Stage Hydrographs Research Articles

Dynamic routing modeling for flash flood forecast in river system

A real-time flood-forecasting method coupled with the one-dimensional unsteady flow model was developed for the Danshuei River system in northern Taiwan. Based on the flow at current time, the flow at new time is calculated to provide the water stage forecasting during typhoons. Data, from two typhoons in 2000: Bilis and Nari, were used to validate and evaluate the model capability. First, the developed model was applied to validate and evaluate with and without discharge corrections at the Hsin-Hai Bridge in Tahan Stream, Chung-Cheng Bridge in Hsintien Stream, and Sir-Ho Bridge in the Keelung River. The results indicate that the calculated water stage profiles approach the observed data. Moreover, the water stage forecasting hydrograph with discharge correction is close to the observed water stage hydrograph and yields a better prediction than that without discharge correction. The model was then used to quantify the difference in prediction between different methods of real-time water stage correction. The model results reveal that water stages using the 1–6 h forecast with real-time stage correction exhibits the best lead times. The accuracy for 1–3 h lead time is higher than that for 4–6 h lead time, suggesting that the flash flood forecast in the river system is reasonably accurate for 1–3 h lead time only. The method developed is effective for flash flood forecasting and can be adopted for flood forecasting in complicated river systems.

An optimized routing model for flood forecasting

A conceptual flow routing model for flood forecasting is adopted for a reach of river given only historic upstream and downstream stage hydrographs and the associated in‐bank rating curves, local rainfall, and minimal additional information. The ungauged lateral inflows are generated by a unit hydrograph rainfall‐runoff model. The model is calibrated by optimizing the parameters of the functional form for the average cross section along the reach, the base lateral inflow and the peak of the unit hydrograph, and the rating curve extensions downstream and upstream. The model is confirmed by applying it to a synthetic river reach and then to the forecasting of floods in a reach of the River Wye, UK.

Characterizing Storm Hydrograph Rise and Fall Dynamics With Stream Stage Data1

Abstract: Storm‐flow transients (i.e., hydrograph rise and fall dynamics) may represent an important aspect of understanding streamflow dynamics. However, little is known about how temporal resolution of transient data and climate variability may color these potential indicators of hydrologic pattern or condition. Warm‐season stream stage and rainfall were monitored continuously (5 min) during the 2002 water year in eight tributaries of the Little Miami River (Ohio), which drain 17‐58 km2 catchments. Rise rates generated using 5‐min data were different than those generated with mean daily data [calculated with the Indicators of Hydrologic Alteration (IHA) software], though fall rates were similar for fine and coarse temporal data. This result suggests that data with low temporal resolution may not be adequate to fully represent the dynamics of storm rise rates. Conversely, fall rates based on daily stage data (via IHA) were similar to those based on the 5‐min data, and so daily mean data may be appropriate for characterizing fall rates. We next analyzed the possible correlations between rainfall variability and storm‐flow stage dynamics. We derived rise and recession rates from storm stage hydrographs by assuming exponential rise and decay of a runoff peak. We found that raw rise rates (Rraw) were correlated with both the maximum rainfall rate and the time to the centroid of a rain event. We subsequently removed the trend based on these rainfall characteristics, which yielded new representations of rise rates abbreviated as Rrate and Rtcent, respectively, and that had lower variability than the uncorrected (raw) data. Fall rates were found to be independent of rainfall characteristics. Due to the predominant influence of stream hydrology upon aquatic biota and nutrient fluxes, our work suggests that these stage data analysis protocols can refine or otherwise reduce variability in these indices by accounting for relevant factors such as rainfall forcing. These protocols for derivation of transient indices should be tested for their potential to improve correlations between stream hydrology and temporally aligned biotic data and dissolved nutrient fluxes in streams.

Development and Application of Hydraulic Simulation Model for Irrigation Canal Network

