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This article presents approximate but analytical-based solutions for computing the lateral force (force per unit length) and centroid location induced by horizontal and vertical surcharge surface loads resting on a cross-anisotropic backfill. The surcharge loading types include: point load, finite line load, and uniform rectangular area load. The planes of cross-anisotropy are assumed to be parallel to the ground surface of the backfill. Although the presented solutions have never been proposed in existing literature, they can be derived by integrating the lateral stress solutions recently addressed by the author. It is clear that the type and degree of geomaterial anisotropy, loading distances from the retaining wall, and loading types significantly influence the derived solutions. An example is given for practical applications to illustrate the type and degree of soil anisotropy, as well as the loading types on the lateral force and centroid location in the isotropic/cross-anisotropic backfills caused by the horizontal and vertical uniform rectangular area loads. The results show that both the lateral force and centroid location in a cross-anisotropic backfill are quite different from those in an isotropic one. The derived solutions can be added to other lateral pressures, such as earth or water pressure, which are necessary in the stability and structural analysis of a retaining wall. In addition, they can be utilized to simulate more realistic conditions than the surcharge strip loading in geotechnical engineering for the backfill geomaterials are cross-anisotropic. DOI: 10.1061/(ASCE)1090-0241(2007)133:10(1259) CE Database subject headings: Lateral stress; Lateral loads; Vertical loads; Horizontal loads; Anisotropy; Backfills.

An experimental study of scour countermeasures for wing-wall abutments under mobile-bed conditions is reported. The purpose of the study was to determine the required apron size to protect a wing-wall abutment from scour under mobile-bed conditions, for different flow depths, flow velocities, and apron placement level. Riprap and cable-tied block countermeasures were investigated. It was observed that scour at the abutment undermines the apron, causing the outer edge of the apron to settle. Scour at the abutment can be a combination of localized scour (i.e., contraction scour and local scour) and scour due to the troughs of the bed forms that migrate past the abutment, the latter being the focus of the study presented. As the flow depth and flow velocity are increased, the outer edge of the apron settles into the sand, to a depth proportional to the height of the bed forms developed in the flume. Localized scour may additionally influence the depth of settlement. When the apron width is increased, the depth to which the outer edge settles remains reasonably constant. When the apron is preburied below the average bed level, the settlement of the outer edge is less, but the depth of the outer edge of the apron below the average bed level is the same as for the corresponding apron placed on top of the bed. Riprap and cable-tied block aprons respond in different ways. Stones at the outer edge of riprap aprons tend to roll away from the abutment as they settle, pushing the erosion zone further away from the abutment. Conversely, because cable-tied block mats remain attached to the abutment, apron settlement allows the scour to occur closer to the abutment face. It is concluded that the scour at abutments under mobile-bed conditions is often governed by the size of the bed forms that pass the abutment. Therefore, the design of armored scour countermeasures for abutments under mobile-bed conditions should be based upon the largest expected bed forms, which can be predicted based on existing expressions, together with any effects of localized scour. This will enable the settlement of the outer edge of the apron to be determined, and the required apron width to be chosen, depending on the tolerable distance between the deepest scour and the abutment. An equation is given for prediction of the minimum width of apron remaining horizontal after erosion. DOI: 10.1061/(ASCE)0733-9429(2006) 132:6(563) CE Database subject headings: Abutments; Erosion; Scour; Revetments; Sediment transport; Open channels; Hydraulics; Bedforms.

Block ramps or rock chutes are stream restoration structures used in many hydraulic projects. If the base material presents stability problems, a reinforcement can be used; it consists of placing over the ramp rocks greater in size than the base material in order to increase the flow resistance and reduce the shear stresses on the base material. The presence of these boulders also changes the energy dissipation of the flow over the structure. This work shows the results of experimental tests conducted on reinforced block ramps with slopes varying from 0.08 to 0.33. The effect of the various geometric parameters has been investigated. The aim is to extend existing relationships for a simple block ramp and define a new equation that can be applied to a block ramp with or without the presence of boulders. DOI: 10.1061/(ASCE)0733-9437(2006)132:3(293) CE Database subject headings: Ramps; Energy dissipation; Boulders; Riprap; Bed roughness.

