the maximum water level had a significant effect on the maintenance of the C. aff. teleta population in the lagoon, and sufficiently high water levels enable the dispersion of planktonic larvae to help recover the population quickly, suggesting that it is important to keep the water area connected.

Quantifying the role of openings in the impact of a dam-break-induced flood on a porous building

It becomes necessary to identify the role of openings in the impact of floods on porous buildings to better set up effective strategies for people security within buildings and implement engineering measures for building safety. In this study, a 3D numerical model is applied to identify the role of openings in the impact of a dam-break-induced flood on a porous building under different opening configurations, including different porosities of the front and back walls, various porosities of the back wall and various positions and sizes of the side window. (i) An increasing size of the front and back doors leads to a reduced maximum water level upstream of the building and a reduced area of the wake zone behind the back wall; the maximum longitudinal impact force significantly decays with the porosity in terms of a quadratic function form. (ii) A variation in the size of the back door plays a role in controlling the outflow discharge of floodwater from the building; however, it yields no clear difference in the resultant longitudinal impact force. (iii) In the short-term, the presence of the side window plays no clear role in affecting the flow field around the building; however, in the moderate timeframe, there is a clear lateral exchange: the positions of the side windows play a clear role, whereas the size of the lower side window seems to be less important; the existence of the side window greatly decreases the lateral impact force, especially for the lower sidewall. These results are of value to better understand the physical mechanism of the impact process on a porous building for implementing tailored measures for people security and structural safety.

The role of modeling scheme and model input factors uncertainty in the analysis and mitigation of backwater induced urban flood-risk

Recent flood-related disasters, which affect many areas of the world due to a combination of climate change and increasing urbanization, have prompted researchers to study catastrophic phenomena for which large-scale mitigation strategies are needed. However, lower impact flood events occur more frequently, and although these floods are relatively less destructive, they can be effectively mitigated with local protection measures. This work focuses on understanding the factors that influence the reliable modeling of these lower impact - and less studied - flood events. We propose a procedure that combines the use of a simple but effective numerical model of the last segment of Ticino River with a Global Sensitivity Analysis for an in-depth evaluation of: i) the backwater-induced flooding of an urban area in the historical city of Pavia (Northern Italy) and ii) the potential flood damage due to such events. A 1D, unsteady HEC-RAS model (termed the 3R Model) was set up and validated against historical floods. Then, the 3R Model output was compared with a hybrid 1D/2D model of the same area. Both model schemes provide reliable results and similar predictions of the flood depth and its spatial extent. The 3R Model is demonstrated to be a successful modeling approach, providing a computational cost that is always less than one-tenth of the cost of the hybrid 1D/2D for the simulated floods. The Morris method of sensitivity analysis was performed to identify the most influential factors affecting the results of the 3R Model to help inform local policies aimed at flood risk reduction. The Morris results highlight that the maximum water level of the Po river has a dominant role in determining the flood magnitude for the whole area, with an influence at the control points in the floodplain that is more than triple that of the Ticino maximum flow rate. A Damage Index quantifying the housing loss due to the urban flood extent was introduced and analyzed using the Morris method. The results show that the predicted flood damage is strongly influenced by the uncertainty in the roughness coefficient of the floodplains. The contemporaneity of the floods on the Ticino and Po Rivers was also influential, playing a key role in flood severity within the urban area. A 5-hour delay of the Ticino flood wave (maximum flow rate of 2000 m3/s) with respect to that of the Po River (maximum stage level of 59.8 m a.s.l.) reduces the water level in the flooded area by 8 cm. These results will help the development of flood risk reduction strategies.

