World Environmental and Water Resources Congress 2016: Hydraulics and Waterways and Hydro-Climate/Climate Change

The AAA Industrial Park Drainage Improvement Project is located in the urbanized area of the city of Sedona, Arizona. The project is located in the most downstream basin of the Coffee Pot Watershed with a drainage area of 2.73 square miles. Approximately 30% of the watershed area is outside the city limits and within the United States Forest Service (USFS) land. The existing drainage facilities were two corrugated metal pipes; a 108-inch by 76-inch corrugated metal arch pipe and a 96-inch diameter corrugated metal pipe. The existing pipes were 350-feet and 220-feet in length, respectively, conveying flow through an industrial park with the outfall on USFS land. The existing facilities were only able to safely convey about 35% of the 25-year design flow event resulting in flooding issues and substantial damage within the industrial park.

Acoustic Doppler flow meters (ADFMs) are suitable to measure the flow discharge in culverts for the purpose of rating calibration and validation. However, best-measurement guidelines for ADFM placement to measure the flow through gated culverts are not available. Gates in culverts induce a complex flow field consisting of a jet below a hydraulic jump or a submerged eddy depending on whether the tailwater level results in free or full-pipe flow. The architecture and operational principles of ADFMs are suitable for measurements in well-developed flows; however, the distance from the gate where the flow becomes well developed depends upon the ratio of the gate-opening-area to the full-barrel-area (A_G/A₀) and the gate Reynolds number (Re_G). Presently, neither a characterization of the distance from the gate where well-developed flow occurs, nor an assessment of biases in ADFM measurements of full-barrel, gated-culvert flows due to placement of the ADFM where the flow is only partly developed, are available in the literature. Tropea et al. (2007) reported that the reattachment length of a flow at a backward facing step occurs at a distance ~8 times the height of the step. Here we show that discharges measured in two gated culverts with an ADFM at distances (L) equal or larger than 8(D-G) from the gate (D=diameter or box-culvert height; G=gate opening) using as reference discharge measurements by acoustic Doppler current profiler (ADCP) from a moving boat in the discharge canal, have biases of less than 6.4% (estimated as relative errors |Q_ADFM-Q_ADCP|/Q_ADCP). Moreover, our ADFM discharge measurements show biases between 0.4 and 6.4%, depending on the gate opening and culvert geometry. Additional analysis is underway to assess whether Re_G strongly varies with the reattachment distance of the jet-induced eddy pocket and the non-dimensional distance from the gate, where flow becomes well developed L/(D-G).

We propose a rating formula for controlled-submerged (CS) spillway flow of the form Fr_G = α [(H-h)/G]^0.5 where Fr_G=gate Froude number = Q/ [A_G (gG)^0.5], G=gate opening, H=headwater stage, and h=water stage just downstream of the gate, derived from energy balance between an upstream station and a station right after the gate. We validate our formulation with experimental data sets for submerged sluice gate flow in rectangular channels which yielded α ≈ 0.85±0.01& 0.91±0.08, respectively. We then apply it to data collected in the field at a prototype gated spillway of trapezoidal sill. This data comprises discharge measurements by acoustic Doppler current profiler (ADCP), and gate openings and head and tailwater stages monitored at the site near real-time by a SCADA system. Since h is not typically monitored in the field, we estimated the h values in the set of calibration data {Q, H, h, G} by applying continuity and momentum principles between the tailwater station where the stages are monitored and the gate (~ 215 ft apart).The parameter α and respective standard error estimated with the field data was α= 0.924±0.02. In our proposed formulation, the parameter α accounts for the upstream well location, size of the vena contracta, sill geometry, and nonlinear hydrodynamics of the rapidly varying flow near the gate. An advantage of the rating formulation we propose is that it yields estimates of discharge with lower uncertainty limits than those estimated with a rating of the form y_c/G=a [(H-T)/G]^b, [y_c=critical depth and T= water stage downstream of well] since H-T includes nonlinearities of the energy dissipation process between the gate and the tailwater well.

The focus of this study is to investigate the application of six-legged elements around wing-wall abutments experimentally. Six-legged elements have extensively been used for river engineering purposes for scour protection. The experiments were done in a 1m wide laboratory flume with uniform sand material. Four baseline tests were performed in different ratios of flow velocity to critical velocity values (0.65-0.95). The six-legged elements were then placed in three different placement densities on the bed; open (T₁), medium (T₂), and dense (T₃). The amount of created coverage for T₁, T₂ and T₃ densities were 54, 76 and 97 percents, with 63, 76, and 97 pieces respectively. Each alternative was tested under different flow conditions. Generally, the results proved that six-legged elements can considerably reduce the scour depth so as it reduced the maximum scour depth of abutment nose up to 100%. This maximum reduction of scour depth has been obtained when the elements were placed densely. However the extent and intensity of edge failure increased with higher density placements. Displacement of the maximum scour depth from the abutment tip was witnessed during the experiments especially in high Froude numbers. Hence each placement density could leave different effects on the bed topography in the vicinity of the abutment and on the downstream of the bridge; this gives alternatives to the designer for selecting six-legged elements placement densities with respect to the features of each placement density and conditions of the site.

Hydraulic jump formed in broken-back culverts was investigated experimentally by using energy dissipation devices. This paper investigates the reduction in scour downstream of a broken-back culvert by forming a hydraulic jump inside the culvert. A broken-back culvert in the laboratory is modeled to represent 150 foot prototype. The drop between inlet and outlet was 12 feet with a 1 (vertical) to 2 (horizontal) slope after the upstream inlet and then continuing 126 feet at a one percent slope. Three flow conditions were simulated, consisting of 0.8, 1.0 and 1.2 times the culvert depth. The results were analyzed in terms of the inlet Froude number. All experiments were conducted under pressure flow which is defined by the fluid exerting pressure against the top of the model. The Froude number of the hydraulic jump created in the mild part of the culvert ranges between 1.80 and 2.50 which indicates a “Weak jump”. To locate the jump near the toe, different sill and friction block arrangements were tested. For new culvert construction, the best option to maximize energy dissipation under pressure flow conditions is to use two sills, one 2.5-foot sill at 62 feet from the end, and one 3.33-foot sill at 45 feet from the end of the culvert. Friction blocks had minimal impact on energy dissipation in the culvert. The length of the prototype culvert can be reduced by 40 to 45 feet. Such a scenario is important where right-of-way problems exist for culvert construction.

Vertical gates are important hydraulic structures that control the regime and characteristics for both downstream and upstream flows of streams and canals. In this study, laboratory tests were conducted to find a relationship between gate opening, as function of upstream water depth, and downstream flow conditions. The study was conducted in a laboratory flume, within a range of fourteen (14) discharges, seeking to identify an optimum vertical gate opening at which flow stability occurs; fuzzy theory concepts were used to define “stability.” Ten (10) of the tested discharges were used as calibration data and four (4) were used in validation. A regression model, based on fundamental dimensionless parameters, was developed, and is, herein presented, which links optimum gate opening as function of upper water depth and critical discharge. The model offers a validated (i.e., within the scope of the experiments) new relationship that can be used to best operate vertical gates ensuring stable flow characteristics.

Swath bathymetry of the main stem of the St. Clair River was collected in 2007 and again in 2012, providing the data sets required for a thorough analysis of conveyance change in that river. Conveyance change in the St. Clair River is examined through multiple methods and models. Each method and model are explored to gain a sense of how the conveyance capacity of the river may be changing. Depth change and cut-fill analyses with and without accounting for survey error show change in the river but net change is minimal especially after accounting for survey error. Hydrodynamic modeling of the same discharge/water level scenarios in the 2007 geometry versus the 2012 geometry also show minimal change with a maximum of 1 cm change in water levels at a single location.

Flow rating at hydraulic structures is very crucial to the water resource management and environmental integrity of South Florida. In practice, engineers are facing various challenges in their effort to improve water quality in the Everglades Watershed and throughout the South Florida ecosystem. Due to site constraints, manufacturer limitations, and special design needs etc., new structure types or new flow conditions, which are not considered in the current flow algorithms very often occur and call for developing new algorithms to properly estimate the flows. Three-dimensional computational fluid dynamics (CFD) is a powerful and cost-effective technique, which allows to fully investigate the flow mechanism as the rating development is needed to capture specific features. In this paper, CFD was applied for improving and developing the new culvert full pipe equation. The developed algorithms are verified with field stream flow measurements collected at prototype structure sites. In comparative analyses, good agreement between rated and measured flows have been achieved and the algorithms derived from CFD applications are employed to the real practices.

