Maximum Flood Discharge Research Articles

Study of Flooding Behavior and Discharge from Karot Dam in the Event of a Possible Breach by Using the Hydrodynamic Model

This study utilizes the MIKE 11 hydrodynamic model developed by the Danish Hydraulic Institute to simulate flood behavior downstream of Karot Dam under multi-year in-flow conditions. The key parameters analyzed include breach characteristics, flood duration, water depth, flow velocity, discharge rate, and downstream distance. After dam failure, the peak discharge reaches 33,171 m3/s, exceeding the 10,000-year recurrence peak flow of 32,300 m3/s, with a breach duration of 2 h. The estimated peak discharge after simulation using empirical equations and comparative analyses showed maximum flood discharges of 28,187 m3/s, 28,922 m3/s, and 29,769 m3/s, with breach widths of 181 m, 256 m, and 331 m, respectively. The peak discharge predicted to reach the outlet with travel time ranging from 4 h 25 min to 4 h 40 min. Under multi-year average inflow conditions, Mangla Dam faces no risk of failure, with a maximum outflow of 12,097 m3/s and a spillway capacity of 30,147 m3/s. The model accurately predicted discharge values, with a strong correlation coefficient of R2 = 0.9653, indicating strong agreement between the actual water level data and predicted discharge. These insights are essential for developing effective emergency response strategies to mitigate the risks associated with dam failure.

Hydraulic performance analysis of piano key weirs with curvilinear keys: a numerical and experimental study

ABSTRACT A significant number of dams worldwide are very old and thus require a reassessment of maximum flood discharges due to siltation and climate change effects. The Piano Key Weir (PKW) is a relatively new labyrinth-type weir that has emerged as a viable solution for dam rehabilitation and new projects with space constraints. While various studies have been conducted in the past to investigate the influence of geometrical parameters of PKW, there is a lack of information regarding the effect of non-linear slope profile of keys on the discharge efficiency. In this paper, ogee profiles have been introduced in the outlet keys to study their influence on the discharge coefficient. The experiments were performed at the Hydraulics Laboratory, IIT Roorkee, India, using a flume 15 m long, 0.39 m wide and 0.52 m deep. These experiments involved four PKW models with different slope profiles in the outlet key. The results of the laboratory studies and RANS model simulations indicate that the PKW models with ogee shaped outlet keys are more efficient than the linear shaped counterpart for heads higher than their design head. The maximum increase in discharge coefficient for the PKW models with curvilinear outlet keys was 9%.

Hydrological Regime of Rivers in the Periglacial Zone of the East European Plain in the Late MIS 2

At the end of the Pleniglacial and the first half of the Late Glacial period, approximately between 18 and 14 ka BP, rivers of the central and southern parts of the East European Plain had channels up to 10 times as large as the present day channels of the same rivers. These ancient channels, called large meandering palaeochannels, are widespread in river floodplains and low terraces. The hydrological regime of these large rivers is of great interest in terms of the palaeoclimatology of the late Marine Isotope Stage 2 (MIS 2). In this study, we aimed at quantitative estimation of maximum flood discharges of rivers in the Dnepr, Don and Volga basins in the late MIS 2. To approach this, we used massive measurements of the morphometric characteristics of large palaeochannels on topographic maps and remote sensing data—palaeochannel width, meander wavelength and their relationships with river flow parameters. The runoff depth of the maximum flood, which corresponds to the maximum depth of daily snow thaw during the snowmelt period, was obtained for unit basins with an area of <1000 km2. The mean value for the southern megaslope of the East European Plain was 44.2 mm/day (6 times the modern value), with 46 mm/day for the Volga River (5.5 times), 45 mm/day (6.3 times) for the Don River and 39 mm/day (8 times the modern value) for the Dnepr River basins. In general, the Dnepr basin was drier than the Don and Volga basins, which corresponds well to the modern distribution of humidity. At the same time, the westernmost part of the Dnepr River basin was relatively wet in the past, and the decrease in humidity from the past to the modern situation was greater there than in the eastern and central regions. The obtained results contradict the prevailing ideas, based mainly on climatic modeling and palynological data, that the climate of Europe was cold and dry during MIS 2. The reason is that palaeoclimatic reconstructions were made predominantly for the LGM epoch (23–20 ka BP). On the East European Plain, the interval 18–14 ka BP is rather poorly studied. Our results of paleoclimatological and palaeohydrological reconstructions showed that the Late Pleniglacial and the first half of the Late Glacial period was characterized by a dramatic increase in precipitation and river discharge relative to the present day.

