Jinn-chuang Yang - Academia.edu (original) (raw)

Papers by Jinn-chuang Yang

Stochastic Hydraulics 2000, 2020

Advances in Applied Mathematics and Mechanics, 2014

This study presents a numerical solution to the three-dimensional solute transport in heterogeneo... more This study presents a numerical solution to the three-dimensional solute transport in heterogeneous media by using a layer-integrated approach. Omitting vertical spatial variation of soil and hydraulic properties within each layer, a three-dimensional solute transport can be simplified as a quasi-three-dimensional solute transport which couples a horizontal two-dimensional simulation and a vertical one-dimensional computation. The finite analytic numerical method was used to discretize the derived two-dimensional governing equation. A quadratic function was used to approximate the vertical one-dimensional concentration distribution in the layer to ensure the continuity of concentration and flux at the interface between the adjacent layers. By integration over each layer, a set of system of equations can be generated for a single column of vertical cells and solved numerically to give the vertical solute concentration profile. The solute concentration field was then obtained by solvi...

Flood Risk Management [Working Title], 2018

Continuing land subsidence can diminish the effectiveness of an existing flood mitigation system ... more Continuing land subsidence can diminish the effectiveness of an existing flood mitigation system and aggravate the flood hazard. This chapter demonstrates that, through groundwater management with an effective pumping scheme, flood hazard and related flood damage in land subsidence area can be reduced. The chosen study area is in the southwest coast of Taiwan, which has long been suffering from frequent and widespread flooding primarily due to land subsidence induced by groundwater overpumping. Numerical investigation in the study area clearly shows that effective management of groundwater pumping can play an important role in long-term sustainable solution for controlling the spatial-temporal variability of future land subsidence, preventing the flood hazard from worsening, reducing the flood damage, and satisfying the groundwater demand.

Journal of Flood Risk Management, 2018

Continuing land subsidence can aggravate flood hazard and diminish the effectiveness of existing ... more Continuing land subsidence can aggravate flood hazard and diminish the effectiveness of existing flood mitigation systems. This paper presents a study of groundwater-pumping management for mitigating flood hazard in a subsidence infested area in the southwest coast of Taiwan. An optimal groundwater-pumping model is developed for preventing flood hazard from worsening and for satisfying the groundwater demand. In an area where the land is susceptible to pumpinginduced subsidence, the study shows that proper long-term pumping strategy to manage spatial-temporal variation of future land subsidence should be an integral part of flood risk management as it can sustain the effectiveness of the flood mitigation measures.

Environmental Earth Sciences, 2010

Groundwater Updates, 2000

Due to its simplicity and efficiency, the conventional quasi three-dimensional concept has been w... more Due to its simplicity and efficiency, the conventional quasi three-dimensional concept has been widely applied in analyzing groundwater flow in multiaquifer system, especially for regional problem. But the conventional quasi three-dimensional concept is not able to deal with the discontinuous and interconnected strata and fully three-dimensional flow. Therefore, in order not only to overcome these shortcomings but also to maintain efficiency, we propose a new layer based three-dimensional concept to develop a groundwater simulation model. This new concept assumes that the pore pressure of every aquifer and aquitard in the vertical direction can be depicted by the quadratic polynomial interpolation function, then the vertical integration is performed on each layer to ensure the continuity of pore pressure and flux at the interfaces between any two layers. The finite analytical numerical method is adopted to develop the present groundwater simulation model. The results show that the present model is capable of simulating fully three-dimensional flow pattern.

Water Resources Management, 1994

The presence of uncertainties in assessing benefits and costs detracts from deterministic economi... more The presence of uncertainties in assessing benefits and costs detracts from deterministic economic evaluation. This paper examines three probabilistic economic evaluation procedures: stochastic dominance, expected gain-confidence limit, and Hurwicz criterion. Their relative performances are evaluated through an example. Furthermore, the paper investigates the effects of (1) distributional assumptions of benefit and cost items, (2) uncertainty in project life, and (3) distribution of net present value on the project selection.

Stochastic Environmental Research and Risk Assessment, 2005

In hydrosystem engineering design and analysis, temporal pattern for rainfall events of interest ... more In hydrosystem engineering design and analysis, temporal pattern for rainfall events of interest is often required. In this paper, statistical cluster analysis of dimensionless rainfall pattern is applied to identify representative temporal rainfall patterns typically occurred in Hong Kong Territory. For purpose of selecting an appropriate rainfall pattern in engineering applications, factors affecting the occurrence of different rainfall patterns are examined by statistical contingency tables analysis through which the interdependence of the occurrence frequency of rainfall patterns with respect to geographical location, rainfall duration and depth, and seasonality is investigated. Furthermore, due to inherent variability of rainfall mass curves or hyetographs within each classified rainfall pattern, a practical procedure to probabilistically generate plausible rainfall patterns is described. The procedure preserves the inherent stochastic features of random dimensionless rainfall hyetograph ordinates, which in general are correlated non-normal multivariate compositional variables.