A three-dimensional environmental fluid dynamics code model was calibrated and applied to simulate unsteady flow patterns, dye distributions and concentration in the Bankhead River-Reservoir System in Alabama, USA. A series of sensitivity model runs were performed under different large releases (140 m³/s) from Smith Dam Tailrace (SDT) when other input variables were kept unchanged. The cold-water current from SDT moves to MSF (~11 km) during the 4-hr single large release (SLR) and advances to ~18 km in 1 day after the release stops. In the following 4 days with constant small release only (after SLR stops), the dye moves downstream very slowly, less than 4 km. Daily repeated large releases (DRLRs) with longer durations push the dye to move further downstream. In the period without the large release, the dye spreads and mixes with the surrounding water due to turbulent diffusion and dispersion (due to backwater effect). When the next large release comes, the dye released at SDT is pushed downstream again. For the 4-hr DRLR, the dye moves to UPJ (~22 km from SDT), MJC (~33 km from SDT), Cordova (~43.7 km from SDT) and GOUS (~64.3 km from SDT) at 12 hrs, 34 hrs, 60 hrs, and 145 hrs after the dye release from SDT. For the 4-hr DRLR, the momentum effect has some impacts at Cordova but does not reach GOUS. For the 6-hr DRLR, the momentum effect definitely reaches Cordova and the dye pattern repeats daily, and also has certain impact at GOUS.

Hydraulic scale models are widely used to investigate design and operation issues in hydraulic engineering. In these model studies geometric, kinematic and dynamic similarities should be followed strictly. In reality, however, it is difficult to follow all similarity laws. In many cases, some aspects of similitude may be neglected, and only those most important factors can be preserved. This will inevitably lead to some difference between the prototype and scale model results, which is called model scale effects. In this paper, computational fluid dynamics (CFD) modeling is used to study the hydraulic model scale effects. The discharge capacity of flow passing through an ogee spillway and flow fields in pump intake are used as two case studies. These case studies illustrate the significance of using similarity laws in the hydraulic scale model, and illustrate the feasibility of using CFD model to indirectly investigate hydraulic model scale effects.

A levee/dam breach failure may cause tremendous economic damage and loss of human lives. To mitigate or limit the damage caused by a levee/dam breach, it is necessary to evaluate levee breach flooding risks. This entails prediction of the volume of water that is released from the breach with reasonable accuracy and also requires properly simulating flood wave propagation throughout the floodplain in order to generate floodplain inundation maps. Although there have been many years of observations and a plethora of research on how to represent a dam breach to derive vital breach parameters such as breach width, breach height and breach side slope needed for generating breach outflow hydrograph, there has been no single accepted methodology for determining these critical parameters. This study will review the existing methods for dam breach analyses, and discuss their advantages and shortcomings, and challenges that lies ahead in dam breach analyses.

As wetlands are increasingly used worldwide for environmental benefits, wetland hydraulics and vegetation resistance parameters have become extensively studied subjects. Vegetation resistance parameters are valuable not just for the design and operation of treatment wetlands, but also for continuous monitoring of the health of the vegetation. A method is introduced in this paper to calculate basic vegetation resistance parameters using the shape of the wave front, and particularly the relatively steep gradient, observed during sudden discharges into wetlands. Vegetation resistance, its variation over the depth, and the level of turbulence dictate the shape of the wave front. Field experiments were carried out in storm water treatment areas (STAs) in south Florida managed by the South Florida Water Management District (SFWMD) to collect data on the movement and the shape of the wave front. Results of the experiment include water surface profiles of the steep wave fronts observed during the movement of the front. Mass balance conditions at the leading edge of the wave front were used to develop approximate values of vegetation resistance in terms of hydraulic conductivity or transmissivity. The results show that the transmissivities obtained using the method agree with the transmissivities obtained using generated water waves.

This paper describes new approach in the application of computational fluid dynamics (CFD) to evaluate the performance of hydraulic design and operation. As an alternative to traditional reduced-scale physical model, this paper promotes a CFD-based numerical investigation to provide detailed 3D flow fields, pressures, water surface elevations, flow and structure interactions, and other flow physics to assess the performance of different hydraulic structures under various operational scenarios. Two CFD applications of hydraulic structures design and operation at Everglades Restoration Project are presented in this paper. Both case studies show how CFD can be iteratively used to optimize the design and operation of hydraulic structures, and to predict their future behavior under various operational conditions in a very cost effective way.

Hurricane Sandy in late October 2012 battered the U.S. east coast, including New York and the low-lying areas in New Jersey, due to inundation and coastal erosion driven by storm surges and waves. It was the deadliest and most destructive hurricane of the 2012 Atlantic hurricane season, and the second-costliest hurricane in United States history. In the study, the storm surges and waves driven by Hurricane Sandy (2012) were computed by using an integrated coastal and ocean process model, CCHE2D-Coast. The surface wind and air pressure fields of the cyclone were reconstructed by a parametrical cyclonic wind model, which was developed to include the decay effect of hurricane landfall. The simulated wind, wave, and water elevations were compared with the observation data by NOAA and USGS. This preliminary numerical result indicates that this coast-ocean model reproduced well the storm surge tides and waves in the entire east coast of the U.S. All the computations were accomplished on a PC with reasonable CPU hours, which made large-scale storm-surge modeling convenient, efficient, and economic.

This paper is about development of a new algorithm to compute flow at lock structures using computation fluid dynamics (CFD). CFD was first applied to generate stream flow data at ship lock structures on the Kissimmee River. These CFD flow data were then used to develop the flow rating equations for future flow estimation. Based on the physical characteristics of these ship locks, the new flow equations were developed starting from a Parshall Flume flow equation. Since a ship lock is not a standard Parshall Flume, a discharge coefficient based on CFD data is applied to the equation to reflect the flow physical characteristics inherent to those locks. The flow was adjusted due to submergence, using the Villemonte Equation. The study shows that the flows computed using the proposed formula and the discharge coefficient of Cd = 0.79 compare very well to CFD data generated at S65, and S65 A ship locks. The new rating was also validated using the some available streamgauging data at S65A and other locks. The proposed approach will be applied for flow estimation at other ship locks within Kissimmee River Basin.

The St Marys Rapids at the outlet of Lake Superior is a vital habitat for a wide range of aquatic species. The regulation of the outflows from Lake Superior can lead to rapid changes in hydraulic characteristics of these rapids and potentially adverse conditions for biota living there. This study details the types of data collected to help minimize effects of changing the outflow through the St. Marys rapids.

The South Florida Water Management District (SFWMD) complex network of man-made canals and water control structures provides flood control in south Florida. Most of the canals ultimately discharge into the ocean through gated spillways. These facilities were designed by the U.S. Army Corps of Engineers (1950s and 1960s) assuming static hydraulic head conditions. Coastal structures are operated to maintain canal stages within pre-determined ranges (USACE Water Control Manuals), where gates are opened when the canal head water stage rises above its upper limit and closes when the head water stage drops below its lower limit. Gates are also closed to prevent reverse flow of salt water into the canal during high tide. The SFWMD is determining the current level of service (LOS) for flood control, which is to be established under dynamic rainfall conditions, regular and extreme (tropical storm) tidal conditions, different sea-level rise projections and different return frequencies. Transient hydraulic models are required to simulate stages and flows within a basin under these conditions. The first LOS pilot study was applied to the C-4 watershed located in Miami-Dade County. The HEC-RAS computer model (USACE) was selected for this purpose. This paper describes the process used to incorporate real-time structure operations into the model, along with customized structure flow rating equations developed by the SFWMD. Examples of modeling techniques for the operation of coastal spillways and pump stations are presented along with descriptions of the problems encountered, the solutions implemented and any unresolved issues.

This paper presents an advancing reduction technique for 2D quality triangulation in computation domains with complex geometries and its applications to a 2D hybrid FVM model. The advancing reduction technique coarsens a fine initial equilateral triangle mesh (ETM) covering the whole domain by doubling the cell edge length progressively, so that the whole domain can be decomposed into multiple zones with different densities. Each density zone consists of a number of equilateral triangles with different edge lengths; and the density zones are connected to each other with transition layers. The generated triangle meshes are applied to a 2D depth-integrated hydrodynamic model for surface flow simulations, where the unsteady depth-integrated Reynolds equations are solved using a finite volume method (FVM) on a hybrid (triangles and quadrilaterals) unstructured mesh system with collocated variable arrangement. In this model, a new evaluation method for computing the gradients at the cell edges was proposed to improve the solutions affected by the mesh irregularity and non-uniformity. Examples of triangular mesh generation and numerical simulation of hydrodynamic problems will be presented.

