Design Water Level Research Articles

Analysis of extreme water levels on Feiyun River (Rui’an section) based on peaks-over-threshold (POT) model

ABSTRACT Feiyun River (Rui’an section) is a tidal reach, and the design water levels within different return periods are difficult to determine. The POT analysis methods were used to study the water level maximums of the river section. The study results indicate that skew surges has a measurable impact on extreme water levels and are characterized by a sharp increase in wind speeds at the estuary, followed by a sudden decrease, leading to a significant storm surge event. When the return periods are 50 years, 100 years and 200 years, the corresponding water levels of Feiyun River (Rui’an section) are 5.59 m, 6.04 m and 6.49 m, respectively. The proportion of skew surges in extreme water levels increases with the return period length, and it exceeds 50% when the return period is 200 years. The calculation results based on skew surges are often more reasonable in long return periods.

Influencing Factors, Design Methods, and Buoyancy Reduction Measures for Basement Anti-Flotation Engineering

Basement anti-flotation design is crucial in modern urban construction. An increase in groundwater buoyancy can cause basement structures to uplift, leading to structural instability or even damage. To ensure the stability and safety of underground structures under various hydrogeological conditions, anti-flotation design must comprehensively consider factors such as construction, design, supervision, structure, and hydrology. During construction, improper dewatering measures or unreasonable construction progress may lead to an abnormal rise in groundwater levels, increasing the risk of anti-flotation. Design considerations must include sufficient safety margins, supervision must fully recognize the impact of groundwater, and the structural dead load must be adequate. Anti-flotation stability verification includes both overall and local anti-flotation, involving the calculation of groundwater buoyancy, structural self-weight, and overburden, and selecting appropriate anti-flotation stability safety factors. The assessment and selection of the anti-flotation design water level are also critical. Common anti-flotation measures include adding counterweights, tension-resistant piles, compression and tension-resistant piles, and hydro-pressure reduction methods, while reinforcement and repair methods include epoxy resin grouting and steel plating reinforcement. Through systematic analysis and comprehensive research, scientific basis and technical support are provided for anti-flotation design, enhancing design efficiency and reliability and ensuring the safety and stability of underground spaces. Future research will develop more accurate calculation methods, improve design standards, and explore new anti-flotation technologies and materials.

Evaluating Design Flood Levels Using a Machine Learning-based Costal Compound Flood Level Model

Coastal floods, a type of compound disaster, results from the interactions between rainfall and tides. However, in Korea, the design flood level for coastal areas typically relies on the average water level according to the tide, ignoring this interaction. This study aimed to address this gap by developing a machine learning-based compound flood level model that incorporates the interactions between rainfall and tides. It also evaluated the adequacy of the design water level in the Taehwa River basin, a representative tidal river. Before developing the model, Discrete Wavelet Transformation (DWT) was used to identify the components of the compound flood level. The DWT results indicated that the compound flood level comprised three elements: rainfall-runoff, tides, and noise. A Long Short-Term Memory (LSTM) model was then created using these elements as input to estimate the compound flood level for a 200-year frequency, which is the design frequency of the Taehwa River. The compound flood level calculated by the model was 6.15 m, which is higher than the established design flood level of the Taehwa river (5.79 m). This discrepancy indicates that the current flood measurements for the Taehwa River are inadequate in accounting for compound flooding. Based on these findings, we recommend incorporating the compound flood concept when calculating the design water levels in coastal areas.

