Warning Water Level Research Articles

Spatial diversion and coordination of flood water for an urban flood control project in Suzhou, China

Suzhou City, located in the Yangtze River Delta in China, is prone to flooding due to a complex combination of natural factors, including its monsoon climate, low elevation, and tidally influenced position, as well as intensive human activities. The Large Encirclement Flood Control Project (LEFCP) was launched to cope with serious floods in the urban area. This project changed the spatiotemporal pattern of flood processes and caused spatial diversion of floods from the urban area to the outskirts of the city. Therefore, this study developed a distributed flood simulation model in order to understand this transition of flood processes. The results revealed that the LEFCP effectively protected the urban areas from floods, but the present scheduling schemes resulted in the spatial diversion of floods to the outskirts of the city. With rainstorm frequencies of 10.0% to 0.5%, the water level differences between two representative water level stations (Miduqiao (MDQ) and Fengqiao (FQ)) located inside and outside the LEFCP area, ranged from 0.75 m to 0.24 m and from 1.80 m to 1.58 m, respectively. In addition, the flood safety margin at MDQ and the duration with the water level exceeding the warning water level at FQ ranged from 0.95 m to 0.43 m and from 4 h to 22 h, respectively. Rational scheduling schemes for the hydraulic facilities of the LEFCP in extreme precipitation cases were developed according to flood simulations under seven scheduling scenarios. This helps to regulate the spatial flood diversion caused by the LEFCP during extreme precipitation.

Warning water level determination and its spatial distribution in coastal areas of China

Abstract. The warning water level is the default water level at which storm surges may occur along a coast and indicates a stage of alert. This level forms the basis for storm-surge forecasting, and prewarning is an important reference for governments and aids in the decision-making process for storm-surge prevention and disaster risk mitigation. The warning water level has four categories (blue, yellow, orange, and red) based on water level observational data. Taking into account the actual defense capability of the shore, we determined the warning water level by comprehensively analyzing factors, including the high water level at the typical return period of each shore section, wave exposure degree and defense capability of storm-surge protection facilities, and the shore-section importance level. Here, we proposed a quantitative method for determining the warning water level, and the application of this method was introduced by determining the warning water level at the shore section of Zhifu District (Yantai City, Shandong Province, China) as an example. We analyzed the spatial distribution characteristics of the warning water levels for 259 shore sections along the coast and revealed their current marine disaster prevention capabilities. Our findings provide a valid direction for determining future warning water levels and a reliable scientific reference for redetermining warning water levels in coastal areas while improving marine disaster prevention and protection capabilities.

Optimization of Drought Limited Water Level and Operation Benefit Analysis of Large Reservoir

As an important water conservancy engineering project, reservoir regulation plays a crucial role in the insurance of water resources supply and demand balance and sustainable development and utilization, especially during drought seasons. The drought limited water level (DLWL) is the characteristic controlling water level of reservoir regulation operation during dry seasons, and the construction of reliable controlling schemes of DLWL is of great significance for the improvement of regional water resources utilization efficiency. Therefore, basing on the variation analysis of water inflowing series and water resources utilization characteristics among different sectors of Meishan Reservoir in Shihe Irrigation Area of China, firstly, the Hausdorff Dimensional Fractal (HDF) method was applied to divide drought early-warning periods of Meishan reservoir. Then, the initial scheme of DLWL of reservoir was determined through reservoir water inflow and water supply processes analysis during each drought warning periods of different typical hydrological years. And finally, the optimal dynamic controlling scheme of DLWL, described by drought warning water level (DWWL) and drought depleted water level (DDWL) respectively, was eventually proposed in this study based on the establishment of simulation and regulation model of reservoir and irrigation areas system. Moreover, the reliability and effectiveness of the proposed optimal controlling scheme of DLWL was further testified in terms of drought risk analysis of reservoir and irrigation area system under typical consecutive and annual drought scenarios, and meanwhile, the agricultural crop yield loss risk due to drought events corresponding to different controlling schemes of DLWL was also determined. The related research findings of this study could be favorable and beneficial for guiding drought-resistance regulation of reservoir and irrigation area system during drought seasons and providing reasonable decision-making basis of water resources utilization schemes as well.

