http://localhost:8081/jspui/handle/123456789/118 2025-07-01T06:46:34Z 2025-07-01T06:46:34Z Mohanty, Harihar http://localhost:8081/jspui/handle/123456789/17384 2025-06-30T13:38:15Z 2013-06-01T00:00:00Z

Title: A PRACTICALLY VIABLE SIMPLIFIED HYDRODYNAMIC STAGE-HYDROGRAPH ROUTING METHOD Authors: Mohanty, Harihar Abstract: The simplified flood routing methods such as the Muskingum method and its variants are well established in the hydrological literature [Chow et al., 1988], and the modest data requirements of these methods make them suitable for practical applications. Generally routing methods employ discharge as the routing variable. But for flood forecasting purposes and in conditions where the civic authorities are involved in the evacuation of people from flood inundation areas, it is necessary to know the stage of the stream rather than discharge for planning emergency evacuation action plans. Since, the stage information can be collected more easily and economically, sometimes it is advantageous to route a stage hydrograph rather than a discharge hydrograph to know the stage or flow depth along the channel reach at the point of interest. Hence, this study emphasizes on the continued interest in improving the stage-hydrograph routing, especially, in the form of the classical Muskingum method. Over the past decades, a number of simplified discharge flood routing methods have been developed. However, in the literature, only a few researchers, such as Hayami [1951] and Perumal et al. [2007, 2010] have developed the simplified stage-hydrograph flood routing methods. The added advantage of the latter method is that it enables also to estimate the discharge hydrograph corresponding to the routed stage hydrograph, a feature generally not available in simplified routing methods. Perumal et al. [2007] developed the VPMS routing method by directly applying the approximate convection-diffusion (ACD) equation in stage formulation [Perumal and Ranga Raju, 1998], using the finite difference approximations of mixed order of accuracy, which resulted in significant volume error in the solutions of the VPMS method [Perumal et al., 2007,2010]. To overcome this problem, the present study investigates the development of an improved variable parameter Muskingum stage-hydrograph routing ((henceforth, identified with the acronym IVPMS) method by revising the current form of the VPMS method advocated by Perumal et al. [2007, 2010]. In this study, the ACD equation is applied along the mid-time level within the computational grid bounded at the top and bottom by two consecutive computational time levels, and bounded along the spatial direction at the two ends of the computational reach length & by the input and output sections. Such a finite difference grid arrangement enables the application of the governing ACD partial differential equation at the mid-point of the grid using the second order accurate finite difference equation. The parameters of the method vary at every computational time interval of the routing process as adopted in the earlier VPMS method, but with changes in the structure of the parameter relationships and their applications in the routing process at every time-step. The VPMS method developed by Perumal et al. [2007, 2010] uses the prismatic cross-section details along with single Manning's roughness coefficient, n, for routing a given stage-hydrograph. Such an approach is appropriate when routing stage-hydrograph in artificial channels like irrigation canals. However, it is difficult to apply such a method for routing stage-hydrographs in natural rivers as it requires first to approximate the river reach to that of a nearest prismatic section reach as required by the method and then subsequently apply this method for routing. Hence, it is considered necessary to improve the VPMS routing method for routing floods in natural rivers by using only the rating curves information available at the two end sections of a given routing reach along with the information of the associated cross-section geometries available at these end sections. The study is undertaken with the following objectives: 1) To replace the current finite difference scheme employed in the representation of the Approximate Convection-Diffusion equation used in the existing VPMS routing method by the second order finite difference scheme representation of the spatial and temporal derivatives leading to the development of the improved VPMS method; 2) To study the celerity-stage relationship of river flood wave required for field application of the IVPMS method; 3) To enhance the field applicability of the IVPMS routing method by replacing the direct use of the reach cross-section information for routing with the rating curves information available at the end sections and the information of the associated cross-section geometries of these respective gauging stations along a river reach; and 4) To develop the applicability criterion for the IVPMS routing method. The capability of the IVPMS method is demonstrated by routing the given hypothetical input stage hydrographs in different types of hypothetical prismatic channel reaches each characterised by different sets of uniform roughness and bed slopes as applied in the study of VPMS method by Perumal et al. [2007,2010]. The routing was carried out for a -4 specified reach length in each of the hypothetical channels using the IVPMS method, and the routed stage hydrographs and the estimated discharge hydrographs arrived at the end of the reach using the IVPMS and the VPMS method were compared with the corresponding benchmark hydrographs obtained using the MIKE 11 model [DHJ, 2008]. The study demonstrates that the hypothetical routing results of the IVPMS method closely reproduce the benchmark solutions of the stage-hydrographs. However, when the longitudinal gradient of the water depth I(1/So) (oy/ax)Imax >0.4 estimated at the inlet of the routing reach, the discharge hydrograph estimated using the routed stage hydrograph of the IVPMS routing method is not able to reproduce the benchmark discharge hydrographs better than the corresponding estimated discharge hydrographs obtained using the VPMS routing method. Besides, it is seen that the mass conservation capability of the method is far better than that of the earlier version of the VPMS method with most of the simulations estimating less than one percent mass conservation error. In general, simplified flood routing methods employ two routing parameters, viz., the travel time which accounts for the convection dynamics of the flood wave, and a parameter accounting for its diffusion characteristics. The parameter characterizing the travel time is directly linked to the wave celerity, i.e., the velocity with which a given stage or discharge propagates along the given routing reach under unsteady flow condition. The celerity- discharge relationship of natural rivers was studied by Price [1975], and Wong and Laurenson [1983, 1984] carried out for UK and Australian rivers, respectively. As no celerity-stage relationship has been studied earlier, the same has been developed on the similar lines as investigated by Wong and Laurenson [1983, 1984] for Australian rivers. The purpose of developing such a celerity-stage relationship for a given routing reach is for its use in hypothetical and practical flood routing studies using the IVPMS routing method. The study based on the hypothetical routing results of the IVPMS method demonstrates that the routing procedure developed based on the IVPMS method using only the reach end sections rating curves and associated cross-section geometries information are capable of closely reproducing the benchmark solutions of the stage-hydrographs. The IVPMS routing method is able to reproduce the benchmark discharge hydrographs closely when I(1/So)(ay/ax)Imax estimated at the inlet of the reach is less than 0.4. For such a verification, two different types of hypothetical prismatic channel reaches, such as: (i) Ackers' [1993] hypothetical river channels consisting of two-step compound trapezoidal section with single and multiple roughness values at a section and (ii) hypothetical channels of Price [2009] with a given Maiming's roughness for the main channel and a different Maiming's roughness for the floodplain section of the channel were employed. The practical usefulness of this method is also demonstrated by routing different flood events in two channel reaches of the Upper Tiber River in Central Italy for river reach lengths of 15 km and 50 km. It is pertinent to point out herein that the applicability of the IVPMS method is restricted by the assumptions of no lateral flow and no effect of downstream disturbances in the study reach. The routed stage hydrographs arrived at the end of these two channel reaches using the IVPMS routing method and the corresponding estimated discharge hydrographs reproduce the respective observed hydrographs more closely for many of the events better than the respective reproductions obtained using the VPMS method [Perumal et al., 2010]. This in essence clearly confirms the efficacy of the IVPMS routing method over that of the VPMS routing method studied earlier by Perumal et al. [2007, 2010]. The applicability criterion of the VPMS method was established by Perumal and Sahoo [2007] based on the limit of longitudinal water surface gradient obtained using a number of hypothetical routing experiments and was compared with the corresponding benchmark solutions obtained using the solution of the Saint-Venant equations. In the same manner, the applicability criteria of the IVPMS routing method are also assessed and quantified based on the magnitudes Of(1/So)(ÔY/ÔX)max. Considering a 95% level of model performance, the experiments indicate that the applicability limit of the IVPMS method for stage routing is (1/So)(ay/ax),,,l .0 ; while for the simultaneous computation of the discharge hydrograph corresponding to the routed stage hydrograph, this method can be applied up to (1/So)(3y/3x),0.86, which reveals a significant improvement of the applicability criteria over the VPMS method. The IVPMS routing method is advantageous over all the simplified flood routing methods for its capability to route the stage hydrograph and enable the estimation of concurrent discharge hydrograph by closely reproducing the benchmark solutions. Also the method has better mass conservative ability than the VPMS method and, thus, can be used by the river engineers and field hydrologists in practice. The study reveals that this simplified hydraulic routing method has ample scope for its extension for meso-scale river basin modelling, especially, as a component module of the land-surface scheme of the climate change models.

