Showing papers in "Journal of Hydraulic Engineering in 1980"
TL;DR: In this article, a theory based on the Monin-obukhov length was introduced for open channel flow with suspended sediments, and a velocity distribution equation based on this theory showed a good agreement with the measured velocity distribution.
Abstract: Characteristics of open channel flow with suspended sediments were theoretically investigated introducing a theory based on the Monin-Obukhov length First, a velocity distribution equation based on the theory showed a good agreement with the measured velocity distribution Second, the hydraulic resistance and the distribution of suspended sediment concentration observed in experiments were explained theoretically Third, a transport rate formula for suspended sediments, in which classical equations were included as a particular case, was obtained; and this formula, in cooperation with a reference concentration derived in the present study, showed agreement with experimental results Finally, the critical condition for deposition of suspended particles and the collapse of turbulence were derived and verified by experiments
221 citations
TL;DR: In this paper, a method to determine and apply the biomechanical properties of vegetative channel linings is presented, which is used to evaluate the stiffness of vegetation commonly used to protect earth channels from erosion.
Abstract: A method to determine and apply the biomechanical properties of vegetative channel linings is presented. The method is used to evaluate the stiffness of vegetation commonly used to protect earth channels from erosion. Using the vegetation stiffness and stem length, the deflected height of the channel lining is predicted to yield a relative roughness under given flow conditions. The relative roughness is used to calculate a value of the Darcy-Weisbach friction factor or Manning's n. A method to design a vegatated channel is included.
202 citations
TL;DR: In this article, the longitudinal profile of the lobate snout is satisfactorily analyzed by applying the theory of one-dimensional translation wave on an open channel, where the resistance coefficient is a function of concentration, depth, and grain diameter.
Abstract: Reviews on the yield strength and viscosity of the interstitial clay slurry in debris flow prove that ordinary debris flow may be modeled as a dilatant fluid in which the intergranular forces dominate. Theoretical velocity distributions in dilatant fluid compare well with the experimental results when the value of a numerical constant is appropriately selected. The longitudinal profile of the lobate snout is satisfactorily analyzed by applying the theory of one-dimensional translation wave on an open channel, where the resistance coefficient is a function of concentration, depth, and grain diameter. A remarkable segregation of particles, in which the larger ones move upwards, occurs in debris flow due to the effects of collisions of particles. The accumulation of boulders in the front part of debris flow is a result of the faster transportation of the larger particles in the upper layer of the flow than that of the smaller ones in the lower layer.
189 citations
TL;DR: In this paper, the authors proposed a non-dimensional triangular hyetograph based on the statistical mean of the first time moment of recorded rainstorms and triangular representation of the hyetographs, which are nondimensionalized using the rainfall duration and depth.
Abstract: Improved methods for design and pollution control of storm drainage facilities require not only the average rainfall intensity but also the time distribution of the rainfall. Since the temporal pattern of rainfall varies with storms and the patterns of future storms cannot be predicted exactly, the design hyetograph can only be determined probabilistically using statistical values of past events. The nondimensional triangular hyetograph method is based on the statistical mean of the first time moment of recorded rainstorms and triangular representation of the hyetographs, which are nondimensionalized using the rainfall duration and depth. For a given season the expected nondimensional triangular hyetographs for heavy rainstorms are nearly identical, being insignificantly affected by the duration of rainfall. The established nondimensional triangular hyetograph can then be used to produce the design hyetographs by simple procedures. Results of an analysis of 7,484 rainstorms at three locations indicate that such a method is feasible.
156 citations
TL;DR: In this article, an analytical formulation of critical droughts was derived by making use of the theories of random number of random variables and runs and the results obtained are valid for independent and lag-one Markov processes only.
Abstract: Analytical formulations of critical droughts either as longest drought duration or maximum deficit sum have been derived by making use of the theories of random number of random variables and runs. The results obtained are valid for independent and lag-one Markov processes only. The numerical solution of derived analytical expressions yields any order of statistical moments the most important one is the expected value of critical droughts. It has been quantitatively observed that the drought duration and severity are dependent on the correlation structure, sample size, and truncation level.
139 citations
TL;DR: In this article, the role and constitution of the lag has been clarified by inspecting the instability analysis compared with theory of bed load transport process, and an instability analysis has been conducted and the possibility of instability of bed surface has been investigated against hydraulic conditions.