Water level retrieval for the past and prediction for the next 30 years at Lake Fuxian

在极端气候事件频发和人类活动加剧的背景下，抚仙湖水位波动显著，尤其是2009—2012年极端干旱事件的发生，使抚仙湖平均水位（1721.31 m）低于法定最低水位（1721.65 m），给生态环境安全带来严重威胁.因此，找到合适有效的湖泊水位模拟方法，对气候变化影响下的未来水位进行预测，并做好相应的应对准备，对湖泊生态系统的保护至关重要.本文运用DYRESM水动力模型对抚仙湖1959—2050年水位进行了模拟.因抚仙湖流域尚无长时间序列的历史水文观测数据，故利用模型和水量补偿法对抚仙湖入湖水量进行反推，构建了降水量-入湖水量的回归方程，并通过有效的实测入湖水量和水位数据，对回归方程的精度进行了检验.利用全球气候模式BCC-CSM2-MR中SSP245和SSP585两种情景提供的未来气候预估数据，运用DYRESM预测了抚仙湖2021—2050年水位变化趋势.结果表明：（1）构建的DYRESM水动力模型和降水-入湖水量回归方程精度较高，模型结果能很好地反映抚仙湖水位的年际和年内变化趋势，且能有效捕捉到抚仙湖的水位峰值.（2）在SSP245和SSP585两种情景下，抚仙湖2021—2050年多年平均水位分别为1722.98和1723.93 m，较1959—2017年平均水位1721.77 m分别升高1.21和2.16 m.两种情景下抚仙湖未来水位均有部分时段超过法定最高蓄水位（1723.35 m），但均高于法定最低水位.因此，未来气候变化对抚仙湖水量的影响有限，并不会导致水位过低，当水位超过法定最高蓄水位时，可通过控制出流闸门将水位调节在合理范围内.;With frequent extreme climate events and intensive human activities, the water levels at Lake Fuxian have fluctuated significantly in the past especially during 2009-2010 with an extreme drought. The average water level from 2009 to 2012 was (1721.31 m) lower than the minimum required value (1721.65 m), which caused a great threat to the lake ecosystem. So, it is very important to find an effective method or tool for predicting the water levels under the climate change in the future and to make corresponding adaptation. In this paper, a one-dimensional hydrodynamic model (DYRESM) was used to simulate the water levels at Lake Fuxian from 1959 to 2050. Due to lack of observation of inflow volumes, we developed a regression model between inflow and precipitation to produce the missing lake inflows using DYRESM, existing inflow measurements and rainfall. The model was then verified and used to simulate the water levels for 2021-2050 based on rainfall predicted by a global climate model (BCC-CSM2-MR) under Scenario SSP245 and Scenario SSP585. The results show that DYRESM and the regression model had satisfied performance. The average lake water levels from 2021 to 2050 under Scenario SSP245 and Scenario SSP585 were 1722.98 and 1723.93 m respectively, which will be 1.21 and 2.16 m higher than those for 1959 to 2017. The predicted water levels might be intermittently higher than the maximum warning water level (1723.35 m), but will not be lower than the minimum warning water level (1721.65 m). In conclusion, the climate change in the future might have limited impact on the water volume of Lake Fuxian.