Improving the performance of the major irrigation projects is one of the economically viable options in meeting the growing water demands and sustaining the productivity of irrigated agriculture under present financial, environmental, and physical constraints. Hydraulic simulation models offer unlimited opportunities for improving the performance of the irrigation systems by studying the flow behavior in a large and complex canal network under a variety of design and management scenarios. This paper presents a hydraulic simulation model developed for steady and unsteady flow simulation in irrigation canal network. The model uses the implicit four-point Preissmann scheme for discretization of the Saint-Venant equations and solves the resulting equations using the sparse matrix solution technique. The model is applicable for simulating flow in a series of linearly connected reaches, and branched as well as looped canal networks. The different boundary conditions that can be modeled are discharge hydrograph at the source node(s) and stage hydrograph, rating curve, uniform flow, and discharge hydrograph at the terminus node(s). The model is capable of handling different hydraulic structures such as weirs, sluice gate, drops/falls, pipe outlet, and imposed discharge. It also allows computation of gate opening for a given full supply level and discharge at the cross-regulator and offtaking points, respectively. For entering and editing canal network description and boundary conditions, including different hydraulic parameters and displaying the results, a user friendly graphical user interface has been provided. Accuracy and numerical stability of the model tested using the mass conservation test and test with ramp discharge as inflow hydrograph, indicated that the model performs satisfactorily. Comparison of simulated and observed discharges at the tail regulator of the Right Bank Main Canal of Kangsabati Irrigation Project showed that the model performs satisfactorily for most of the irrigation events. Further, comparison of the model simulated stage and discharge with that of the HEC-RAS model showed that the results of both the models are almost identical. The different simulation results, thus, suggest that the developed model can be successfully used as a tool for hydraulic simulation of canal network.

Effects of a Small, Century-old Dam on a Secondorder Stream in the Virginia Piedmont

The geomorphology, hydrology, and ecology of a second-order stream in central Virginia were compared to that of an adjacent reference stream in order to determine the impact of a small, 100-yrold dam. The dam had little effect on stage hydrographs, but surface release of water resulted in temperatures 2–5°C warmer than the reference stream during spring and summer months. Stream geomorphology was not highly altered by the dam, being influenced more strongly by valley geology and topography, but riffle sediment size distributions were affected by sediment trapping in the reservoir. Macroinvertebrate populations just below the dam appeared impaired, while sites 1 km downstream and on the reference stream scored well on ecological metrics. Bluegill fish (Lepomis macrochirus) which likely originate in the lake were abundant in the dammed creek, whereas the reference stream was dominated by native dace (Phoxinus and Rhinichthys spp.) and creek chubs (Semotilus atromaculatus). Overall, the impact of the dam on the creek is only moderate and declines significantly within 1 km downstream.

Distributed Flood Simulations with Coupling Gauge Observations and Radar-rainfall Estimates

This study used a two-dimensional diffusion hydrodynamic model for the simulation of extreme flood events that occurred in the Shihmen reservoir watershed from 1989 to 2001. The alternating direction explicit scheme (ADE) with various horizontal spacings from 120 to 240 m at an incremental interval of 40 m was conducted for flood simulations. Spatial precipitation was provided by the gauge interpolations and weather radar rainfall estimate schemes. A case study, Typhoon Nari on September 16–18, 2001, was then performed using radar-derived rainfall with coupling two-dimensional diffusion hydrodynamic model in flood routing investigations. Numerical results revealed acceptable agreement between the observed and simulated reservoir stage hydrographs. Results of 120 and 160 m spacing had similar values on error indicators while the 160 m grids can greatly reduce computational time by 40% than that of 120 m grids. Precipitation is identified to be the main factor forcing model result.

Applicability criteria of the variable parameter Muskingum stage and discharge routing methods

The applicability criteria of the variable parameter Muskingum stage hydrograph (VPMS) and the variable parameter Muskingum discharge hydrograph (VPMD) routing methods are assessed and quantified. The assessment is made by studying the propagation characteristics of hypothetical stage hydrographs of the form of a four parameter Pearson type III distribution and its corresponding discharge hydrographs in uniform rectangular and trapezoidal channels using the VPMS and the VPMD methods, respectively, in comparison with the propagation characteristics of the respective hydrographs simulated by solving the Saint‐Venant equations, which form the benchmark model. For each of the uniform rectangular and trapezoidal shape channel categories, a total of 2880 numerical experiments covering various combinations of Manning's roughness coefficient, channel bed slope, peak stage and respective time to peak, and shape factors of the stage hydrographs were conducted for each of these VPMS and VPMD methods, respectively, by routing the hypothetical stage and the respective discharge hydrographs for a reach length of 40 km. The routed stage and discharge hydrographs were compared with the corresponding Saint‐Venant solutions using four performance measures, namely, percentage variance explained, percentage error in volume, percentage error in peak, and percentage error in time to peak. Considering a maximum error of 5% of these measures, the experiments indicate that the applicability limit of the VPMS method for stage routing is (1/So)(∂y/∂x)max ≤ 0.79, while for the simultaneous computation of the discharge hydrograph corresponding to the routed stage hydrograph this method can be applied up to (1/So)(∂y/∂x)max ≤ 0.63 (where So is the channel slope and ∂y/∂x is the water profile gradient). The VPMD method is applicable up to (1/So)(∂y/∂x)max ≤ 0.43 for both discharge routing and the corresponding stage computation. The applicability of the VPMD method is compared with the variable parameter Muskingum‐Cunge (VPMC) method, an alternative method for discharge hydrograph routing, and it is found that for the same 5% error criteria of the VPMD method, the VPMC method is applicable only up to (1/So)(∂y/∂x)max ≤ 0.11. Thus it is seen that the VPMD method has an improved performance and wider applicability range than the VPMC method.

