Discharge Hydrograph Research Articles

3D WCSPH modelling of landslide-water dynamics during 1963 Vajont disaster

This study illustrates the full-scale 3D numerical simulation of the coupled water-landslide dynamics of the 1963 Vajont catastrophic event. The focus is given to the early phase of the event when about 270 million cubic meters of rock fell into the reservoir within an estimated runout time of about 25 s. A complex surge wave system developed throughout the basin in the first 40–55 s, producing maximum run-up of 270 m above the dam crowning. The mesh-free Lagrangian Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method is adopted to discretize and solve the coupled system of governing equations for the landslide and water dynamics. The adopted model, which is based on SPHERA v.9.0.0 (Amicarelli et al. Comput Phys Commun, 2020), has been derived by introducing relevant modifications in the research code SPHERA (RSE SpA). The derived model is validated and the influence of water saturated soil on prediction of surge wave run-up is analysed. The average values from technical literature are assigned to mechanical parameters without tuning or calibration. The maximum flooding on the opposite side of the valley and the peak flow rate of the discharge hydrograph through the dam section show good agreement with reference data and improvements with respect to published results. The validated derived model proves to be a promising engineering tool for quantifying the level of risk in analogous applications.

A framework for analyzing the most relevant indicators of ecohydrology in a changing environment

ABSTRACT Human activities and climatic changes have altered the hydrological ecosystem of the Min River Basin and affected in-river biodiversity. In this paper, the year of abrupt hydrological change was identified using multiple tests, and the drivers of ecohydrological change were quantified in conjunction with the Budyko coupled hydrothermal equilibrium theory. Combined with ecological flow indicators (ecological surplus (ES) and ecological deficit (ED)) calculated based on discharge hydrographs and multiple hydrological indicators (ES/ED), the degree of river hydrological alteration in the Min River Basin was comprehensively evaluated, and its impacts on in-river biodiversity analyzed. The results of the study showed that: (1) according to the Budyko theory, the influence of human activities on the runoff changes in the Min River Basin reached 56.80%, which was the main influence factor, followed by climatic factors (41.56% for precipitation and 1.64% for evapotranspiration); (2) dam construction has generally resulted in an increase in seasonal ES and a decrease in seasonal ED; (3) the combination of the ecological flow indexes with the ecologically relevant hydrological indicators not only reduces the redundancy between the parameters, but also reflects the essential hydrological information and ecological connotations, and it is an effective method for evaluating ecohydrological mechanisms.

Combined dam-break modes between upper and lower reservoirs of pumped storage hydropower stations and associated flood risk assessment

ABSTRACT With the increasing construction of pumped storage hydropower projects in China, dam-break risk has become a matter of great concern. Typical pumped storage hydropower stations have relatively small storage capacity but are vulnerable to complicated combinations of dam breaks between their upper and lower reservoirs. This paper provides basic principles for determining different dam-break classes that could initiate at a pumped storage hydropower station and summarizes these in terms of risk source. After idealizing the breach development process, a simple dam-break model and a planar two-dimensional depth-averaged shallow flow model are used to calculate the discharge hydrograph of the dam-break flood and simulate the temporal and spatial characteristics of downstream inundation. Taking a montane rockfill-pumped storage project as an example, 12 dam-break schemes are used to examine different types of combined flow patterns driven by upper and lower dam breaks with modes that are gradual and/or instantaneous. It is found that predicted dam-break discharge hydrographs and downstream inundation indexes under adverse schemes fit common features of dam-break floods in mountain rivers. Downstream disaster losses are evaluated and flood evacuation routes are recommended. The findings of this study should be useful in ensuring the safe management of pumped storage hydropower stations.