Analysis and Design of a Box Culvert Using Bentley Culvert Master Software

Box culverts are utilized in situations where natural stream flow intersects with roads and railway lines. This research utilizes a digital elevation model and the water Modeling System software to assess the catchment area of the primary valley and identify the factors contributing to flooding in Qoshtapa City. The study involves an analysis of the existing culvert and generated the necessary data for the design of a new culvert. Despite the presence of the existing culvert, floodwater levels rose to over 1 m above the roadway elevation of Erbil-Kirkuk during the last flood event in 2021–2022. The research collected hydrological and climatic data for the study area, conducted soil type analysis using the Harmonized World Soil Database software, and performed hydraulic calculations to estimate the maximum flood discharge of the valley using the Hydrological Engineering Center-Hydrological Modeling System software for flood return periods of 50, 100, and 200 years, for design, to select the best economic alternative. The new culvert design was executed using Bentley Culvert Master software to ensure that floodwaters can flow through the culvert without rising to street level. The results indicated that the new culvert design surpasses the capacity of the existing one. The results show that the best economic alternative hydraulic design is the first alternative capacity of 201 m3/s of a 100-year return period; the new design cross-section area of the culvert is 52.5 m2.

FLOOD MODELLING OF RIAM KIWA WATERSHED USING HEC-HMS

At the end of 2021 to early 2022 several areas in Banjar Regency were flooded. This incident had a major impact on the surrounding area and became a national concern. One of the causes of the disaster was high-intensity rainfall which caused the water in the Riam Kiwa River to overflow. HEC-HMS software was used to simulate the designed flood discharge. This research aims to model the magnitude of the designed flood discharge with return periods of 5, 25, 50, and 100 years. Due to limitations of rainfall data from the field, satellite data from GSMaP were collected. In the distribution of rainfall frequency analysis, the Log Pearson type III method was chosen for calculating designed rainfall. Then, the Modified Mononobe Method was applied to calculate hourly rainfall intensity. Other data i.e., soil types, slope gradient and land use were analyzed using ArcGIS application. These three data produced hydrological parameters which were used as input values in the HEC-HMS using the Soil Conservation Service (SCS) method. Three parameters’ values show that Riam Kiwa watershed has more than 90% clay with a slope gradient of 83.58% (steep slope) and land use is predominantly consisted of mixed dryland agriculture (47.73%). From HEC-HMS simulation, it was found that Riam Kiwa watershed with an area of 1781.77 km2 produces maximum flood discharge ranges from 8,822.3 m3/s to 17,058.6 m3/s; with a water volume ranges from 182,991.9 m3 to 340,889.6 m3 in 5 years to 100 years return periods, respectively. From the results, it can be concluded that impermeable clay soil and steep slope are the two major factors that contribute to the flooding occurrence in the area.

ANALYSIS OF FACTORS FOR FORMATION OF THE CHUMYSH RIVER MAXIMUM RUNOFF (WESTERN SIBERIA)