A methodology for discharge estimation and rating curve development at ungauged river sites

A methodology for estimating discharges and development of rating curves at ungauged river sites is presented. The methodology employs a routing method, which is an extension of the variable parameter Muskingum stage hydrograph (VPMS) routing method developed by M. Perumal and K. G. Ranga Raju, for routing a given upstream stage hydrograph in a channel reach characterized by trapezoidal compound cross section to arrive at the stage hydrograph at the downstream site. Furthermore, the VPMS method also enables us to estimate the discharge hydrographs at the upstream and downstream sites. It is assumed that there is no lateral flow within the routing reach. For establishing the rating curve at the ungauged river site the following concept employed in the development of the VPMS method can be conveniently exploited: During unsteady flow, there exists a one‐to‐one relationship between the stage estimated at the ungauged site and the corresponding steady discharge, which occurs somewhere downstream of that location, and using the method employed in the VPMS method, one can estimate that steady discharge. By linking this discharge with the stage estimated at the ungauged site the rating curve can be established. This approach of developing the rating curve is verified for a number of hypothetical data sets, obtained using the MIKE 11 model, which is used as the benchmark model in this study. Furthermore, the appropriateness of the proposed extended VPMS routing method is verified using two sets of experimental data on unsteady flows, obtained from a laboratory channel with rectangular compound flow section. The methodology is also field tested using six sets of concurrent stage hydrograph data obtained at the upstream and downstream sites of a 15 km reach length of the Tiber River in central Italy, out of which only one set of data was used for calibrating the reach‐averaged Manning's roughness coefficient. The close reproductions of the rating curves and discharge hydrographs recorded at the upstream and downstream sites demonstrate that the proposed methodology can be confidently used for rating curve development and discharge estimation at ungauged sites, thus avoiding the manual discharge measurement at any river site not subjected to backwater effects.

Modelling stage—discharge relationships affected by hysteresis using the Jones formula and nonlinear regression

Gauging stations where the stage—discharge relationship is affected by hysteresis due to unsteady flow represent a challenge in hydrometry. In such situations, the standard hydrometric practice of fitting a single-valued rating curve to the available stage—discharge measurements is inappropriate. As a solution to this problem, this study provides a method based on the Jones formula and nonlinear regression, which requires no further data beyond the available stage—discharge measurements, given that either the stages before and after each measurement are known along with the duration of each measurement, or a stage hydrograph is available. The regression model based on the Jones formula rating curve is developed by applying the monoclinal rising wave approximation and the generalized friction law for uniform flow, along with simplifying assumptions about the hydraulic and geometric properties of the river channel in conjunction with the gauging station. Methods for obtaining the nonlinear least-squares rating-curve estimates, while factoring in approximated uncertainty, are discussed. The broad practical applicability and appropriateness of the method are demonstrated by applying the model to: (a) an accurate, comprehensive and detailed database from a hydropower-generated highly dynamic flow in the Chattahoochee River, Georgia, USA; and (b) data from gauging stations in two large rivers in the USA affected by hysteresis. It is also shown that the model is especially suitable for post-modelling hydraulic and statistical validation and assessment.

A real-time stage Muskingum forecasting model for a site without rating curve

An adaptive model for on-line stage forecasting is proposed for river reaches where significant lateral inflow contributions occur. The model is based on the Muskingum method and requires the estimation of four parameters if the downstream rating curve is unknown; otherwise only two parameters have to be determined. As the choice of the forecast lead time is linked to wave travel time along the reach, to increase the lead time, a schematization of two connected river reaches is also investigated. The variability of lateral inflow is accounted for through an on-line adaptive procedure. Calibration and validation of the model were carried out by applying it to different flood events observed in two equipped river reaches of the upper-middle Tiber basin in central Italy, characterized by a significant contributing drainage area. Even if the rating curve is unknown at the downstream section, the forecast stage hydrographs were found in good agreement with those observed. Errors in peak stage and time to peak along with the persistence coefficient values show that the model has potential as a practical tool for on-line flood risk management.

