Flood Peak Discharge Research Articles

Dynamic relations for the deposition of sediment on floodplains and point bars of a freely-meandering river

Fluvial features such as floodplains and point bars are built by sediment deposition and sculpted by erosion. Long-term measurements (38 yr) of the cross-section topography of active floodplains and point bars along the freely-meandering Powder River in southeastern Montana, USA (mean daily discharge of 12.5 m3 s−1), were used to develop dynamic relations between annual sediment deposition and peak-flood discharge. Five floodplain sections and five point-bar sections were selected from 24 cross sections along a 90-km study reach. At each cross section the sediment deposition volume per unit streamwise distance was computed as the difference between two topographic surveys made in consecutive years.Snowmelt floods were found to be the dominant annual process. However, other processes such as flash floods, ice breakup floods, and autumnal floods were important episodically. The dynamic relations were linear for both fluvial features. The snowmelt deposition-discharge relations showed, in general, that point bars were about two times more efficient at trapping sediment than floodplains. Each relation had a discharge threshold that must be exceeded before sediment was deposited. Although these discharge thresholds for floodplains and point bars had essentially the same mean value (69 and 71 m3 s−1, respectively), they represented different processes. Thresholds for other rivers will probably differ from those for Powder River because of different channel geometry and sediment characteristics.

ANALISIS BANJIR DAN TINGGI MUKA AIR PADA RUAS SUNGAI CILIWUNG STA 7+646 s/d STA 15+049

The problem of flooding in DKI Jakarta is considered normal because almost every year can hit the city of Jakarta especially during the rainy season. In DKI Jakarta itself there are several rivers, one of which is Ciliwung River which is the most influential river in DKI Jakarta which often cause flood every year. The purpose of this research is to know the location of flood / river flood that occurs in the segments along Ciliwung River STA 7 + 646 s / d STA 15 + 049. Data processing begins with the calculation of average rainfall, frequency analysis, and then hour-time rain distribution. Method of calculation of flood discharge using the synthetic unit of Nakayasu and Gama I synthetic data. Rainfall data using 2 observation stations for 3 years rain (2014-2016). In the frequency analysis used Gumbel distribution berdasrkan test results suitability data Smirnov- Kolmogorov and Chi-Square. The result of flood peak discharge design with HSS Nakayasu on return period Q5 = 687,80 m3 / dt, Q10 = 743,21 m3 / dt, Q20 = 796,36 m3 / s, Q50 = 865,15 m3 / dt, Q100 = 916,71 m3 / s, while flood peak discharge design with HSS Gama I on return period Q5 = 347,03 m3 / s, Q10 = 372,12 m3 / s, Q20 = 396,20 m3 / s, Q50 = 427, 36 m3 / s, Q100 = 450,71 m3 / s. The design flood discharge value approaching the measured debit value is HSS Nakayasu. Steps continued using HEC-RAS 4.1.0 software to determine the capacity of river catchment by using Nakayasu discharge. After analyzing using the software, most stationing of the Ciliwung River at STA 7 + 646 to STA 15 + 049 can not accommodate the planned discharge during the 20th anniversary period, hence the need for river improvements in the form of river normalization and elevation of dikes.

Different Flooding Behaviors Due to Varied Urbanization Levels within River Basin: A Case Study from the Xiang River Basin, China

Booming urbanization due to a fast-growing population results in more impervious areas, less infiltration, and hence greater flood peak and runoff. Clear understanding of flood responses in regions with different levels and expansions of urbanization is of great importance for regional urban planning. In this study, comparison of flooding responses to urbanization processes in terms of flood peak and runoff volume in the upper, middle, and lower Xiang River Basin (XRB), China, was carried out using the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) model. From 2005 to 2015, urbanization level and intensity were higher in the lower XRB compared to the upper and middle XRB, and the overall expansion rate of urban areas was 112.8%. Modeling results by the HEC-HMS model indicate elevated flood peak discharges and volumes due to fast urbanization in the XRB from the 1980s to 2015. This rapid increase is particularly the case in the lower XRB. The study also revealed different hydrological responses of flood regimes—urbanization tends to have larger impacts on peak flood flow rather than on flood volume in the lower XRB, which further corroborated urbanization-induced intensifying flood processes in terms of peak flood flow. Urbanization has increasing impacts on flood volume from the upper to the lower XRB, which can be attributed to accumulated runoff down the river system. This study provides a reference for basin-wide land use and urban planning as well as flood hazard mitigation.