One of the barriers to Steelhead recovery on Trabuco Creek in San Juan Capistrano, CA is at the Metrolink Rail Crossing where a grouted rock drop structure has been installed to protect existing utility crossings and bridge piers and now impedes upstream passage for adult and juvenile fish. The elevation drop at the barrier has increased by 20 feet since 1940 and continues to grow, requiring frequent repairs to the grouted riprap. An engineered fishway and a replacement drop structure and flood channel have been proposed to provide sustainable protection to existing infrastructure and provide passage for the southern California Steelhead, a federally listed endangered species. The fishway design uses a combination of natural rock materials and concrete and because of its configuration, length, and drop height would be the first of its kind in California. The design of the fishway, flood channel, and diversion is critical to ensure fish passage over a wide range of creek flows, prevent sediment from clogging the fishway, and force large flood flows into the floodway. A 1:6 and 1:20 scaled physical hydraulic model were constructed of the proposed fishway and flood channel which allowed designers and stakeholders to verify the stability of the proposed channels over a wide range of flows, optimize the diversion between the fishway and floodway, and adjust the fishway design to improve passage characteristics for juvenile and adult fish. The physical models were used to identify modifications that resulted in significant improvements to the hydraulic performance of the design.

Algebraic water hammer (AWH) represents a simplified and more compact form of the classical method of characteristics (MOC) for solving the 1-D equations of unsteady-compressible pressurized flow. Unlike the MOC, AWH focuses on the transmission and reflection of waves at nodal boundaries. The characteristic expressions are extended over multiple pipe reaches (with fewer variables), so they are conveniently summarized in a system equation using incidence matrices; accordingly, global AWH (GAWH) is readily implemented and well-suited to the analysis of large pipe networks. Additionally, the solution of complex and coupled boundary conditions does not require lengthy mathematical formulae, for they are inherently resolved within the formulation. To compensate for the loss of spatial resolution, a flexible scheme is proposed to maintain accuracy for wave attenuation. The current work is demonstrated using a small looped pipe network. Simulation results are compared against those from an MOC-based model, and it is shown that both yield nearly identical results.

A sewer geyser is an explosive overflow of a mixture of gas and water through a vertical pipe of a sewer system. According to reported field observations, the explosive overflows occurred in a form of ejecting water columns that persisted for several seconds. In previous studies, the presence of entrapped air pockets in sewer systems were argued to be the direct cause of the sewer geyser occurrence. The mechanisms of air-water interaction in a vertical pipe during a sewer geyser lease were investigated. A one-dimensional numerical model was developed to simulate the flow. The vertical shaft was closed at the bottom and open to the ambient pressure at the top. Initially, the lower section of the vertical shaft was filled with compressed air and the water column sat above the air pocket. Once the simulation was triggered, the interaction between the pressurized air and the water column exhibited an oscillatory motion which decayed over time. The results were compared with three dimensional numerical simulations conducted using a commercial computational fluid dynamics software.

A comparison is made of the flow-energy loss associated with channel restoration structures utilizing spurs and submerged vanes. The comparison is limited to subcritical flows and structures that are submerged and angled upstream into the oncoming flow at relatively small angles of attack. The energy loss is calculated from standard, high-Reynolds-number-drag force relations. The drag coefficient for submerged vanes that are located away from banks is obtained from analogy with airfoil theory. The relationships are validated in laboratory tests. The study shows that a system of submerged vanes can be designed to provide the same erosion protection of a given stream bank as can a system of upstream-angled spurs or rock dikes, designed according to NRCS standards, and can accomplish the task at comparable, and sometimes less, energy expenditure. When placed away from the bank submerged vanes are more efficient (in terms of energy expenditure) than spurs in creating vertical mass transfer.

In the study, an integrated coastal and ocean process model, CCHE2D-Coast, is validated by assessing the model skills in simulating coast-ocean circulations driven by the astronomical tides in the U.S. Northeast and Mid-Atlantic coast. Through the skill assessment, discrepancies between numerically simulated water surface elevations and observed tidal elevations at NOAA tide gages are quantified. The model skill indices such as the normalized root-mean square, the coefficient of determination, the scatter index, and the bias are calculated from comparisons of the errors. On the other hand, statistical errors of the tidal constituent parameters, amplitudes and phases, are also determined by using a newly-developed parameter identification approach. Good agreement between the model-identified phases and amplitudes of the harmonic constituents with the values provided by NOAA is obtained. The skill assessment results reveal that the model can produce accurate tidal elevations in the regional domain covering the U.S. east coast.

Xiaowan Reservoir was created by the construction of Xiaowan Dam on Mekong River. This dam is the second highest arch dam in the world with 292 m tall and 902 m long. The reservoir is about 178km from upstream to the dam, and the surface area is around 189 km². The water depth near the dam is very deep, which normally varies from 200 to 270m seasonally. For such a deep reservoir, the vertical temperature distribution show a significant stratified structure. In this study, a three dimensional numerical model was developed for simulating the flow fields and temperature distribution in Xiaowan reservoir near the dam. The effects of buoyancy on the momentum equations and turbulence transport equations was considered. For turbulence closure, the buoyancy-extended version of k-ϵ model was used. The model was first validated using a laboratory case of turbulent buoyant flow in a curved open channel, and then it was applied to simulate the flow and temperature in Xiaowan Reservoir. The numerical results were compared with field measurements, and the physical characteristics of flow pattern and temperature distribution in the reservoir were discussed.

Boat wave induced erosion can be a major concern in rivers and other navigable waterways. When they reach the banks, boat-generated waves can produce velocities and shear stresses near the water surface much larger than those generated from streamflow. This is mainly due to the high level of turbulence produced by wave breaking. Recurrent wave action along cohesive banks due to boat traffic may cause undercutting and eventual failure. Estimation of the relative contribution of boat waves to stream bank erosion requires the knowledge of the spatial and temporal distribution of instances of boat passage in addition to the boat wave properties. Despite of the substantial contribution of boat-induced waves to the bank erosion, the availability of historic boat-wave data for hydraulic modeling purposes is extremely limited. In this study, a partially deterministic method for generating long-term boat-traffic data from a field campaign is presented. Boat-generated wave data (water depth, wave height and wave period) was collected for four months between May, 2015 and September 2015 at three sites along a reach of the Connecticut River, MA. The collected data was then used to predict 15-year boat traffic and boat-wave properties at 25 sites along the same reach of the river, by combining measured daily and weekly variations of boat traffic, together with information on seasonal variations, boat ownership statistics and historic rainfall data obtained form various sources.

Engineering projects in river environments may positively or negatively impact riparian habitat to varying degrees, contingent upon the nature of the project and design choices. Aquatic habitat remains an elusive parameter to fully consider during project design. Hydraulic conditions favorable to habitat vary across species, geographical location, and the literature. When specific conditions are available for a given species, they typically exist in the form of a habitat suitability index indicating predilections for a range of hydraulic or substrate conditions. Coupling habitat suitability indices with hydraulic parameters requires tools to estimate hydraulics for quantification of potential habitat impacts. Indices are commonly reported as a range of depth-averaged parameters, including flow depth, shear stress, or velocity magnitude; for many applications, the use of a two-dimensional numerical hydraulic simulation provides information on the scales needed for index comparison. This proceeding presents results of a practical application of habitat impact assessments for proposed river alterations to the Grand River, MI. Habitat for two critical species, the snuffbox mussel (Epioblasma triquetra) and the lake sturgeon (Acipenser fulvescens), is examined at existing and proposed conditions using a comprehensive literature review of habitat suitability indices, development of new indices based on field surveys, and application of computational fluid dynamics models. Results provide evidence of the power of coupled ecologic and hydraulic models to assess effects on aquatic habitat and serve as a design tool for overall riparian health.

Dynamics of air-water flows plays an important role in hydraulic engineering. Air can influence water flows in a variety of ways, such as the formation of air cavity, air entrapment and geysering in circular pipes. Cavity outflows with shock waves are not well investigated according to the existing literature. Experimental studies of geysering in transient flows are also scarce. A large physical model was established to study the cavity outflow and geysering in circular pipes. Critical non-dimensional flow rates were developed for cavity outflows according to distinct air-water interface patterns and characteristics of shock waves were determined. The effect of a vent pipe is also studied on its influence on the pressure distribution. Geyser phenomena were investigated using a 2% slope pipe connected by a horizontal one. Pressure data and recorded videos show that the pressure drop corresponds to air release in all geysering scenarios.

Sediment transport is typically simulated using deterministic models. However, the intermittent and stochastic features of sediment transport make it suitable to be described by discrete random processes. We attempt to develop a stochastic framework that could account for random-sized batch arrivals (RSBA) of incoming sediment particles into receiving waters. In the proposed framework, the stochastic diffusion particle tracking model (SD-PTM) and particle deposition and resuspension process are included to simulate the random transport trajectories of suspended particles. The most distinguished characteristics of this framework are that random number of particles can arrive at the control volume at random times by applying the random-sized batch arrival process (RSBA) including the random occurrences and probabilistic quantity of incoming sediment particles. The random occurrences of arrivals are simulated by Poisson process while the number of sediment particles in each arrival can be simulated by a binominal distribution. Simulation results can offer a probabilistic description for discrete sediment transport through ensemble statistics (i.e., ensemble means and ensemble variances) of sediment concentrations and transport rates.