Plunge pool scour involves a significant risk with trajectory spillways because of structural undermining at a dam foot or destabilization of adjacent valley slopes. An experimental program towards the understanding of plane plunge pool scour of a completely disintegrated rock surface was conducted, in which the following items received attention: jet shape, jet velocity, jet air content, tailwater elevation, granulometry, upstream flow to the scour hole, and the end scour profile in terms of the basic scour features. These effects were experimentally investigated based on a systematic variation of the governing scour parameters. The results of this paper allow answering questions that have so far not been addressed. Design equations were proposed to sketch the main tendency of the data sets. The significant effect of the densimetric particle Froude number was substantiated. This research may be used to estimate the prominent scour features for nearly two-dimensional jet arrangements involving a pre-aerated high-speed flow. DOI: 10.1061/(ASCE)0733-9429(2006)132:5(450) CE Database subject headings: Air water interactions; Hydraulic structures; Scour; Spillways; Pools.

After long-term operation, a variety of hidden defects will occur in hydraulic structures, which will endanger the safety of a water conservancy project. In particular, hidden defects located below the water surface cannot be easily recognized by conventional methods and thus constitute the main reason for occurrence of dangerous situations in such hydraulic structures. It is therefore necessary to carry out periodic checks on the underwater structures. Ground-penetrating radar (GPR) is a high-resolution, nondestructive technology for detection of underground objects using a high-frequency electromagnetic pulse, and has been extensively applied to a variety of fields such as engineering/geologic exploration, underground archaeological survey, detection of scour holes around bridge piers, etc. In order to investigate the capability of GPR in detecting hidden dangers to underwater hydraulic structures, the authors have conducted GPR application-related experiments for more than 20 hydraulic projects since 1996, and in order for the GPR application to be successful in narrow spaces such as lock chambers, the authors also designed an antenna that can be directly operated on the water's surface. Experimental results demonstrate that GPR can be used not only to detect hidden dangers with high precision, such as uneven settlement and cracking at impervious blanket or apron water bottoms, but also to detect hidden dangers to underwater hydraulic structures, such as damage of reverse filter below the sloping clay core of a dam, settlement and cracking of the antiseepage geomembrane at the bottom of a reservoir, concentrated seepage channel, etc. The application effect will be demonstrated in this paper based on some practical examples of using the GPR technique for such types of detection. CE Database subject headings: Water resources; Hydraulic structures; Underwater structures; Geophysical surveys; Radar; Structural safety; Research; Case reports.

A conventional proportional integral (PI) controller is modified with a nonlinear activation function (sigmoid function) applied directly to the controller output in order to improve the stability and target fidelity of the system response to large variational inputs in both state and internal controller gain variables. The controller is implemented in a simulated water management role applied to a major subregional pumping station between Lake Okeechobee, the Loxahatchee National Wildlife Refuge (WCA1), and the West Palm Beach supply canal (C51) in the South Florida geographic region. The simulation consists of an integrated hydrological numerical model implemented in the Regional Simulation Model (RSM), which is currently under development at the South Florida Water Management District. Analysis of the modified controller in the Laplace domain establishes the expected control behavior, and subsequent results of the simulation for the conventional PI and the sigmoid modified controller are presented and compared. The modified controller achieves significant improvement in stability while simultaneously reducing the control signal energy. CE Database subject headings: Water management; Flow control; Control systems; Hydraulic structures.

This paper presents the results of a laboratory study of the structure of flow in a diversion structure with a vertical angled wedge-wire fish screen. This screen had a 10 x 25 mm mesh and was tested at three angles of 10.4, 17.5, and 26.8[degrees], to the direction of the approaching flow, for two mean velocities of 0.5 and 0.8 m/s, with a depth of flow of about 0.75 m. In this water and fish diversion (channel or) structure, it was found that the depth of flow at any section is approximately constant with a drop at the screen on the side of the canal and decreased towards the bypass located at the downstream end. The distribution of the velocity component u in the direction of the approaching flow as well as the perpendicular component w and the resultant velocity V was uniform in the vertical direction. The depth averaged mean velocity [bar.v] for different verticals at any section in the diversion structure increased with the longitudinal distance x and was correlated with the relative width, [b.sub.s]/b (in the diversion structure for all five experiments. Correlations have been found for the depth averaged transport velocity [bar.u'] and the impinging velocity on the screen [bar.w'] in terms of the approach velocity U. A general relation has also been developed for the attack angle of the flow on the screen. The downstream part of the screen carried more flow into the canal compared to the upstream part as a result of the uniform mesh size used in this study. The results of this hydraulic study should be useful, particularly for freshwater adult fish, in designing screens in irrigation canals and for micro-hydro sites that use diversion canals. DOI: 10.1061/(ASCE)0733-9429(2005)131:4(294) CE Database subject headings: Fish habitats; Intakes; Open channel flow; Canals; Hydraulic structures.