Aplikasi Program HEC-RAS 5.0.7 untuk Pemodelan Banjir di Sub-sub DAS Martapura Kabupaten Banjar

Rainfall data is one of cause factor for flooding in some areas in Indonesia. An extreme rainfall event occurred in the end of 2020 until early 2021 have resulted a severe flooding in West Martapura District, Banjar Regency, South Kalimantan Province. As a tributary to Barito River, Martapura River experienced high water level that gave negative impact to the surrounding areas. HEC-RAS (Hydrologic Engineering Center's River Analysis System) 5.0.7 software combined with ArcGIS 10.8 were applied to model flooding spatially. Mononobe method was used to calculate rainfall intensity for 5-year, 50-year, and 100-year return periods. From the results of the flood modeling, the maximum flood water level elevation was obtained as deep as 3.8 m (5-year return period), 5.2 m (50-year return period), and 9.6 m (100-year return period) with a maximum flood discharge of 34.84 m3/s (5-year return period), 81.68 m3/s (50-year return period), and 142.64 m3/s (100-year return period), respectively.

Assessment of the Effects of Leachates on Groundwater Quality in Igwuruta, Ikwerre Local Government Area of Rivers State, Nigeria

This study focuses on the assessment of the effects of leachates on groundwater quality in Igwuruta, Ikwerre Local Government Area of Rivers State, Nigeria. Ten (10) water samples comprising of five (5) leachate and five (5) borehole water samples were collected and analyzed as well as measurement of static water level (SWL). The sampling was done by using standard techniques. These analyzed parameters were compared with the World Health Organization guidelines for drinking water quality. The analyzed parameters were below the permissible limits of water quality guidelines, except for the leachate samples that were analyzed for chloride which concentrations ranges from 2850 - 3100mg/l below the 250mg/l and sulphate concentration ranges from 170.5 - 289.2mg/l below the 250mg/l. Iron concentration ranges from 3.6 - 4.7 mg/l above the permissible limits of 0.3 mg/l. The high concentrations of iron in the leachate is probably due to the dumping of metal scraps at the dumpsites, which corrodes, leaches out and infiltrates to contaminate the groundwater. The hydrochemical facies of the leachate samples corresponds to the region of saline water type (Na+ -K- Cl-- SO4 2-) as a result of the high concentration of Sodium. The static water level (SWL) of the area ranges from 2.5m to 8.7m. The water level data was determined in different boreholes in the study area. The maximum static water level in the study area occurs around BH4, at 8.4m below ground surface followed by BH2, with 6.2m below the ground surface. Values of static water level decreased in BH5 at 5.7m, BH1, 3.4m and BH3 at 2.5m. These values show shallow water levels which makes the aquifer in the area vulnerable to contamination from leachate and solid wastes. It is recommended that proper waste management practice(s) should be carried out in order to maintain a high level of environmental protection and sustainability as low as reasonably practicable.

Evaluation of the hydraulic behavior of the composite hydraulic structure considering a bed flume with special obstacle

The experimental simulation between the composite hydraulic structure and the found obstacles in the downstream region is a challenging process due to the energy losses and kinematic dissipation. The current work focuses on a comparative analysis of free flow conditions that exist without obstacles and submerged flow conditions that occur due to obstacles. It indicates the evaluation of hydraulic variables and geometrical variables of composite hydraulic structure for both flow conditions. In addition, it includes an investigation of the interaction among these variables. The hydraulic variables include actual discharge, flow velocity, flow cross-sectional area that crosses the gate, downstream water depth, discharge coefficient, Reynolds number and, Froude number, while the vertical distance between the weir and gate represents the geometry variable. The interference between the weir discharge and gate discharge plays a significant role in the result fluctuation and variation for both flow conditions, while the form and size of the obstacles only have a major effect on the submerged flow. For both flow conditions, the water depth is investigated; there would be a drastic increase in water depth by using obstacles in the downstream area as compared with not using the obstacles. This study adopts different obstacles in shape and size, therefore, the variation of maximum and minimum water levels related to the location will occur.