Reservoir Effects on Flood Peak Discharge at the Catchment Scale

AbstractThis paper proposes a method to easily quantify the attenuation due to a reservoir on downstream flood peak discharges, that is, to the downstream flood frequency curve. Using a parsimonious Instantaneous Unit Hydrograph‐based model, we show that the flood peak attenuation is mainly controlled by three system characteristics: (1) the reservoir position along the river channel, (2) the spillway dimensions, quantified by the reservoir storage coefficient; and (3) the storage capacity. These three system characteristics are quantified by three dimensionless numbers, which are derived analytically for an idealized catchment. The degree of flood peak attenuation increases for increasing storage capacity and spillway dimensions, in different ways depending on the reservoir position along the river channel. An optimal position exists, which maximizes the degree of flood peak attenuation, and is in general different from the outlet of the catchment. Interestingly, for large reservoirs with relatively small spillways, a range of quasi‐optimal positions exists. With the Instantaneous Unit Hydrograph‐based model, we also investigate how the duration of extreme rainfall relevant for determining the maximum flood peaks at the catchment outlet changes depending on the three system characteristics. Some of the assumptions of the method (i.e., catchment simple morphology and linearity of reservoir response) are relaxed in a real‐world example, which demonstrates that the synthetic results approximate well what would be obtained by a more realistic model.

Development and Evaluation of Automatic Discharges Measurement Technology for Small Stream Monitoring

Small streams have flood effects on both national and local streams located further downstream. Moreover, damages are increasing in these basins, making the development of adaptive prevention and response measures an urgent necessity. However, the challenge is that small streams remain non-measuring sites. Furthermore, there are about 22,800 small streams, which are too many for the local governments to measure during the flood season. Thus, in this study, a CCTV-based automatic discharge measurement technology was developed to support local governments in monitoring, and minimize the labor required. To evaluate the new technology, discharges were measured in Jungsunfil-chun of Ulju-gun, which is a test bed operated by the National Disaster Management Institute, and compared with the Aquatic Doppler Velocimetry (ADV) based discharges and the weir discharges. The results show that measurements using the new technology are in good agreement with the ADV based discharges. Furthermore, the new technology has the advantage of being able to capture peak flood discharges with short measurement times. Moreover, it is a sustainable measurement method to support flood control by verification of stream flow and situational influences, and provides stable measurements by using a non-contact measurement method. It is expected that the new technology may be used to increase the number of monitoring sites, and the hydraulic data sets collected from various small stream test beds can be used to enhance the design code for estimating flood discharges and the small stream flood warning system to reduce damage in small streams. Keywords: Small Stream, Sustainable Measuring Method, Automatic Discharge Measurement Technology, Acoustic Doppler Velocimetry, Weir Discharges

Runoff-sediment dynamics under different flood patterns in a Loess Plateau catchment, China