Millsite Dam, closed in 1971, is typical of the hundreds of NRCS dams constructed in the United States. Built for water storage, the original 18,000 acre-ft of storage has been reduced by about 3,000 acre-feet due to reservoir sedimentation. The nature of sediment deposition in reservoirs is such that most sediments deposit in the active pool rather than in the dead pool. Deposition in the active pool reduces water availability for irrigation and municipal and industrial water supply. The least expensive method of maintaining reservoir storage at Millisite Dam involves dredging deposited sediment and either storing it offsite or passing it downstream to Ferron Creek. Permits (401 and 404) were requested for the operation. The permits, approved after about 18 months, require that the sediment concentration in the outflow not exceed that in the inflow on an average daily basis. Downstream dissolved oxygen must exceed 3 mg/L during the operation, and sediment deposition in excess of 1.5 ft at any of the seven surveyed cross sections downstream much be removed and stored offsite. The permits allow sediment to be reintroduced into the downstream Ferron Creek, where turbidity will increase for some distance and for the duration of the dredge and removal operation. Operations were carried out for the first time in 2015, but for only three days, as the freely spilling water from Millsite Dam was in decline. A request for a change in operation is under consideration that would allow higher concentrations of sediment to be passed downstream during the operation subject to similar constraints.

Developing methods to quantify erosion dynamics of cohesive sediments is challenging due to the complexity of many physical, chemical, and biological processes involved. Even though several empirical formulas were introduced in literature to calculate the erosion rate of cohesive sediments, there are still substantial uncertainties in determining the erosion coefficients. In this study, the relationships of erosion coefficients with sediment properties have been investigated. First, the erosion coefficient in the linear erosion formula is found to be a function of the critical shear stress based on a large number of measurement data from literature. Then, an existing empirical formula is tested to predict the erodibility coefficient when the clay percentage and dry specific weight of soil are given. Finally, the critical shear stress of cohesive soils is related to the dry density and solid-void volume ratio by using measurement data.

The Jingjiang Reach of Yangtze River has significantly changed its sediment regime since the beginning of this century, i.e., the once equilibrium reach has become starved of sediment due to the impoundment of the Three Gorges Dam. Recent measurements in the Jingjiang Reach have revealed anomalous vertical profiles of suspended sediment. Without appropriate modification, traditional suspension formulae, e.g. Rouse Equation may cause up to 40% errors when applied to estimate the sediment flux in those unsaturated flows. Compared to Rouse Equation, Han’s Equation for nonequilibrium sediment-laden flow performs better in the upper part of a vertical, but still underestimates the concentration near riverbed, i.e. within 10% of water depth, where the observed value is much higher than its theoretical expectation. To solve the problem, this study develops a fractional advection-diffusion equation to characterize the dynamics of nonequilibrium sediment suspension. After validating the equation against field measurements in the Jingjiang Reach, we find that the proposed physical model can describe the real-world sediment profiles in “starving” river reaches. The promising stochastic approach shows good application future since more large dams are to be built in West China.

Based on the daily discharge and sediment concentration recorded at eight hydrology stations in the Xiaolangdi–Lijin reaches of the Lower Yellow River from 1950 to 2003, the relationship between water discharge and suspended-sediment concentration (SSC) was analyzed. The relationship between SSC and discharge was fitted by the sediment rating curves of third-order polynomial regression. The maximum SSC of years after 1968 is larger than that of years before 1968 at XLD and SK-LJ reach, and the corresponding discharge with maximum SSC decreases at these five stations. Besides, the SSC of XLD, SK, AS, LK and LJ stations will decrease after reaching its maximum concentration at a certain discharge. Sediment rating curve at XLD displays a downward trend of SSC for the same water discharge from the first to the second periods. Moreover, H-G reach is sensitive to flow rate, sediment concentration and particle size.

The Texas coastline is exposed to the dynamic zone of current convergence. Storm surge caused by hurricanes and tropical storms can remove large quantities of sand from the shoreline, resulting in eroding vast areas of land and destroying property. The study objective is to investigate the possible shoreline protection solutions. A schematic shoreline model using the Em2 Geomodel was developed to simulate erosion caused by Hurricane Ike (HDR Project No. 166742 report) with the average erosion rate as 60 ft /day, i.e. 2.5 inches every 5 minutes. A series of experiments were set up to reach 2.5 inch / 5 minutes with an equivalent shoreline slope 2% as the field geometry under the wave condition generated by manually pushing a wood block. Three common shoreline erosion control measures: lining the shoreline with rocks (A), with vegetation (B), and the implementation of jetties (C) were applied. The experiment results demonstrate that method (A) does not work as well as anticipated, while method (B) and (C) can reduce 50% of the erosion. A wave generator has been designed to control wave motion and an empirical total longshore sediment transport equation has been determined for the wave generator under different water depth, wave conditions, and slopes of the beach. Three erosion control measures have been tested under the same wave condition using wave generator, the results also indicate method (B) and (C) can reduce the erosion effectively, while the method (A) does not reduce the erosion.

The Beki River basin, Assam, India is the major southward draining interstate river basin which has a trans-boundary counterpart called Kurichu in Bhutan. The river and its drainage channels flow through the plains of Assam for about 85 km and drain an area of 26,243 sq. km. approximately. Erosion and the recurring floods of characteristically high magnitude by Beki River have been heavily affecting the agricultural lands, crops, cattle and people of Barpeta district of Assam. As such, the need for extensive model studies, for evaluating the performance of different structural and river training and bank protection measures is highly recommended. Therefore, a two dimensional mathematical model for simulating unsteady flow in this river is programmed for evaluation of the effectiveness of the new anti-erosion structures. Using the model, some areas of the river reach are provided with some non-submersible spurs, depending upon the vulnerability. However, considering economic feasibility, optimization has been done to select the viable option for practical applications. This resulted in reduction of flow velocity in the protected portions while higher flow velocity could be observed in unprotected portions of the bank.

Soil erosion and soil degradation are critical concerns worldwide. Developing comprehensive techniques to assess soil erodibility is in direct response to the need for quantifying this characteristic. Soil erosion rate is commonly estimated by the excess shear stress, the amount of shear stress acting on a soil surface in excess of critical shear stress (τ_c), and conditioned by the erodibility coefficient (K_d). The submerged jet erosion test (JET) is a widely used technique to measure the excess shear stress parameters based upon the impinging jet theory. Recent studies, however, have shown that the JET result is highly dependent on test conditions and jet hydrodynamics. Therefore, this study seeks to investigate the effects of changing test conditions on soil erodibility. We designed a series of experiments using one type of soil and intended to record the resulting scour depth for a narrow range of impinging heights and nozzle velocities. The main objective of the study is to improve the JET methodology and to quantify the effect of variable test conditions. The scour depth was quantified using point gauge reading and photogrammetry technique. Data collected at set time intervals for a maximum of seven hours from the beginning of the JET test. The results demonstrate that current JET methods should be revisited to make them consistent and independent of the test conditions.

Erosion properties of cohesive soils can be defined with respect to excess shear stress and are dependent on two fundamental properties of soil: a threshold critical shear stress and erodibility coefficient. However, the prediction of cohesive soil erodibility is challenging in that limited advancements have occurred in developing an improved prediction model, especially compared to granular non-cohesive sediments. The inter-particle attraction in cohesive soils is one main reason behind this difficulty since the particle-level interactions are influenced by physical, geochemical and biological properties. In different geological locations, these properties vary spatially along both the stream bank and bed. No empirical approach has been published to date in which the engineering community has significant confidence with its predictability. This study was conducted in a geologically diverse region in the United Sates in order to improve the understanding of cohesive soil erosion processes. Field data were collected using the mini-jet tester from 21 streams in four geological regions of Tennessee. Soil samples were collected from the jet testing locations for laboratory measurement of physical and geochemical properties. Jet-tester field data were analyzed using the Blaisdell (1981) approach for estimating the critical shear stress (τ_c) and erodibility coefficient (k_d) of the cohesive soils. Finally, multivariate statistical approaches were applied on these data for developing a predictive relationship of cohesive soil erodibility based on significant soil properties. Relationships among different geological regions were analyzed as well. Findings from this research identified key soil properties strongly correlated to τ_c and k_d parameters.

In this study, the movement of sediment particles around a bridge pier was investigated using the OpenFOAM software. The object is to track the transport of sediment particles and get insight of scour hole forming processes around bridge piers. A three dimensional hydrodynamic model coupling with fluid-particle transport over mobile bed, CFDEM coupling open source, was used in this study. The motion of particles was resolved using a discrete element model (DEM), and the flow field was simulated by a computational fluid dynamics (CFD) model. To verify the simulated results of scour depth, experiments were conducted in an open channel flume by using a high speed camera. Flow velocity was obtained around the piers after processing the images captured by the camera. To verify the simulated results, the experiment data were compared with the simulated results of sediment transport and scour depth. This integrated numerical and experimental study allows us to investigate sediment dynamic at the particle scale.