A Demonstration of a Simple Methodology of Flood Prediction for a Coastal City Under Threat of Sea Level Rise: The Case of Norfolk, VA, USA

AbstractMany coastal cities around the world are at risk of increased flooding due to sea level rise (SLR), so here a simple flood prediction method is demonstrated for one city at risk, Norfolk, VA, on the U.S. East Coast. The probability of future flooding is estimated by extending observed hourly water level for 1927–2021 into hourly estimates until 2100. Unlike most other flood prediction methods, the approach here does not use any predetermined probability distribution function of extreme events, and instead a random sampling of past data represents tides and storm surges. The probability of flooding for 3 different flood levels and 3 different SLR projections are calculated, and the results are consistent with more sophisticated methods. Under intermediate‐low SLR projection an empirical formula is found to estimate the lower bound of flooding time, showing that water level that exceeds the high tide (Mean Higher High Water, MHHW) occurred ∼0.3% of the time in the 1960s, increased to ∼6% in 2021, and projected to occur 100% of the time by ∼2080. Under intermediate SLR projection, 1000 simulations of the probability of maximum annual water level were conducted, showing that storm surges may reach ∼2 m over MHHW by 2050 and ∼3 m over MHHW by 2100; in comparison, storm surges in Norfolk over the past 90 years reached 1.6 m only once. The method derived here could be adopted to other locations and help planning mitigations and adaptation strategies for cities at risk.

Specifying the morphometric parameters of grottoes and galleries of the Kungur Ice Cave following the results of the topographic and geodetic surveying

Introduction. The Kungur Ice Cave’s complex morphology indicates several stages of formation, starting with hypogenic (phreatic), and then epigenic (vadose) stages of speleogenesis. Cave formation conditions determined its specific water content and unique morphometry. Research objective was to create an actual topographic plan of the cave to establish morphometric parameters of the underground cavity (length, average width and height of the grottoes, amplitude, area and volume, etc.). Methods of research consisted in the graphical interpretation of the data obtained during topographic surveys performed by modern geodetic instruments and an alternative method of surveying underground cavities using a modified laser rangefinder. The surveys were carried out in the cave in the period from 2018 to 2021. Research results. For the first time, the volumes of individual grottoes and passages were calculated for the cave. In the protected part of the cave, the levels of lakes, the sole and roof of galleries were tied to absolute heights. The area occupied by the mantle ice in the cave was determined. The areas of lakes during the period of minimum and maximum water levels are calculated, as well as the strength of rocks over the entire cave. The area occupied by the mantle ice at the beginning of 2022 was determined. Within the framework of structural mapping, genetic types of cracks were recorded (tectonic, intrastratal, separation, hydration and tension, dissolution cracks), their total length was more than 38 km. We obtained marks of clay-dolomite interlayers separated in the ice-cave pack and marks of the stable water level at the time of the cave formation (10–12 thousand years ago). For the first time, the sole of the Nevolinskaya sequence was mapped in absolute hights, the area and number of organ pipes were revealed, and the zone of areal development of sulfate and carbonate breccia was identified. The scope of the results. The analysis of the obtained structural mapping data will allow us to assess the stability of the walls and the vaulted part of the grottoes, which will further increase the safety of visiting the excursion part of the cave.

Water Level Prediction Model Applying a Long Short-Term Memory (LSTM)–Gated Recurrent Unit (GRU) Method for Flood Prediction

The damage caused by floods is increasing worldwide, and if floods can be predicted, the economic and human losses from floods can be reduced. A key parameter of flooding is water level data, and this paper proposes a water level prediction model using long short-term memory (LSTM) and a gated recurrent unit (GRU). As variables used as input data, meteorological data, including upstream and downstream water level, temperature, humidity, and precipitation, were used. The best results were obtained when the LSTM–GRU-based model and the Automated Synoptic Observing System (ASOS) meteorological data were included in the input data when experiments were performed with various model structures and different input data formats. As a result of the experiment, the mean squared error (MSE) value was 3.92, the Nash–Sutcliffe coefficient of efficiency (NSE) value was 0.942, and the mean absolute error (MAE) value was 2.22, the highest result in all cases. In addition, the test data included the historical maximum water level of 3552.38 cm in the study area, and the maximum water level error was also recorded as 55.49, the lowest result. Through this paper, it was possible to confirm the performance difference according to the composition of the input data and the time series prediction model. In a future study, we plan to implement a flood risk management system that can use the predicted water level to determine the risk of flooding, and evacuate in advance.