Link for citation: Samoilova S.Yu., Lovtskaya O.V., Kudishin A.V., Arnaut D.V. Analysis of factors for formation of the Chumysh river maximum runoff (Western Siberia). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.116-128. In Rus. The relevance of the study stems from the necessity to refine the methods of medium-term flood forecasts when sufficient hydrometeorological data are not available. The purpose of the work is to assess probable application of spatially distributed precipitation models to forecast runoff volume of flood, to develop stochastic models for predicting flood volume and its maximum discharge using hydrometeorological observation data, distributed precipitation datasets from reanalysis and remote sensing data of high spatial and temporal resolution. Methods include geoinformation, complex geographical and hydrometeorological analysis, statistical methods (correlation and regression analysis). Results. The Chumysh basin moistening was estimated due to the data from spatially distributed precipitation models and hydrometeorological observation data; the relationship of total precipitation with runoff volume and maximum flood discharge was analyzed. A comparative evaluation of the obtained dependencies made it possible to identify key predictors for deriving the multiple linear regression equation. The statistical model was developed for predicting volumes and maximum discharges of Chumysh flood at Talmenka settlement using hydrometeorological observation data and reanalysis ones of high spatial and temporal resolution.

PERENCANAAN BENDUNG TETAP UNTUK JARINGAN IRIGASI BANDA MUSAJIK D.I GUMARANG KECAMATAN PELEMBAYAN KABUPATEN AGAM

Banda Musajik, which is located in Jorong Alahan Anggang, Nagari Tigo Koto Silungkang, Agam Regency, West Sumatra Province, is one of the irrigation networks in D.I Gumarang, under the authority of the UPTD Balai SDA and BK North Sumatra Province. The service area is 30 ha, the water source comes from Batang alahan anggang. Weir planning is based on the design flood discharge with a return period of 100 years. The discharge plan uses 10 years of rainfall data. Rainfall stations that affect the Alahan Anggang watershed are Gumarang Station and Kampuang IV Station. The area's average rainfall was determined by the Thiessen Polygon method, the planned rain by the log normal method and the frequency analysis test using the chi square test. Maximum flood discharge (Q100) 13.54 m3/s. The effective width of the dam is 11.42 m, one flush door is 0.80 m wide, one pillar is 0.50 m thick. The type of lighthouse is round with a radius of 0.80 m and a height of 1.52 m. The stilling pool is planned for the Vlugter type with the height of the weir, the length of the pool floor and the radius of the weir of 3.74 m. The length of the flood embankment from the weir to the upstream is 19 m with a height of 0.50 m from the flood water level. From the analysis of the forces acting on the body of the weir, the number of vertical forces (ΣRV) is 5,916 T, the number of horizontal forces (ΣRH) is 8,397 T, the number of holding moments (ΣMT) is 352,678 T.m, the number of overturning moments (ΣMG) is 344,87 T.m. stability of the weir body against overturning 1.31 1.3 , against shear 1.42 1.3, Eccentricity ( e ) 5.05 78.74 Maximum stress 1.90 78.74, minimum stress -0.36 78.7, the design of the weir body is safe against shearing, overturning, and the bearing capacity of the ground.Key words : Hydrological analysis, Hydraulic design of weir, Weir stability.

Analysis of Peak Flood Discharge in Small-Scale River Flow Area

Purpose: Flood discharge is a critical component in reducing the impact of flooding in a given location. An analytical technique based on a watershed's morphometric properties is a method for those without a gauge, particularly in small-scale watersheds.
 Design/methodology/approach: The synthetic unit hydrograph (HSS) approach is used in this study to analyze flood output. This study was conducted in the Akelaka watershed, a sub-watershed of Tayawi. This analysis relies on spatial and attributes data. A spatial study of watershed morphometric properties was obtained by integrating digital elevation model (DEM) data into geographic information system-based applications (GIS). Meanwhile, using rainfall data from 2019 to 2021, a statistical approach is used to calculate the design rainfall intensity, which is then used as an input variable in the HSS analysis.
 Findings: The findings of hydrographic analysis using Nakayasu HSS demonstrate that the peak flood time (Tp) is 2.8 hours with a maximum flood discharge (Qp) of 56.636 m3/s, 76, 987 m3/s, 88,091 m3/s, and 101,279 m3/s for return periods of two years, five years, ten years, and 25 years.
 Paper type: Research paper