Canals or open channels that convey water often consist of pools in series separated by control structures. Successful implementation of water-level control with these structures using decentralized proportional integral (PI) controllers depends heavily on the tuning of the control parameters. These parameters are hard to determine due to the interactions between the pools and the varying flow conditions in the canal. This paper presents a procedure for tuning any linear controller (including decentralized PI controllers) that guarantees stability of the controlled canal. It minimizes a cost function that weights the water-level deviations from the target level against control efforts at both low- and high-flow conditions. The procedure is tested on a model of the Umatilla Stanfield Branch Furnish Canal in Oregon. The tests show the capability of the procedure to deal with the pool interactions. The results of a realistic turnout schedule applied to the controlled canal show the high performance of the controllers (small water-level deviations in all pools) over varying flow conditions. DOI: 10.1061/(ASCE)0733-9437(2005)131:2(190) CE Database subject headings: Optimization models; Canals; Open channels; Control structures; Hydraulic structures.

The failure of two reinforced concrete structures is recounted, one involving a warehouse structure and the other an offshore platform base structure. Design details and factors leading to the collapses are identified and discussed. The structures were subsequently analyzed using nonlinear finite-element analysis procedures, taking into account relevant second-order behavior models. The analyses provided an accurate assessment of the load capacities and failure modes observed, as well as meaningful insights into the underlying behavior mechanisms and factors leading to the failures. This paper supports the view that nonlinear analysis techniques have become useful everyday tools for design office applications, particularly in forensic work, and also gives evidence suggesting that errors in the design of modern structures can be potentially more catastrophic than in the past, and that advanced assessment techniques will assume increased importance as a result. CE Database keywords: Structural failure; Concrete structures; Finite element method; Shear.

The Brent Reservoir was constructed in the mid-1830s and its siphon spillways were completed in 1936 to protect the dam from overtopping in the event of an extreme flood. Since completion, there have been problems with the hydraulic performance of the siphons, some of which primed simultaneously, causing flooding downstream. A physical hydraulic model study has been conducted to investigate the hydraulic performance of the siphons in order to establish reliable stage discharge relationships. The existing bellmouth siphon system was found to be unsuitable, causing the siphons to prime suddenly at discharges of around 3 [m.sup.3]/s. This was due to the sudden removal of an air pocket from the siphon's crown. The model tests were carried out in two stages. In the first stage, the existing geometry was examined. Based on the results from stage 1 of the experiments, it was concluded that the air inlet requires redesign and various options to improve the air regulation should be considered. In the second stage, various options to regulate the inlet of air and establish stable siphon performance over the entire range of discharges were considered. It was found that the most stable conditions are provided by an air slot being cut into the spillway hood at an appropriate level. This geometry provides excellent air-regulated stability, unimpaired spillway capacity, and is insensitive to tail water level and wave conditions in the reservoir. DOI: 10.1061/(ASCE)0733-9429(2002)128:6(562) CE Database keywords: Case reports; Hydraulic performance; Siphons; Spillways; Reservoirs; Aeration; Two-phase flow.

A general solution scheme for determining ground-water levels for channel/group-water systems with recharge is developed and verified. The analytical solution uses the Laplace transform method to solve a linearized form of the Boussinesq equation. Unlike other solutions, this scheme allows for both boundaries and sources/sinks to vary as a function of time and space. To verify the analytical scheme, three one-dimensional case studies of flow between two line sources in an unconfined aquifer were explored through a base run and a set of sensitivity analyses. These runs involved comparisons to MODFLOW and changes in the boundary conditions and dimensions. As noted, the flow equations were linearized about a point called the representative flow depth. A value of havg, defined as the average water depth between the initial and steady flow conditions, was used as the representative flow depth. Results of the proposed method matched very well with MODFLOW solutions for all times and locations using an optimal linearization point. In addition, using havg improved the solutions compared to those obtained previously.