The Dominguez channel and Greater Los Angeles and Long Beach harbor waters toxic pollutants total maximum daily loads was developed to attain water quality standards and protect beneficial uses in San Pedro Bay, California. Waters of the LA/LB harbor and greater San Pedro Bay are listed as impaired by heavy metals and organic pollutants in sediment and/or or fish tissue. The harbor toxics TMDL specifies waste load allocations and load allocations to limit the discharge of metals and bioaccumulative organic pollutants. A scientifically-sound basis of the TMDL requires a calibrated model capable of simulating the complex three-dimensional (3D) flows, sediment transport, and chemical fate throughout the LA/LB harbor. Since the combined Port of Long Beach and Los Angeles is the busiest port in the United States, thousands of vessels of various types and sizes visit the harbor every year. The re-suspension of contaminated sediment in the bed can be a source of contaminants to the harbor water. This paper presents the incorporation of propeller induced re-suspension of sediment and associated contaminants into the 3D sediment and chemical fate model developed for the LA/LB harbor for the TMDLs.

This paper presents the development and calibration of a 3D sediment transport and chemical fate model for the LA/LB harbor using the environmental fluid dynamic code (EFDC), as well as specially-designed field programs with low detection limits to collect organics from stormwater and harbor waters. In addition to the new data obtained for the calibration of organics, the hydrodynamic and sediment transport component of the model was calibrated for both dry and wet weather conditions using extensive field data collected throughout the LA/LB harbor over multiple years.

Waves generated by high-speed recreational boats can play a significant role in bank erosion and failure along riverbanks. Frequent passes of these boats in confined channels increase suspended-sediment concentration and turbidity at relatively shallow water depths, and increase the erosion rate by wave breaking and long-shore currents. In the current study, boat-generated waves and turbidity were measured in the Connecticut River along a reach between Vernon Dam, Vernon, VT and French King Bridge, Miller Falls, MA. Two-meter-long self-powered, self-logging wave staffs were used to measure the water level and waves at three sites. Based on these uninterrupted measurements, boat-generated wave-characteristics were obtained for a period of four months between May 2015 and September 2015. As part of this study, turbidity and wave measurements at these three sites were carried out during a series of in situ experiments with a 5.7 m long tri-hull motorboat. The experiments included a total of 36 controlled passes parallel to the shoreline at speeds ranging from 8 km/h up to 55 km/h. Boat speed and path was measured with a GPS logger and the turbidity level near the bank was measured using two optical backscatter sensors. Relations between the wave height, wave period and turbidity level were investigated. This paper presents the results of these additional measurements and discusses relations between turbidity levels and boat-generated waves.

This paper presents the results of laboratory experiments to investigate the effects of permeable hydraulic flashboard spur dike (PHFSD) on scour and deposition using a movable-bed physical model. The study included two sets of experiments. The first set of tests focused on the effect of PHFSD on scour and deposition near the bank. The second set of tests investigated the factors influencing flow velocity retardation and promotion of deposition. Experiments were carried out with both permeable and solid flashboard spur dikes to investigate the influence of relative spur dike length, geometry and arrangement of holes, and coefficient of permeability on the scour and deposition characteristics. Average flow velocity and deposition height at cross sections upstream and downstream of the spur dike, and the maximum scour depth at the spur dike head were measured. The results show the influence of these factors on the scour and deposition characteristics and the effectiveness of the PHFSD.

The present study focuses on the sediment deposition and consequent dredging issues in Lower Ohio River at the Olmsted Locks and Dam area-river mile (RM)-964.4 during the ongoing in-the-wet construction methodology. The study reach is between locks & dam 53 (RM 962.6) at upstream, and RM 970 at downstream. One dimensional (1D) HEC-RAS numerical modeling in conjunction with Arc-GIS was employed. Streamflow measurements, velocity, incoming sediment concentration, bed gradation, and annual hydrographic survey data acquired from public archives of USGS and USACE Louisville District were used as inputs. The first model applied was the 1D quasi-unsteady HEC-RAS module. Calibration and validation of the hydrodynamic and sediment models were performed using measured water surface elevation, velocity, and sediment loads at measured sections. Post-model calibration and validation, deposition to excavated cross-sections for future dam shells at Olmsted were predicted, validating the need for dredging. Sensitivity analysis for transport capacity functions provided the basis of model validation. Moreover, the capability of 1D-HEC-RAS quasi-unsteady model was assessed in prediction of sediment accumulation in the construction area (dam shells excavation area). A temporal deposition prediction model was developed that could potentially replace the current ad-hoc approach used to determine the dredging schedule. A representative environmental risk associated with sedimentation in the study area was examined. This model could potentially be used as a decision support tool to analyze the long term impact of sedimentation in the vicinity of Olmsted locks and dam if further updates on the river bathymetry and specific field data are supplemented to the model.

Both 2D and 3D numerical modelling are carried out for flow hydraulics along the Fremont Weir section of the Sacramento River, California. The models predict flow features such as velocity, turbulence and flow acceleration, as well as the diverse hydraulic conditions present, which are inputs to the agent-based fish movement model to be carried out. Various model runs and comparisons are reported in order to shed light on: (a) difference of two different 2D models; (b) ability of 2D models in predicting velocity field in rivers with sharp bends; (c) difference between 2D and 3D models; (d) model performance in comparison with field data; and (e) the appropriateness of models under practical and complex river environment. The study provides additional 2D and 3D model verifications when applied to practical rivers; it also provides guidelines on how to use 2D and 3D models for river projects.

A improved multi-phase numerical model by direct numerical simulation (DNS) is developed to simulate gravity current that is frequency encountered in both natural and artificial environments. Several two-dimensional (2D) numerical simulations are conducted. Typical characteristics of gravity currents can be captured by our numerical method. The time-dependent front location of gravity currents is compared with data from numerical and laboratory experiments. The satisfying consistence demonstrates the present 2D numerical simulation can well reproduce the development of gravity currents. The influence of suspended particles to turbidity currents is also investigated. After an initial stage, gravity current gradually advances faster than turbidity current as the suspended particles are constantly lost. The simulation results can provide a detailed research into gravity and turbidity currents.

Recent investigation has led to the understanding that geyser formation can be caused by the uncontrolled release of air pockets that become entrapped in storm water systems. Such occurrences are deleterious in the public health point of view and may cause property and structural damage. Causes, frequency, magnitude, and location of geysering events are still poorly understood, and thus an experimental program has been initiated at Auburn University to study such episodes. A 302mm schedule 40 clear PVC apparatus has been constructed to study sudden release of entrapped air pockets leading to geysers. Various vertical shafts with diameters ranging from 50mm to 300mm and lengths up to 5.2m have been used. The idea of these tests is to assess strength, amplitude of water level changes, and other characteristics of these geysers. This work focuses on presenting characteristics of the apparatus, the methodology used in this large-scale testing, and preliminary results comparing the strength of geysers in cases with and without background flows in the horizontal conduits. These tests are expected to help in the development of geometries of ventilation structures in storm water systems that will avert geysering.

Assessment of the dissipation of total dissolved gases (TDGs) is important in the downstream of hydropower facilities which often encounter TDG supersaturation. An analysis of the two consecutive spill events at the Peace River hydropower system, which includes the Bennett Dam and the Peace Canyon Dam, showed that the percent saturation of TDG and dissolved oxygen (DO) varied with spill rates, pre and post-spill conditions. The decay of TDG was comparatively slower than DO and the rates decreased with the drop of spill flows. For spill of 1,160 m³/s at the Peace Canyon Dam, the decay rate for TDG at the dam tailrace and at a distance 7 km downstream was found to be 0.005 and 0.0014 hr^-1, respectively. A conceptual computational fluid dynamics model of the reservoir indicated that density driven currents could affect the TDG dissipation.

This study presents analysis methodology and results of characterizing the spatial and temporal distribution of rainfall used for design purposes by the Nevada Department of Transportation (NDOT). An assumption of uniform rainfall over watersheds can lead to unreasonably large peak flow rates, especially in regions where rainfall is highly variable or isolated in areal extent. Analysis of actual storm events in terms of temporal and spatial distributions is expected to be more representative of rainfall experienced in Nevada, thus making design of drainage infrastructure more efficient.

