Design Water Level Research Articles

Risk analysis of construction diversion scheme

The determination of diversion risk in the construction of water conservancy and hydropower projects is a key problem related to the guarantee of project safety, saving project investment, giving full play to benefits in advance and facilitating construction. According to the design data, considering the influence of the uncertain factors such as hydrology and hydraulics, this paper analyses the relationship between the elevation of the upstream cofferdam and the upstream design water level, uses the Monte Carlo method to simulate the construction flood process and the discharge capacity of the diversion buildings, makes statistical analysis and determines the risk corresponding to the upstream water level distribution of the cofferdam and the water retaining height of the cofferdam, and establishes the calculation model of the construction diversion risk.

Return Period of Low Tide Level in the Yangtze Estuary based on Nonstationarity Analysis

Due to the influence of climate change and human activities, stationarity of hydrologic time series is being challenged. The Yangtze Estuary is a region with highly developed hydraulic structures and shipping. Stationarity analysis of water level in the Yangtze Estuary is of great significance. In this study, the return period of low tide level in the Yangtze Estuary is estimated with nonstationarity considered. Conventional frequency analysis and the time-varying moment method are used to analyze the annual minimum tide level (AMTL) records of Wusongkou Station and Baozhen Station on the basis of temporal change analysis. Abrupt changes are detected at 1996 and 1990 for Wusongkou Station and Baozhen Station separately. The GEV distribution with linear time-varying parameter fits best for Wusongkou Station and Baozhen Station. The AMTL series of both stations reveal a slight increasing trend. The 100-year low tide level of Wusongkou Station is approximately 0.261 meters, which is about -0.041 meters for Baozhen Station. The corresponding return period is 150 years and 119 years respectively, which indicates the existing channel standard more secure and the recalculation of design water level necessary in the Yangtze Estuary.

Design of Water Level Detection Using Ultrasonic Sensor Based On Fuzzy Logic

Water is one of the natural resources that are needed by creatures on earth. And the need for clean water is increasing, so the price of water, both bottled water and the price of water from the PDAM. Therefore, it is necessary to have a design that can control water needs, such as the water level for filling the required containers, controlling the water level in the reservoir, etc. according to human needs so that no waste of water occurs. This research was conducted to design water level detection by combining hardware and software, namely ultrasonic sensors as detection, Arduino Uno microcontroller as a process, and fuzzy logic as an analysis of data delivered by ultrasonic sensors. So, this design can be utilized in various fields both industrial and home. This water level detection is designed using ultrasonic sensors as distance monitoring, servo motor, LED warning, and buzzer. Fuzzy logic is applied to the ability of a tool designed by determining the desired set point of water. Test results that have been carried out with Fuzzy Logic with 5 levels, are level 1 (0 – 6 cm), level 2 (6.1 – 12 cm), level 3 (12.1 cm – 18 cm), level 4 (18.1 cm – 24 cm), and level 5 (24.1 – 30 cm).

Nonstationary joint probability analysis of extreme marine variables to assess design water levels at the shoreline in a changing climate

In the present study, a recently developed novel approach (Bender et al. in J Hydrol 514:123–130, 2014) has been further extended to investigate the changes in the joint probabilities of extreme offshore and nearshore marine variables with time and to assess design the total water level (TWL) at the shoreline under the effects of climate change. The nonstationary generalised extreme value (GEV) distribution has been utilised to model the marginal distribution functions of marine variables (wave characteristics and sea levels), within a 40-year moving window. All parameters of the GEV were tested for statistically significant linear and polynomial trends over time, and best-fitted trends have been detected. Different copula functions were fitted at the 40-year moving windows, to model the dependence structure of extreme offshore significant wave heights and peak spectral periods, and of wave-induced sea levels on the shoreline and nearshore sea levels due to storm surges. The most appropriate bivariate models were then selected. Statistically significant polynomial trends were detected in the dependence parameters of the selected copulas, and time-dependent most likely bivariate events were extracted to be used in the estimation of the TWL at the shoreline. The methods of the present work were implemented in three selected Greek coastal areas in the Aegean Sea. The analysis revealed different variations in the most likely estimates of the offshore wave characteristics and nearshore storm surges in the three study areas, as well as in the time-dependent estimates of TWL at the shoreline. The approach combines nonstationarity and bivariate analysis, blends coastal and offshore marine features and finally provides non-trivial alterations in the response of coastal sea level dynamics to climate change signals, compared to former work on the subject. The methodology produces reasonable estimates of design quantities for coastal structures and boundary conditions for the assessment of flood hazard and risk in coastal areas.