Utility of different data types for calibrating flood inundation models within a GLUE framework

Abstract. To translate a point hydrograph forecast into products for use by environmental agencies and civil protection authorities, a hydraulic model is necessary. Typical one- and two-dimensional hydraulic models are able to predict dynamically varying inundation extent, water depth and velocity for river and floodplain reaches up to 100 km in length. However, because of uncertainties over appropriate surface friction parameters, calibration of hydraulic models against observed data is a necessity. The value of different types of data is explored in constraining the predictions of a simple two-dimensional hydraulic model, LISFLOOD-FP. For the January 1995 flooding on the River Meuse, The Netherlands, a flow observation data set has been assembled for the 35-km reach between Borgharen and Maaseik, consisting of Synthetic Aperture Radar and air photo images of inundation extent, downstream stage and discharge hydrographs, two stage hydrographs internal to the model domain and 84 point observations of maximum free surface elevation. The data set thus contains examples of all the types of data that potentially can be used to calibrate flood inundation models. 500 realisations of the model have been conducted with different friction parameterisations and the performance of each realisation has been evaluated against each observed data set. Implementation of the Generalised Likelihood Uncertainty Estimation (GLUE) methodology is then used to determine the value of each data set in constraining the model predictions as well as the reduction in parameter uncertainty resulting from the updating of generalised likelihoods based on multiple data sources.

Floodplain Mapping and Visualization for Flood Risk Assessment and Decision Support in Sarawak Kanan River

Sarawak Kanan River is one of the tidal rivers frequently affected by flood in Sarawak, Malaysia. Over the years, physical development has been concentrated in the middle valley town of Bau, where the center of administration and commerce for the district is located. The town of Bau and surrounding areas is a well known flood-prone area, for being geographically located in the floodplain of Sarawak Kanan River. Major floods of February 2003 and January 2004 had Bau and surrounding areas flood-stricken. The area has little hydrological information to ponder with, thus indicating a need of a flood visualization model to have a better explanation of the flooding scenarios in the floodplain areas. For this purpose, the flooding of Sarawak Kanan River was modeled using the InfoWorks RS one-dimensional hydrodynamic model. The inputs consist of observed discharge hydrographs of upstream Buan Bidi sub-catchment and lumped synthetic discharge hydrographs of ungauged sub-basins. Observed stage hydrographs measured at Siniawan were used as downstream input. This article outlined the methodology for flood mapping and visualization to enable flood risk assessment and decision support modeling for future development in floodplain protection and control. The model was capable of providing an acceptable estimate of flood depths with a correlation coefficient of 0.83.

Reproduction of Hysteresis in Rating Curves

The well-known Jones formula has long been used to convert a stage hydrograph to a discharge hydrograph under many unsteady flow situations. The logic behind the formula can be explained with the use of the approximate convection–diffusion equation in its development. However, its applicability criterion has not yet been quantified. Assessment of the applicability of the Jones formula is studied herein. In addition, two variations of the Jones formula have been developed: one, incorporating the inertial forces of the one-dimensional momentum equation and the other, incorporating a refined estimate of ∂y/∂x, the longitudinal gradient of the water depth, accounting approximately for the parabolic variation of the water surface. The suitability of these three formulas in converting a given hypothetical stage hydrograph to a discharge hydrograph is assessed under varying channel conditions. The study shows, that the Jones formula and its variants developed in this study, indicate a limit of |(1/S0)∂y/∂x|<0.5,...

Explicit Estimation of Aquifer Diffusivity from Linear Stream Stage

Different approaches are available for estimation of aquifer hydraulic diffusivity from a linear stream-stage variation and corresponding groundwater heads. These approaches require interpolation from tabulated values or computation of hydraulic gradient at the stream aquifer interface. Certain methods use approximation or interpolation of tabulated values for an infinite series. These methods are prone to errors in the estimated aquifer hydraulic diffusivity. An alternative approach is to use a closed-form solution of the problem and develop an explicit expression for the aquifer hydraulic diffusivity, which is free from errors of using infinite series, interpolation, and computation of hydraulic gradient. Such an alternative method is developed for a linearly varying stream stage. The new method can yield the estimate of hydraulic diffusivity even from a single observation. The proposed method would be applicable to practical hydraulic engineering problems keeping in view that most of a rising part of a stream stage hydrograph can be approximated by a linear rise and certain rivers may show a linearly varying stream stage. Use of the new method is demonstrated on published and field data, which shows that the estimates obtained using the new method are comparable to that obtained using an optimization approach.