Flood risk zoning of cascade reservoir dam break based on a 1D-2D coupled hydrodynamic model: A case study on the Jinsha-Yalong River

Large-scale earthquakes and huge landslide surges may cause the failure of cascade reservoirs, resulting in massive downstream flooding. The flood risk zoning of cascade reservoir dam breaks is crucial for local governments to formulate emergency plans and for individuals to garner their awareness of the flood risks. This paper presents a flood risk zoning approach based on a one-dimensional and two-dimensional coupled hydrodynamic model. The flooding area simulated by the coupled hydrodynamic model was divided into a Deadly Zone (D-zone) and an Escape Zone based on whether there is sufficient time for the public to evacuate the danger area under a specific evacuation generation time (EGT). A case study was conducted on the Jinsha-Yalong River (JYR), a confluence river located in Panzhihua City, to map the risk zones. This study considered a dam-break flood in Yalong River encountering two river flood scenarios in Jinsha River (scenario A: the annual average flow; scenario B: a 1000-year return period flood). Two evacuation scenarios (EGT of 30 and 60 min) were also considered; thereafter, four combined evacuation scenarios (A-EGT30, A-EGT60, B-EGT30, and B-EGT60) were simulated. The coupled hydrodynamic model is demonstrated to be effective through the analysis of water balance and hydrographs of special section discharge. The results show that: (1) in comparison to scenario A, scenario B reached its maximum flood extent approximately 5 min earlier, signifying that flood spread speed increases with the increase in flood magnitude; (2) the D-zone area was 127.7 % larger in scenario A-EGT60 compared to A-EGT30 and 120.8 % larger in scenario B-EGT60 compared to B-EGT30. These findings underscore the importance of flood scenarios and EGT on flood risk zones. The proposed risk zoning method can help government agencies in the JYR and major river regions worldwide with flood management and emergency strategy development.

Nature-based solutions for effective flood mitigation: potential design criteria

Few studies attempt to measure changes to discharge hydrographs during floods resulting from nature-based Solutions (NbS) for risk mitigation. The Q-NFM project in the UK has sought to measure and compare such changes for a wide range of NbS pilots applied to managed grasslands and woodlands. Also measured were underlying shifts in key hydrological processes leading to flood hydrograph changes of enhanced evaporation, hillslope-, channel- and floodplain-storage, and infiltration. How well particular NbS pilots changed these processes to reduce flood hydrographs was found to depend on the attributes of the NbS features and scheme. This learning is presented for the first time to highlight, with supporting evidence, seven potential criteria to help practitioners of flood risk management to improve existing and future designs of NbS for more effective flood mitigation within temperate grassland and woodland environments.

Experimental and numerical study of unsteady flows in a compound open channel

Unsteady flows are investigated in a compound open-channel flume, consisting of a Main Channel (MC) and an adjacent Flood Plain (FP). Two types of inflow hydrographs are studied, i.e., a discharge hydrograph with, at any time: a slightly unbalanced inflow partition between MC and FP (Case I); and a noticeably unbalanced inflow partition (Case II). Ensemble averages of the time-varying discharges, water depths and velocities are estimated based on 100 successive runs. The main focus of the experimental study is on assessing (i) the time-varying lateral discharge and depth-averaged Reynolds stress at the MC/FP interface, and (ii) the influence of the inflow partition on the downstream flow parameters. The experimental flows are then simulated using a 1D (one-dimensional) code that was adapted to implement the 1D+ Independent Sub-sections Model (ISM) (Proust et al. in Water Resour Res 45:1–16, 2009). The numerical study aims at validating the ISM under unsteady flow conditions, using classical 1D simulations as benchmark. It is experimentally found that 90 successive runs are required to get convergence of the ensemble averages of sub-section discharges and flow depth, while interfacial velocity is not fully converged after 100 runs. The influence of the inflow partition on the downstream parameters is felt along the whole flume. The ISM simulations are closer to the measurements than the classical 1D simulations. The ISM can accurately predict the time-varying flow depths and interfacial lateral discharge, and can approximate the interfacial Reynolds stresses.

Ciujung river basin flood risk assessment due to climate change and its countermeasure

Ciujung River is experiencing recurrent flooding, which was caused by climate change factor and extensive land use change. Therefore, this study carried out risk assessment in this basin area. First, hydrology analysis was carried out using HEC-HMS software to obtain flood discharge hydrograph, with obtained peak discharge of 3534.3 m3/s for 25-year return period. This hydrograph was then modeled into an inundation map using HEC-RAS two-dimensional model to calculate hazard index. Meanwhile, the vulnerability and capacity index were calculate using the demographic data. Finally, the risk index was calculated by combining hazard, vulnerability, and capacity index using raster calculator on Arc-GIS. Overall, the flood risk analysis shows a medium level. The results shown that hazard index is the most contributing factor in causing a high risk index. Thus, in this study we proposed a structural approach to reduce the hazard index. An embankment with a length of 50.37 km was applied and remodeled to analyze its effectiveness. The modeling results show high effectiveness with a significant reduction in inundation area. The reduction of inundated area reached 39.6%, while the reduction of affected buildings reached 49.9%. Hopefully, the result of this study can provide theoretical support and recommendations for future development.