Stochastic Model for Estimating Extreme Water Level in Port and Coastal Engineering Design

Extreme water level is an important consideration when designing coastal protection structures. However, frequency analysis recommended by standard codes only considers the annual maximum water level, whereas water levels should actually be regarded as a combination of astronomical tide and storm surge. The two impacting factors are both random variables, and this paper discusses their dependency structures and proposes a new joint probability method to determine extreme design water levels. The lognormal, Gumbel, Weibull, Pearson type 3, traditional maximum entropy, and modified maximum entropy distributions are applied to fit univariate data of astronomical tides and storm surges separately, and the bivariate normal, Gumbel-Hougaard, Frank and Clayton copulas are then utilized to construct their joint probability distributions. To ensure that the new design method is suitable for use with typhoon data, the annual occurrence frequency of typhoon processes is considered and corresponding bivariate compound probability distributions are proposed. Based on maximum water level data obtained from Hengmen hydrological station in the Pearl River Basin, China, these probability models are applied to obtain designs for extreme water levels using the largest sum of the astronomical tide and storm surge obtained under fixed joint return periods. These design values provide an improved approach for determining the necessary height of coastal and offshore structures.

Frequency Analysis of Storm-Surge-Induced Flooding for the Huangpu River in Shanghai, China

Shanghai, as a coastal city, is vulnerable to various types of flooding. The floodwalls along the Huangpu River provide protection against typhoon-induced flooding. However, there is limited insight into the actual safety level of the flood defences in Shanghai, and recent failures have highlighted their vulnerability. Therefore, the aims of this paper are to derive a series of new flood frequency curves for the Huangpu River, and to evaluate the level of protection of the floodwall system. This paper analysed over 100 years (1912–2013) of annual maximum water levels for three stations at near-sea, mid-stream and inland locations along the Huangpu River. Best-fit curves were determined for a number of selected probability distributions using statistical performance indicators. As a result, new flood frequency curves of the water levels for different storm surge return periods were produced. The results showed that generalised extreme value (GEV) was identified as the most suitable probability distribution for the datasets. Analysis showed that the current design water levels correspond to exceedance probabilities of 1/500 per year at the near-sea and mid-stream stations, and no more than 1/50 per year at the inland station of the Huangpu River, whereas the intended safety standard is 1/1000 per year. A comparison of the findings with a dataset of the crest heights of the floodwalls showed that the current protection level of the floodwalls along the Huangpu River is expected to be around 1/50 per year in terms of overtopping for the lowest sections. The results of this study can be utilized to provide future recommendations for flood risk management in Shanghai.

Effects of climate change on peak runoff and flood levels in Qu River Basin, East China

The impact of climate change on regional hydrological extreme events has been a research topic that has received much attention in recent years. This paper aims to provide a general overview of changes on future runoffs and water levels in the Qu River Basin, upper reaches of Qiantang River, East China by combining future climate scenarios, hydrological model and 1D hydraulic model. The LARS-WG (Long Ashton Research Station Weather Generator) statistical downscaling method is used to downscale the GCM (Global Climate Model) outputs (including BCC, BNU, CanESM and CSIRO under RCP4.5 and RCP8.5 scenarios) and generate 50 years of synthetic precipitation and maximum and minimum temperatures to drive the GR4J hydrological model and the 1D hydraulic model for the baseline period 1971–2000 and the future period 2021–2050. Finally, the POT (Peaks over Threshold) method is applied to analyze the change of extreme events in the study area. The results show that design runoffs and water levels all indicate an increasing trend in the future period for Changshangang River and Jiangshangang River at most cases, especially for small return periods, and for Qu River the increase becomes larger, which suggests that the risk of flooding will probably become greater and appropriate adaptation measures need to be taken.