Theoretical models for hydraulic network analysis often assume idealized pipe networks. Practical network packages, however, allow for a variety of necessary controlling elements. Sometimes these are introduced as generalized pipe elements, thus hiding the inherent discontinuous operation of nonreturn valves and pressure reduction valves. It is well known that the inclusion of such elements may cause numerical difficulties because of singularities. This paper presents an algorithm based on loop equations. It features a dynamic loop structure that is updated automatically according to the state of the controlling elements, It is shown that this provides a logical solution to the discontinuous operation of the controlling elements and also results in a highly efficient network simulation algorithm.

This paper demonstrates how the use of appropriately scaled model experiments can effectively be used to evaluate the dynamic performance of a new gate system. The physical scale models studied in this investigation are exact replicas of the innovative hydraulically actuated wickets to be placed at the Olmsted Locks and Dam for controlling water flow and maintaining a navigable pool on the lower Ohio River. Operating shapes of the flow-induced gate motion at critical configurations are compared with the wet characteristic modes of the wicket to determine the potential resonant vibration problem. These wet modes are extracted such that the effects of structural and hydraulic boundary conditions of the flow field are accounted for in the modal experiment. Experimental results indicate that random energy contents of an ambient excitation can readily be used to estimate the physical characteristic modes of a wet structure. The study also shows that operational deflected shapes for potentially alarming excitations can be compared with such wet natural modes to identify resonance problems. This evaluation procedure demonstrates the convenience in using ambient vibration for the detection of self-excitation problems during the service life of the system.

This paper introduces a new design concept for energy dissipation below flow regulators. Instead of using a single-leaf sluice gate, a double-leaf gate design is suggested. The two leaves are arranged in such a way that a jet issues at an angle toward the water surface through the opening between the two leaves. The bottom leaf remains fixed while the top leaf (control leaf) is moved up and down to regulate the flow. By using this arrangement, the high velocity supercritical stream is deflected away from the bed to the water surface. In addition to minimizing erosion, a lifting device of smaller capacity will be adequate for operating the control leaf. The existing regulators can be modified by adding an upward sloping sill just below the gate. The flow patterns, velocity decay, momentum decay, and bed-shear stress for different submergence and offset ratios are studied experimentally. The main characteristics of the deflected jet and the surface jet are also investigated and compared with those of the free and submerged jumps and surface jets. The new dissipator performs well in comparison with free and submerged jumps.

This paper studies the liquid holdup within the mixing zone of the slug. The results of the study show that the liquid holdup begins at the liquid holdup of the liquid film before the slug and then increases until the end of the mixing zone is reached. Once past the mixing zone of the slug, the average liquid holdup becomes constant. As the height of the liquid film and/or viscosity increases, so does the liquid holdup at any given film Froude number. Since the liquid holdup becomes constant once past the mixing zone of the slug, the mixing zone length was determined for the film Froude numbers studied. The results show that the mixing zone length increases linearly with film Froude number and is independent of the viscosity of the liquid in the slug for a viscosity range of 1 to 16.6 cP.

The traditional approach for estimating the exit gradient [i.sub.e] downstream of water retaining structures due to steady seepage is to assume homogeneous soil properties and proceed deterministically, perhaps using flow-net techniques. Once the exit gradient is estimated, a large safety factor of at least five or six is applied. The reason for this conservative approach is twofold. First, the consequence of piping and erosion brought about by [i.sub.e] approaching the critical value [i.sub.c] can be very severe, leading to complete and rapid failure of civil engineering structures with little advance warning. Second, the high safety factors reflect the designer's uncertainty in local variations of soil properties at the exit points and elsewhere within the flow domain. This paper presents an alternative to the safety factor approach by expressing exit gradient predictions in the context of reliability-based design. Random field theory and finite-element techniques are combined with Monte-Carlo simulations to study the statistics of exit gradient predictions as a function of soil permeability variance and spatial correlation. Both two- and three-dimensional boundary-value problems are considered. The approach enables conclusions to be drawn about the probability of critical conditions being approached and hence failure at a given site. The reliability approach is thought to represent a more rational methodology for guiding designers in the decision-making process.