Batang Bayang River Flood Modeling Based on Rain Return Period

West Pasaman Regency is one of the regencies in West Sumatra that experiences flooding the most. In 2020, in April and September, floods occurred in the West Pasaman district, more precisely around the Nagari Ujung Gading area, Lembah Melintang District. Floods most often inundate the Jorong Lombok and Jorong Irian areas. The flood that occurred was caused by the overflow of the Batang Bayang river. Puddles of water inundated at least 150 residents' houses until the water level reached a height of 1 meter. The problem of flooding almost every year is felt by residents who live near the location of the Batang Bayang river. This study aims to determine the flood discharge of the Batang Bayang river with return periods of 2, 5, 10 and 25 years. Then this study also aims to determine the ability of the Bayang Bayang River to flow flood discharge for 2, 5, 10 and 25 years return periods. The results show that the 2-year return period produces a maximum flood discharge of 47.2 m/s3. In the 5-year return period it produces a flood discharge of 110 m/s3, in the 10-year return period it produces a flood discharge of 143.6 m/s3 and at the return period of 25 years resulted in a flood discharge of 189.2 m3/s. The cross section modeling in the 2 year return period resulted in a water elevation of 21.07 meters. The 5-year return period modeling results in a water level elevation of 22.4 meters. The 10-year return period models the water at an elevation of 23.01 meters and the 25-year return period produces a water level of 23.72 meters.

Modeling Extreme Stochastic Variations using the Maximum Order Statistics of Convoluted Distributions

Modeling extreme stochastic phenomena associated with catastrophic temperatures, heat waves, earthquakes and destructive floods is an aspect of proactive mitigation of risk. Hydrologists, reliability engineers, meteorologist and researchers among other stakeholders are faced with the challenges of providing adequate model for fitting real life datasets from the extreme natural hazardous occurrences in our environment. Convoluted distributions (CD) and generalized extreme value (GEV) distribution for r- largest order statistics (r-LOS) have been some of the prominent existing techniques for modeling the extreme events. This study explored the properties of order statistics from the convoluted distribution as alternative procedure for analyzing the extreme maximum with the aim of obtaining superior modeling fit compared to some other existing techniques. The new procedure called MAXOS-G employed the potential properties of the Maximum Order Statistics (MAXOS) and the flexibilities of convoluted distributions where G is taken to beWeibull-Exponential Pareto (WEP) and the New Kumaraswamy-Weibull (NKwei) distributions. The maximum order statistics of the WEP distribution (MAXOS-WEP) and NKwei distribution (MAXOS-NKwei) was derived and applied to three datasets consisting of annual maximum flood discharges, annual maximum precipitation and annual maximum one-day rainfall. Some properties of the MAXOS-WEP was investigated including the moment, mean, variance, skewness, and kurtosis. Characterization of WEP distribution by the L-moment of maximum order statistics was presented and coefficient of L-variation, L-skewness and L-kurtosis were derived. The results from the application to three datasets using R-software justified the importance of this new procedure for modeling the maximum events. The MAXOS-NKwei and MAXOS-WEP models provide superior goodness-of-fit to the datasets than the WEP and NKwei distributions and better than some previously proposed convoluted distributions for modeling the datasets.

An Investigation on the Effect of Outliers for Flood Frequency Analysis: The Case of the Eastern Mediterranean Basin, Turkey

Flood frequency analysis is accepted as one of the most important applications of water resource engineering. Measurements with higher and lower values, such as outliers, can be seen in hydrological data sets based on longer observation periods that extend the overall range. This study used 50 and 25 years of annual maximum flow data from 1962 to 2011 and from 1987 to 2011 from the Stream Gauging Stations (SGS) numbered 1712, 1717, and 1721 located within the borders of the Eastern Mediterranean Basin. The flood discharges were estimated using Normal, Gumbel, and Pearson Type III probability distributions. The study adopted Kolmogorov–Smirnov (K-S) and Chi-squared goodness-of-fit tests to investigate the suitability of probability distribution functions. The maximum flow rates were obtained by utilizing Normal distribution in the 2-year and 5-year return periods for the flood values calculated with the raw data; however, after the modification of the outliers, maximum flood discharges were estimated by adopting the Pearson Type III function. While the maximum discharges for the 1717 SGS were determined using the Gumbel distribution, the Pearson Type III distribution function was utilized for the 1712 and 1721 SGSs. As a result of the K-S and Chi-squared tests, it was determined that adjustment of the outliers resulted in positive goodness-of-fit results with the Pearson Type III function.