Historically, a systematic means of providing accurate, detailed analyses of precipitation associated with a recent extreme storm event has been difficult to achieve given lack of reliable data, particularly in near real-time. Enhanced radar data, improved satellite data, consolidated rain gauge observations, and innovative method for integrating these sources are making detailed storm analyses faster and more accurate than in the past. We help, manage, and maintain the largest known consolidated and quality-controlled precipitation gauge dataset in the United States, which is vital in “ground truthing” precipitation associated with extreme storms. Dual-polarization radar-estimated precipitation has shown to quantify extreme rainfall more accurately than traditional radar and has provided a significant increase in extreme event analysis accuracy. Meanwhile, satellite-estimated precipitation data continues to improve and provide “gap filling” in areas lacking gauge and/or reliable radar data. Using these datasets and a series of innovative algorithms makes near real-time near real-time, systematic storm analyses possible. Storm analyses of this nature support media inquiries, hydrologic modeling calibration and validation, flood responses, forensic cases, insurance claims, emergency management, situational awareness, and help build a storm database for use in future engineering design applications. This presentation will provide an overview of our efforts to advance the state-of-science associated with extreme precipitation event analysis.

Self-similarity conditions and scale invariance of unsteady one-dimensional bedload sediment transport are investigated through the application of the one-parameter Lie group of point scaling transformations. Determining the suitability of scaling bedload transport equations has been plagued by empiricism. Two bedload transport equations are investigated to determine a representation of the transport regime that will be self-similar and scale invariant at a variety of different scaled domains. Furthermore, one-parameter Lie group point scaling transformations required to physically scale the transport process without scaling the sediment material properties are investigated. By applying the Lie group scaling method to the governing equations for one-dimensional non-equilibrium bedload sediment transport, a simplified approach to bedload sediment transport modeling is sought. The proposed scaling approach carries the advantage of identifying the self-similarity conditions due to the initial and boundary conditions of the corresponding initial and boundary value problem along with those due to the governing equations, expanding scaling of transport to unsteady, non-equilibrium conditions.

This study focusses on evaluating the long term changes in four hydrologic variables, i.e., precipitation, temperature, minimum temperature, and maximum temperature in the Midwest United States. Annual averages of hydrologic variables for 106 climate divisions in the 12 Midwest states are analyzed for trends and steps for a period of 120 years (1895–2014). Nonparametric Mann-Kendall (MK) Test and Pettit’s Test are used to evaluate the changes in hydrologic data at a significance level of p≤ 0.05. The study also takes in to consideration the effect of short term persistence (STP) on the trends. The results from the MK test indicated increasing trends in the hydrologic variables for majority of the climate divisions in the Midwest. An increasing trend in mean temperature was detected in the eastern Midwest and it ranged from 0.04 to 3.09 °F/century. The climate divisions showing increasing trend in mean temperature also showed an increasing trend in precipitation (0.03 to 0.57 mm/century). While minimum temperature showed an increasing trend throughout the Midwest (0.25 to 3.8 °F/century), maximum temperature showed an increasing trend only in the northwest region of Midwestern states (0.01 to 3.46 °F/century). The Pettitt’s Test results indicated that shift, which were statistically significant, in all hydrologic variables occurred in the decades of 1980s and 1990s. Overall, the analysis from the current study provides a detailed view of changing temperature and precipitation in Midwest and the results are expected to aid water resources managers to effectively manage the available resources in the agriculture dominated region.

We investigated the changes in streamflow (water-year basis) and evaluated the spatial and temporal relationship of the streamflow (averaged for three seasons) across the U.S. with Pacific and Atlantic Ocean climate variability using data from 240 naturalized flow stations for the period 1951 to 2010. Statistical tests (Mann-Kendall and Pettitt’s Tests) were used to evaluate the gradual (trend) and abrupt (step) changes. Walker test was used to compute the field significance. The coupled relationship between oceanic-atmospheric indices [Sea surface temperature (SST) and geopotential height at 500-mbar (Z₅₀₀)] and the seasonal continental U.S. streamflow was evaluated utilizing singular value decomposition. Majority of streamflow stations in the eastern U.S. showed increasing streamflow trend, while most of the stations in Pacific Northwest showed trend that were decreasing. Early period of 1970s and late period of 1980s were detected with shift, following the long term trend. Z₅₀₀ represented the seasonal variability in streamflow better, compared to SST. Strong correlation with the streamflow stations in the Midwest, Arkansas-White-Red, Souris-Red-Rainy, Pacific Northwest regions were noticed mainly by the Pacific and Atlantic Z₅₀₀. Strong correlations between Pacific SST and the streamflow stations in southern South-Atlantic-Gulf, Midwest and regions of Pacific Northwest were detected. Likewise, the SST of the Atlantic Ocean showed statistically significant correlations with the New England, Midwest and regions of South-Atlantic-Gulf. The findings from the current study helped in understanding the long term changes and can be used to improve streamflow forecasting models, which may help managing water resources in response to climate change.

This study focuses on the climate change impact on the hydrologic processes at watershed-scale in a snow-dominant watershed, with bias-corrected climatic data from coupled model intercomparison project phase 5 (CMIP5). Lehman Creek, a typical snow-dominant watershed, located in Great Basin Nation Park, eastern Nevada, was studied. Quantile-quantile (Q-Q) mapping technique was applied to three climatic variables, precipitation, maximum temperature and minimum temperature, from 12 global climate models (GCMs), from CMIP5 data (BCCA, RCP6.0), with reference data of historical PRISM observations for 1981–2010 as baseline period. In order to study the hydrologic impacts brought by climate change, a physical-based distributed parameter hydrologic model was developed using precipitation-runoff modeling system (PRMS). The bias-corrected climatic data of 12 GCMs for baseline period (1981–2010) and projected period (2011–2099) are the forces to drive the calibrated PRMS model to simulate the hydrologic processes. Results show that compared to historical period, both positive and negative changes could occur in long-term streamflow; decreasing trends were observed in summer season (June to October) and increasing trends in spring season (January to May). The greatest streamflow increase is noticed in April (6%) and decrease in June (5%). The results of the study may help water resources management with better understanding of climate change influence on the streamflow in Lehman Creek watershed.

This paper serves 2 objectives: (i) to establish a spatial representative rainfall stations from existing nextwork in Northern Chao Phraya River Basin; and (ii) to use of multivariate geostatistical algorithm for incorporating relatively cheaper elevation, humidity, and temperature data into the spatial prediction of rainfall at the study site. Ping, Wang, Yom, and Nan Basins are located in the upstream Chao Phraya River Basin and serve as an upstream control for the main Chao Phraya River Basin. The technique was illustrated using monthly and annual rainfall observations measured at 326 rain gauge stations covering the entire Basin and its vicinity. The precipitation prediction maps, generated by Thiessen polygon, inverse square distance, and ordinary Kriging were used t o determine the sensitivity of the rainfall data to the prediction results by constructing the covariance surface map. Digital elevation, humidity, and temperature models were incorporated into the spatial prediction of rainfall using multivariate geostatistical algorithms. The prediction performance of geostatistical interpolation were cross validated with the straightforward linear regression of rainfall against elevation, humidity, and temperature. The results revealed that the multivariate geostatistical algorithm outperformed the linear regression approach, stressing the importance of accounting for spatially dependent rainfall observations in addition to the co-located elevation. The digital elevation data were highly correlated to monthly monsoon-induced precipitation in the study area. Humidity and temperature data exhibited a lower degree of correlation to the monthly precipitation data, especially when the Basin size is considerably larger.

Kızılırmak river, with a drainage area of more than 75,000 km², is the longest river among the rivers which originate and end in Turkey. A coupled atmospheric-hydrologic model based real-time precipitation and flood forecasting system for Kızılırmak river basin was developed and became operational recently. This real-time forecasting system utilizes the Global Forecast System (GFS) global numerical weather forecasts as the initial conditions and the boundary conditions for the mesoscale atmospheric model WRF (weather research and forecasting) over Kızılırmak river basin. The WRF regional atmospheric model dynamically downscales the GFS global numerical weather forecasts over Kızılırmak river basin and provides the initial and boundary conditions to the snow model component of the forecasting system. Details of the atmospheric and snow model components of the forecasting system will be presented separately. Here, the physically based hydrologic model component, WEHY, of the atmospheric-hydrologic model based precipitation and flood forecasting system for Kızılırmak watershed will be described and some preliminary results will be presented.

Starting from a time-space nonstationary general random walk formulation, first the general fractional random walk model of transport by time-space nonstationary flow in fractional time space is presented. From this general fractional random walk model, the development of the pure advection and advection-dispersion forms of the fractional ensemble average equations of solute transport by time-space nonstationary stochastic flow fields in fractional time-space are then presented. The purely advective form represents the Lagrangian form of the ensemble average mass conservation equation for solute transport in fractional time-space. In the case of the fractional ensemble average advection-dispersion transport equation, the moment and cumulant forms of the equation are quite different, and are both presented. Next, the developed fractional ensemble equations of transport, in their purely advective, and moment and cumulant advective-dispersive forms, are evaluated by numerical simulations against the corresponding Monte Carlo solutions. These comparisons show that the cumulant form of the advective-dispersive ensemble average fractional transport equation is generally superior in simulating the shape and mode of the ensemble average concentration of the contaminant. The derived fractional ensemble average equations of transport can accommodate both the non-Fickian and the Fickian behavior of transport.