Investigating the suspended sediment dynamic is useful for gaining a more comprehensive understanding of runoff and sediment yield process. The study analyzes the sediment flow behavior in relation to the flood patterns in the Xichuan River catchment on the Loess Plateau. Based on 23-year hydrological data collected from Zaoyuan hydrological station and K-medoids clustering method, one hundred and twelve flood events data were classified into four flood patterns. The hydrologic features of different flood patterns exhibit significant differences. The values of the mean runoff depth, the mean flood duration, and the mean flood peak discharge decreased as the following order: Pattern A > Pattern C > Pattern D > Pattern B. Each flood pattern results in differing levels of the event sediment yield (SY), the SY of Pattern A (10,275.33 t·km−2) and Pattern C (1196.39 t·km−2) were larger than those from Pattern B (218.84 t·km−2) and Pattern D (693.84 t·km−2). These results indicated that greater attention should be paid to Pattern A and Pattern C because of the largest sediment delivery effect. Multiple stepwise regressions analysis suggested that the contribution of main runoff-related factors to event sediment yield varied with different flood patterns. In addition, hysteretic analysis between suspended sediment concentration and runoff suggested that counter-clockwise and figure-eight loops were the dominant loops. The results provided a useful information to flood pattern classifications and suspended sediment dynamics research, and enriched the sediment control theory at the watershed scale.

Intercomparison of Rainfall Estimates of EV1 Distribution for Estimation of Peak Flood Discharge for Ungauged Catchments

Intercomparison of Rainfall Estimates of EV1 Distribution for Estimation of Peak Flood Discharge for Ungauged Catchments

Controls of flash flood peak discharge in Mediterranean basins and the special role of runoff-contributing areas

During the complex dynamic interactions between rainfall and basin properties, different portions of the basin produce runoff at different moments. Capturing this spatiotemporal variability is important for flood analysis, but knowledge of this subject is limited. The presented research aims at improving the understanding of runoff-contributing areas (RCA; hillslope sections from which water flows, reaches the stream network, and consequently the basin outlet) and at examining their relationship with the magnitude of a flash flood's peak discharge. A distributed hydrological model (GB-HYDRA) that enables computing RCA and flood discharge was developed. The model was applied to four medium-size basins (18–69 km2) in a Mediterranean climate and 59 flash flood events were analyzed. The correlation between basin input flux (basin area multiplied by the basin maximal rain intensity averaged over the time of concentration) and output flux (observed peak discharge) was poor (R2 = 0.16). However, using a newly developed index, termed IRCA, to calculate the input flux accounting only for the RCA extent and rainfall intensity over it, resulted in a substantially higher correlation (R2 = 0.64) across a wide range of flood magnitudes. The highest correlation was found using a 50-min time window, which is shorter than the time of concentration. Flood events were categorized according to their magnitude and the differences of several factors among the groups were examined. Pre-storm soil moisture content was found to be similar for all event magnitudes; however, pre-peak soil moisture content was substantially different between moderate and large–extreme events. Other important properties that differed between magnitudes were: RCA extent and its averaged rain intensity and ratio of convective rainfall. Finally, areas with land-uses characterized by low runoff potential became dominant and contributed mainly during large and extreme events. Although the RCA and its extent full potential is yet to be fulfilled, it is proposed as a significant tool for understanding processes of flash flood generation at the basin scale in future research.

Study on the storm-sediment yield model of the Baizhang Creek small watershed

Mastering the sediment yield in the watershed was the basis for the comprehensive management planning of the basin, the prevention and control of soil erosion, the rational utilization of the water resources. Due to the simple structure of the statistical model and the convenient calculation, the statistical prediction model of sediment yield was a powerful tool for the prediction of sediment yield. Based on the measured data of the Baizhang Creek small watershed in Zhejiang province, the impact factors of sediment were systematically analyzed. And then the main factors were considered to be rainfall, runoff depth, flood peak discharge and mean rainfall intensity, which were used to established statistical model of sediment yield in rainstorm. The statistical prediction model had a certain precision.