What could we have learnt from the previous flood data to predict losses caused by the 1980, 1986, and 1998 catastrophic floods in Ukrainian Transcarpathian?

This paper explores some aspects relating to retrospective predicting the confirmed monetary losses caused by the disastrous floods of 1980, 1986, and 1998 in the Tisza River basin within the Transcarpathian region of Ukraine. The research was based on two time series – the losses because of past floods and the maxima water discharges gauged at the hydrological station near the village of Vylok, Vynohradiv district. The main aim of the research was to make out whether it had been the possibility to predict the losses due to those floods in advance.In solving the task, there was revealed and modelled the dependence of the risk of losses due to the floods in Transcarpathia on the maximum water discharges of the Tisza River gauged at the “Vylok” hydrological station. Predicting was based on the hypothesis of the stationary random process for maximum water discharges, which allowed using an empirical distribution function of a random variable regarding flood water discharges assessing the risk of flood losses.Retrospective predicting of the losses caused by the floods of 1980, 1986, and 1998 was carried out by means of a combined situational-inductive predictive modelling method (CSIPMM), being an original author’s development. The method relates to predicting the behaviour of complex dynamic systems based on monitoring findings presented as time series data reflecting evolutions of a resulting (dependent) variable and an explaining (independent) variable (predictor). The method uses extrapolation-regression type models. According to this method, the prediction task is performed in two stages. The first stage realises the retrospective situational modelling task aiming to obtain a set of simple regressions (situational models) built on data of sample time series. The situational models are accepted to be adequate or relevant ones only within certain periods of time determined as situations. In the second stage, based on the generalization (on an ensemble) of the obtained retrospective situational models, inductive “levels” models are built, which reflect the behaviour of a controlled parameter of the system or process (a resulting variable) at several fixed values of a predictor in time. The inductive models are used in extrapolative predicting situational models belonging to future periods (situations).In total, three predictions were made: (1) taking into account the annual maximum flood discharges from 1954 to 1979 (before the flood of 1980); (2) the same from 1954 to 1985 (before the flood of 1986); (3) the same from 1954 to 1997 (before the flood of 1998). The study found that there had been a possibility to predict the confirmed monetary losses inflicted by the flood of 1986 and 1998 (relative predicting errors of 7.2-8.7% and 6.0-12.8% depending on the prediction options).

ANALISA SENSITIVITAS DURASI HUJAN PADA PERHITUNGAN DEBIT BANJIR DAS TENGGANG DAN SRINGIN

Design flood is one of the important aspects in the design of water structures. Calculation of the design flood is very dependent on the existing rain data in the watershed area. The amount of flood discharge is not only influenced by the value of rainfall but also depends on the duration and distribution of rainfall per unit of time.This study was conducted to determine duration of rainfall that produces the maximum flood discharge for Tenggang and Sringin River. Calculation of flood discharge for Tenggang and Sringin River was carried out using a rainfall distribution pattern (hyetograph) for rainfall durations of 2 hours, 3 hours, 4 hours and 5 hours with the distribution of rainfall distribution referring to hourly rain data at Maritime Station. Results of analysis show that different distributions are produce different flood discharge values. For Tenggang and Sringin rivers, the maximum flood discharge value is obtained at a rain duration of 2 hours.Keywords: flood discharge, rainfall duration, hyetograph

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.