Embankment weirs, often found in engineering applications with a side slope 1V:2H, are considered in this paper. For free overflow, the discharge coefficient is determined in terms of relative crest length for long broad-crested, broad-crested, short-crested, and thin-crested weirs. A considerable increase of capacity is noted when compared to broad-crested weirs with vertical faces. For submerged overflow, four regimes are identified: (1) A-jump: (2) plunging jet; (3) surface wave; and (4) surface jet. Particular attention is focused on plunging jets and surface waves. The flow regimes are discussed in terms of submergence, crest length, and modular limit. A description is given of the forward and backward (recirculation) zones with indications of typical lengths. Also, the entire velocity field is described, including the maximum forward and backward velocities, and the velocity distribution in arbitrary sections of the tailwater region. It is found that plunging jets and surface jets are hydraulically similar, and that the profile of one regime can be transformed into the other profile by inversion about the median. All results are generalized and can be directly applied.

This paper describes the experimental and numerical study of the vortex formation during the passage of a solitary wave over a rectangular structure submerged in water. The transient patterns of the separated flow (R = 82,000) behind the block are visualized by tracing the motion of injected dye in a laboratory flume. The related numerical solution is calculated by using the stream function-vorticity formulation in a transient boundary-conformed grid system to satisfy the full nonlinear free-surface conditions. Both experimental and numerical results illustrate that a large vortex is first formed at the rear of the block, accompanied by a secondary eddy below it, as the solitary wave hits this block. Then the vortex is bulgy but decays with time, and the secondary eddy continues to grow in both size and strength as the primary vortex diffuses. The time development of these calculated flow patterns, including vortex shedding and vorticity transportation, agrees quite well with experimental observations.

The Bureau of Reclamation changed its research policy regarding hydraulic structures by focusing on water management. The bureau developed technological innovations for the preservation of hydraulic infrastructure, environmental restoration of water systems and conservation of water resources. It administered a dam safety program, additional spillway capacity, protection systems of embankments, regulation of water temperatures for reservoirs and fish population management.

Presently available formulas for estimating the maximum depth of scour near bridge piers often lead to unreliable results. A fully three-dimensional hydrodynamic model is therefore used in this study to simulate the flow occurring at the base of a cylindrical bridge pier within a scour hole. The results of the numerical simulation are compared with laboratory observations by Melville and Raudkivi (1977). Quantitative and qualitative agreement between the studies is quite good. Discrepancies between the results of the two studies are of an order that may be attributed to choices in numerical model parameters. The simulations may be supplemented by Lagrangian particle-tracking to estimate the depth of the equilibrium scour condition.

Introduction In agricultural areas, non-point contamination of shallow unconfined aquifers is common. As a matter of convenience and economy, high-capacity irrigation wells within these regions are often used to collect [...]

Introduction The single-well, 'push-pull' test method (Istok et al. 1997) is useful for obtaining quantitative information on a wide variety of aquifer physical, chemical, and microbiological characteristics in situ. The [...]

An irrigation module delivers nearly constant discharge irrespective of water-level fluctuations in the supply channel. Low discharge baffle-sluice modules have been designed for the field outlets considering the desirable features of a good module. The flow-regulating characteristics of three baffle-sluice modules with the option of reduced module width and baffle heights are discussed in detail. The modules are found to deliver discharges within [+ or -]5% of the design value in a modular range of 10 cm. Thus the concept of baffle-sluice modules already conceived and designed can contribute to the modernization of water management systems in supplying the requisite amounts of irrigation water depending on crop requirements.

The effect of permeability on the stability of homogeneous and multilayered rubble bases is investigated. The approach consists of theoretical modeling of the interaction of water waves with a caisson-type breakwater and its rubble foundation, and then employing predicted flow fields in a stability model to determine the required stone size. The permeability is shown to have significant effect on the stability. The results indicate that the stability increases with increasing the rubble-base permeability at intermediate water depths, and increases with decreasing the rubble-base permeability in shallow water. The armor-layer permeability has little effect on the stability at intermediate water depths, but in shallow water the permeability of the armor layer has little effect on the stability only for rubble bases of low core permeability. The significant effect of permeability on the stability implies a need for including permeability effects in hydraulic modeling. An analysis or scaling of experimental data without taking the effect of permeability into account may lead to confusing conclusions or just incorrect results, which is demonstrated on the basis of the laboratory results commonly applied in design.