Physical Model Study Of Standing Wave Impact Loads On Gates And Decks Of The Existing Discharge Sluices In The Afsluitdijk The Netherlands

To anticipate the rising sea level and to meet the increased flood safety standards the Afsluitdijk in the northwest of The Netherlands is currently being reconstructed. The Afsluitdijk is the dam, with a length of 30 km, that closes the IJsselmeer basin, the former Zuiderzee. Outside the dam lie the Waddenzee and the North Sea. The reconstruction of the dam includes the reinforcement of the dam and the raising of the crest level, the renovation of the existing discharge sluices and the building of new pumping stations, discharge sluices and flood gates. Higher design waves and water levels, including the effects of sea level rise, present determining loads for drawing up the strength and stability of these hydraulic structures. One of these loads is the wave impact load on the gates, supporting beams and bridge decks of the discharge sluices. At first, these loads have been calculated using a design approach which has been based on analytical models, only partially validated (Almeida and Hofland, 2020). It showed that these loads due to vertical wave impacts can be higher than the strength of the gates and the existing bridge decks. Therefore, load reduction measures are required. To better predict the wave impact loads, which strongly depend on the configuration of the gates and decks, a physical model study in a wave flume has been carried out at Deltares (Capel and van der Werf, 2023). This abstract is about the results of this model study, focusing on the wave impacts on the existing discharge sluices near Kornwerderzand, because at this location these loads are the highest.

Beach protection model in Palu Bay coastal area post tsunami 2018

Talise Beach is a coastal area that has the potential of marine products and also as a means of tourism for the local community. Recently, Talise Beach and several areas along Palu Bay have experienced a lot of erosion by the impact of waves that threaten Country Road (Trans Sulawesi), settlements and other public places as a result of the earthquake and tsunami that occurred in 2018 with a wave height of 3-4 m which resulted in erosion and retreating of the coastline and even damaged several main road infrastructure and several other public facilities. The erosion problem is handled by constructing a Revetment-type coastal protection along the Talise Beach. The purpose of this study was to determine the height of the waves at Talise Beach, then to plan the technical design of the coastal protection structures at Talise Beach and to calculate the shear stability of the planned buildings. To test the stability of the Revetment, secondary data are needed in the form of wind data for 10 years (2011-2020), land contour data and tidal data for sea water and waves that are observed directly in the field. The results obtained from the calculation are the Hs is 4.466 meters, Ts is 4.5 seconds, the elevation of the lighthouse is 4.8 meters, the design water level elevation is 2.494 m. The revetment that is built consists of 3 layers using the main material is crushed stone.

FIELD DATA ANALYSIS OF HOME-BASED STORMWATER ON-SITE DETENTION SYSTEM

This paper describes the field test of a stormwater detention system which is a system designed to hold a specific volume of water and release it slowly over time, in this test case precast concrete modular units are assembled in a residential car porch and connected to a partial roof catchment via a downpipe. Stormwater is held and stored temporarily within the chambers created by the precast concrete pieces. Rainfall and flow data associated with the detention system in terms of the inflow, outflow and water levels data are collected and verification process are performed by comparing the collected data to design data for the intended system. Analyses of five storm events confirm that the estimated design inflow, outflow and water levels in response to 5- and 10-minute 10-year Average Recurrent Intervals (ARI) design rainfall are safe against the actual rainfall and actual detention and discharge performances.

Generating reliable estimates of tropical-cyclone-induced coastal hazards along the Bay of Bengal for current and future climates using synthetic tracks