Evolving Threshold of Flood-Leading Precipitation in a User-Oriented Forecast System Based on the TIGGE Dataset

Specific users play a key role in interactive forecast systems through user-oriented information (UOI). For hydrological users, a key component of the user-oriented forecast system (UOFS) is to determine the threshold of flood-leading precipitation (TFLP) as a target of the forecast by considering the decision-making information at the user end. This study demonstrates a novel way of simulating TFLP via the inverse simulation of a hydrological model, combined with the flood hazard assessment in the upper reaches of the Huai River Basin controlled by the Wang Jiaba (WJB) hydrological station. The flood hazard, defined as the probability of precipitation beyond the daily evolving TFLP for the next day, was evaluated by using the THORPEX Interactive Global Grand Ensemble (TIGGE) datasets, including 162 members retrieved from 5 TIGGE archive centers. Having integrated the real-time monitored water level (as the UOI) into the UOFS, we applied it to the flood season of 2008 as a case study to evaluate the flood hazard generated by the UOFS for the WJB sub-basin. The simulated TFLP corresponded well with the gap between the monitored and warning water level. The predicted flood hazard probability showed good agreement with the first two flood peaks at 100% accuracy, while exceeding 60% accuracy for the third flood event in that season. Thus, the flood hazard could be better quantified via integration of the forecasted flood-leading precipitation. Overall, this study highlights the usefulness of a UOFS coupled with interactive UOI of real-time water level to determine the dynamical TFLP for flood hazard evaluation with ensemble precipitation forecast. The early flood warning which resulted from such integrated UOFS is directly applicable to operational flood prevention and mitigation.

Analysis of Impact Factors for Flood Early Warning, a Case Study in Wangjiaba Basin of Huai River

Wangjiaba station locates in the junction of the middle reach and upstream of the Huai River. Due to its specific location, the hydrological conditions of the Wangjiaba station can be treated as important indicators for flood forecasting and disaster controlling in the Huai River basin. In this study, 62 flood events, with peak flows exceed the warning water level of the Wangjiaba station over the past 60 years, are selected. On the basis of quantitatively analysis of the watershed status variables and flood forecasting input data, three easily available impact factors including rainfall, initial water level, and rainfall distribution were chosen as flood warning indexes in the Wangjiaba station. Analysis results show that rainfall is the most important factor for flood generation. After that, by introducing the initial water level as additional factor, the positive correlation between the peak flow and the impact factors becomes more significant. At last, with the addition of the rainfall distribution as one more factor, the peak flow forecasting accuracy can be further improved.

Variation in flood-discharge capacity of Chenglingji-Hankou reach in the middle Yangtze River and analysis of influencing factors since the onset of the Three Gorges Reservoir

受上游水库运行的影响，自2003年后长江中游河段河床调整，引起河道自身过流能力的变化.本文选取长江中游城陵矶-汉口河段作为研究对象，根据实测资料计算了2003—2016年两个水文断面的水位-流量关系及特征流量变化，并采用一维水动力学模型计算了河段尺度的平滩流量.结果表明：（1）螺山站及汉口站2003—2016年的水位-流量关系呈现枯水流量下水位降低、洪水流量下水位抬升的特点；（2）两站年最大流量下对应的水位整体抬升，警戒水位下对应的流量分别减小9%和16%；（3）2003—2016年城汉河段平滩流量有增有减，无明显单向变化趋势，2014年后呈减小趋势.分析断面的过流能力变化，发现螺山站与汉口站警戒流量与动床阻力呈明显的反比关系，过流能力由于河道阻力的增大而减小；床沙粗化、河道相对水深的减小及洲滩植被覆盖度的增大是引起河道阻力增大、过流能力减小的原因.;Since the onset of the Three Gorges Project (TGP) in 2003, the sediment load entering the middle Yangtze River (MYR) has been reduced sharply, leading to remarkable channel degradation, which greatly influenced the flood-discharge capacity of this reach. In order to have a better grasp on this situation, there is a need to investigate the variation in flood discharge capacity in this area. Therefore, Chenglingji-Hankou reach (CHR) of the MYR was chosen as a typical reach for this study. Based on the cross-section profiles and hydrologic data surveyed annually from 2003 to 2016, the variations in the relationship between discharge and water-level, the corresponding water-level under the maximum discharge annually, and the characteristics of discharges under certain stages were analyzed at Luoshan and Hankou Stations. The results show that: (ⅰ) water-level under the same discharge decreased in dry season and changed slightly in flood season; water-level under the annual maximum discharge increased compared with that from 1954 to 2002; (ⅱ) the relative discharge under warning water-level at Luoshan and Hankou Stations decreased by 9% and 16%, respectively; (ⅲ) There is no obvious trend in the temporal variation of reach-scale bankfull discharge. The influence factors of the variation in the section-scale flood-discharge capacity were analyzed. It was found that the discharges under the warning water level (at Luoshan and Hankou Stations) were negatively correlated with the bed roughness, which implies that the increase in river resistance is probably one of the main causes of the variation in discharge capacity. Besides, the decrease in relative water-depth ratio and the increase in vegetation coverage on central bars may also show obvious influences on the discharge capacity of the study reach.