Uncertainty Analysis of Bivariate Design Flood Estimation and its Impacts on Reservoir Routing

The bivariate hydrological quantile estimation may inevitably induce large sampling uncertainty due to short sample size. It is crucial to quantify such uncertainty and its impacts on reservoir routing. In this study, a copula-based parametric bootstrapping uncertainty (C-PBU) method is proposed to characterize the bivariate quantile estimation uncertainty and the impact of such uncertainty on the highest reservoir water level is also investigated. The Geheyan reservoir in China is selected as a case study. Four evaluation indexes, i.e. area of confidence region, mean horizontal deviation, mean vertical deviation and average Euclidean distance, are adopted to quantify the quantile estimation uncertainty. The results indicate that the uncertainty of quantile estimation and the highest reservoir water level increases with larger return period. The 90% confidence interval (CI) of highest reservoir water level reaches 1.56 m and 2.52 m under 20-year and 50-year JRP respectively for the sample size of 100. It is also indicated that the peak over threshold (POT) sampling method contribute to uncertainty reduction comparing with the annual maximum (AM) method. This study could provide not only the point estimator of design floods and corresponding design water level, but also the rich uncertainty information (e.g. 90% confidence interval) for the references of reservoir flood risk assessment, scheduling and management.

Reliability-based assessment and design of stone-filled crib seawalls for shoreline protection

ABSTRACTIn this study, an efficient reliability-based design tool for stone-filled crib seawalls is developed. The first-order reliability method is integrated into spreadsheet to facilitate the reliability analysis for practical application. Using this spreadsheet tool, the effects of several major uncertain factors on the seawall design, including design water level, material property, and wave forces, are explicitly explored. In addition, the impact of progressive scour on the seawall stability is demonstrated through a time-dependent reliability analysis. This developed reliability-based design tool for seawalls is validated through comparing with the Monte Carlo simulation. This seawall design tool is easy to use and can be readily adapted in various aspects in the seawall design for shoreline protection.

Extreme water level and wave estimation for nearshore of Ningde City

The high and low design water levels are calculated by observation tidal data in sea areas of Ningde offshore wind power project from September 2010 to August 2011, with the value 318 cm and -246 cm, respectively. The extreme high and low levels are also calculated using synchronous difference ratio method based on station data from 1973 to 2005 at Sansha station. The value is 431 cm and -378 cm respectively. The design wave elements are estimated using the wave data from Beishuang Station and Pingtan station. On this basis, the SWAN wave model is applied to calculating the design wave elements in the engineering sea areas. The results show that the southern sea area is mainly affected by the wave effect on ESE, and the northern is mainly affected by the E waves. This paper is helpful and useful for design and construction of offshore and coastal engineering.

A Development of Nonstationary Frequency Analysis Model using a Bayesian Multiple Non-crossing Quantile Regression Approach

Global warming under the influence of climate change and its direct impact on glacial and sea level are known issue. However, there is a lack of research on an indirect impact of climate change such as coastal structure design which is mainly based on a frequency analysis of water level under the stationary assumption, meaning that maximum sea level will not vary significantly over time. In general, stationary assumption does not hold and may not be valid under a changing climate. Therefore, this study aims to develop a novel approach to explore possible distributional changes in annual maximum sea levels (AMSLs) and provide the estimate of design water level for coastal structures using a multiple non-crossing quantile regression based nonstationary frequency analysis within a Bayesian framework. In this study, 20 tide gauge stations, where more than 30 years of hourly records are available, are considered. First, the possible distributional changes in the AMSLs are explored, focusing on the change in the scale and location parameter of the probability distributions. The most of the AMSLs are found to be upward-convergent/divergent pattern in the distribution, and the significance test on distributional changes is then performed. In this study, we confirm that a stationary assumption under the current climate characteristic may lead to underestimation of the design sea level, which results in increase in the failure risk in coastal structures. A detailed discussion on the role of the distribution changes for design water level is provided.