Analysis of Ocean Parameters as Sources of Coastal Storm Damage: Regional Empirical Thresholds in Northern Spain

This contribution aims to explore the role of oceanographic parameters on the damage caused by storms at the eastern Cantabrian coast (1996–2016). All wave storms affecting the study area were characterized in terms of several oceanographic parameters; among them, damaging storms (responsible for direct and tangible loss) were identified. Cross-referencing both databases makes it possible to find some thresholds that explain storm conditions associated with property damage. Particularly relevant are those responsible for significant and widespread damage: maximum significant offshore wave height >6.5 m, maximum total water level >6 m, SPI > 1700 m2h, and a storm duration >48 h. These values are exceptionally high, mostly exceeding the 95th percentile. A comparison has been made with other thresholds described in the literature. The concurrence of high wave height and high tidal level is crucial as the greatest damage is caused by the combination of wave impact and over-wash, so a long duration of the storm is necessary to coincide with high tide. An empirical Intensity-Duration threshold has also been obtained with the following function I = 248.7 D−0.45. Damage can occur with moderate storms, but with severe effects only with exceptional wave and sea-level values, during long-lasting storms.

A Gis-Based Parametric Analysis of Irrigational Tanks in the Oldest Civilized City in India-Madurai

The irrigational tanks being traditional Water harvesting structures designed by rulers and chieftains dating back centuries. These are constructed in such a way that they act as a major water resource in drought-prone rural communities. The main aim of this paper is to develop a GIS-based Parametric Maps of Maximum Capacity(MC), Maximum Water Level(MWL), Ayacut Area(AA), Water Spread Area(WSA), Sub-basins and Basins of irrigational Tanks which form the basic irrigation information system to assist agriculturalists, farmers, and Government organization for the proper maintenance of irrigation tanks with suitable indexing parameters, to mitigate & forecast the water and food requirements by evaluating currently available water for the given population density and irrigation lands. The study area selected is the oldest civilized city in India which is in the state of Tamilnadu-Madurai district, which is served by the Vaigai River and consists of 1338 tanks. This GIS-based information system assists the decision-makers to perform surveillance, evaluate the efficiency of the tank at any space & time and take proper managerial methods to utilize the resources economically.

Modeling interactions between tides, storm surges, and river discharges in the Kapuas River delta

Abstract. The Kapuas River delta is a unique estuary system on the western coast of the island of Borneo, Indonesia. Its hydrodynamics are driven by an interplay between storm surges, tides, and river discharges. These interactions are likely to be exacerbated by global warming, leading to more frequent compound flooding in the area. The mechanisms driving compound flooding events in the Kapuas River delta remain, however, poorly known. Here we attempt to fill this gap by assessing the interactions between river discharges, tides, and storm surges and how they can drive a compound inundation over the riverbanks, particularly within Pontianak, the main city along the Kapuas River. We simulated these interactions using the multi-scale hydrodynamic model SLIM (Second-generation Louvain-la-Neuve Ice-ocean Model). Our model correctly reproduces the Kapuas River's hydrodynamics and its interactions with tides and storm surge from the Karimata Strait. We considered several extreme-scenario test cases to evaluate the impact of tide–storm–discharge interactions on the maximum water level profile from the river mouth to the upstream part of the river. Based on the maximum water level profiles, we divide the Kapuas River's stream into three zones, i.e., the tidally dominated region (from the river mouth to about 30 km upstream), the transition region (from about 30 km to about 150 km upstream), and the river-dominated region (beyond 150 km upstream). Thus, the local water management can define proper mitigation for handling compound flooding hazards along the riverbanks by using this zoning category. The model also successfully reproduced a compound flooding event in Pontianak, which occurred on 29 December 2018. For this event, the wind-generated surge appeared to be the dominant trigger.