Improved general unit hydrograph model for dam-break flood hydrograph

Dam breaks pose significant risks, necessitating simple and effective predictive models for disaster management. This study aims to enhance the understanding of dam-break flood hydrographs, an aspect less emphasized in traditional research focusing mainly on peak discharge and flow depth values. Employing a series of experiments, an improved general unit hydrograph model was used to analyze both discharge and flow depth hydrographs. This model is then critically compared with the standard gamma and log-normal asymmetric distribution models. The results reveal that the improved unit hydrograph model significantly outperforms these traditional models, particularly in predicting the rising stage of discharge hydrographs, evidenced by a 65 % reduction in root mean square error. Comparison of this model with real dam failures in natural river valleys shows its potential to be applied to changes in river slope and different dam-break rates. These advancements present a more precise methodology for predicting dam-break flood hydrographs, offering benefits for disaster management strategies.

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

AbstractThe river morphology of a braided‐type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. Over the past few decades, scientific attention has been directed toward understanding the coexistence of alternating bars and the consequent emergence of confluences and divergences, all of which interact intricately with the process of bank erosion. It is still rather challenging to estimate or predict the total sediment transport rate in this type of river, especially by considering various hydrologic data and climate effects. This study is focused on the reach of the Devoll River in Albania, located upstream of the Banja dam. Understanding the morphodynamics of this river reach holds significance due to the expanding delta upstream of the dam reservoir. The objectives of the two‐dimensional depth‐averaged approach of the present study are to investigate the temporal variation of braided intensity of Devoll River and the effect of using a discharge hydrograph from hydrologic data compared to the regulated one from the upstream dam on the morphodynamics and sediment transport of the river. After evaluating various parameters such as 11 different sediment transport functions, the best results were reached for a cell size of 5 × 5 m2, Manning roughness coefficient of 0.03, Meyer‐Peter and Müller's sediment function, Hayashi et al. (1980) hiding function, and Van Rijn bed roughness predictor in this study. In addition, the results of comparing satellite images and modeling the river from 2019 to 2023 show that the braided index decreased, and this can be due to the fact that the real scenario of the river has a regulated discharge compared to the non‐regulated discharge from hydrologic data, in the mentioned period.

Convolution, deconvolution, the unit hydrograph and flood routing

Convolution equations are used to relate the input and the output of a system such as rainfall and runoff, or inflow and outflow of a river reach. There have been numerous reports of unsatisfactory results from the deconvolution necessary to calculate the connecting transfer function. The cause is that the equations are ill-conditioned, and it is shown here that the fundamental theoretical solution is that of wild oscillations such as has often been found computationally. A spectral method is proposed for numerical solution, where, instead of individual point values, the transfer function is expressed as series of given continuous functions, where the problem is to determine the coefficients of those functions. The resulting equations have been found to be well-conditioned, and solutions obtained were smooth, bounded, and enabled a certain amount of physical interpretation of the transfer function. The method has been applied to several problems, including typical rainfall–runoff ones and flood routing and wave propagation problems, with quite satisfactory results. Another problem for deconvolution is found to be the traditional use of truncated equations. A remedy is only to use later output data points where convolution with input data does not reach back beyond the initial one. For the routing of larger flood events, the linear methods employed were found to be not so accurate. However as they are a first approximation that requires no knowledge of stream geometry or resistance, and as either discharge or water level hydrographs can be used, they may be useful.