Three-dimensional physical models of low-crested, detached rubble-mound breakwaters were built, with their individual sections representing the following components of the breakwater: front slope, crest, back slope, total section (combination of the three previous sections), front head, and back head. The stability of the armor units in each of these sections was assessed, for different freeboards, using irregular waves. In a 1992 paper, Vidal et al. presented the stability criteria for the different trunk sections of this model breakwater. This paper focusses on test results from the head sections. A comparison between the stabilities of the head and trunk sections is also discussed. The stability of the back head (BH) section is found to be highly freeboard-dependent. For fully submerged conditions, the back head is one of the most stable sections of the breakwater. On the other hand, when the breakwater is nonovertopping, it is the least stable section. The front head (FH) section's behavior is similar to that of the front slope section of the breakwater trunk; its stability increases linearly as the freeboard decreases (i.e., as the breakwater becomes immersed).

Linear potential theory is applied to the analysis of wave motion through a two-layer porous structure. For special cases, the characteristics of waves in nondissipative, weakly, as well as strongly, dissipative media and their relations with the inertial and resistive properties of the media are explored. It is noted that in a nondissipative medium, the wave components are either nonpropagative or nondecaying. In a dissipative medium, however, they are always propagative and decaying as well. The reflection, transmission, and dissipation of monochromatic incident waves by a rectangular block, with typical dissipative characteristics and various thickness as well as submergence of its crest, are studied by the method of matched velocity potentials. It is found that there is an optimum thickness for a porous structure beyond which any further increase of the thickness may not lead to an appreciable improvement of its functional performance in reducing the transmission and reflection. It is also discovered that a medium of moderate permeability may be favorable in the design of a wide-crested breakwater if the wave heights on both front and lee sides of the structure are required to be controlled.

This paper is concerned with the modifications of the Extended Bellmouth Weir (EBM weir) earlier designed by Keshava Murthy. It is shown that by providing inclined sides (equivalent to providing an inward-trapezoidal weir) over a sector of a circle of radius R, separated by a distance 2t, and depth d, the measurable range of EBM can be considerably enhanced (over 375%). Simultaneously, the other parameters of the weir are optimized such that the reference plane of the weir coincides with its crest making it a constant-accuracy linear weir. Discharge through the aforementioned weir is proportional to the depths of flow measured above the crest of the weir for all heads in the range of 0.5R less than or equal to h less than or equal to 7.9R, within a maximum deviation of + or - 1% from the theoretical discharge. Experiments with two typical weirs show excellent agreement with the theory by giving a constant-average coefficient of discharge of 0.619.

A commercially available 30.5-cm (1-ft) Parshall flume was installed in the recirculating flume in the hydraulic laboratory of Colorado State University and tested for lateral-slope or cross-slope settlement. A series of 11 tests were conducted with the flume for cross slopes of + or - 3%, and for submerged outfall conditions. The results indicated that the Parshall flume accuracy is slope and submergence dependent. The flume rating was in error 3%, 5%, and 11% for 70%, 80%, and 90% of submergence, respectively, for lateral settlement of + or - 2%. The accuracy of the Parshall flume is reduced as the cross slope deviates from the horizontal. A method for correcting the flow rating for lateral settlement is presented as a function of the flume cross slope. A correction factor for submergence C(sub k) is incorporated into the discharge rating equation. Extrapolation of these results beyond cross slopes of 3% is not recommended. These results are applicable only to submerged conditions.

This paper addresses a new design technique for sprinkler irrigation laterals with equally spaced sprinklers and constant longitudinal slope. The technique uses the Darcy-Weisbach friction formula and accounts for the variation of the friction coefficient for a significant practical portion on a Moody diagram. The head loss in sprinkler risers as well as losses in lateral pipe fittings are considered. A computer program employing this technique is designed so as to provide sprinkler outflows and pressure head distributions along the lateral pipe. The results from two numerical examples are compared with results obtained from a widely used classical method. In some cases it is found that designs are substantially different.

In areas of steep terrain, concrete lined channels designed for supercritical flow are often used to convey stormwaters. During dry conditions, concrete channels attract playing animals, children, and adults. These channels are hazardous during storms because of the high water velocities. Even more hazardous, a trash rack placed in the channel has the potential to pin a person to the rack, preventing escape from the waters. A parabolic shaped grate designed to deliver victims to safety is modeled. Results show that the grate can be appropriate for supercritical flow channels. The parabolic shape works with the velocity profile of the water by providing a flatter slope as the velocity of the flow increases. Floating objects sweep up the grate out of the flow of the water. A severe clogging factor has little effect on the grate. If the channel is designed with a hydraulic jump induced on the grate, the jump can aid in pushing a victim up the grate.