Abstract. Deriving reliable estimates of design water levels and wave conditions resulting from tropical cyclones is a challenging problem of high relevance for, among other things, coastal and offshore engineering projects and risk assessment studies. Tropical cyclone geometry and wind speeds have been recorded for the past few decades only, thus resulting in poorly reliable estimates of the extremes, especially in regions characterized by a low number of past tropical cyclone events. In this paper, this challenge is overcome by using synthetic tropical cyclone tracks and wind fields generated by the open-source tool TCWiSE (Tropical Cyclone Wind Statistical Estimation Tool) to create thousands of realizations representative of 1000 years of tropical cyclone activity for the Bay of Bengal. Each of these realizations is used to force coupled storm surge and wave simulations by means of the processed-based Delft3D Flexible Mesh Suite. It is shown that the use of synthetic tracks provides reliable estimates of the statistics of the first-order hazard (i.e., wind speed) compared to the statistics derived for historical tropical cyclones. Based on estimated wind fields, second-order hazards (i.e., storm surge and waves) are computed that are generated by the first-order hazard of wind. The estimates of the extreme values derived for wind speed, wave height and storm surge are shown to converge within the 1000 years of simulated cyclone tracks. Comparing second-order hazard estimates based on historical and synthetic tracks shows that, for this case study, the use of historical tracks (a deterministic approach) leads to an underestimation of the mean computed storm surge of up to −30 %. Differences between the use of synthetic versus historical tracks are characterized by a large spatial variability along the Bay of Bengal, where regions with a lower probability of occurrence of tropical cyclones show the largest difference in predicted storm surge and wave heights. In addition, the use of historical tracks leads to much larger uncertainty bands in the estimation of both storm surges and wave heights, with confidence intervals being +80 % larger compared to those estimated by using synthetic tracks (probabilistic approach). Based on the same tropical cyclone realizations, the effect that changes in tropical cyclone frequency and intensity, possibly resulting from climate change, may have on modeled storm surge and wave heights was computed. As a proof of concept, an increase in tropical cyclone frequency of +25.6 % and wind intensity of +1.6 %, based on literature values and without accounting for uncertainties in future climate projection, was estimated to possibly result in an increase in storm surge and wave heights of +11 % and +9 %, respectively. This suggests that climate change could increase tropical-cyclone-induced coastal hazards more than just the actual increase in maximum wind speeds.

Dynamic Response Analysis of Dual-Flow Channel Pump Station Structure under Water Pressure Pulsation

The RNG k-ε model turbulence model is used to carry out a CFD numerical simulation of the dual-flow channel pumping station. Through the model test, the accuracy of the numerical simulation of the dual-flow channel pump device is verified. Using the harmonic response analysis method, the water pressure fluctuating load calculated under different startup conditions under the design water level is applied to the pumping station. In this way, the dynamic response law of the pump station structure under the action of water pressure pulsation is studied. The calculation results show that the values of pressure pulsation in the drainage condition and the water diversion condition are relatively close, and the main difference is the difference in the water levels of the inlet and outlet water. Under different working conditions, the amplitude of the pumping station building basically shows the characteristics that the vertical amplitude is greater than the horizontal amplitude. The maximum dynamic displacement under drainage condition is greater than that under the diversion condition, and the maximum dynamic displacement appears at the control gate. Under the three working conditions, the maximum dynamic stress of each characteristic part of the pumping station building is low. The maximum total dynamic stress under the drainage condition is greater than that under the diversion condition.

Numerical Simulation of a 3D Seepage Field of an Asphaltic and Concrete Core Rockfill Dam in an Arid Area

This investigation focused on the three-dimensional (3D) seepage field simulation of an asphaltic concrete core rockfill dam (ACRD) under the design water level conditions. At first, the finite element theory of seepage is introduced in the arid area; then, a hydro-junction projection on the Nuer River in Xinjiang is selected as engineering background, the finite element model of a seepage field of an asphaltic and concrete core rockfill dam under the design water level condition is established, and a boundary condition is determined, and the next distribution of a seepage field of different profiles are plotted, and the monitoring value of different points is compared with the finite element solution; conclusions can be drawn that when the antiseepage system of the dam foundation is good, the water level at the downstream side of the core wall is greatly reduced; for the dam foundation, the effects of reducing head of the cutoff wall are rather obvious, and for the dam body, certain leakage defects at the joint of an impermeable body in the cross sections 0 + 456.5 m and 0 + 540 m can exist. For the dam-around seepage, the hydrogeological condition conforms to the actual conditions. These conclusions can provide great significance for the future design.