Flood peak estimation for the keureuto watershed using the hydrological modeling system HEC-HMS

The Keureuto watershed has been the water resource used mainly for irrigation and municipal use. Extreme rainfall along with changes in the system may trigger rainfall excess causing flood at downstream. The occurrences may impact the usability of the system that supports the water resources supply. Investigating the impact of the floods requires initial research on the rainfall-runoff process of the watershed system. Rainfall-runoff modeling is an approach widely used for estimating the discharge hydrograph of the river as the result of the processes. The HEC-HMS rainfall-runoff model tool is applied in this study to estimate the peak flood discharge for the Keureto watershed located in the North Aceh region. The data used are satellite Global Precipitation Measurement (GPM) data and Automatic Water Level Recorder (AWLR) data at the watershed outlet. The 302 km2 Keureuto Watershed is divided into 23 sub-basins for the HEC-HMS model. The SCS Curve Number is applied to the model. The simulated freturncompared to the observed flow using the Nash Sutcliffe Efficiency criteria which returns the NSE value of 0.38 for seven years simulation, based on data of year 2015 to 2021. At an event based on October 2020 to March 2021, the NSE value returns 0.52, satisfactory for the simulation data range. The highest peak of the event is captured by the model simulation in the timing and the magnitude which value lower 20% from the observed flow.

Pemanfaatan Teknologi Informasi HEC-HMS Pada Potensi Penerapan Rainwater Harvesting Di Perumahan Bumi Kilu Permai Kota Manado

Abstract - Flood disasters are a seasonal threat that always occurs, an increase in surface flow discharge which has the impact of flooding due to lost absorption capacity and drought in the dry season. Techniques or methods are needed to prevent this, such as the eco-drainage concept that can be applied, including Rainwater Harvesting (RWH). Community participation in maintenance is needed to maintain the success of the ecodrainage system. It is hoped that the people living in the Bumi Kilu Permai Housing Complex can set an example in environmental maintenance implemented in their respective homes in dealing with the possibility of flooding. This research evaluates the potential for implementing a rainwater harvesting system in managing environmentally sound drainage. The method used to calculate the capacity of rainwater harvesting facilities uses monthly storage simulations. Rain distribution uses the HEC-HMS application to determine flood discharge hydrographs, Log Pearson Type III frequency analysis method. Calculation of discharge in gutters and also calculation of rainwater harvesting. The application of rainwater harvesting in the Bumi Kilu Permai housing complex by applying HEC-HMS 4.2.1 software shows that the peak flow hydrograph is 390 mm/hour. The use of an open rectangular gutter of 15 cm x 15 cm is still safe for a return period of 2 to 100 years with discharge on the roof is 0.210 m3/s. The average rainfall calculated using HEC_HMS 4.2.1 software was 25,527.32 liters. The tower used for rainwater harvesting is 1000 liters in size. With the monthly amount of water that can be stored for 1 month, it is 186,000 liters, while the amount of water that can be stored in the tower is 180,440.73 liters. Implementing rainwater harvesting for 1 house can reduce 1000 liters of surface water runoff. If 300 can withstand 300,000 liters of surface water runoff or runoff. Of course, this can help minimize the probability of flooding in Paniki Satu Village, which is located in front of the Bumi Kilu Permai Housing Complex and is in the Paniki Watershed. Keywords: Rainwater Harvesting, HEC-HMS, Manado Abstrak - Bencana banjir adalah ancaman musiman yang selalu terjadi, peningkatan debit aliran permukaan yang membawa dampak terjadinya banjir akibat kapasitas resapan hilang dan kekeringan di musim kemarau. Diperlukan teknik atau metode untuk mencegah hal tersebut, seperti konsep ekodrainase yang dapat diterapkan diantaranya adalah Rainwater Harvesting (RWH). Peran serta masyarakat dalam hal pemeliharaan sangat dibutuhkan untuk tetap menjaga keberhasilan sistem ekodrainase.

Megaflood Erosion on Mars—How Lava‐Filled Craters Became Mesas (With Insights From Lava Physics, Stream Power, and Rock Mechanics)