Stochastic Environmental Research and Risk Assessment, 2006

Occurrence of rainstorm events can be characterized by the number of events, storm duration, rain... more Occurrence of rainstorm events can be characterized by the number of events, storm duration, rainfall depth, inter-event time and temporal variation of rainfall within a rainstorm event. This paper presents a Monte-Carlo based stochastic hourly rainfall generation model considering correlated non-normal random rainstorm characteristics, as well as dependence of various rainstorm patterns on rainfall depth, duration, and season. The proposed model was verified by comparing the derived rainfall depth-duration-frequency relations from the simulated rainfall sequences with those from observed annual maximum rainfalls based on the hourly rainfall data at the Hong Kong Observatory over the period of 1884-1990. Through numerical experiments, the proposed model was found to be capable of capturing the essential statistical features of rainstorm characteristics and those of annual extreme rainstorm events according to the available data.

Natural Hazards, 2010

This study presents a risk analysis model to evaluate the failure risk for the flood-control stru... more This study presents a risk analysis model to evaluate the failure risk for the flood-control structures in the Keelung River due to the uncertainties in the hydrological and hydraulic analysis, including hydrologic, hydraulic, and geomorphologic uncertainty factors. This study defines failure risk as the overtopping probability of the maximum water level exceeding the levee crown, and the proposed risk analysis model integrates with the advanced first-order and second-moment (AFOSM) method to calculate the overtopping probability of levee system. The proposed model is used to evaluate the effects of the freeboard and flood-diversion channel on the flood-control ability of the levees in the Keelung River, which were designed based on the 3-day, 200-year design rainfall event. The numerical experiments indicate that the hydrologic uncertainty factors have more effect on the estimated maximum water level than hydraulic and geomorphologic uncertainty factors. In addition, the freeboard and the flood-diversion channel can effectively reduce the overtopping probability so as to significantly enhance the flood-control capacity of the levee system in the Keelung River. Eventually, the proposed risk analysis successfully quantifies the overtopping risk of the levee system under a scenario, the increase in the average 200-year rainfall amount due to climate change, and the results could be useful when planning to upgrade the existing levee system.

Journal of Water Resources Planning and Management, 2007

This paper presents a stochastic groundwater management model explicitly considering land subside... more This paper presents a stochastic groundwater management model explicitly considering land subsidence. Through the use of response matrix technique and one-dimensional consolidation equation, a deterministic management model is first developed. By Latin hypercube sampling technique, along with numerical subsurface flow simulation, statistical features of unit response coefficients due to random hydrogeologic parameters, including hydraulic conductivity ͑K͒ and Lame constants ͑ and ͒, are quantified. The first-ordervariance-estimation method is adopted to analyze the uncertainties of drawdown and land subsidence based on which the concept of chance-constrained programming is applied to transfer the original deterministic management model into its stochastic form. The stochastic management model enables the determination of optimal total pumpage subject to the constraints that drawdown and land subsidence do not exceed the allowable values with a specified reliability. A hypothetical example is utilized to demonstrate the applicability of the stochastic model to five cases in which various levels of parameter uncertainty are considered. The results indicate that joint consideration of drawdown and land subsidence is essential, and the proposed stochastic management model can be generally applied for regional groundwater resources management in conjunction with controlling land subsidence.

Journal of Hydro-environment Research, 2011

This study proposed a modified nonlinear storage function runoff model to take into account the s... more This study proposed a modified nonlinear storage function runoff model to take into account the storage hysteresis effect, in which there exists difference of the storageedischarge relationship between the rising and recession limb. Since the modified storage function runoff has seven parameter, a parameter-calibration method, which combines the genetic algorithm with the least square criterion. For model calibration and validation, twenty rainfallerunoff events (1968e2005) recorded at Wudu gage in Keelung River in northern Taiwan were used in the study. The results of model validation reveal that the modified storage function runoff model not only produces the realistic storageedischarge relationship, but also provides a good estimation of the runoff.