EFFECTS OF UNSTEADINESS, PLANFORM AND CROSS-SECTIONAL FORM OF CHANNELS ON HYDRAULIC CHARACTERISTICS OF FLOOD FLOW

We have conducted laboratory flood experiments by applying the similarity law to real flood in meandering compound rivers. Comparing steady and unsteady flow in meandering compound channel with unsteady flow in meandering single channel, we investigated the hydraulic effects of plan and cross-sectional shapes of channel on flood flow.In the case of a unsteady meandering compound channel flow, the discharge and velocity had two values for the same depth; on rising and falling stages. Comparing stage hydrographs for meandering compound channel and meandering single channel it was observed that, compound meandering channel had early response giving high values during rising stage and delayed response giving high values during falling stage. Also for both compound meandering channel and meandering single channel, increase of sinuosity and unsteadiness the maximum velocity occurred early on flood flow.

Variable-Parameter Stage-Hydrograph Routing Method. II: Evaluation

The variable-parameter simplified stage-hydrograph routing method developed in Part I of this series is studied to determine its limitations, the criterion for its applicability, and its accuracy based on the assumptions used for its development. This method is evaluated by routing given hypothetical input-stage hydrographs through uniform rectangular cross-section channels and comparing the results with the corresponding numerical solutions of the Saint Venant equations. The discharge hydrographs as computed by the method are also compared with the corresponding Saint Venant solutions. The method closely reproduces the stage and discharge hydrographs obtained from the Saint Venant solutions subject to compliance with the assumptions of the method.

Modelling floodplain conveyance in compound channel flows

Floodplain conveyance in compound channel flows is examined through applications of the dynamic flow routing model DWOPER to both laboratory and field data sets. Three different approaches regarding the modelling of off-channel storage are considered, namely, the single-channel approach and two interface-plane methods, which artificially separate main channel flows from floodplain flows, using (i) vertical and (ii) diagonal interface planes. The single-channel method, which views composite flow fields as single units without storage, produced significant differences between simulated and observed stage and discharge hydrographs. The vertical interface method gave generally good results in the case of the laboratory data, but was less successful when applied to the field data. The diagonal interface method, which in this instance applied outward-facing diagonal interface planes at the junctions of the main channel and floodplain zones, produced superior results overall. Key words: floodplain, conveyance, unsteady flow, compound channels, off-channel storage, interface planes.

Hydraulic study of a two‐stage river channel

AbstractMany regulated rivers have compound or two‐stage cross‐sections consisting of a deep main channel flanked by one or two floodplains. Existing methods of assessing discharge capacity in such channels can lead to serious errors, and hence there is a need for the acquisition of flow data to validate models suggested as improvements to existing methods. Stage and discharge data, under both steady and unsteady conditions, were collected from a reach of the River Main in Northern Ireland, which has been reconstructed for flood defence purposes to form a two‐stage channel. The data were analysed using a steady flow computational model to yield water surface profiles and values of Manning's resistance coefficient at various flow depths. The complex nature of flow resistance in two‐stage channels is demonstrated. Unsteady stage hydrographs were linked to a computational model which illustrates the magnitude of errors incurred in applying conventional methods of discharge estimation in compound rivers.

Hydrodynamic derivation of a variable parameter Muskingum method: 2. Verification

Abstract The hydrodynamic derivation of a variable parameter Muskingum method and its solution procedure for estimating a routed hydrograph were presented in Part I of this series (Perumal, 1994a). In this paper, the limitations of the method, the criterion for its applicability and its accuracy are discussed based on the assumptions used. The method is verified by routing a given hypothetical inflow hydrograph through uniform rectangular cross-section channels and comparing the results with the corresponding numerical solutions of the St. Venant equations. The stage hydrographs as computed by the method are also compared with the corresponding St. Venant solutions. It is demonstrated that the method closely reproduces the St. Venant solutions for the discharge and stage hydrographs subject to the compliance of the assumptions of the method by the routing process.

Hydrodynamic derivation of a variable parameter Muskingum method: 1. Theory and solution procedure

Abstract An approach is presented for directly deriving a variable parameter Muskingum method from the St. Venant equations for routing floods in channels having any shape of prismatic cross-section and flow following either Manning's or Chezy's friction law. The approach also allows the simultaneous computation of the stage hydrograph corresponding to a given inflow or the routed hydrograph. This first paper also describes the solution procedure for routing the discharge hydrograph. A second paper (Perumal, 1994b) presents a verification of the methodology.