Abstract: Kennedy clarified that the lag of sediment transport for bed form plays an important role for sand bed instability, but this lag could not been evaluated quantitatively to date. In this study, the role and constitution of the lag has been clarified by inspecting the instability analysis compared with theory of bed load transport process. Particularly, based on the writers' research on bed load transport process by stochastic approaches, the lag distance of bed load transport rate for bed shear stress has been reasonably clarified. Furthermore, improving the flow model based on the potential flow theory by introducing the effect of flow acceleration or deceleration which can be expressed by local variation of flow depth, the phase lag between bed shear stress and bed form has been estimated. After clarification of these lags, an instability analysis has been conducted and the possibility of instability of bed surface has been investigated against hydraulic conditions.
133 citations
TL;DR: In this article, the authors quantified bar resistance empirically using data from rivers in Alberta, Canada, and used the device of slope division of reach-averaged bed stress.
Abstract: Gravel-bed streams with bankfull channels of low sinuosity are considered. At flood stages, most of the resistance is grain resistance. Thus, depth-discharge relations can be predicted with existing method, although the inherent scatter is large. At lower stages, however, from resistance due to the presence of bars becomes increasingly important. Bar resistance is quantified empirically using data from rivers in Alberta, Canada, and the device of slope division of reach-averaged bed stress. Further reduction leads to predictive design graphs for depth-discharge relations. A numerical example is provided.
127 citations
TL;DR: An experimental investigation of the deleterious effect of microbial slime layers on the hydraulic performance of water conduits is presented in this paper, where the underlying mechanisms that lead to an increase of frictional losses in the conduit are explored and their relative importance is discussed.
Abstract: An experimental investigation of the deleterious effect of microbial slime layers on the hydraulic performance of water conduits is presented. The underlying mechanisms that lead to an increase of frictional losses in the conduit are explored and their relative importance is discussed. It is shown that although the slime layer is viscoelastic and filamentous, its effect on frictional resistance can be adequately represented through an increase in rigid equivalent sand roughness of the conduit wall.
123 citations
TL;DR: In this article, a rational method has been developed to predict the regime geometry of straight active gravel streams, which is based upon a resistance equation, a bed load equation, and the condition of minimum stream power for gravel streams in equilibrium.
Abstract: A rational method has been developed to predict the regime geometry of straight active gravel streams. The analytical model is based upon a resistance equation, a bed load equation, and the condition of minimum stream power for gravel streams in equilibrium. The analytical channel geometry so obtained is in general agreement with previously established relations and observations. The analytical channel width is proportional to Q 0 . 4 7 , in which Q is the bank full discharge. Except for steep slopes, the width is essentially only a function of the discharge. The analytical depth increases with the discharge but decreases with the slope. On steep slopes, the width increases rapidly with the slope. This rapid increase in width accompanied by a decrease in depth indicates braiding tendency for steep gravel streams. As the bed load approaches zero at the lower boundary, this model for active streams reduces to the threshold theory.
120 citations
TL;DR: In this paper, the land cover requirements of the Soil Conservation Service (SCS) model used to develop volume of runoff for hydrograph synthesis in suburban areas were modified to be compatible with Landsat digital data.
Abstract: The land cover requirements of the Soil Conservation Service (SCS) model used to develop volume of runoff for hydrograph synthesis in suburban areas were modified to be compatible with Landsat digital data. Curve numbers obtained with these alternate land cover categories compared well with those obtained in published example problems using conventional categories. Synthetic Flood Frequency relationships computed for a test watershed showed that the conventional approach based on aerial photos agreed well with the Landsat-based approach to land cover determination.
119 citations
TL;DR: In this article, the curve number runoff equation of the U.S. Department of Agriculture, Soil Conservation Service, is treated as a transformation from rainfall distribution to runoff frequency distribution, and reasonable agreement between observed and hypothesized result was obtained on four of the five watersheds shown.
Abstract: The curve number runoff equation of the U.S. Department of Agriculture, Soil Conservation Service, is treated as a transformation from rainfall distribution to runoff frequency distribution. Reasonable agreement between observed and hypothesized result was obtained on four of the five watersheds shown. The hypothesis failed for the watershed tested in the arid southwest.
TL;DR: In this paper, the problem of aggradation due to an increase in the rate of sediment supply in excess of what the stream can carry has been investigated, where the supply of sediment is assumed to be continuous and at a constant rate.
Abstract: The problem of aggradation due to increase in the rate of sediment supply in excess of what the stream can carry has been investigated. The supply of sediment is assumed to be continuous and at a constant rate. A relationship for the depth of aggradation at any time and at any distance from the section of sediment addition has been developed. Since the mathematical model used was based on many simplifying assumptions it needed verification against a known set of data. Experiments were, therefore, performed in the laboratory and these have enabled suitable modification of the analytical results.