DAS Ampal Analisa Fungsi dan Pengaruh Bangunan Pengendali Banjir DAS Ampal Kota Balikpapan

Ampal Catchment Area has 25.273 km2 area and 4.699 km main river length, which planned to have 13 flood control construction. Until 2017, this catchment area has only three flood control construction. The watershed has only three built-in batters that are used to reduce the amount of flood discharge flowing on the Ampal river. Based on these conditions, it is necessary to analyze the magnitude of the difference of flood peak discharge on the existing condition (three bendali) compared with the condition of the plan (thirteen bendali). Therefore, analyzed the function and influence of flood control construction in Ampal Catchment Area by counting the flood peak discharge in each condition. From the analysis result, obtained the amount of peak discharge flowing in Ampal river existing condition is equal to 170,40 m3/s while at the condition of plan is equal to 83,80 m3/s. From the results of analysis, it is stated that the magnitude of the decrease of debit (ΔQ) after all the builds is 86.60 m3/s.

KAJIAN KERUGIAN RISIKO BANJIR PADA SUNGAI KRUENG MEUREUBO

Krueng Meureubo River is one of the big river through the West Aceh district. Krueng Meureubo River has a length of ± 188 km and a catchment area of 1.632 km2. The aims of this study is to conducting inundation and the value of losses caused by floods in Krueng Meureubo river. The scope of this study includes analysis of rainfall plans, flood discharge plans, and the value of losses caused by floods. Based on data processing at 4 (four) rain stations, the annual maximum annual rainfall is obtained at each station for 10 years. Analyzing the frequency of rainfall data plan is by using several distributions, namely: Distribution Distribution Gumbel Type I, Distribution Distribution Log Pearson Type III, Distribution Normal Distribution and Distribution Log Normal. The results of the distribution test analysis to estimate the magnitude of the flood discharge with a certain repeat period, the rainfall data is closer to a distribution, calculation of Distribution and Smirnov-Kolmogorof test of each station to produce a rainfall plan. Based on the result of the test by using Smirnov-Kolmogorof test shows the suitable distribution is following the Log Pearson distribution III. Analyzing the estimated flood discharge on the Krueng Meureubo catchment area determine with a 2-year, 5-year, 10-year, 25-year, 50-year and 100-year re-period. The peak flood discharge estimated by using Hidrograf Satuan Sistetis (HSS) Gama I. The inundation area is obtained from the height of the flood from the cross section of the Krueng Meureubo river. The cross section used in this study is the cross section of KN 7 located in Rundeng village, Johan Pahlawan sub district. The value of losses due to floods that occur when the discharge of Q100 year (1,516 m3 / s) is Rp468.098.453.000, - which consists of loss of damage to residents settlements and rice fields.

Assessment of the flood hazard arising from land use change in a forested catchment in northern Iran

The provinces of northern Iran that border the Caspian Sea are forested and may be prone to increased risks of flooding due to deforestation and other land use changes, in addition to climate change effects. This research investigated changes in runoff from a small forested catchment in northern Iran for several land use change scenarios and the effects of higher rainfall and high antecedent soil moisture. Peak discharges and total runoff volumes from the catchment were estimated using the U.S. Soil Conservation Service “Curve Number” (SCS‐CN) method and the SCS dimensionless unit hydrograph. This method was selected for reasons of data availability and operational simplicity for flood managers. A geographical information system (GIS) was used to manipulate spatial data for use in the catchment runoff modelling. The results show that runoff is predicted to increase as a result of deforestation, which is dependent on the proportion of the catchment area affected. However, climate change presents a significant flood hazard even in the absence of deforestation. Other land use changes may reduce the peak discharges of all return period floods. Therefore a future ban on timber extraction, combined with agricultural utilisation of rangeland, could prove effective as “nature‐based” flood reduction measures throughout northern Iran.