2013-06-01T00:00:00Z Taxak, Arun Kumar http://localhost:8081/jspui/handle/123456789/17014 2025-06-23T12:33:34Z 2014-06-01T00:00:00Z

Title: LAND USE LAND COVER CHANGE IMPACT ON THE HYDROLOGY OF WAINGANGA BASIN UNDER CHANGING CLIMATE Authors: Taxak, Arun Kumar Abstract: The present study analysed the impact of Land Use Land Cover (LULC) changes on the streamfiows in Wainganga basin at Ashti station under changing climate. Changes in rainfall and temperature trends were analysed using Mann-Kendall test and Sen's Slope Estimator test. Detection of change point in trends of rainfall and temperature were carried out using Pcttitt-Mann-Whitney test. Overall, it was found that annual rainfall has decreased by 8.45% in the basin during 1901-2012. and 2.93 % during 1972-2007. The most probable change point in annual rainfall was found at 1948. Analysis of temperature trends shows an increase in temperature by 2.530C during 1901-2012. and by 0.81°C during 1972-2007. The probable change point in annual temperature was detected at 1975. LULC data were derived from remote sensing data for the years 1972, 1989 and 2008. Analysis of LULC classes have shown that there are two prominent classes in the basin namely Crop Land and Forest cover. Overall, Crop Land has increased by 3.51% during 1972-2008 whereas Forest cover has decreased 4.67 % during the same period. Variable Infiltration Capacity model was used for simulating streamflows in the basin at Ashti station. Nash-Sutcliffc efficiency. Coefficient of Determination and Relative error during calibration period (1972-1991) was found 0.8422, 0.9197 and -4.05 % respectively. and 0.72. 0.85, and 0.01% during the validation period (1992-2007). Simulation with different land use land cover during 1972-2008 depicts reduction in mean annual streamfiows by 0.42%. The model was run with 2008 LULC data during 1972-2008 to assess the impact of climate change only. Analysis demonstrate a non-significant decreasing trend in the basin showing 3.98 % decrease in mean annual flows. VIC model was also run to study the combined effect of LULC and climate change for the entire period (i.e from 1972 to 2007) using three LULC data 1972, 1989 and 2008 representing durations 1972-1980, 1981-1998 and I 999-2007, respectively. Annual streamfiows demonstrate a non-significant decreasing trend in the basin with a 4.34% decrease in mean annual flows.