TL;DR: In this paper, a one-dimensional integral energy model (mixed-layer model) is used to simulate the seasonal temperature cycle of three, morphometrically different, temperate lakes.
Abstract: A one-dimensional integral energy model (mixed-layer model) is used to simulate the seasonal temperature cycle of three, morphometrically different, temperate lakes. In the model, turbulent kinetic energy supplied by wind shear is used to entrain denser water into the upper mixed layer by working against gravity. The model is calibrated with data from one lake for 1 yr and verified against data from two other lakes and also against data from other years. Predictions of the onset of stratification, surface and hypolimnetic temperatures, mixed layer depths, and periods of turnover are all in agreement with data.
TL;DR: In this article, a three-dimensional numerical model was developed to study hydrodynamic circulations produced in coastal zones due to tide and wind action, which consists of a mixed finite-difference/finite element solution of the simplified fluid momentum and continuity equations.
Abstract: A three-dimensional numerical model has been developed to study hydrodynamic circulations produced in coastal zones due to tide and wind action. The model consists of a mixed finite-difference/finite element solution of the simplified fluid momentum and continuity equations. A numerical splitting technique is used to reduce the size of model solution matrices while the finite element approach is used over the flow depth to enable irregular sea beds to be tackled easily. Model errors arising from the numerical method are minimized by the use of a Galerkin weighted-residual procedure. The problems associated with modeling the turbulence closure of the basic momentum equations are also investigated with a simplified form of the model and the need for high levels of closure is demonstrated. The potential use of the three-dimensional model is illustrated by prediction of wind-induced flows in Thessaloniki Bay in the Aegean Sea.
TL;DR: In this paper, the minimum stream power for stable alluvial channels has been derived and a method incorporating this condition with a flow-resistance formula and a sediment-discharge formula has been developed to compute the width, depth, and slope of stable channels for a given set of water and sediment discharges.
Abstract: The hypothesis of minimum stream power for stable alluvial channels has been used to derive a condition for alluvial channels in equilibrium. A method incorporating this condition with a flow-resistance formula and a sediment-discharge formula has been developed to compute the width, depth, and slope of stable alluvial channels for a given set of water and sediment discharges. Applying this method yields a design chart that provides the stable width and depth of alluvial canals with trapezoidal shape for a given set of water discharge, channel slope, sediment size, and side slope. Comparing data from some regime canals and small experimental canals has shown good agreement between the observed data and analytical predictions.
TL;DR: In this paper, the authors attempted to determine if an exponent of 2 would give best results for estimating thunderstorm rainfall in the Southwest and if there were definable relationships among gages, distance and exponents in the reciprocal distance method.
Abstract: In this paper, the writers attempted to determine if an exponent of 2 would give best results for estimating thunderstorm rainfall in the Southwest and if there were definable relationships among gages, distance and exponents in the reciprocal-distance method.
Journal Article•
TL;DR: A Task Committee (TC) of the Surface Water Hydrology Committee was organized in 1976 to determine the types of low-flow information needed, to describe available methods of characterizing low flows, and to identify needed analyses and data collection as mentioned in this paper.
Abstract: A Task Committee (TC) of the Surface Water Hydrology Committee was organized in 1976 to determine the types of low-flow information needed, to describe available methods of characterizing low flows, and to identify needed analyses and data collection. Responses to a TC survey of users of low-flow information indicated the need for better estimates of low-flow characteristics at ungaged sites. Available analytical methods are described and evaluated, sources of low-flow information are given, and some recently proposed techniques are reported. Low-flow data on many additional streams are needed.
TL;DR: In this paper, a model based on the streamflow partial duration series (PDS) is proposed to estimate the time-dependent random variables of a 38-yr series of floods on the Melezza River at Camedo, Ticino, Switzerland.
Abstract: The proposed model is based on the streamflow partial duration series (PDS). Both the occurrence time and the magnitude of the floods (instantaneous hydrograph peaks) are time-dependent random variables. An estimation method, based on the maximum likelihood concept, is also proposed. The derivation of the law of extremes from the basic model shows the strong influence of the time-dependence assumptions on the extreme values. Application of the model to a 38-yr series of floods on the Melezza River at Camedo, Ticino (Southern Switzerland) shows good agreement between theoretical and observed values.
