Surat is a highly developed, thickly populated cosmopolitan character city with full of various activities going on day and night. Any natural calamity which causes loss of lives to property and infrastructure along with effects on industrial processes going on has serious impact on economy of the state. Therefore, it becomes highly necessary that flood events are studied and analyzed properly in order to propose adequate flood control and protection measures in time to come. Many research organizations like Central Water Commission (CWC), Gujarat Engineering Research Institute (GERI), Central Water Power and Research Station (CWPRS), are already involved in study of flood phenomena of Tapi River. It appears to be of vital importance to initiate studies as an extension in lights of finding of such studies, using modern computer, model and software technology. In this research paper in detail, morphological processes in Tapi River Basin studied. It is also studied presently available mathematical models by proving them for Tapi flood data and to develop an “Optimization Process” to minimize the flood impacts. It is further attempted to validate the model with studies on physical model development with studies on physical model developed/constructed by any Govt. or Semi Govt. organization like CWC, GERI, and CWPRS etc. Subsequent to construction of Ukai dam large urban developments have taken place along Tapi river banks. With the moderation of flood at Ukai reservoir, no major floods were experienced at Surat and Hazira till 1994. During 1994, 1998 and 2006 floods of the order of 14870 m3/s (5.25 lakh cfs), 19820 m3/s (7.00cfs) and 28315 m3/s (9.10lakh cfs) were experienced. Large portion of Surat area was inundated along with large scale flooding at Bhata, Bharatpur, Surat, and surrounding areas. There were heavy damages of industrial and urban properties costing 21000 Crores. This paper presents CHARIMA mathematical model for prediction of water levels in Tapi Creek under influence of flood and tide. This mathematical model is capable of handling unsteady floods in river channel network validated for September 1998 flood situation and then applied for predictions with 28315 m3/s (10 lakh cfs flood discharge). On the basis of the results this study the necessary measures to be taken for flood forecast and flood protection schemes to minimi Tapi river flood impacts on Surat, Gujarat, India, have been suggested.

Water level determination during a flood is always a challenging task for river engineers. During the flood, river channel becomes compound consisting of the main river channel which carries low flows and floodplains that carry overbank flows.  Flow velocity and structures are affected by vegetation, the degree to which depends on vegetation density, flexibility, type, and whether it is in a submerged or emergent condition. Water surface modeling help for the study of flood waves, water level calculation during flood, stage discharge relation, design of water work structures. This work develops a model which can be used to simulate water surface profile in compound channel with vegetated floodplains with various vegetation covers. To predict the water surface, experiments have been conducted in the laboratory for different hydraulic conditions. It can be seen from the results that the trend of stage-discharge relationships is found to be an exponential function giving a high value of R2. A multivariable regression model (MRM) has been developed to predict the water surface profile for such channels. The dependency of water surface profiles on four different non-dimensional parameters such as canopy arrangement, canopy density, relative depth and relative distance are analyzed. Using the relevant experimental data, non-linear regression has been performed. The results obtained from the present water surface profile model shows good agreement with the observed data.

A side weir is a hydraulic structure with free flow, which is installed at one side and parallel to an open channel. It allows the water to overflow when the surface of the water in the channel rises above the weir crest. This structure affects the depth and the flow rate in the channel. Awareness regarding the effect of this structure on the depth of water and flow rates can affect decision making for the proper hydraulic design of the channel and its side weir. In this research, 36 semi elliptical side weirs were tested in 298 settings, varying in an experimental main channel geometrical characteristics, and subcritical conditions. The range of discharge was varied from 10 to 70 lit/s. The water surface profiles over semi elliptical and rectangular side weirs were investigated and interpreted through velocity profiles. Additionally, the effects of increasing the discharge in the main channel, and varying the height, length and curvature of weir on the water surface profile were examined for this type of weir were studied. Moreover, the result of experimental water surface profiles were compared with the water surface profiles calculated by the Runge-Kutta method over rectangular and semi elliptical side weirs. The results indicated that the accuracy of this method was increased by raising the height and length of the weir, and the reducing the discharge.

This paper presents an in-depth study of water surface calculation of rockfill detention structures in series. Different flow characteristics in porous media were investigated, explaining the influence of velocity, hydraulic gradient and geometric media characteristics. Two mathematical models were presented based on the fundamental relationships in gradually varied flow theory in open channels and combining it with the pore velocity equations of Wilkins and Forchheimer. The analytical solutions were evaluated using laboratory data sets of three angular rockfill materials and four employed discharges. It was observed that presented analytical solutions can accurately predict the water surface profile. However, the Forchheimer equation needs the calibration of two coefficients in comparison to the Wilkins equation with one coefficient. Also, the results show a good association between the Froude number and Manning's coefficient in the power form trend. It was seen that power variation provides a suitable interpretation of the flow coefficient for all flow and rockfill geometric conditions.