Formulation and Implementation of Short-Term Optimal Reservoir Operation Schemes Integrated with Operation Rules

To narrow the gap between theoretical research and practical application of short-term optimal reservoir power generation operation under uncertain conditions, a comprehensive study is conducted on the formulation, evaluation, and implementation of operation schemes throughout the entire procedure of optimal operation. Firstly, the three implementation modes of the optimal operation scheme are assessed with the post-evaluation method. After the optimal implementation mode is determined, the formulation and implementation of optimal operation schemes are improved by combining the advantages of conventional and optimal operation and using the concept of warning water level in operation rules. Finally, the Xiaoxuan Reservoir is taken as an example for simulation calculation under different operating conditions. The results show that the operation model integrated with operation rules has both the security of conventional operation and the profitability of optimal operation. The accordingly-formulated optimal operation schemes, when implemented with the output control mode, can provide valuable guidance for the actual operation of hydropower stations.

Identifying Flood Events over the Poyang Lake Basin Using Multiple Satellite Remote Sensing Observations, Hydrological Models and In Situ Data

The Poyang Lake, the largest freshwater lake in China, is famous for its ecological and economic importance as well as frequent flood characteristics. In this study, multiple satellite remote sensing observations (e.g., GRACE, MODIS, Altimetry, and TRMM), hydrological models, and in situ data are used to characterize the flood phenomena over the Poyang Lake basin between 2003 and 2016. To improve the accuracy of the terrestrial water storage (TWS) estimates over the Poyang Lake basin, a modified forward-modeling method is introduced in the GRACE processing. The method is evaluated using the contaminated noise onboard observations for the first time. The results in both spectral and spatial domains infer a good performance of the method on the suppression of high-frequency noise while reducing the signal loss. After applying forward-modeling method, the TWS derived from the GRACE spherical harmonic coefficients presents a comparable performance with the solution derived from the newly released CSR Release05 mascon product over the Poyang Lake basin. The flood events in 2010 and 2016 are identified from the positive anomalies in non-seasonal TWSs derived by GRACE and hydrological models. The flood signatures also coincide with the largest inundated areas estimated from MODIS data, and the observed areas in 2010 and 2016 are 3370.3 km2 (30% higher than the long-term mean) and 3445.0 km2 (33% higher), respectively. The water levels in the Hukou station exceed the warning water level for 25 days in 2010 and 28 days in 2016. These continuous warning-exceeded water levels also imply the severe flood events, which are primarily driven by the local plenteous precipitation in the rainy season (1528 mm in 2010, 1522 mm in 2016).

Evaluation of Loss Due to Storm Surge Disasters in China Based on Econometric Model Groups

Storm surge has become an important factor restricting the economic and social development of China’s coastal regions. In order to improve the scientific judgment of future storm surge damage, a method of model groups is proposed to refine the evaluation of the loss due to storm surges. Due to the relative dispersion and poor regularity of the natural property data (login center air pressure, maximum wind speed, maximum storm water, super warning water level, etc.), storm surge disaster is divided based on eight kinds of storm surge disaster grade division methods combined with storm surge water, hypervigilance tide level, and disaster loss. The storm surge disaster loss measurement model groups consist of eight equations, and six major modules are constructed: storm surge disaster in agricultural loss, fishery loss, human resource loss, engineering facility loss, living facility loss, and direct economic loss. Finally, the support vector machine (SVM) model is used to evaluate the loss and the intra-sample prediction. It is indicated that the equations of the model groups can reflect in detail the relationship between the damage of storm surges and other related variables. Based on a comparison of the original value and the predicted value error, the model groups pass the test, providing scientific support and a decision basis for the early layout of disaster prevention and mitigation.