TL;DR: In this paper, the steady-state solution of the flow distribution in a pipe network is presented, which relies on an iterative linearization procedure to solve for junction heads, and is highly suited for use on small computers.
Abstract: A previously unpublished numerical method for the steady-state solution of the flow distribution in a pipe network is presented. It relies on an iterative linearization procedure to solve for junction heads, and is highly suited for use on small computers. Its relationship to other solution methods is explicitly developed. This new method is extremely simple to formulate, and requires minimum data preorganization for computation.
TL;DR: In this article, the results of an experimental investigation of the flow characteristics of a submerged horizontal jet flowing over a partly rigid and erodible bed are presented; the diffusion characteristics of the jet, growth of boundary layer thickness, velocity distribution within the boundary layer, critical shear stress at equilibrium stage, and the time variation of shear stresses at the location of maximum scour have been investigated.
Abstract: The results of an experimental investigation of the flow characteristics of a submerged horizontal jet flowing over a partly rigid and erodible bed are presented. The diffusion characteristics of the jet, growth of boundary layer thickness, velocity distribution within the boundary layer, critical shear stress at equilibrium stage, and the time variation of shear stress at the location of maximum scour have been investigated. The expression of critical shear stress has been obtained from the solution of Von Karman's integral equation. A functional relationship of time variation of shear stress has been found out by correlating the dynamic pressure drop recorded by a Preston tube with the velocity distribution law developed from experimental data.
TL;DR: In this paper, it is proposed that deviations from Gaussianity of observed profiles of the concentration of a solute in a cloud as it passes the measuring station in a river, estuary or similar flow should be explicitly measured by recording the non-dimensional skewness and kurtosis.
Abstract: It is proposed that deviations from Gaussianity of observed profiles of the concentration of a solute in a cloud as it passes the measuring station in a river, estuary or similar flow should be explicitly measured by recording the nondimensional skewness and kurtosis. Examples of applications of the proposal are examined. It is shown that observed profiles can be fitted well by Edgeworth series provided the skewness and kurtosis are not too large. Review of the way in which different causes of deviations from Gaussianity can be classified in terms of the evolution of the skewness and kurtosis with downstream position is given, and it is argued that this is the most important point of the proposal.
TL;DR: In this article, the results of laboratory experiments on scour around circular piers in cohesionless bed material at high flow velocities are presented and a special technique is used to measure scour depths.
Abstract: The results of laboratory experiments on scour around circular piers in cohesionless bed material at high flow velocities are presented. A special technique is used to measure scour depths. The scour depth in the sediment transport regime first decreases and then increases with increasing velocity. A formula to predict scour depth for flows with Froude numbers is developed.
TL;DR: In this article, a scientific approach to systematically account for the uncertainties and their interactions in the selection of safety factors and return periods for various risk levels in hydraulic design is presented, which can be used to develop risk-safety relationships for various return periods and expected service life.
Abstract: Hydraulic structures are designed with reference to some natural events which could be imposed on the structure during its expected service life. Conventionally return period design methods fail to systematically account for the many uncertainties in design. By systematically analyzing the component uncertainties and their interactions using the concepts of reliability theory and first-order analysis of uncertainties, a composite risk and reliability can be defined. This paper presents static and dynamic risk and reliability models that can be used to develop risk-safety relationships for various return periods and expected service lifes that can be used in design. The static models consider single loading application and the dynamic models consider repeated application of random loadings to define a composite risk. The models are applied as examples of the methodology to develop risk-safety curves for culvert design. This work presents a scientific approach to systematically account for the uncertainties and their interactions in the selection of safety factors and return periods for various risk levels in hydraulic design.
TL;DR: In this paper, a linear programming model is developed for the optimal determination of unit hydrographs by minimizing the sum of deviation between observed and calculated runoff hydrograpes.
Abstract: A linear programming model is developed for the optimal determination of unit hydrographs. The model determines the best unit hydrograph by minimizing the sum of deviation between observed and calculated runoff hydrographs. The principles of linearity and superposition of unit hydrograph theory are the basis of the model. Several multiperiod rainfall events can be considered simultaneously for the optimal unit hydrograph determination. The model is tested using both hypothetical and actual rainfall events.
TL;DR: In this paper, the transverse mixing coefficient of three river reaches, under both open water and ice-covered conditions, is analyzed and the results show that the coefficient ranges between 0.01 m²/s and 0.09 mµ/s.