无资料感潮河段设计洪水位计算

感潮河段的洪水过程由于既受上游河道径流和下游潮汐的双重作用，使感潮河段的水文情势尤为复杂。本文针对无资料感潮河段设计洪水位计算，提出根据短期潮位对比观测，通过准同步比较，将长期潮位观测站逐年实测潮位资料转引至工程海域后，对逐年的极端高潮位采用PIII型频率曲线进行适线计算，得到不同频率设计高潮位，从而解决不同频率潮位计算问题；针对河流洪水计算，由于缺乏实测河流流量资料，采用水库最大下泄流量加区间流量作为上游流量边界，采用一般大潮高潮位作为下游水位边界，同时对河口地形根据不同时期影像资料进行了适当假定，采用水动力模型进行了河流洪水计算，得到满足工程需要的设计洪水位；上述所述方法对无资料感潮河段设计洪水位计算提供了重要参考。 The hydrological regime of the tidal reach is complicated because it’s influenced by both the upstream runoff and the downstream tide. This paper focuses on the design water level calculation for tidal river in ungauged basin based on the short-term tidal level observation, the long term tidal observation and short term tidal level observation relationship. After the quasi-synchronous comparison, the tidal level data of long-term tide observation stations are transferred to the engineering sea area. By using the P-III frequency curve, the extreme tidal level of each year is estimated for different design tide levels. As a result, the problem of different frequency tide calculation is solved. As to the river flood design water level calculation, because the lack of observation river flow data, the maximum reservoir discharge flow and interval flow is used as the upstream flow boundary conditions, the average high tidal level is used as the downstream water level conditions. Besides, based on different time of the remote sense image at the estuary, the rational assumptions of estuarine topography is put forward using the hydrodynamics model, the design water level satisfied the project need is calculated. The above-mentioned methods provide an important reference for the calculation of the design flood level of tidal reach inungauged basins.

Hydrologic Analysis of Highway Bridge Crossing Tributary

In order to improve the accuracy of hydrologic calculation of highway bridge crossing tributary, two calculation methods were listed in this paper. Based on the analysis and comparison of the hydrologic calculation of bridge design flood flow and water level at certain frequency crossing tributaries in the main river system, the hydrologic analysis of bridge is introduced. The important applications of hydrologic analysis of highway bridge community along river that need to be solved are discussed.

THE MOVEMENT OF SAND DUNES AND ITS EFFECTS ON WATER CHANNELS IN THE PROJECT OF SOUTH VALLEY

Toshka project is located in a desert area where sand dunes spread making it an exhibition on a permanent basis to sand, in addition to low water velocity most of the year, and low water depth in many reaches, all these factors make an ideal environment for the growth and spread of weeds in water. The reaches affected by sand movement in Sheikh Zayed canal from kilometer 24.750 to kilometer 43.000 with different lengths. The accumulative quantities, of sand that expected to fall in Sheikh Zayed canal and its branches ranged between 221.74m3/year to 8948.16 m3/year. Differences between actual and design water levels results from deposits and low drawn water, physical and chemical properties of water and soil for canals varying from site to other. (SOBEK program) shows that the main canal required 333m3/s to reach to design water level.