Estimating the Influence of Sea Level Rise and Climate Change on Coastal Defences in Western Taiwan

Situated in the Western Pacific Ocean, Taiwan is frequently affected by powerful typhoons. The present research evaluates the storm surges that could take place along the western coastline of Taiwan, and the design water level that will likely be required by coastal structures in the course of the 21st century to protect coastal settlements. To do so, the intensity of a given case study typhoon (Soudelor, which caused great damage to Taiwan in 2015) that could affect the target case study area (Yunlin county) was modified by taking into account climate change and sea level rise (SLR), by changing the sea surface temperature (SST), atmospheric air temperature (AAT), and relative humidity (RH) in an ensemble of 14 GCMs in CMIP5 according to RCP4.5 and RCP8.5, targeting the year 2041~2060 and 2081~2100 time horizons. The Advanced Research Weather Research and Forecasting Model (WRF-ARW) and the Unstructured Finite Volume Community Ocean Model (FVCOM) were utilized to simulate the typhoons and storm surges. The hindcasting of the historical typhoon showed good agreement with the observed data provided by the Central Weather Bureau (CWB) in Taiwan, and the simulations under future climate change scenarios forecasted an increase in typhoon intensity, especially the maximum wind speed. However, the storm surge simulations indicated a limited increase in storm surge height, and even a decrease when considering also SLR. Nevertheless, the estimated maximum water level, including both effect of SLR and future storm surge height, can increase up to 3.53 m and 3.84 m relative to mean sea level at the tidal stations in Yunlin and Chiayi County, respectively. The results showed that storm surges in the study area, characterized by a shallow bathymetry with many sandbars and land reclamation projects, are highly influenced by the change in water depth due to SLR and tidal changes, and the existence of the Central Mountain Range, which can greatly affect the accuracy of the simulated typhoon wind fields.

Potential of tidal power plants with least square method on Toaya Beach

The use of energy, especially electrical power, is needed by the wider community— lots of alternative energy from nature, especially in Indonesia that can be utilized to produce electricity. One of the newest alternative examples is the energy produced by tides. Tidal energy is a type of renewable energy that is relatively more predictable in number. One method that can process the waves is the Least Square Method. Where the results of data processing using this method can be known based on tidal observations for 15 days on Toaya Beach located in Donggala Regency, Central Sulawesi, the types of tidal types that occur based on the results of Formzahl’s count is 0.357 that the tidal types that occur are varied types leaning to double daily, with a Root Mean Square Error (RMSE) of 0.028, which means that the difference between predictive results and observational data is accurate. Then also obtained the value of the design water level elevation that is the highest high water level (HHWL) is 2.7 meters, and the lowest low water level (LLWL) is -0.3 meters with a height difference is 3.0 meters. So with the high height difference, the total energy generated by two times a day with a sea area of 9 km2 which is capable of producing energy movement from seawater can be calculated the potential energy generated from the waves of Toaya Beach, which is 5,53 MW.

Experiments on Stability of Tetrapods on Rear Slope of Rubble Mound Structures under Wave Overtopping Condition

In this study, hydraulic model tests were performed to investigate the stability of armor units at harbor side slope for rubble mound structures. The Korean design standard for harbor and fishery port suggested the design figures that showed the ratio of the armor weight for each location of rubble mound structures and it could be known that the same weight ratio was needed to the sea side and harbor side (within 0.5H from the minimum design water level) slope of rubble mound structures. The super structures were commonly applied to the design process of rubble mound structures in Korea and the investigation of the effects of super structures would be needed. The stability number (Nod = 0.5) was applied (van der Meer, 1999) and it showed that the armor (tetrapod) weight ratio for harbor side slope of rubble mound structures needed 0.8 times of that for sea side slope.