2014-06-01T00:00:00Z Shrestha, Bidur Man http://localhost:8081/jspui/handle/123456789/17013 2025-06-23T12:33:12Z 2014-06-01T00:00:00Z

Title: AN APPROXIMATE PHYSICALLY BASED DIFFUSIVE WAVE CHANNEL ROUTING METHOD Authors: Shrestha, Bidur Man Abstract: The present study aims to develop a simplified channel routing method based on the approximate diffusive wave equation for routing flood waves in different prismatic channels. This method is derived directly from the diffusive wave equation developed from the Saint-Venant equations without considering lateral inflow. To evaluate the routing capabilities of the developed method, a set of 25 types of channels with each set of channels characterized by trapezoidal, rectangular and triangular channel sections and each of these channels characterized by a unique slope selected from the range of So = 0.0001 to 0.002 and a unique roughness coefficient selected from the range of n0.01 to 0.06 are used for routing a given hypothetical inflow hydrograph using the proposed method. The benchmark solutions required for comparative evaluation of the proposed routing method were obtained using the well known software package HEC-RAS (version 4.1). The routed discharge hydrographs and the corresponding estimated stage hydrographs arrived at using the proposed method are compared with the respective benchmark solutions based on the reproduction of some pertinent characteristics of the benchmark discharge and stage hydrographs using appropriate evaluation measures. The solutions of the proposed method are also compared with the Variable Parameter McCarthy-Muskingum (VPMM) method proposed by Pérumal and Price (2013) and the Variable Parameter Muskingum-Cunge-Todini method proposed by Todini (2007) with and without considering the diffusion coefficient correction introduced by Cappelacre in 1997.It was concluded by Todini (2007) that the MCTc method has better accuracy in routing a given discharge hydrograph than the MCT method. It is inferred from the study that the proposed method has the same order of accuracy as that of the VPMM and MCTc methods in reproducing the benchmark discharge and stage hydrographs. This method is fully mass conservative

2014-06-01T00:00:00Z Khatri, Supindra http://localhost:8081/jspui/handle/123456789/17012 2025-06-23T12:32:55Z 2014-06-01T00:00:00Z

Title: SIMULATION OF JUNE 2013 FLOOD AT TEHRI DAM Authors: Khatri, Supindra Abstract: Tehri Dam is located in River Bhagirathi, around 1.5 km downstream of confluence point between Bhagirathi and Bhilangana in Tehri Garhwal District of the state Uttarakhand. The height of the earth and rock-fill dam is 260.5 m from its deepest foundation level. The main purpose behind the construction of high dam is to collect the large volume of water during the flash floods and use them for power generation, supply drinking water and irrigation in a controlled manner throughout the year. The average water availability at Tehri dam is 8000.0 MCM out of which about 39% comes from melting of glaciers in the Himalayas where as the rest 61% is trapped from the flash floods during the short monsoon season. The design flood discharge adopted for the spillways design of Tehri dam is 15,540.0m3ls. Recently on 171h June 2013, the maximum flood discharge measured at the dam axis was 7535.0 m3/s, which is nearly half of the design discharge. In the present study, June 2013 flood at Tehri dam is analyzed and simulated by different geomorphologic approaches in order to develop a flood estimating and forecasting model for Tehri dam for similar floods in future. For the study purpose the whole catchment is divided into three major parts on the basis of catchment physiography. The Geomorphological IU1-1, Geomorphoclimatic IUH and GIULINash model are used for the simulation of 16th , 17th and 18th June 2013 flood. The resultant flood hydrographs from each model is compared with the observed hydrographs. Similarly the flood volume retained in the Tehri reservoir during the period is compared with the simulated volume from different model. The observed peak flood discharge is 7535.0m3/s and the simulated discharge from GIUH, GcIUH and GIUH-Nash model are 6856.0m3/s, 6980.0m3/s and 6901.5m3/s respectively. The gross inflow volume retained in the Tehri reservoir is 748.9 MCM and the simulated volume by GIUH, GcIUH and GIUH-Nash model work out to be 723.8 MCM, 733.5 MCM and 735.6 MCM respectively. The Nash-Sutcliff efficiency for GIUH, GcIUI-1 and GIUHNash models are 75.8%, 79.1% and 80.5% respectively. The results of GIUH-Nash model interms of model efficiency, percentage error in time to peak and percentage error in observed volume are better than that of GcIUH and GIUH model.

2014-06-01T00:00:00Z