Decrease in Fishery Yields in Response to Hydrological Alterations in the Largest Floodplain Lake (Poyang Lake) in China

Habitat degradation has caused reduction in fishery yields in many freshwater ecosystems, particularly recession of water levels in natural lakes. Poyang Lake, the largest freshwater lake and one of the most exploited regions in China, has exhibited a dramatic variation in the water level for decades, especially after the operation of the Three Gorges Dam. We evaluated the long-term dynamics of fishery yields and the relationship to hydrological variability of Poyang Lake from 1990 to 2016. There was a strong positive effect on the annual maximum water level (Hmax), the minimum water level in April (HMmin4), the maximum water level in August (HMmax8), the average water level in October (HMmean10), and the number of days when the water level was above the wet threshold (Wetdays) on fishery yields. The all-subsets regression model identified the best variable combination subset which contains eight hydrological variables (R2 = 0.9493), and the HMmin4, HMmax8, and HMmean10 variables were the most important variable predictor for fishery yields (contributing to 63.03% of the explained variability). The Mann–Kendall test showed that the time series of the fishery yield of Poyang Lake had significant decreasing trends over the past few decades. Moreover, Wetdays, HMmin4, and HMmean10 also showed significantly decreasing abrupt changes, and the abrupt changes’ time of HMmean10 was the same as that of the fishery yield in 2005. The mean fishery yield and HMmean10 dropped from 42,581 tonnes and 14.15 m during 1990–2005 to 27,464 tonnes and 11.78 m during 2006–2016, respectively. This study is critical for implementing effective strategies for the protection of fish resources and lake ecosystems.

Research on Seepage Field and Slope Stability Considering Heterogeneous Characteristics of Waste Piles: A Less Costly Way to Reduce High Leachate Levels and Avoid Accidents

Due to the characteristics of high heap and large volume, the complex layers of waste, high-water level of leachate, environmental pollution, and slope instability are easily produced. Although many researchers have studied landfill two-dimensional leachate migration law, three-dimensional seepage and stability of landfill sites have been rarely studied. This paper focuses on the heterogeneous characteristics of the landfill piles and analyzes the seepage field and slope stability of the landfill using statistical and numerical analysis methods. The calculated results are compared with the field measurement and literature research data to verify the reliability of the model, which may provide the basis for the design and safe and eco-friendly operation of the landfill. Taking an actual landfill as the research object, the saturated–unsaturated transient model of heterogeneous waste is applied to practical engineering. Considering the landfill process and heterogeneous permeability, the calculated maximum water level is higher. Compared with the homogeneous material, the difference in the water level of each waste layer is about 0.08∼1.88 m, which is not good for the stability of the landfill. Combined with the engineering characteristic distribution of a landfill, the heterogeneous stability model is applied to the actual project to study the influence of different unit weight and shear strength distribution on landfill stability. The established model is suitable for the study of two-dimensional and three-dimensional slope stability of landfill sites. Through the slope stability analysis of the three-dimensional landfill site, it is found that the bank slope of the reservoir is steep and prone to instability failure. In most studies, only the instability of the landfill is of concern, but the bank failure is ignored. In the process of landfill operation and management, while considering the capacity of the landfill, the stability of the bank slope should also be paid attention to, and if necessary, bank slope reinforcement or slope ratio improvement should be carried out.

Local-Scale Damming Impact on the Planktonic Bacterial and Eukaryotic Assemblages in the upper Yangtze River.

Dam construction and impoundment cause discontinuities in the natural biophysical gradients in rivers. These discontinuities may alter distinctive habitats and different microbial community assembly mechanisms upstream and downstream of dams, which reflect the potential impacts of damming on riverine aquatic ecosystems. In this study, we investigated the planktonic microbial assemblages of three large dams in the upper Yangtze River by using high-throughput sequencing. The results revealed that the alpha diversity indexes increased downstream of the dams. In addition, more eukaryotic ASVs solely occurred downstream of the dams, which indicated that a large proportion of eukaryotes appeared downstream of the dams. The nonmetric multidimensional scaling analysis indicated that there was no obvious geographic clustering of the planktonic microbial assemblages among the different locations or among the different dams. However, the dam barriers changed dam-related variables (maximum dam height and water level) and local environmental variables (water temperature, DOC, etc.) that could possibly affect the assembly of the planktonic microbial communities that are closest to the dams. A co-occurrence network analysis demonstrated that the keystone taxa of the planktonic bacteria and eukaryotes decreased downstream of the dams. In particular, the keystone taxa of the eukaryotes disappeared downstream of the dams. The robustness analysis indicated that the natural connectivity of the microbial networks decreased more rapidly upstream of the dams, and the downstream eukaryotic network was more stable. In conclusion, damming has a greater impact on planktonic eukaryotes than on bacteria in near-dam areas, and planktonic microbial assemblages were more susceptible to the environmental changes. Our study provides a better understanding of the ecological effects of river damming.