Assessment of the position of the project water flow in the lower reaches of hydroelectric facilities, using the example of the novosibirsk hydroelectric power station

Construction of large hydroelectric complexes on the plain rivers of Western Siberia, such as the Ob, as well as other types of anthropogenic impact (infill development, quarrying of nonmetallic building materials, carrying out track works, laying communications, wastewater discharges, etc.) lead to a change in water and channel regimes, hydrological characteristics, channel deformation in the downstream. One of these changes is the landing of water level in the section of the lower pond of the Ob from the Novosibirsk hydroelectric complex to the mouth of the Tom River, which adversely affects navigable conditions of this stretch, operation of water intakes, port and sluice, and also damages the fish industry. The landing of the water level continues to this day, and in order to maintain the design water level, it becomes necessary to increase navigation releases. The design level was changed several times after the commissioning of the Novosibirsk hydroelectric complex due to its low availability, a further change in the availability will lead to a change in the design level mark, or rather its lowering. Therefore, the purpose of the study is to assess the position of the design flow rate at the established design level and make a forecast of changes in water flow depending on the time that has passed since the start of operation of the Novosibirsk hydroelectric complex, taking into account the impact on the channel, carried out dredging works, as well as other types of anthropogenic impacts.

STABILITY ANALYSIS OF THE GRAVITY ANCHORAGE OF A SUSPENSION BRIDGE BASED ON LARGE-SCALE FIELD TESTS


 
 
 The stability of gravity anchorages is critical to the safe operation of suspension bridges. The purpose of this paper is to study the stability of a gravity anchorage under the tension of main cables. Large-scale load tests and direct shear tests under the nature state and the saturated state were carried out in the adit at the bottom of the gravity anchorage, because the bottom surface of the gravity anchorage is below the design water level of a reservoir to be built. Representative rock samples in the anchorage area were selected for indoor tests. The basic parameters of the rock mass and the characteristic value of subsoil bearing capacity were obtained based on the field and indoor tests results. The static theory was used to calculate the anti-sliding stability coefficient, anti- overturning stability coefficient and contact stress of the gravity anchorage. The finite element software was used to calculate the horizontal displacement, vertical settlement and contact stress of the gravity anchorage. The calculation results met the relevant requirements, and it can be considered that the gravity anchorage was stable under the tension of main cables. It would provide a reference for the stability study of the gravity anchorage of suspension bridges.
 
 

TEGAL BESAR BEACH REHABILITATION WITH SCALLOPED CONCRETE BLOCK REVETMENT

Klungkung has a coastline of 113 km out of a total of 5780.06 km2 the coastline in the province of Bali, but about 25 km is eroded. One of the critical areas occurs in Tegal Besar beach which caused erosion of 0.08875 to 3.0915 m/yr. Revetment with scalloped concrete blocks is expected to protect land from the wave attack. Concrete blocks have uniform size and shape, showing the aesthetic aspect so as not damage the beauty of the beach. Analysis of wind, tidal, bathymetry and soil data are carried out to obtain the structure and stability of the revetment. The results of this design can be used to rehabilitate the condition of the Tegal Besar beach. From the analysis, the design wave height with a return period of 25 years (H25) = 0.891 m, while the height with the breaking wave (Hb) = 1.003 m and the breaking wave depth (db) = 1.068 m and the design water level elevation (DWL) = 2.061 m calculated from MSL. The revetment structure has a height of 4.00 m, a peak width of 1.50 m, the weight of the first layer of protection is 300 kg and the second is 30 kg with a thickness of 1.00 m. Toe protection are 1.25 m high, 3.00 m wide and weigh 150 kg. The results showed that the revetment was stable against overturning, shearing, and the bearing capacity of the soil was declared safe with the results of overturning stability 22,075 > 2, slidding stability 2.249 > 1.5 and the bearing capacity of the soil 57,993 > 3 so that the revetment can be eligible to be applied at the site.

Design Water Level Calculation And Analysis Of Chittagong Power Plant Project In Bangladesh

The design water level calculation methods in the Chinese and foreign codes are different. The design high and low water levels and extreme high and low water levels in the Chinese norms are calculated using historical cumulative frequencies with tide level data of not less than 1 year and 20 years, respectively. In foreign norms, the average high and low tide levels of spring tides are mostly used as the design high and low water levels, and for the sea areas lacking long-term measured data, the water level combination method is mostly used to determine the extreme water levels. This paper compares the results of different methods used to calculate the design water level using the Chittagong Power Plant in Bangladesh as an example. The calculations show that it is safer to use the tidal eigenvalue method to determine the design high and low water levels, and that the Water Level Combination Method is more suitable for extreme water level determination than Bangladesh National Building Code.