한반도의 해수면 상승을 고려한 설계조위 산정에 관한 연구

이산화탄소의 배출 증가와 지구온난화, 엘리뇨 현상, 라니냐 현상 등과 같은 이상기후 현상의 발생빈도 증가로 인하여 전 세계적으로 내륙과 해안의 온도가 상승하고 있다. 지구온난화로 인한 바닷물의 열팽창 그리고 빙하의 해빙 등으로 인한 지구의 해수면은 매년 2.0mm/yr(전 세계 평균값)의 속도로 상승하고 있다. 그러나 해안에 인접한 수리구조물 혹은 해안 수리구조물을 설계할 시 기준이 되는 설계조위는 과거 관측된 조위 값으로부터 4대 분조 및 조화상수를 분석하거나 수치모형 실험에 의해 결정된다. 따라서, 설계조위는 구조물의 설계빈도에 상응하는 해수면의 상승속도를 감안해야 할 필요가 있다고 사료된다. 본 연구에서는 국립해양조사원(Korea Hydrographic and Oceanographic Administration; KHOA)에서 운영하고 있는 46개소의 조위관측소를 대상으로 관측개시일부터 2015년까지 시단위로 조위자료를 수집하였다. 우리나라를 크게 남해동부, 남해서부, 동해남부, 동해중부, 서해남부, 서해중부, 제주로 총 7개의 해역으로 구분하여 월별, 연별 변동추이 및 연평균 상승률 분석을 수행하였다. 향후 국지적 해수면상승의 원인규명 및 설계조위 고려 시 기초자료로 활용가능 할 것으로 판단된다. The air temperatures of the coast and inland are rising due to an increase in carbon dioxide emissions and abnormal climate phenomena caused by global warming, El Nino, La Nina and so on. The sea levels of the Earth are rising by approximately 2.0 mm per year (global average value) due to the thermal expansion of sea water, melting of glaciers and other causes by global warming. On the other hand, when it comes to designing a hydraulic structure or coastal hydraulic structure, the standard of the design water level is decided by analyzing four largeness tide values and a harmonic constant with the observed tidal water level or simulating numerical model. Therefore, the design tidal water level needs to consider an increasing speed of the seawater level, which corresponds to the design frequency. In the present study, the observed tidal water levels targeting 46 tidal stations operated by the Korea Hydrographic and Oceanographic Administration (KHOA) from the beginning of observations to 2015 per hour were collected. The variation of the monthly and yearly and increasing ratio were performed and divided into 7 seas, such as east and west part of the Southern Sea, south part and middle of the East Sea, south part and middle of the Western Sea, and Jeju Sea. The current study could be used to determine the cause of local seawater rises and reflect the design tidal water level as basic data.

해수면 상승을 고려한 하천 외수위 결정에 관한 연구

The sea level of the Earth is rising approximately 2.0mm per year (global average value) due to thermal expansion of sea water, melting of glaciers and other causes by global warming. However, when it comes to design a river, the standard of design water level is decided by analyzing four largeness tide value and harmonic constant with observed tidal water level. Therefore, it seems the external water level needs to consider an increasing speed of the seawater level which corresponds to a design frequency. In the present study, the hourly observed tidal water level targeting 47 tidal stations operated by Korea Hydrographic and Oceanographic Administration (KHOA) from beginning of observation to 2015 per hour has been collected. The variation of monthly and yearly and increasing ratio have been performed divided 4 seas such as the Southern, East, Western, and Jeju Sea. Also, the external water level existing design for rivers nearby a coast was been reviewed. The current study could be used to figure out the cause of local seawater rise and reflect the external water level as basic data.