Journal of Hydraulic Engineering, 1989

Discussion by Jinn-Chuang Yang 3 Numerical modeling of sediment transport in alluvial channels ha... more Discussion by Jinn-Chuang Yang 3 Numerical modeling of sediment transport in alluvial channels has been extensively studied for the past decade. A number of models have been developed for the corresponding specific problems. However, as the authors pointed out, most of the papers do not discuss the effect of At and Ax on the simulation results. Based on the bed-perturbation celerity relation proposed by de Vries and the use of a simple sediment-transport predictor, the authors have derived Eqs. 21 and 24 for determining the most appropriate At and Ax to avoid the numerical instability. Nevertheless, as far as the nonuniform sediment transport is concerned, the bed perturbation is induced not only by the bed-level change but also by the variation of the composition of bed material. In view of Eqs. 21 and 24, the time and space steps At and Ax are related to the Froude number, mean flow velocity, and sediment concentration. It is obvious that the perturbation caused by the nonuniformity of the bed material is not considered. Therefore, strictly speaking, Eqs. 21 and 24 should only be valid for the uniform sand transport model. In addition, the relations derived are based on the simple power law relation, Eq. 20, for a sediment discharge predictor, which is not consistent with Eq. 4. Therefore, the use of Eqs. 21 and 24 may give the wrong indication of A? and Ax selection. The necessity of appropriately selecting At and Ax is resulted from the explicit scheme used by the authors for the sediment continuity equation. One can probably use the implicit scheme such as Preissmann's four-point scheme, which is unconditionally stable, to avoid the Courant-number constraint. Although the existence of multiple time (or length) scales may lead to an instability problem, with the careful choice of space weighting factor one need not worry about the instability caused by an unsuitable choice of Af and Ax (24).

Journal of Hydraulic Engineering, 1994

As computation speed increases, Monte Carlo simulation is becoming a viable tool for engineering ... more As computation speed increases, Monte Carlo simulation is becoming a viable tool for engineering design and analysis. However, restrictions are often imposed on multivariate cases in which the involved stochastic parameters are correlated. In multivariate Monte Carlo simulation, a joint probability distribution is required that can only be derived for some limited cases. This paper proposes a practical multivariate Monte Carlo simulation that preserves the marginal distributions of random variables and their correlation structure without requiring the complete joint distribution. For illustration, the procedure is applied to the reliability analysis of a bridge pier against scouring.

Journal of Hydraulic Engineering, 2004

The characteristics method by using the cubic-spline interpolation is comparable to the Holly-Pre... more The characteristics method by using the cubic-spline interpolation is comparable to the Holly-Preissmann scheme in solving the advection portion of the advection-diffusion equation. In order to conduct a cubic-spline interpolation, an additional constraint must be specified at each endpoint. In general, four types of endpoint constraints are available, i.e., the first derivative, second derivative, quadratic, and not-a-knot constraints. The goal of this paper is to examine each type of endpoint constraints. Two hypothetical cases are used to conduct the investigation. Among the four types of constraints examined herein, the not-a-knot constraint and the first derivative constraint with high-order finite difference approximation yield the best results. However, as far as accuracy and simple implementation are concerned the not-a-knot constraint should be the best choice in solving the advection-diffusion equation

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1996

International Journal for Numerical Methods in Fluids, 1992

A new method combining the Preissmann four‐point scheme and the Holly–Preissmann reach‐back schem... more A new method combining the Preissmann four‐point scheme and the Holly–Preissmann reach‐back scheme is introduced to solve the rapidly varied flow problem in an open channel. The Preissmann four‐point scheme is well known for the computation of one‐dimensional unsteady flow. The Holly–Preissmann reach‐back scheme integrates the Holly‐Preissmann two‐point scheme with the concept of reach‐back characteristics, which allows the characteristics to project several time steps beyond the current time level. A spontaneous surge formation case is used to demonstrate and evaluate the applicability of the new method. It has been found that the results from this method are quite compatible with those of Preissmann four‐point scheme. In addition, with the appropriate choice of the number of reach‐back time steps, this new method can always avoid the numerical oscillation which usually exists when one uses the Preissmann four‐point scheme for the condition of Courant number not close to unity.

International Journal for Numerical Methods in Fluids, 1991

The Holly‐Preissmann two‐point finite difference scheme (HP method) has been popularly used for s... more The Holly‐Preissmann two‐point finite difference scheme (HP method) has been popularly used for solving the advection equation. The key idea of this scheme is to solve the dependent variable (i.e. the concentration for the pollutant transport problem) by the method of characteristics with the use of cubic interpolation on the spatial axis. The interpolating polynomials of higher order are constructed by use of the dependent variable and its derivatives at two adjacent grid points. In this paper a new interpolating technique is introduced for incorporation with the Holly‐Preissmann two‐point method. The new method is denoted herein as the Holly‐Preissmann reach‐back method (HPRB) and allows the characteristics to project back several time steps beyond the present time level. Through stability analyses it has been observed that the increase of the reach‐back time step numbers for the characteristics indeed reduces the numerical damping and dispersive phenomena. A schematic model has b...