HYDROLOGICAL PREDICTION FOR MAPPING THE POTENCY OF BREAK IN THE SAGULING DAM, WEST JAVA PROVINCE, INDONESIA

Dams are structures built across bodies of water to hold the water back. They offer various economic, environmental, and social benefits, including large-scale water storage, hydroelectric power generation, tourism, and recreation. However, in addition to offering benefits, dams are also associated with certain risks. One of the biggest risks is the possibility of a dam breaking, which may occur if the discharge inflow is overly high at the point it enters the reservoir. A very high discharge inflow can result in a probable maximum flood (PMF) discharge. This study investigates the potential of hydrological analysis with regard to mapping the dam break potency of the Saguling Dam in Indonesia. The reservoir system on the Citarum River consists of three reservoirs, namely Juanda (Jatiluhur), Cirata, and Saguling. Together, they comprise a cascade reservoir system. The Saguling Dam is located in the upstream, the Cirata Dam is in the middle stream, and the Juanda Dam is under the Cirata Dam. This study focuses on the Saguling and Cirata Dams. It analyzes the PMF using the Nakayasu, ITB-1, Gama-2, and Snyder methods. Moreover, the rainfall analysis involves the Thiessen polygon and the frequency distribution of the Gumbel, Log Pearson-III, and Log Normal, while the hourly rainfall is analyzed using the PSA-7 currently being investigated in Indonesia. The intensity of the rainfall in the catchment area of a dam is directly related to the level of the discharge inflow that enters the reservoir. The Saguling Dam faces a similar risk, which explains the need to conduct a comprehensive hydrological analysis to assess and map one of the key risk factors for the dam breaking.

Upaya Pengendalian Banjir Kawasan Sub-Das Celeng Pra Pembangunan Embung Imogiri

Flood on March 17 in the Celeng River, Wukirsari Village, D.I. Yogyakarta became the biggest flood that ever happened on the Bog River. Floods are caused by heavy flow of water from the hills in the Imogiri and Dlingo areas. The Celeng River overflowed and submerged four hamlets in Wukirsari Village, Imogiri District. This study aims to determine flood control efforts in the Celeng sub-watershed area. The research location is in the Kali Celeng sub-watershed, Wukirsari, Imogiri, D.I. Yogyakarta with the control point located in the lower reaches of the Celeng River right at the confluence of the Celeng River and the Oyo River. The hydrological analysis was calculated using the Gamma 1 unit hydrograph method with a return period of 10 years. The maximum flood discharges for each of the Celeng sub-watersheds are 75.73 m3/s, 38.22 m3/s, 37.20 m3/s, 18.54 m3/s, and 21.57 m3/s, and 26.29 m3/s, while the 10-year return flood discharges for the Oyo watershed is 959.60 m3/s. The hydraulic analysis was carried out by modeling the 13.35 km long Celeng River channel with HEC-RAS 4.1 software. The flow simulation is carried out steadily. The simulation results show that during the simulation of the existing state there are several points of the section of the Celeng River that overflow. The overflowing sections are then normalized with certain groove dimensions that are adjusted to the location of the flood point. The results of the flow simulation after normalization show that most of the Celeng River channel can accommodate the flood discharge that occurred. The sections that still overflow after normalization are then given embankments with an average height of 0.75 m.

Joint Modelling of Flood Hydrograph Peak, Volume and Duration Using Copulas—Case Study of Sava and Drava River in Croatia, Europe

Morphodynamic changes in the riverbed may be accelerated by the climate change-induced effects, mostly through the increase of the frequency of extreme climatic events such as floods. This can lead to scouring of the riverbed around the bridge substructure and consequently reduces its overall stability. In order to better understand hydromorphological processes at the local scale, the influence of floods on bridge scour requires a detailed analysis of several interacting flood hydrograph characteristics. This paper presents a multivariate analysis of the annual maximum (AM) flood discharge data at four gauging stations on the Drava and Sava Rivers in Croatia (Europe). As part of the hydrograph analysis, multiple baseflow separation methods were tested. Flood volumes and durations were derived after extracting the baseflow from measured discharge data. Suitable marginal distribution functions were fitted to the peak discharge (Q), flood volume (V) and duration (D) data. Bivariate copula analyses were conducted for the next pairs: peak discharge and volume (Q–V), hydrograph volume and duration (V–D) and peak discharge and hydrograph duration (Q–D). The results of the bivariate copula analyses were used to derive joint return periods for different flood variable combinations, which may serve as a preliminary analysis for the pilot bridges of the R3PEAT project where the aim is to investigate the influences on the riverbed erosion around bridges with installed scour countermeasures. Hence, a design hydrograph was derived that could be used as input data in the hydraulic model for the investigation of the bridge scour dynamics within the project and a preliminary methodology is proposed to be applied. The results indicate that bivariate frequency analysis can be very sensitive to the selected baseflow separation methodology. Therefore, future studies should test multiple baseflow separation methods and visually inspect the performance.