The research status of flash flood warning in China

The article discusses from the disaster mechanism of flash flood to the current situation of early warning system. The formation of flash flood is closely related to rainfall intensity, underlying surface conditions and antecedent soil moisture content, and analysis of the physical process of flash flood disasters is crucial for the study of flash flood warning. Flash flood disaster warning indexes are mainly divided into two types: rainfall warning index and water level warning index. Data-driven statistical induction method and hydro-hydraulic methods based on physical mechanisms are used to determine rainfall warning index; The water level warning index can be directly determined by the upstream and downstream corresponding water level method or by the disaster water level. And summed up the current situation and development trend of China's flash flood warning research.

Methodology to set trigger levels in an urban drainage flood warning system – an application to Jhonghe, Taiwan

ABSTRACTA wireless water-level monitoring system for an urban drainage flood warning is developed, and stations equipped with pressure sensors are installed to monitor water levels. The water levels for flood warning are investigated. Two stages of warning water level for “larger” conduits are set based on the rate of rising water levels. In a similar way, only one stage of the warning water level is set for “smaller” conduits. The average rates of rising water levels for different scenarios are estimated using the US EPA Storm Water Management Model (SWMM). When evaluating the impact of flooding, the outflows from manholes simulated by the SWMM are used as sources for a two-dimensional overland flow simulation. The integrated system is successfully executed in Jhonghe, New Taipei City, Taiwan, which has experienced urban drainage floods. Therefore, this system can provide urban drainage flood warnings to the authorities to take disaster reduction measures.

Warning Water Level Determination for Luchaogang of Shanghai

Based on “specification for warning water level determination” (GB/T17838-2011), long-term tidal data at Luchaogang are used to determine warning water level along the Luchaogang Coast. The influence of Seawall defense standards, the social and economic situation behind the dikes, and historical storm surge disasters are also taken into account to calculate the warning water level. Four levels, Red, Orange, Yellow and Blue, of warning water level are obtained with the value of 5.40m, 5.13 m, 4.87 m and 4.60m, respectively. The results are verified against the observed daily high water levels in 1977-2010. It reveals that the extreme water levels occurs mostly during typhoon period.

A storm surge intensity classification based on extreme water level and concomitant wave height

Storm surge is one of the predominant natural threats to coastal communities. Qingdao is located on the southern coast of the Shandong Peninsula in China. The storm surge disaster in Qingdao depends on various influencing factors such as the intensity, duration, and route of the passing typhoon, and thus a comprehensive understanding of natural coastal hazards is essential. In order to make up the defects of merely using the warning water level, this paper presents two statistical distribution models (Poisson Bi-variable Gumbel Logistic Distribution and Poisson Bi-variable Log-normal Distribution) to classify the intensity of storm surge. We emphasize the joint return period of typhoon-induced water levels and wave heights measured in the coastal area of Qingdao since 1949. The present study establishes a new criterion to classify the intensity grade of catastrophic storms using the typhoon surge estimated by the two models. A case study demonstrates that the new criterion is well defined in terms of probability concept, is easy to implement, and fits well the calculation of storm surge intensity. The procedures with the proposed statistical models would be useful for the disaster mitigation in other coastal areas influenced by typhoons.