AbstractRound mesas up to 500 m high occur in Martian outflow channels. Mesas in Ravi and Elaver Valles occur in deepest parts of the channels where the most intense megaflood erosion occurred. I theorize that Noachian basalts poured into craters which acted as lava traps, similar to Kilauean lava lakes. Subsequent flood basalts buried the infilled craters. Hesperian megafloods stripped away hundreds of meters of basalts, exhuming erosion‐resistant strata. Lava solidification theory is explored to assess the role of cooling in governing the structure and strength of the Martian basalts. The postulated lava lakes that formed the Ravi Vallis mesas would have needed millennia to cool. The larger Elaver Vallis mesa may have needed up to 20,000 years to solidify. Long cooling times led to coarse, doleritic mineral textures and reduced numbers of cooling joints, greatly increasing bulk rock strength and resistance to hydrodynamic erosion. Using rock mechanics theory, cores of exhumed lava‐filled craters would have bulk rock strengths at least 5 to 30 times greater than more highly fractured basalts. Discharge hydrographs for the Morella Crater breach flood that carved Elaver Vallis peak at ∼2.1 × 107 m3 s−1. Stream power per unit streambed area ranged up to >150,000 W m−2 as the breach grew in size. The calculations provide an envelope of power sufficient to erode hundreds of meters of basalts, but not great enough to remove the large mesa. Thus the legacy of an ancient, lava‐filled crater is a high mesa on the floor of Elaver Vallis.

Sediment-Nitrogen (N) connectivity: suspended sediments in streams as N exporters and reactors for denitrification and assimilatory N uptake during storms

Nitrogen (N) pollution in riverine ecosystems has substantial environmental, economic, and policy consequences. Various riverine N removal processes include permanent dissimilatory sinks such as denitrification (Uden) and temporary assimilatory sink such as microbial N uptake (Uassim). Both processes have been extensively evaluated in benthic sediments but only sparsely in the water column, particularly for storm flows producing high suspended sediment (SS) concentrations. Stormflows also increase the sediment bound N (Sed-N) export, and in turn, the overall N exports from watersheds. The balance between N removal by Uden and Uassim vs. Sed-N export has not been studied and is a key knowledge gap. We assessed the magnitude of Uden and Uassim against stormflow Sed-N exports for multiple storm events of varying magnitude and across two drainage areas (750 ha and 15,330 ha) in a mixed landuse mid-Atlantic US watershed. We asked: How do the Uden and Uassim sinks compare with Sed-N exports and how do these N fluxes vary across the drainage areas for sampled storms on the rising and falling limbs of the discharge hydrograph? Mean Uden and Uassim as % of the Sed-N exports ranged between 0.1–40% and 0.6–22%, respectively. Storm event Uassim fluxes were generally slightly lower than the corresponding Uden fluxes. Similarly, comparable but slightly higher Uden fluxes were observed for the second order vs. the fourth order stream, while Uassim fluxes were slightly higher in the fourth-order stream. Both of these N sinks were higher on the falling vs. rising limbs of the hydrograph. This suggests that while the N sinks are not trivial, sediment bound N exports during large stormflows will likely overshadow any gains in N removal by SS associated denitrification. Understanding these N source-sink dynamics for storm events is critical for accurate watershed nutrient modeling and for better pollution mitigation strategies for downstream aquatic ecosystems. These results are especially important within the context of climate change as extreme hydrological events including storms are becoming more and more frequent.

The testing of a multivariate probabilistic framework for reservoir safety evaluation and flood risks assessment in Slovakia: A study on the Parná and Belá Rivers

Abstract Intense floods represent a challenge to risk management. While they are multivariate in their nature, they are often studied in practice from univariate perspectives. Classical frequency analyses, which establish a relation between the peak flow or volume and the frequency of exceedance, may lead to improper risk estimations and mitigations. Therefore, it is necessary to study floods as multivariate stochastic events having mutually correlated characteristics, such as peak flood flow, corresponding volume and duration. The joint distribution properties of these characteristics play an important role in the assessment of flood risk and reservoir safety evaluation. In addition, the study of flood hydrographs is useful because of the inherent dependencies among their practice-relevant characteristics present on-site and in the regional records. This study aims to provide risk analysts with a consistent multivariate probabilistic framework using a copula-based approach. The framework respects and describes the dependence structures among the flood peaks, volumes, and durations of observed and synthetic control flood hydrographs. The seasonality of flood generation is respected by separate analyses of floods in the summer and winter seasons. A control flood hydrograph is understood as a theoretical/synthetic discharge hydrograph, which is determined by the flood peak with the chosen probability of exceedance, the corresponding volume, and the time duration with the corresponding probability. The framework comprises five steps: 1. Separation of the observed hydrographs, 2. Analysis of the flood characteristics and their dependence, 3. Modelling the marginal distributions, 4. A copula-based approach for modelling joint distributions of the flood peaks, volumes and durations, 5. Construction of synthetic flood hydrographs. The flood risk assessment and reservoir safety evaluation are described by hydrograph analyses and the conditional joint probabilities of the exceedance of the flood volume and duration conditioned on flood peak. The proposed multivariate probabilistic framework was tested and demonstrated based on data from two contrasting catchments in Slovakia. Based on the findings, the study affirms that the trivariate copula-based approach is a practical option for assessing flood risks and for reservoir safety.