Flood–Ebb and Discharge Variations in Observed Salinity and Suspended Sediment in a Mesotidal Estuary

To explore the spatial and temporal variations in salinity and suspended-sediment concentration in the Danshuei River estuary of northern Taiwan, two intensive field surveys were conducted in July 2016 and 2019 to assign high- and low-flow conditions, respectively. According to the analysis of tidal characteristics, the duration during ebb tide was longer than that during flood tide, while the maximum ebb discharge was higher than the maximum flood discharge, causing the occurrence of tidal asymmetry during ebb and flood tides. The barotropic forcing dominated during high flow, resulting in lower salinity and a shorter distance of saltwater intrusion. Based on the analyzed results using stratification indices, most of the time was spent in the state of partial mixing at the Guandu Bridge and good mixing at the Taipei Bridge during high flow, while most of the time was spent in the states of partial mixing and good mixing at both Guandu Bridge and Taipei Bridge during low flow. More stratification occurred during high flow at high slack tide compared to that during low flow. The freshwater discharges from upriver reaches controlled the suspended-sediment concentration (SSC) in tidal estuaries. The higher SSC appeared downstream of the tidal estuary at ebb tide during high flow. Observations also revealed that there was an estuarine turbidity maximum at the bottom layer of Guandu Bridge.

Evaluation of WMS model in basins without statistical data in southwestern Iran using Dicken's experimental method (case study: Kuhgel Basin of Khuzestan Province)

Floods are important in studies related to water resources utilization, dam construction, basin management and hydrological studies. Therefore, to a large extent, the accuracy of these studies and the safety of water facilities depends on the flood study methods. The aim of this study was to investigate the WMS model in determining the maximum flood discharge in three sub-basins with areas of 10.3, 1.5 and 7.3 square kilometers in the Kuhgel region located in southwest of Iran. Comparing the results of the model with the results of the Dicken's experimental method in the region showed that the maximum flood discharge and flood volume estimated by the WMS model are well consistent with the values of the Dicken's experimental method. Therefore, the relative error percentage index, root-mean-square error and Nash–Sutcliffe coefficient of the model were calculated equal to 6.12, 0.51 and 0.82, respectively. The results also revealed that the mean of model estimates was approximately 0.16% higher than Dicken's experimental method. Based on Student's t-test, the difference between the model values and Dicken's experimental method was not significant at the level of one percent. The results show that the WMS model simulates flood values with appropriate accuracy for basins with no statistical data in southwest of Iran. Due to the high sensitivity of the SCS method in the WMS model to rainfall distribution, rainfall analysis in the study area is necessary to achieve the desired results and the rainfall distribution and its time distribution should be as close as possible to the actual values in the region.

Study on The Making Of a Breakwell For Water Standing Management in Sitinggil Residence Jember

Drainage is one of the facilities used to drain water so that it does not cause puddles that can disrupt people's activities and the economy. In the de sitinggil residential area, Patrang District, Jember Regency, there are flood problems caused by high rainfall and significant land use changes. Changes in land use from rice fields or empty land to settlements. The change in land use results in a larger runoff. Besides that, there is sediment deposition which reduces the wet cross-sectional area, as a result the dimensions of the existing drainage channels cannot accommodate the maximum flood discharge. To anticipate the problems that occur because, it is necessary to plan an absorption well. So based on the existing process, several conclusions can be drawn, namely the runoff discharge at the 10 year return period in the housing of 0.445 m3 / s by making 20 communal infiltration wells which will be able to reduce flooding that enters the river.