Reduction of water resources and low efficiency of irrigation networks makes it necessary to pay attention to the management methods and the proper operation of the irrigation canals. In each irrigation network, there is a large number of offtake and cross-regulators that any change in their operating situation affects the behavior of other structures and lead to decrease in the hydraulic performance of canals. The structural perturbation is formed under partial changes in the setting of offtake and cross-regulator, which causes variations of the design depth and water surface profile. Partial changes in the inflow of a canal discharge lead to hydraulic perturbation and variation in water surface profile. In this research, in order to investigate the influence of structural and hydraulic perturbation on the flow depth, the governing Gradually Varied Flow (GVF) equation was linearized by Taylor's expansion and an analytical equation was developed to calculate the water depth changes. Then, for various hydraulic conditions, the results of the numerical solution of the governing GVF equation and the developed analytical formula were compared. The results showed that the errors of the presented formula to calculate the water surface profile changes under structural and hydraulic disturbances were less than 4% and 3.8%, respectively.

Side channel spillways have a common usage in conveyance and distribution networks, high dams, water and wastewater treatment plants, and surface drainage networks. A side channel carries spatially varied flow with increasing discharge and their water surface profiles is a main feature in the design process. Usually, the bottom width of the channel is flared in the flow direction and an end sill is also installed at the downstream end to provide a control section and to generate an even water surface profile. In this study, the impact of installing an end sill on the flow characteristics in a non-prismatic side channel is presented. Six distinct longitudinal profiles were clearly observed in each run and the difference between the mid points of the maximum and the minimum profiles of each run was used to evaluate the sill effects on the water surface profile and the energy dissipation. The results indicated that the maximum and the minimum differences are, respectively, equal to critical depth and half of it generated at the channel downstream end. Also, based on an envelope of the data, a method was proposed to determine the maximum potential impact of an end sill that might have on the flow depth, which could also be considered as a guideline in the design process.

Rockfill material is frequently used in construction of hydraulic structures. The cross flow regime which is mostly None-Darcy regime and estimation of friction coefficients have been investigated frequently. Many researchers have studied the relationship between Reynolds number and friction coefficient in both power and fractional forms. In this research, by using two types of rock material namely with: median diameters of d50=1.1cm, d50=1.6cm, three entrance discharges and three hydraulic gradients the important factors in estimation of friction coefficients was investigate. Results showed that against results of previous studies, in flow through rockfill media, having free water surface, the Froude Number demonstrated a better relationship with friction coefficient rather than Reynolds Number. Also it was observed that due to the formation of M2 longitudinal profile through the rackfill media, the active cross section along the profile decreases and consequently the friction coefficient towards exit of media decreases. Further it can be concluded that the computed friction coefficients for completely flow through the medias are much higher than friction coefficients of channel free surface flows. Finally an attempt was made to draw the relationships in power form between effective none-dimensional parameters like Froude number, geometric ratio of flow depth and rock diameter and friction coefficients in two form of Manning and darcy-weisbach. Using combination of two none-dimensional parameters (Froude number and geometric ratio of flow depth and media diameter) two applicable relationships for darcy-weisbach and manning coefficients have been presented which have estimation accuracies of 14 and 26 percent respectively.

Side weirs are structures that are installed along a channel and when the height of water is exceeding the crest, extra flow inters to the subsidiary channel. In this research, a solution for differential equation of water surface profile over trapezoidal broad-crested side weir in rectangular channels based on the Haar wavelet transform method is reported. Also, the water surface profiles for different width, height and side slope of the weir were measured and compared to those calculated by using the Haar wavelet method. The Lowest error percentage in calculating y1 (maximum error) was observed in the side slop of side weir of 1.5, width of 8 and height of 10 cm. When height and side slope of the side weir were increased, the accuracy of water surface profile estimations using the Haar wavelet method was decreased. The Haar wavelet method is also compared with Runge-Kutta Method. The correlation coefficient of Haar wavelet method and experimental data was more than 0.979 which was greater than the calculated one for the Runge-Kutta method. This result indicates that the Haar wavelet method can estimate the water depths with higher accuracy than the Runge-Kutta method.