Improving the carrying capacity of irrigation canals: Al-Tawfiky diversion

ABSTRACT The morphological changes in the irrigation channel cross-section affect its hydraulic efficiency and carrying capacity with time. Periodic maintenance activities are applied to reach maximum carrying capacity. In many cases, removing the total amount of deposit inside canal cross-section above the design bed level is not the optimum maintenance solution hydraulically and economically. Additional discharge must be applied to canal intake to achieve the design water level. Al-Tawfiky Diversion is one of the main irrigation canals in the Delta region. It extended with a length of 175 km to serve 716,540 feddan. The study encloses the first reach from intake to km 36.400 upstream Jamjara regulator. This research aims to detect the most inefficient reaches along the selected study canal reach based on the actual characteristics of the surveyed canal cross-sections, and identifying the most proper maintenance scenario hydraulically and economically. Three hundred and fifty-one cross-sections along the study reach were surveyed. The different hydraulic parameters of these cross-sections were calculated. The data was analyzed and criterion for detecting the most inefficient sub-reaches was introduced. An empirical equation connecting the applied maintenance activities with channel conveyance was deduced. A mathematical model for the study reach was built and calibrated using (SOBEK-1D) to evaluate the proposed four maintenance scenarios.

Research on Stability of Gabion Slope on Seepage-stress Coupling

Based on an example of a basalt fiber gabion ecological slope protection project, this paper uses ABAQUS finite element software to conduct seepage-stress coupling modeling and calculation for the undisturbed slope and gabion protection under two conditions of low water level and design water level. Based on the theory of direct coupling method and strength reduction method, the slope instability evaluation criterion is based on the displacement mutation of the model and the formation of the plastic penetration zone of the soil. The safety factor of the coupled gabion protection is greater than that of the original slope. The results show that the overall stability of the slope after being supported by stone cages and grid protection pads is enhanced, which shows the feasibility and good application prospects of the engineering practice of stone cage slope protection. The research conclusions of this paper can provide reference for the study of seepage-stress coupling in water conservancy projects and provide reference for the stability analysis of similar engineering slopes.

The Joint Effect of River Flow and Tides on the Determination of Design Flood Levels in the Han River

Li, L. and Jun, K.S., 2020. The joint effect of river flow and tides on the determination of design flood levels in the Han River. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 257–261. Coconut Creek (Florida), ISSN 0749-0208.In tidal rivers, flood water levels are driven by a joint effect of upstream river discharge and downstream tidal level. Design flood level, which is used to design structures for flood protection, is usually determined by a steady-state flow model using constant values of upstream river discharge and downstream water level as inputs. However, the approach applying a steady-state flow model can overestimate water levels in tidal rivers because flood wave attenuation and the joint effect of river flow and tides are not taken into consideration. In this study, to investigate the effect of river-tide interaction on water levels along tidal rivers, a time series of design flood flow at the upstream boundary and a large number of tide scenarios at the downstream boundary are forced into a one-dimensional hydrodynamic model of the Han River, resulting in peak water levels along the river. Design flood levels are determined through a statistical analysis of the obtained peak water levels. The design water levels estimated by the proposed approach tend to be lower than that determined by a steady-state flow model. Moreover, a significant difference in the estimated peak water levels is observed near the downstream boundary due to different tide scenarios.

Design water level for flood control of water conservancy projects at the inlet and confluence of branches in river basins: A case study from Guiping Shipping Hub, Xijiang River, Pearl River Basin

Design water level for flood control of water conservancy projects at the inlet and confluence of branches in river basins: A case study from Guiping Shipping Hub, Xijiang River, Pearl River Basin