This study proposes a decision support tool (SDEXRAIN) for assessing the climate change impacts on extreme rainfall processes at a given location. More specifically, the SDEXRAIN consists of two components: (i) a spatial statistical downscaling model to describe the linkage between global climate variables and daily annual maximum rainfalls at a given site; and (ii) a temporal statistical downscaling model to describe the relations between daily and sub-daily annual maximum rainfalls. Results of a numerical application of this tool using NCEP re-analysis and observed precipitation data available at two locations with completely different climatic conditions (Seoul station in South Korea and Dorval station in Canada) have indicated that the proposed SDEXRAIN could accurately describe the relations between global climate predictors and daily and sub-daily annual maximum rainfalls at a given site. Hence, this tool can be used for assessing the climate change impacts on extreme rainfalls at a location of interest.

In ecohydrologic projection, the evapotranspiration is the key component in hydrologic water balance cycle. The complementary relationship was established based on the physics of energy and mass transfer at land surface—atmosphere interface and defines the large-scale interaction between actual (ET_a) and potential (ET_p) evapotranspiration with respect to moisture availability. The change of regional complementary relationship due to climate change is paramount importance in understanding and predicting the future ecohydrologic impacts. In this paper, the complementary relationship hypothesis was validated in Soyang-gang dam basin with 2,783 km² of basin area along with the other major dam basins in Korea. Then, the representative raw and downscaled GCM (global climate model) outputs with RCP (representative concentration pathways) 4.5 and 8.5 scenarios were validated in the context of the complementary relationship hypothesis established using the observation data. To calculate the complementary relationship, the moisture availability was defined as annual precipitation and ET_p from GCM and observation data were estimation by applying the Hargreaves et al. (1985) equation that uses a minimum of meteorological data. ET_a was estimation by applying each of the GCM data with attributes of evapotranspiration and the water balance method using observation data. The bias correction process for raw GCM output is essential for properly use for projecting the future regional hydro-environmental impacts. The projection of the river flow regime considering the increase of actual evapotranspiration shows the changing (increasing) rates of the river flows from high to low flow range are attenuated in comparison with relatively high increasing rate of precipitation. The increase of actual evapotranspiration and consequent decrease of effective precipitation may possibly be the cause.

Design storms that are representative of local or regional climatology are needed for hydrologic and hydraulic modeling of projects involving watershed response to rainfall. Representativeness includes both the temporal and spatial distribution of rainfall. Considering dynamic storms, the temporal and spatial distribution are related because the motion determines the point-scale hyetograph, while the spatial and temporal distribution of the moving storm determine the depth-area-duration relationship of the storm total. Radar offers a unique opportunity to measure the movement of storms in terms of motion, both speed and direction, and for depth-area reduction factors. This presentation examines how these design storm characteristics can be derived from radar and rain gauge data. Storm motion properties measured for a range of climatic conditions are examined for application to hydrologic/hydraulic design and risk reduction.

In climate change conditions, warmer temperature accompanied by greater precipitation could lead to the formation of larger snowpack and earlier spring melting of the snowpack, which in turn could increase the magnitude of runoff in a cold region basin. Conversely, lower temperatures accompanied by lesser precipitation could lead to a decrease in runoff within the basin. Both scenarios, along with other climate change scenarios, could alter the basin runoff in a confounding manner and challenge the validity of parameters used in the designs of embankment dams. Spillways, stilling basins, and outlet structures will be impacted most as compared with other appurtenances of the dams. Rivers emptying into reservoirs deposit sediments on the bottom of reservoirs, and the built up over the productive years could decrease the water storage volume. In the scenario with greater precipitation and surface runoff, the frequency of having flooding and overtopping events increases. The above climate change impact factors were investigated for Renwick Dam in North Dakota by having the upper basin areas modeled by HEC-HMS and SWAT. After both models were calibrated, the behaviors of the reservoir during the future time periods were simulated using downscaled climate change data as the inputs. The results provided by both models are compared. There are interesting differences observed. A sensitivity analysis scheme is also used to derive some rational inferences on the uncertainties of the model calibration results and the implications of the design parameters.

South Florida is home to about 8 million people. The region is characterized by low relief, flat topography, and hydrology driven by a delicate balance between rainfall and evapotranspiration, high surface-water and groundwater interaction, presence of urbanized areas along the coast, significant agricultural areas, and a protected natural area—the Everglades. The water resources of this complex region is managed by the South Florida Water Management District (District). The district operates this system for flood control, water supply, water quality treatment, and ecosystem restoration. The hydrology of this region is driven mainly by rainfall and evapotranspiration. Thus, knowledge of changes in future climate parameters that affect these hydrologic components is critical for (i) projecting water resources availability, (ii) identifying water management system vulnerability, and (iii) designing adaptation measures. In an attempt to evaluate future water resources availability of the region, downscaled daily bias-corrected and constructed analogs of precipitation, minimum temperature and maximum temperature projections from the World Climate Research Programme’s Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model dataset were analyzed. Data analysis included (i) identification of future trends in precipitation and temperature based on a total of 119 models and three climate forcing scenarios, (ii) evaluation of future seasonal water availability of the region, and (iii) assessing the impact of changes in precipitation, temperature and sea level on south Florida’s water management system. The results of this study will be beneficial for water resources planners to design climate change adaptation measures that enhance the resiliency of the water management system.

Problems with efficient dewatering following heavy rainfall events are not uncommon already today because of urbanization beyond the sewer system capacity. Sewer drainage system evaluation are required in many cities and a key issue in this situation is whether to take climate change into account. In this study a simulation model for rainfall-runoff and flood inundation model with a vector-based catchment delineation are used. The set-up of this model is based on so-called “urban landscape GIS delineation” that faithfully describes the complicated urban land use features in detail. Modelling was performed using as inputs design storm with 3 year return periods of 180 minutes duration for climate change scenarios. These future design storms were increased by factors of 10%, 20%, 30%, and 40% and the impacts of incremented rainfall events on the urban drainage system were assessed. It was indicated that the surface runoff would increase at higher percentages than infiltration loss and final surface storage.

Many parts of the Mississippi River Basin are experiencing vastly different hydrologic conditions than they did 100 years ago as a result of changes in the magnitude of hydrologic inputs and withdrawals. These changes can be attributed to factors such as altered amounts and timing (seasonality) of precipitation, changes in rainfall-runoff relations due to altered land use, and anthropogenic disturbances to streams and river systems. Data from thousands of NOAA precipitation gages and USGS flow stations in the basin were used. This study uses HUC4 basin boundaries within the major river systems (i.e., Missouri, Ohio, etc.) draining to the Mississippi River to spatially subdivide the approximately 100-year data set. Results show that in general, although most of the Mississippi River Basin is receiving more rainfall than it did 100 years ago that there are vast areas where water yields have decreased significantly, particularly in the western part of the basin and particularly in spring. Parts of the western basin are experiencing 25 to more than 50% less discharge per unit area than they did 100 years ago. Precipitation has also shifted temporally such that winter precipitation has significantly decreased in many areas while spring and autumn precipitation has generally increased. The anthropogenic influence on water yield, appears to be large over vast areas, with values of water yield per unit precipitation also decreasing between 25 to more than 50% throughout much of this area. Not all areas of the basin, however, are experiencing decreases in water yield.

A real-time flood forecasting system was developed over the Kızılırmak river basin (KRB) in Turkey by means of a physically-based atmospheric-hydrological model. The real-time flood forecasting system utilizes the weather research and forecasting (WRF) model and the WRF data assimilation (WRFDA) system as its atmospheric component. Real-time global atmospheric forecasting data are obtained from global forecast system (GFS) operated by the national centers for environmental prediction (NCEP). The real-time global atmospheric forecasting data are utilized as initial and boundary conditions of the atmospheric component. The atmospheric component synthesizes real-time upper-air sounding data and ground observations into the initial conditions by the three-dimensional variational (3DVAR) data assimilation system. After the assimilation, the atmospheric component dynamically downscales the real-time global atmospheric forecasting data into 4 km horizontal resolution and hourly temporal resolution. The real-time flood forecasting system is in operation now. Some preliminary forecasted results by the atmospheric component are shown in this presentation.

Climate change analysis on historical precipitation was conducted over two study watersheds in Northern California: the Upper Feather River watershed and the Yuba River watershed. It is difficult to obtain sufficient observed precipitation data for a long-term period over such mountainous watersheds. In this study, therefore, historical precipitation was reconstructed for 141 water years from October 1, 1871 thought September 30, 2012 by means of dynamical downscaling of a long-term reanalysis, 20CRv2. After validation with observation data, the reconstructed precipitation was utilized for climate change analysis. The climate change analysis shows that annual basin-average precipitation has significantly increased over the study watersheds during the historical period. An upward trend of monthly basin-average precipitation is significant in drier month whereas it is insignificant in wet months except for February.