Illuminating the complexity of hydrogeological regimes in fault-influenced, anticlinal karst aquifers: Insights into the recharge patterns in tectonically complex karst catchments

For many countries, karst aquifers are a significant source of potable water; thus, understanding their hydrogeological behavior is of great importance. However, in tectonically complex karst areas, knowledge of their hydrogeological behaviors has remained largely limited due to the high heterogeneity, often necessitating the use of costly and time-consuming techniques. In this study, spring discharge hydrographs, water balance estimates, hydrochemical and stable isotopic analyses, geomorphological surveys, and a consideration of the geological and structural setting of the study area were used to investigate the hydrogeological function of karst aquifers drained by two large permanent springs: the Bibitalkhone (Bt) and Sabzab (Sa) springs, located in a highly faulted catchment in the Zagros Mountains (southwest Iran). The results obtained from these different approaches suggested that fault-controlled, external waters from neighboring karst aquifers are responsible for more than two-thirds of the total discharge recorded at both springs. In this study, this predominantly conduit-type recharge is referred to as “regional (or external) autogenic recharge”. A smaller portion of the springs’ discharge (∼25% and ∼5% of the Bt and Sa springs’ discharge, respectively) originates from internal waters associated with the springs’ host aquifer, which is supplied by rainfall and infiltrates into the subsurface via joints and fractures. This type of recharge is largely diffuse and is referred to here as “local (or internal) autogenic recharge”. A relatively large portion of the Sa Spring’s discharge (∼35%) originates from a nearby dam reservoir, which can leak into the host spring aquifer through joints and fractures. This type of recharge is described as “local (or internal) allogenic recharge” and is primarily diffuse. The results of this study demonstrate that the karst aquifers in the downstream catchments can supply a stable and continuous source of potable groundwater that can meet the region’s annual consumption, agricultural, and industrial demands. This study will provide insights into the hydrogeological regimes of fault-influenced aquifers, contributing to the sustainable development and proper management of water resources in tectonically complex karst catchments.

Parameter sensitivity and uncertainty of a one-dimensional morphodynamic model in the Lower Yellow River

One-dimensional morphodynamic models are effective tools to conduct flood risk assessment and sediment management of alluvial rivers. In order to gain better understanding of morphodynamic models and improve the simulation efficiency and accuracy, a comprehensive investigation into parameter sensitivity and uncertainty has been conducted for a one-dimensional morphodynamic model. This model was calibrated using the measured flow and sediment data in the Lower Yellow River (LYR). The variance-based Sobol' and GLUE (Generalized Likelihood Uncertainty Estimation) tools were applied to quantify the parameter sensitivity and uncertainty to the simulation of different hydrological indicators in the meandering reach, with various model response surfaces selected. Results show that the importance of input parameters varied with different model outputs. The simulated water level and discharge hydrographs were more sensitive to the roughness coefficient at middle and high flows, with high total- and first-order sensitivity indices to the NSEs and RMSEs, while the simulated sediment concentration was more sensitive to the input parameters related to sediment transport capacity (K and M) and recovery coefficient (bd). Notably, the pairwise interactions between K and different roughness coefficients were significant in the simulated sediment concentration hydrographs. Spatio-temporal variability in the effect of input parameters is also revealed. The most contributing factor was screened as K for the maximum sediment concentration in the uppermost and lowermost reaches of the meandering reach, which turned to be bd in the middle reach. The most sensitive parameter to the simulated sediment concentration was screened as K in the initial period and then turned to be the exponent of recovery coefficient in case of erosion (be), which was bd in the last period over the simulation period. An analysis of parameter uncertainty indicates that the morphodynamic model can obtain satisfactory accuracy with most observed data concentrating in the 95% confidence interval, and the uncertainty of simulation outputs increased downstream. Improved understanding of parameter sensitivity and uncertainty in morphodynamic modelling can provide the scientific guidance for factor prioritization in the future model calibration.