Optimal Design of Check Dams in Mountainous Watersheds for Flood Mitigation

One of the measures for flood control is to construct a series of small barriers, known also as check dams, on tributaries of watershed stream network. Check dams are generally used in mountainous areas in order to control sediment transport and attenuate flood peak. In this paper, a simulation-based optimization model is developed to determine size, shape and the number of check dams for flood mitigation. HEC-HMS model is used to simulate watershed rainfall-runoff process considering various check dam designs. The model is coupled with a multi-objective evolutionary algorithm, called non-dominated sorting differential evolution (NSDE), to find the trade-off solutions considering three objective functions: 1) minimizing the investment cost, 2) minimizing the flood peak discharge and 3) maximizing the time to peak discharge. The proposed model is applied to a mountainous watershed in Iran and (near) optimal strategies, including the suitable number of check dams in each sub-watershed, and optimal dam size (e.g. optimal height, bottom width and side angles) in each sub-watershed are obtained. The results show that cost-effective designs can decrease peak discharge up to 53%, 54 and 54% corresponding to 2-yr, 5-yr and 10-yr flood return period scenarios, respectively. In addition, the check dams can also increase the time to peak for up to 88%, 81 and 77%, corresponding to 2-yr, 5-yr and 10-yr flood scenarios, respectively.

A new method for estimating flood peak discharge and extreme rainfall: Case study for Firat basin.

The commonly-used design parameter for hydraulic structures is the annual maximum instantaneous streamflow recorded by conventional gauging stations. Increased hydroclimatic variability in recent years and the resultant flooding raise questions concerning the flood risk estimations from the short flow records in Turkey. The method described in this study has been selected according to the likely estimates for the peak flow values at different return periods for the gauged basins. Hence, estimation of the peak flow values for regions with poor or rich discharge datasets could be implemented. In theory, this developed method may be used to estimate the peak flow values at any point on a river network, and not only at basin outlets. In this research, a case study has been conducted on Firat basin, on which the largest dams in Turkey have been built, by employing a novel approach for developing a new method that calculates the peak flood flows and extreme rainfall. The results demonstrate that the approach is sound and can be employed in prediction of peak rainfall and flow parameters in river basins.

Long-term runoff dynamics assessment measured through land use/cover (LULC) changes in a tropical complex catchment

The estimation of excess rainfall is critically important in water resource management as it provides the basis for calculating flood peak discharge that results in surface runoff. Kelantan River basin in Malaysia is a tropical catchment receiving heavy monsoon rainfall coupled with intense land use/cover (LULC) changes making the area consistently flood prone. The current study is therefore aimed to achieve the following goals: (1) to develop a curve number (CN) and runoff maps for 1984, 2002, and 2013 LULC conditions and (2) to determine runoff dynamics due to changes in LULC as well as to assess how the extent of LULC change will affect surface runoff generation. To achieve the aforementioned goals, land use maps corresponding to 1984, 2002, and 2014 LULC conditions were analyzed and prepared for the calculation of CN values using Soil Conservation Service (SCS-CN) method. CN and runoff maps corresponding to 1984, 2002, and 2013 LULC changes were successfully developed and the performance of the method was tested. The results indicated that forest was found to be the major land use type to have changed in all the LULC conditions across the watershed leading to intense runoff dynamics in the entire watershed. Higher runoff values were observed under 2013 LULC conditions across the watershed mainly due to intense deforestation relative to those of 1984 and 2002. The results of this study indicated that runoff generation is significantly affected by deforestation instead of changes in the rainfall pattern. The findings may be useful to water resource planners in controlling water loss for future planning.

Empirical and semi-analytical models for predicting peak outflows caused by embankment dam failures

Prediction of peak discharge of floods has attracted great attention for researchers and engineers. In present study, nine typical nonlinear mathematical models are established based on database of 40 historical dam failures. The first eight models that were developed with a series of regression analyses are purely empirical, while the last one is a semi-analytical approach that was derived from an analytical solution of dam-break floods in a trapezoidal channel. Water depth above breach invert (Hw), volume of water stored above breach invert (Vw), embankment length (El), and average embankment width (Ew) are used as independent variables to develop empirical formulas of estimating the peak outflow from breached embankment dams. It is indicated from the multiple regression analysis that a function using the former two variables (i.e., Hw and Vw) produce considerably more accurate results than that using latter two variables (i.e., El and Ew). It is shown that the semi-analytical approach works best in terms of both prediction accuracy and uncertainty, and the established empirical models produce considerably reasonable results except the model only using El. Moreover, present models have been compared with other models available in literature for estimating peak discharge.