Global sensitivity analysis in hydrodynamic modeling and flood inundation mapping

Flood simulation with two-dimensional hydrodynamic models is subject to different sources of uncertainties in model configuration, boundary conditions, and model parametrization. HEC-RAS 2D is a widely used hydrodynamic model. Here, we assess the sensitivity of the HEC-RAS 2D to its configuration factors and parameters. We evaluate the impacts of different model configuration factors, including the floodplain and channel roughness coefficients, terrain and mesh size, as well as river boundary conditions on the dynamic of water levels, maximum water level, and flood extent, and determine the importance of these contributing factors for reliable flood inundation modeling using both variogram and variance-based analyses. For our case study, we found that depending on the perturbation scale, the performance measure, and the predicted output, the sensitivity to input factors changes. While for simulation of water level dynamics, the DEM and mesh resolutions are the most important factors, for flood extent mapping the floodplain roughness coefficient and the upstream boundary condition are the key factors. In addition, our analyses indicated that for a reliable simulation of maximum flood water level, modelers need to spend resources on the calibration of floodplain roughness coefficient while using fine DEM and mesh resolutions. Here, we also investigate the role of computational time interval and mesh resolution on the model's run time and accuracy. Our results suggested that reducing the computational time interval has minimum impact, as it increases the model run time without much improving the model accuracy.

Simulation of Poyang Lake water levels and outflow under historical extreme hydrological scenarios

AbstractDue to an intensification of anthropogenic activities and climate change in recent decades, the hydrological connections and relationships between rivers and lakes have been significantly modified globally. Poyang Lake is one of the largest freshwater lakes globally and is one of the few that remain naturally connected to the Yangtze River. To investigate the full hydrological conditions (extreme high and low discharge) of Poyang Lake outflow under current bathymetric conditions, a large‐scale 1D‐ and 2D‐coupled high‐resolution hydrodynamic model of the Poyang Lake basin–Yangtze River system was developed. We simulated the outflow and water levels of Poyang Lake under nine different extreme hydrological scenarios with high precision and computational efficiency. We propose (1) a novel partition calibration method to characterize the roughness coefficient of large water bodies in complicated geographical terrain both for wet and dry seasons; (2) a new method for setting initial conditions for hydrodynamic simulation of large water bodies subject to strong hydrological regulation. Results indicated that (1) maximum outflow and water levels will reach 37,200 m3/s and 22.28 m when Poyang Lake basin floodwater coincides with flooding on the Yangtze River; (2) precipitation over the lake has increased outflow but this has had very limited influence on its changing hydrological pattern; (3) the effect of hydrological conditions within the system differs for both the lake outflow and water level. The research provides important reference conditions for the application of the InfoWorks ICM model in future applications and studies of large river–lake systems.

Optimal Flood-Control Operation of Cascade Reservoirs Using an Improved Particle Swarm Optimization Algorithm