A Physically‐Based Reverse‐Stage Routing Model Considering Lateral Flow for Establishing Normal Rating Curves at Ungauged Upstream River Sections

AbstractMany of the world‐rivers are often ungauged or poorly gauged due to inadequate streamflow monitoring networks. Even with the limited available monitoring stations, only a few of them monitor both stage and discharge data. But when there is a need for estimation of discharges at a gauging station, where only stage data is monitored, one may employ a reverse routing technique using the stage data monitored at a nearby downstream gauging station. This study develops a novel single‐parameter reverse‐stage routing (RSR) model based on the second‐order approximate water surface gradient governing equation to estimate stage and discharge at any scantily‐gauged upstream river section using the known stage information available at the downstream section. A novel criterion is also developed for checking the applicability of the RSR model. Reverse routing experiments, carried out by the RSR model using different hypothetical downstream stage hydrographs in a number of hypothetical trapezoidal and rectangular channel reaches to reproduce the benchmark upstream stage and discharge hydrographs, demonstrate the good performance of the RSR model with the Nash–Sutcliffe Efficiency >98%, absolute volume conservation error <1.5%, and an absolute error in peak ≤1%. Subsequently, the RSR model was tested for three real‐river case studies in India and Italy with good reproduction performances, and along with the development of the corresponding normal rating curves at the upstream river sections. The study results reveal that the parsimonious RSR model has good potential for solving reverse routing problems with stable numerical solutions for rivers under ungauged and scantily‐gauged scenarios.

Effect of bed shear stress on the mobile armor layer at the riverbed

Armoring is forming an armor layer of the riverbed which is preceded by the transportation of bed sediment. Mobile armor occurs when the riverbed reaches equilibrium, then eroded, and the surface of the riverbed recovers. Therefore, protection is formed by moving riverbed material. This research used a simulation model generated through HEC RAS software version 6.1. The model input location was Krasak River, Sleman, Yogyakarta. The data for model input were the topography of the Krasak River from upstream to the point of view, flood discharge hydrograph, and grain size gradations. The simulation combination consisted of three locations with the riverbed material of each location sampled tested for grain size distribution. The running simulations combined the flood discharge at return periods of 2, 5, 10, 25, 50, and 100 years. There were three variations of grain size distribution used as input data. Meanwhile, variations of sediment transport methods used the Meyer-Peter Muller and Wilcock-Crowe methods. Overall, the simulation results show that the shear stress and the proportion of sand-to-grain material affect the armoring process and riverbed changes.

Experimental investigation of loop rating curve on a small 3D printed laboratory channel

The study of flood dynamics is generally complicated because it requires a lot of expensive sensors that might be inoperative when submerged during a flood event. Physical models can be helpful in order to get extra information on flood dynamics, but they are expensive in material, space occupation, and human investment (intervention, maintenance, assistance). The objective of this work is a feasibility study on the possibility of using a small 3D printed model to make hydraulic studies. For this we focus on the reproduction of a complex phenomenon which is the loop rating curve (LRC). In natural rivers or large channels, rating curve is a relation between stage and discharge. Under unsteady flow condition, rating curve may present a hysteresis behavior reflected by a more or less pronounced loop. LRC was historically observed on natural rivers or at large laboratory channels. This study is the first investigation of LRC on a small 3D printed laboratory channel. We measure stage and discharge at the channel outlet and we obtain rating curves as a response to an unsteady discharge hydrograph imposed at the channel inlet. We tested 11 scenarios corresponding to different flow conditions where we varied the following parameters: section control (freefall or weir), channel slope (flat = 0.1% or sharp = 10%), time step of the discharge hydrograph (5 s or 10 s). Our experimental results with a small 3D printed channel are in accordance with experimental observations on large channels or natural rivers, and our experimental rating curves are very well simulated by Jones formula that is classically used on large channels or rivers. These promising results allow the use of 3D printing technique to make small-scale hydraulic models. A further study of the rating curve, but also of other hydraulic characteristics can be considered on more complex geometries and more varied scenarios while paying attention to the scaling (which was not the case in this study). As real scenarios might be considered, this might be of interest from both a pedagogical and an application point of view with a reduced human, material and space occupation cost.