Performance of Retarding Basin in Flood Disaster Risk Mitigation in Welang River, East Java Province, Indonesia

Flood phenomenon caused by high rainfall and sea tides on a watershed seat the tidal area, including the Welang River, commonly occur and the number of events is increasing. Construction of retarding basin is one of flood risk mitigation efforts by reducing the flood peak discharge. Assessment of flood management in Welang River was conducted with hydrology and hydraulic approaches, by using the Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS) 4.0 and Hydrologic Engineering Center–River Analysis System (HEC-RAS) 5.0.3 software. The hydraulic simulation consists of 4 scenarios. Scenario 1 was the current condition, while scenario 2, 3, and 4 were the retarding basin construction with one side spillway, one on the upstream (River Station (RS) 7400), on the middle (RS 6970), and on the downstream (RS 6590), respectively. The height variation of side spillways are 3 m and 4 m. Flood routing simulation result showed that the existing river channel condition could not accommodate of 2-year flood and 10-year flood, which caused peak discharge of 497.7 m3/s and 794.9 m3/s. At the RS 6590, the maximum runoff height of 2-year and 10-year flood were 0.66 and 1.02 m, respectively. Under the 2-year return period of flood, the discharge reduction caused by the retarding basin at control point RS 5341.4 (Karangketug Village), were 39.63 m3/s, 31.83 m3/s, and 41.93 m3/s, respectively for scenario 2, 3 and 4 with the 3 m side spillway height and 14.71 m3/s, 16.76 m3/s, and 13.74 m3/s, respectively for scenario 2, 3 and 4 with the 4 m side spillway height.

Copula-Based Analysis of Flood Peak Level and Duration: Two Case Studies in Taihu Basin, China

AbstractRecently, several bivariate and multivariate methods have been used to analyze the relationship of flood peak discharges with corresponding hydrograph volumes and durations in many basins. ...

An investigation of Digital Elevation Model (DEM) structure influence on flood modelling

Flood is one of the natural calamities that cause huge losses and damages. Flood hazard zonation has been widely produced to face the impact of the disaster. DEM as the primary data to construct the earth surface has been developed from rough to fine resolution. Aster GDEM v.2 within 1arc spatial resolution has an ability to derived DEM and TIN data as bases river geometrics data. Maximum daily peak discharges used to calculate flood peak discharge. Furthermore, steady flow analysis has been used to produce flood inundation model based on four scenarios with return periods 5yr, 10yr, 50yr, and 100yr. The model results have been validated using UAV flood map in 2016 by means of pixel by pixel operation and the result shows that the vertical variance between grid DEM and TIN data about 0.3 m.

Analisis Perubahan Tata Guna Lahan Terhadap Debit Limpasan Pada Subdas Air Betung

The need for land is increasing as the population increases. To fulfill the settlement land and other needs, various efforts are carried out including the transfer of land functions. Improper land conversion will cause a run-off increase in a watershed. The runoff will experience peak discharge at any time and will cause flooding if the volume cannot be accommodated by drenase. This study aims to compare changes in land use to predict the peak flood discharge in the Air Betung sub-watershed in the 10-year re-preode. The research method uses DEM map analysis to obtain the area of ​​the watershed and the length of the main river. For rainfall distribution using two frequency analyzes in 2004-2013 and 2008-2017 and the chosen method is normal distribution. The peak discharge was calculated by the nakayasu synthetic unit hydrograph. Changes in peak discharge caused by land use changes in 2013 and 2017 experienced a change, where for 2013 the Cverages value was 0.36 and peak discharge was 151.37 m3 / sec and for 2017 the Cverages value was 0.33 and peak discharge was 138.95 m3/ sec.