Optimal reservoir operation is an important measure for ensuring flood-control safety and reducing disaster losses. The standard particle swarm optimization (PSO) algorithm can find the optimal solution of the problem by updating its position and speed, but it is easy to fall into a local optimum. In order to prevent the problem of precocious convergence, a novel simulated annealing particle swarm optimization (SAPSO) algorithm was proposed in this study, in which the Boltzmann equation from the simulated annealing algorithm was incorporated into the iterative process of the PSO algorithm. Within the maximum flood peak reduction criterion, the SAPSO algorithm was used into two floods in the Tianzhuang–Bashan cascade reservoir system. The results shown that: (1) There are lower maximum outflows. The maximum outflows of Tianzhuang reservoir using SAPSO algorithm decreased by 9.3% and 8.6%, respectively, compared with the measured values, and those of Bashan reservoir decreased by 18.5% and 13.5%, respectively; (2) there are also lower maximum water levels. The maximum water levels of Tianzhuang reservoir were 0.39 m and 0.45 m lower than the measured values, respectively, and those of Bashan reservoir were 0.06 m and 0.46 m lower, respectively; and (3) from the convergence processes, the SAPSO algorithm reduced the convergence speed in the early stage of convergence and provided a superior objective function value than PSO algorithm. At the same time, by comparing with GA algorithm, the performance and applicability of SAPSO algorithm in flood operation are discussed further. Thus, the optimal operation model and SAPSO algorithm proposed in this study provide a new approach to realizing the optimal flood-control operation of cascade reservoir systems.

Impacts of an extreme flood event on the riparian vegetation of a monsoonal cobble‐bed stream in southern Korea: A multiscale fluvial biogeomorphic framework

AbstractWith climate change increasing the magnitude and frequency of extreme precipitation events, there is a growing demand for investigations on the impacts of extreme flooding on the hydrological characteristics and vegetation of rivers, particularly in monsoonal areas. In this study, we examined multiscale relationships between hydrology, vegetation, and geomorphology after a record‐breaking flood event along the Seomjin River of South Korea in the summer of 2020. We conducted numerical modeling at the broad scale to identify the flow characteristics (e.g., depth and shear stress) of the flood event. A field survey was performed to investigate the impact of the flood on individual plants at the fine scale. The results showed widespread devastation of all vegetation types, from reed and willow communities to large, late‐successional trees taller than 10 m, which typically survive under ordinary flooding conditions. A higher threshold of shear stress was estimated for these trees (124 N m−2) than for willow (120 N m−2) and reed plants (26 N m−2), indicating that a greater level of stress is required to cause vegetation damage as ecological succession progresses. In the presence of vegetation, the average water depth increased by 9%–23% compared to the absence of vegetation. Many rivers in northeast Asia have undergone substantial vegetation expansion and succession due to the infrequency of extreme flood events. Our findings indicate that dense communities of large plants in these systems can raise the maximum water levels of flood events, thereby increasing the future flood risk to surrounding areas utilized for agriculture, transportation, industry, and housing.

Dynamic Control of Water Level in Flood Limited Reservoir Based on Intelligent Calculation

Determining the flood-limited water level is the focus of the contradiction between flood control and profit-making. The dynamic control of the flood-limited water level of the reservoir is an effective way to ensure flood control safety and realize flood resource utilization. Based on the analysis of the availability of forecast information, this paper conducts a study on the dynamic control of the flood-limited water level in Panjiakou Reservoir. The dynamic control area of Panjiakou Reservoir is determined by the “predischarge capacity constraint method.” On the premise of satisfying the flood control safety of the reservoir, the “prestorage and predischarge method” is adopted according to the real-time forecast information, the water conditions, work conditions, disaster conditions, etc. to develop a dynamic control plan for the flood-limited water level in the main flood season of the reservoir. Finally, based on the improved first-order second moment method (AFOSM), the dispatch risk model of the dynamic control of the flood-limited water level of the reservoir is constructed, and the risk analysis of the flood forecasting system is carried out. The results show that (1) the flood forecast accuracy of Panjiakou Reservoir conforms to the standard of the B-level forecasting scheme, and the results can be applied under the condition of considering the forecast error; (2) it is suggested that the maximum water level of the Panjiakou Reservoir in the main flood season is dynamically controlled to be 218 m. In the case of water supply guarantee rate P = 75 % , compared with the current situation of the flood-limited water level of 216 m, the water supply is increased by 40 million m3, and the flow of electricity is increased by 30 million. The flood control risk rate under the rain leakage error is lower than 0.1, which is the minimum risk level, which is acceptable. However, when the net rain leakage error is greater than 25 mm, there may be insufficient leakage or excessive leakage, which will cause inconvenience to downstream flood control.