Abstract: Field tests to determine the transverse mixing coefficients of three river reaches, under both open water and ice covered conditions, are described. To interpret the test results, the streamtube method for mixing calculations, developed earlier by others, is used. For evaluating transverse mixing coefficients, the widely used moments method is modified so as to be consistent with the streamtube approach. Application of the modified method to test data gave consistent results, thus reinforcing the streamtube approach. For the tests described here, the transverse mixing coefficient ranges between 0.01 m²/s and 0.09 m²/s; when this coefficient is nondimensionalized with the hydraulic radius and shear velocity, it lies between 0.4 and 2.5. Open water values of the dimensionless transverse mixing coefficient are less than the corresponding values under an ice cover by as much as two and one-half times.
TL;DR: In this article, it was shown that the skewness coefficient of LP can be estimated from the mean of logarithmic data (Y¯) and the mean coefficient of Pearson type 3 distribution (P(γ) of real data (X¯).
Abstract: Two new methods of moments (MO) which do not use the sample skewness coefficient (CS) are evolved for fitting log Pearson type 3 distribution (LP). The two current MO methods which use CS are: (Method 1) real data are fit to LP; or (Method 2) logarithmic data are fit to P (Pearson type 3 distribution). By virtue of the combined properties of P and LP, it is shown that: (Method 3) skewness coefficient (γ) of LP can be estimated from the mean of logarithmic data (Y¯); or (Method 4) skewness of coefficient of P (γ) can be estimated from the mean of real data (X¯). The values (Y¯) and (X¯) are unbiased estimates while CS is generally a biased estimate. Monto Carlo experiments have indicated that, as sample size becomes small, the estimates for quantiles of LP are: (1) Systematically biased for Method 1; (2) highly positive biased when (γ) is negative, and unbiased to somewhat positively biased when (γ) is positive for Method 2; (3) unbiased to least biased of the four methods when (γ) is negative, and somewhat negatively biased when (γ) is positive for Method 3; and (4) negatively biased for Method 4.
TL;DR: In this paper, a method of calculating bed-load transport is presented, which takes advantage of the rapid bathymetric surveys that can be made in large rivers, and is based on sediment continuity and an assumption for the base level of zero transport.
Abstract: A method of calculating bed-load transport is presented. This method takes advantage of the rapid bathymetric surveys that can be made in large rivers. The proposed equation is based on sediment continuity and an assumption for the base level of zero transport. Experimental data were obtained in a series of flume tests and the measured transport rates are compared with the calculated transport rates using the proposed equation. Comparisons are also made with the Ackers-White Equation.
TL;DR: In this paper, the issue of numerical precision as affected by the use of different routing schemes was investigated, based on the observation that in an application of the Kalinin-Miljukov method, accuracy improved when a more refined difference scheme was used in place of the conventional one.
Abstract: This note will center on the issue of numerical precision as affected by the use of different routing schemes. The investigation is prompted by the observation that in an application of the Kalinin-Miljukov method, accuracy improved when a more refined difference scheme was used in place of the conventional one.
TL;DR: In this article, the authors used the soil conservation service curve number (SCS) curve-number procedure to determine rainfall excess, which is used to estimate the soil type, land use, and precipitation, each of which is relatively easy to estimate.
Abstract: The soil conservation Service (SCS) curve-number procedure is commonly used to determine rainfall excess. The advantage of this method is that the parameters in the relation are the soil type, land use, and precipitation, each of which is relatively easy to estimate. The method does have some shortcomings. The procedure for analysis of intermittent rainfall and for portions of storms where rainfall intensity is less than infiltration capacity is not well defined. In addition the SCS method predicts that the infiltration rate will approach zero during storms of long duration instead of a constant terminal infiltration rate.
TL;DR: In this article, a series of experiments were conducted to study the effect of unsteady flow on turbulence characteristics, including mean velocity profiles, temporal and spatial Reynolds stress profiles, and energy spectra.
Abstract: Field measurements of tidal flow have shown that there is an increase in turbulent parameters (turbulent intensity, Reynolds stress, coefficient of turbulent diffusivity, and the rate of sediment transport) when the flow is decelerating as compared with when it is accelerating. A series of experiments were conducted to study the effect of unsteady flow on turbulence characteristics. The flow in a long flume was accelerated and then decelerated for the same periods of time. Instantaneous velocity components in three directions, water surface slope, and shear stress at bed were measured. From measured data mean velocity profiles, temporal and spatial Reynolds stress profiles, and energy spectra were determined. The results were compared, wherever possible, with those obtained from field measurements.