Single sink depths providing maximum ground-water table decrease during a fixed time interval within a selected area are found for the 2-D and 3-D cases. The curve of the maximal phreatic surface position (underflooding curve) in the aquifer from flood induced variation in water level of the ground-water reservoir is calculated. Well-known analytical solutions based on nonlinear and linear potential theories and the Dupuit-Forchheimer approximation are applied to calculate the objective function, decision variables, and boundary of the fully saturated zone. In the linear case, an explicit analytic solution gives the unique maximum of the water table decrease at the compliance point for a given pumping duration. For small values of sink depth, the linear approach is invalid. In the nonlinear case, complex analysis and series expansions are used. For small values of drain depth, the series technique becomes untenable. For the reservoir-aquifer problem the spreading phreatic surface is a rotating straight line and the underflooding curve is a parabola.

A mathematical model which includes a group of integro-differential equations describes clearly the periodic oscillation modes of a fluttering fountain. Falling sheets of water, such as those found in dams and waterfall fountains, exhibit fluttering oscillations. Experimental and theoretical study yield fluttering fountain frequencies. Closed form solutions are obtained from an analytical simplification of the model, and the equations retain the characteristics of theoretical oscillation behavior. Though these fluttering systems are similar to other oscillating systems, fluttering systems are different from laboratory oscillators.

Knowledge on wave-runup levels is important for a proper design of the crest height of coastal structures. An overall view of the literature supports the assertion that smooth slopes cause the highest possible runup levels. Therefore, various runup data on gentle smooth slopes of coastal structures in a large flume are presented, and a final design formula is given. Then, available data of runup on smooth and rock slopes are compared. The main part of this paper deals with runup on rock slopes, including revetments and breakwater structures. The slopes range from 1:1.5 to 1:4. About 250 tests have been performed, testing stability of armor layers, during which runup was simultaneously measured. First, a qualitative analysis is given on the influence of various parameters on runup. The final analysis results in two sets of design formulas. One set yields formulas for the assessment of various runup levels as a function of the surf similarity or breaker parameter. The other set presents the probability distribution of runup on rock slopes, written as a Weibull distribution.

Robert A. Grace's study on repairing damaged marine outfall diffusers need to address significant questions related to the research. Some of these include the calculation of wave-induced rock instability in the Barbers Point outfall and the potential use of modern navigational technology in securing outfall diffusers from marine vessels such as fishing boats. Furthermore, Grace need to expound more on the insufficiency of analytical techniques in predicting wave forces and initial dilution events.

The downstream depth is not incorporated explicitly in the Avery-Novak equation but merely as boundary condition for the 'optimum depth.' The equation can be used for downstream depths bigger or equal to those determined by equations 14 or 15. However, it is an exaggeration that the transfer efficiency is maximum at tailwater depths 0.6 times the drop height. Nevertheless, field measurements are still the most consistent means of determining the oxygen transfer characteristics of hydraulic structure.

The study by Shengxiang Gui et al. on the reliability analysis performed by the Corps of Engineers on the hydraulic design for a proposed levee project is problematic. The method they proposed for incorporating both hydrologic and hydraulic uncertainty in hydraulic design is somewhat different from that used by the Corps. The method used by the Corps is better since it includes the uncertainty in the stage-flood damage relationship to determine the benefits of the levee project.

Flow through gate openings has been the subject of study by many investigators. Gates are often located on raised crests, as in the case of spillways. In such a situation, the flow is expected to behave similarly to flow through rectangular slots. As flow through a rectangular slot is a particular case of flow through a large orifice, any understanding of it will help in its generalization. Furthermore, because the flow through a slot is intermediate to that of a sluice gate and a rectangular sharp-crested weir, it can be used as a basis of unification. In the present study a discharge equation for flow through rectangular slots has been obtained. In special cases this equation converts to the discharge equations of a sluice gate and a rectangular sharp-crested weir.

Researchers studying the phenomena of local scour that occurs downstream of hydraulic structures such as stilling basins have yet to clearly identify the different phases of the scour hole formation process. Generally, though, the type of scour hole depends on the maximum scour depth and the Froude number. With the rapid rate of the sediment removal and scour depth increase, researchers have developed several scaling models for stabilizing cantilevered pipe outlets, straight drop spillway stilling basins and the SAF stilling basins.