The exceptional influence of storm ‘Xaver’ on design water levels in the German Bight

Design water levels for coastal structures are usually estimated based on extreme value statistics. Since their robustness depends heavily on the sample size of observations, regular statistical updates are needed, especially after extreme events. Here, we demonstrate the exceptional influence of such an event based on storm ‘Xaver’, which caused record breaking water levels for large parts of the southwestern German North Sea coastline on 6 December 2013. We show that the water level estimates for a 1 in 200 years event increased by up to 40 cm due to the update after ‘Xaver’, a value twice as large as the estimated regional sea level rise for the entire 20th century. However, a thorough analysis of different independent meteorological (winds and pressure) and oceanographic components (tides, surges, mean sea level (MSL) anomalies) driving the event reveals that their observed combination does not yet represent the physically possible worst case scenario. Neither tides, nor surges nor MSL anomalies were at their observational maximum, suggesting that there is a realistic risk of a storm like ‘Xaver’ to cause even higher extreme water levels by a few decimetres under current climate conditions. Our results question purely statistical design approaches of coastal structures, which neglect the physical boundary conditions of individual extreme events.

Yet Another 100Yr Storm Surge Event: The Role of Individual Storm Surges on Design Water Levels

On December 6^(th) 2013 the German coastline was hit by the extra tropical cyclone ＂Xaver＂, which caused the highest water levels on record in some places. In the media, the resulting storm surge was quickly referred to as a ＂once in one hundred years＂ event or a ＂century storm surge＂. Based on 12 tide gauges in the German Bight, we estimate return periods of the observed water levels during Xaver and find that they were much lower than 100 years. However, in some places Xaver caused increases in the 200-year return water level estimates, which are often used for the design of coastal defences in the region. This highlights the need to re-assess design levels periodically and especially after such extreme events.

On the possibilities of watershed parameterization for extreme flow estimation in ungauged basins

Abstract. The estimation of design discharges and water levels of extreme floods is one of the most important parts of the design process for a large number of engineering projects and studies. Design flood estimates require a consideration of the hydrological, meteorological and physiographical situation, the legal requirements, and the available estimation techniques and methods. In the last decades changes in floods have been observed (Hall et al., 2014) which makes design flood estimation particularly challenging. Methods of design flood estimation can be applied either locally or regionally. A significant problem may arise in small catchments that are poorly gauged or when no recorded data exist. To obtain the design values in such cases, many countries have adopted procedures that fit the local conditions and requirements. One of these methods is the Soil Conservation Service – Curve number (SCS-CN) method which is often used in design flood estimation for ungauged sites, including those in Slovakia. Since the method was derived on the basis of the specific characteristics of selected river basins in the United States, it may lead to significant uncertainties in other countries with different hydrological conditions. The aim of this study was to test the SCN-CN method and derive regional runoff curve numbers based on rainfall and discharge measurements for selected region in Slovakia. The results show that the classical CN method gives too high estimates of event runoff depths and is not valid in the study area. To avoid the overestimation of runoff caused by extreme rainfall events, the use of the empirically derived regional runoff curves was tested and finally proposed for practical application in engineering hydrology.

The co-incidence of storm surges and extreme discharges within the Rhine–Meuse Delta

The Netherlands is a low-lying coastal area and therefore threatened by both extreme river discharges from the Meuse and Rhine rivers and storm surges along the North Sea coastline. To date, in most flood risk analyses these two hazardous phenomena are considered independent. However, if there were a dependence between high sea water levels and extreme discharges this might result in higher design water levels, which might consequently have implications for flood protection policy in the Netherlands. In this study we explore the relation between high sea water levels at Hoek van Holland and high river discharges at Lobith. Different from previous studies, we use physical models forced by the same atmospheric forcing leading to concomitant and consistent time series of storm surge conditions and river discharge. These time series were generated for present day conditions as well as future climate projections and analysed for dependence within the upper tails of their distribution. In this study, dependence between the discharge at Lobith and storm surge at Hoek van Holland was found, and the dependence was highest for a lag of six days between the two processes. As no significant dependence of the threats was found for cases without time lag, there is no need for considering dependence in flood protection and policy making. Although future climate change is expected to lead to more extreme conditions in river discharges, we cannot conclude from this study that it will change the magnitude of the dependence for extreme conditions.