During the past few decades in Fengshan creek basin of northern Taiwan, land excessive reclamations were conducted and more and more golf courses have been built on the hillside. As rainy and typhoon season comes, heavy rainfall induced flash floods and surface inundations usually brings significant damages to local populations and destroyed their properties. In order to study the impacts as environment changes, the Fengshan Creek basin is selected as our study site. This study, aimed to understand the effects of climate and land cover changes by modeling future scenarios. We used weather generation model (WGEN) and general circulation models (GCMs) to study scenarios of climate change, and the conservation and land use and its effects model (CLUE-s) was applied to model land cover changes. We then applied the software of HEC-HMS to calculate surface runoff on mountainous area, and implemented WASH123D numerical model for entire watershed simulations. Modeling results were linked to hydraulic routing to discuss the scenarios on the periods of (1) near future (2020–2039 years), (2) future (2050–2069 years), and (3) far future (2080–2099 years). Simulations results indicated that the influence of climate change reveals much apparently effects as comparing to land cover changes. And the future climate tends to getting dryer during dry season, and more wetted of raining season in this area. The ground water levels tended to drop down as land cover changes in the future.

Extreme rainstorms with higher intensity and frequency are expected to increase in future climate. Climate change expected potentially to impact the capacity of infrastructure, service level, and the natural environment. Traditional stormwater management plans, procedures and actions are no longer sufficient to deal efficiently with the uncertainty of climate change. Urban stormwater infrastructure has been sized based on assumptions of rainfall intensities. Given that these intensities are shifting upwards as a result of climate change, storm sewer systems and overland flow routes will likely be more often inundated beyond the design capacity. Knowing the relationship between the piped storm sewer network and the above-ground major system has become more critical. Formerly these two systems were calculated independently, but 1D/2D computer modelling allows them to become a single integrated system. An integrated 1D/2D sewer and overland flow model is sophisticated tool that has become feasible for use by practitioners. The use of this type of computer models can provide local authorities with new insights into how infrastructure responds to rainfall events and how best to make the changes that will add resiliency under more extreme climatic conditions. The paper outlines an approach of using an integrated 1D/2D sewer and overland flow dynamic computer models in Hamilton areas. Hydrologic and hydraulic modeling components will be presented with specific case study examples. Through this approach, potential risks of flooding and system responses were evaluated and alternative solutions of flood remediation were developed by considering constraints and opportunities.

This study introduced a new method that unites a hydrologic model using physical infiltration mechanisms with a combination of a hydrologic soil group (soil) and a land use and treatment class (cover) to integrate LULC data into soil data. The new method has been incorporated into the WEHY model to simulate hydrologic conditions over the Cache Creek Watershed (CCW) and Shasta Dam Watershed (SDW) in Northern California. For testing the effects of integrating LULC and soil data on WEHY simulations, this study used four different soil datasets. The first soil dataset (S1) was obtained from the local soil database including SSURGO and STATSGO2. The third soil dataset (S3) is the global soil data SoilGrids-1km obtained from World Soil Information. While the second (S2) and fourth (S4) soil datasets were calculated from the new methodology that integrate the local LULC into the local soil and global soil respectively. With the WEHY model for SDW and CCW validated by historical hydro-climate data and the four different soil datasets, it was possible to demonstrate the effects of different soil datasets on the performance of the WEHY model. The results of this study suggest that this approach is able to provide a fine soil dataset and then improve the performance of WEHY model over the target watersheds. In addition, this approach can then be used for the estimation of the impact of changes in LULC on hydrologic response under future climate change conditions.

This study evaluated the change patterns of the continental U.S. streamflow across 600 stations having a minimum of 30 years of continuous data. To detect the presence of long term trends, several non-parametric Mann-Kendall tests (with modifications accounting for persistence in data) were used. Non-parametric Pettitt’s test was used to evaluate the abrupt shifts and change points across the study period. A subset of the data (237/600 stations) was further analyzed with discrete wavelet transformation (DWT) to evaluate the effect of periodicities on the change patterns using multiple dyadic scales (i.e., two years, four years, and eight years). Water year analyses (along with its dyadic scales) revealed that regions in the northeast and upper-central have experienced an increasing change while regions in the northwest have undergone decreasing change. The seasonal analyses (with dyadic scales) showed wide-ranging changes at different seasons and revealed the seasonal variations. DWT analyses showed that there is a presence of stronger change at a periodicity of 8 years or above at all temporal scales. Coupling effect of multiple climate signals were also observed with the change in streamflow pattern. The study provided comprehensive analyses on the change behavior of U.S. streamflow. Results of the current study can be used in building forecasting models and can also be used for taking water management decisions under changing climate conditions.

Surface characteristics and the availability of moisture are factors influencing evapotranspiration. Energy from incoming solar radiation is fractioned into sensible heat (raising temperature), latent heat (evapotranspiration) and change in stored energy. Non-vegetated dry surfaces appropriate more of the incoming energy into sensible heat resulting in an increase in surface temperature. Evapotranspiration has a surface cooling effect. Surface characteristics and energy flux fractionation have implications on regional hydrologic processes affecting water resources. Land degradation and desert expansion can be attributed to a decrease in vegetated surface and changes in energy fractionation. On the contrary, climate modulating benefits of urban greening, wetland restoration and afforestation can be cited. Case studies of landscape change impact on regional climate have been reported in Africa, Brazil, China and the United States.

Recent flood events caused by tropical storms resulted in large economic impacts in the Northeastern U.S. and catalyzed efforts to understand the complex interactions between human and natural systems. Specifically, the resilience of our transportation infrastructure to climate and the impact of our transportation systems on the aquatic environment are important to both state and federal decision makers. In is important that new, innovative approaches be developed that consider both the robustness of our infrastructure today and its ability to cope with forecasted extremes due to climate change. This paper presents ongoing research associated with the broad regional application of a hydrologic vulnerability framework for road-stream crossings. A calibrated, process-based hydrological model is used to develop estimates of flood flows at various return frequencies. Road-stream crossings are identified and the maximum critical flows for these crossings are calculated. Daily-runoff from the hydrological model is coupled with a statistical index-method to determine the average recurrence interval for flood flows at ungaged locations. Finally, a vulnerability analysis is performed that maps the annual exceedance probability (AEP) of the critical flow through crossing infrastructure to the estimated AEP of flood flows at the crossing locations. This study supports the development of a decision-support tool for prioritizingculvert repair and replacement in the region. It also creates a more robust infrastructure design that suggests adaptation strategies in conjunction with climate information.

Effect of climate change on hydrologic flow regimes, particularly extreme events, necessitates modeling of future flows in order to best inform water resources management. In this study, the future flows were simulated using global climate models (GCMs) and a regional atmospheric model in tandem with a watershed model to make a hydro-climate model (WEHY-HCM), over the Cache Creek Watershed in Northern California. The future climate projections, based on four emission scenarios simulated by two GCMs (ECHAM5 and CCSM3) under several initial conditions, were dynamically downscaled using MM5, a regional climate model. The downscaled future precipitation data were bias-corrected before being input into the WEHY model to simulate the detailed flow at hourly intervals along the main Cache Creek branch and its tributaries during 2010–2099. The results suggest an increasing trend in flood magnitudes and their intensities at the outlet of the study region throughout the 21st century. Similarly, estimates of the 100 and 200-year floods increased throughout the study period. The observed differences in the estimated future flood frequencies between the first half and the second half of 21st century may be an evidence of the non-stationarity in the 21st century hydrological regime over the study region.

Assessment of future drought characteristics requires knowledge of potential evapotranspiration (PET) which is commonly estimated using the Penman-Monteith (PM) method. This method requires knowledge of climatic variables such as relative humidity and wind speed which are not always readily available, particularly for regional-scale studies. Alternate methods such as the Thornthwaite (Th) and Hargreaves (Hg) have been widely-used as they only require temperature input. In this study, we have applied both the Th and Hg methods to a suite of 22 global climate models (GCMs) available from the recently released Intergovernmental Panel for Climate Change Coupled Model Intercomparison Project Phase 5 (IPCC CMIP5) under the Representative Concentration Pathway 8.5 (RCP 8.5) to evaluate the 21st century evolution of PET in different climate divisions of Texas. While both methods produce statistically significant (p<0.01) increasing PETs as we move into the 21st century, the slope of these trends are two to three times greater for the Th compared with the Hg. The Th method appears to be very sensitive to temperature and overestimates PET in response to the increasing temperatures projected by GCMs the under the RCP 8.5, particularly during the summer (June-July-August) months. Studies that use the Th method may thus overestimate future drying due to the pronounced increase in PETs. As such, the Th method appears to be unsuitable for drought assessment studies in Texas and where only temperature data may be available, we recommend the use of the Hg method.