Modeling of Municipal Drainage and Urban Channel Flooding in Coastal City in the South of China

A numerical model has been formatted including ocean, rain drainage, urban channels, and pumps by the software MIKE FLOOD which coupling MIKE URBAN, MIKE 11 and MIKE 21. The different scenarios have been simulated. The flooding warning water level of the urban channel is low to the spring tide height, when the precipitation in 30 years facing the ocean tide in 5 years, the rain flooding in some areas should be stored in the urban channel, waiting for the ocean tide height decrease, then discharge the rain flood. Several conclusions have been drawn as followed: (1) In China, the average impervious surface in the urban area is usually about 55% to 70%, in the commercial central area, the impervious surface is usually about 75%-90%, the impervious surface in Beihai urban area is higher than the average level in China, because the density of the constructs is too high, the land use should be changed and the Sponge City should be constructed, these measures will help to release the urban flooding problem. (2) To carryout low impact development facilities and construct urban flooding storage, drainage system both very important in coastal area, especially in typhoon area. (3)Compare two pipe and channel plans, the results show that the water logging of initial plan was heavy, and the water logging of optimization plan is relieved.

PREDICTION OF STORM SURGE INTENSITY IN COASTAL DISASTER EVALUATION

In coastal area, serious storm surge disasters are frequently caused by the higher tidal level and concomitant huge wave heights toward shoreline. Qingdao is located at the southern tip of Shandong Peninsula of China. The storm surge disaster in Qingdao depends on various influencing factors such as the intensity, duration, and route of the passing typhoon. In order to make up the defects of the warning water level, a Poisson Bi-variable Gumbel Logistic Distribution is presented to predict storm surge intensity. On the basis of observed records of tidal level and simultaneously occurred wave height series that are sampled from typhoon processes in Qingdao coastal area of China since 1949, the return periods of typhoon surge are estimated by this model. Then a new criterion is put forward to classify intensity grade of disaster-induced typhoon surges. A practical case indicates that the new criterion is clear in probability concept, easy to operate, and fits the calculation of typhoon surge intensity. Thus the procedure with the proposed statistical model will be a reference for the disaster mitigation in the other coastal area influenced by typhoons.

Flood Water Level along the Main Channel of the Lower Reaches of the Yangtze River in the Past 40 Years： Variations and Causes

最近十年来,江苏境内长江下游干流汛期最高潮位连续偏高,持续时间亦明显偏长.造成防汛工作紧张,引起政府有关部门的重视,水利部门将治理长江作为重点工作、本文利用长江下游干流大通水文站和以下各潮位站的实测水位流量资料,对1998和1954年的特大洪水水情进行了对比,分析了从六十年代到九十年代长江下游平均洪水量、平均最高水位和平均最高潮位、超过防洪警戒水位的平均天数等的变化规律.通过对长江中、上游来水量和下游东海潮汐等影响因素分析,初步探讨了近十年来长江市游高水位频繁出现的原因.;The highest water level of the lower reaches of the Yangtze River in the area of Jiangsu Province is continuously higher and its duration is obviously longer than before during the last decade. Therefore, the flood control became heavier and heavier, the regulation of the Yangtze River is payed the important attention by central and local government. In the paper, the heavy flood in 1998 is compared with that in 1954, based on data of practical measurements of Datong Hydrologic Station in the main channel and others in its down stream. The variable regularities of the average flood volume, mean of the highest water level, mean of the highest water and the average days when the water level is over the warning water level for flood control in down stream from the 1960s to the 1990s are discussed. Through the analysis of such factors as the water volume from upper and middle reaches of the Yangtze River, the tide from East China Sea, etc., the reason of frequent occurrences of high water level in the lower reaches of the Yangtze River is approached.

On the style of the on-line rainfall-runoff forecasting information

Although the methodology of the on-line rainfall-runoff forecasting has been established basically, there are still many important problems when it is really utilized in river management offices.This paper especially focuses on the problem that the style of on-line rainfall-runoff forecasting information should be easy to be woven into existing management systems, and provides a new algorithm of on-line forecasting for it.Our method can give the information on the whole hydrograph including the probability that the time to peak of discharge has passed the current time, the probability distribution of the total volume of future discharge, the probability that flood will surpass the warning water level, and the probability distribution of flood peak time and peak volume.