Jet-Chau Wen

Effects of Raingauge Distribution on Estimation Accuracy of Areal Rainfall

Rainfall analysis is important to managing water resources. Mean rainfall is usually used to calculate the spatial rainfall status of a region and is the input into various rainfall-runoff models. However, this method relies on an adequate raingauge network. This study identifies the effects of raingauge distribution based on estimation results of areal rainfall using the Thiessen polygon and block Kriging methods. Twelve rainfall events with complete data from 14 raingauges were selected to complete the goal of this study. The block Kriging method in this study uses a dimensionless semivariogram to obtain hourly semivariograms based on a standardized rainfall depth. The power semivariogram model was used to describe the temporal-spatial variation of rainfall. The analytical process in this study uses raingauge weight and rainfall volume as evaluation criteria. All raingauges were in turn removed from the original raingauge network. The effects of removing each raingauge were compared with computations using all raingauges. Comparison results indicate that (1) the block Kriging method can accurately describe rainfall processes in terms of the spatiotemporal structure of a semivariogram. (2) the block Kriging method is better than the Thiessen polygon method at obtaining exact mean rainfall, and (3) the effects of different raingauge distributions on a mean hyetograph warrant further investigation.

How Reliable is X-Ray Fluorescence (XRF) Measurement for Different Metals in Soil Contamination?

Although portable x-ray fluorescence (XRF) technology is widely accepted for environmental use in field screening test regarding the analytical approach, it needs to be evaluated with sufficient data and meet its performance characteristics to be employable for decision making purposes. Usually, for an XRF sample, the most interesting query is: How reliable is the XRF technique in detecting different targeted metals in soil? This study presents pairwise comparisons between the XRF and inductively coupled plasma atomic emission spectrometer (ICP-AES) results for individual elements of Ni, Cu, Zn, Pb, Cd, Cr, Hg, and As. The portable XRF analyzer was used to estimate the concentration levels of eight heavy metal elements, and then pairwise comparisons were made between the XRF and ICP-AES results. Results presented in this paper suggest that the use of XRF testing is highly reliable as a screening technique for the first sample group of metal element (Pb, Zn, Ni, and Cu) concentrations well in excess of the pollution threshold limits (PTLs). The order of reliability of the XRF measurements is Pb > Zn > Ni > Cu, and their relative proximity (RP) ranges from 85%–35%. In contrast, the results of another group of metal elements that include Hg, Cd, Cr, and As show poor correlation. Their RP ranges from 25%–2.3%.

The study of a in GM(1,1) model

Abstract The purpose of this paper is to analyze a predicted error in using the GM(1, 1) model based on the parameter α. The transfer function for the predicted error with the parameter α in the GM(1, 1) model is presented. The algorithm of solving equations in calculus is used to analyze whether the α is adaptive or not. The criterion of α is applied to describe the adaptive criterion of α. Finally, an example of the cagenet amounts of fish in the Peng‐hu area is used to demonstrate the small prediction error due to the optimal α value. The result shows that the criterion for α is applicable for minimizing the predicted error easily.

Identifying hydrograph parameters and their relationships to urbanization variables

Abstract This study examines relationships between model parameters and urbanization variables for evaluating urbanization effects in a watershed. Rainfall–runoff simulation using the Nash model is the main basis of the study. Mean rainfall and excesses resulting from time-variant losses were completed using the kriging and nonlinear programming methods, respectively. Calibrated parameters of 47 events were related to urbanized variables, change of shape parameter responds more sensitively than that of scale parameter based on comparisons between annual average and optimal interval methods. Regression equations were used to obtain four continuous correlations for linking shape parameter with urbanization variables. Verification of 10 events demonstrates that shape parameter responds more strongly to imperviousness than to population, and a power relationship is suitable. Therefore, an imperviousness variable is a major reference for analysing urbanization changes to a watershed. This study found that time to peak of IUH was reduced from 11.76 to 3.97 h, whereas peak discharge increased from 44.79 to 74.92 m3/s. Editor D. Koutsoyiannis; Associate editor S. Grimaldi Citation Huang, S.-Y., Cheng, S.-J., Wen, J.-C. and Lee, J.-H., 2012. Identifying hydrograph parameters and their relationships to urbanization variables. Hydrological Sciences Journal, 57 (1), 144–161.

The study of α in GM(1,1) model

Abstract The purpose of this paper is to analyze a predicted error in using the GM(1, 1) model based on the parameter α. The transfer function for the predicted error with the parameter α in the GM(1, 1) model is presented. The algorithm of solving equations in calculus is used to analyze whether the α is adaptive or not. The criterion of α is applied to describe the adaptive criterion of α. Finally, an example of the cagenet amounts of fish in the Peng‐hu area is used to demonstrate the small prediction error due to the optimal α value. The result shows that the criterion for α is applicable for minimizing the predicted error easily.

Replies to comments on ''A revisit of drawdown behavior during pumping in unconfined aquifers'' by Neuman and Mishra

] Heterogeneity as investigated in our paper, presencesof perched water table aquifers, limited leakage sources,boundary conditions, and many other factors that may mod-ify the shape of a drawdown-time curve. Likewise, ground-water flow is driven by the energy gradient but it can beinfluenced by many different factors. It is not the intent ofour paper to discuss them all. We merely emphasize thefact that the fundamental mechanisms causing the S-shapedcurves are the transition of water release mechanisms andthe vertical flow components. More importantly, our paperadvocates that a multidimensional variably saturated flowmodel, which considers the transition of water releasemechanisms and accounts for heterogeneity, would providea more realistic representation of flow processes in uncon-fined aquifers during a pumping test. These conclusions areindependent from the number of experiments we examined.1.2. Reply to Comments in Paragraph 3[

Typhoon Morakot and Institutional Changes in Taiwan

Typhoon Morakot hit Taiwan in 2009 with numerous rainfalls and caused nearly 700 deaths from mudslides and huge agricultural losses that have been estimated to be reaching NT

Operation of emergency operating centers during mass casualty incidents in taiwan: a disaster management perspective.

14.59 billion. For reconstructing the damaged buildings, traffic and houses and avoiding the same problems happen again, some institutional changes were made in post-Morakot period. The major changes include amending law and establishing new organizations to reduce problems like unclear responsibilities because of the overlapping affairs. Briefly speaking, the major changes are replacing “National Fire Agency” (NFA) by “National Disaster Prevention and Protection Agency” (NDPPA) as a professional institution in dealing with future disasters and gives emphasize on the role of local governments, establishing “Special Reconstruction Regulation for typhoon Morakot” to supply more finical support for houses or industries reconstruction, amending “Disaster Prevention and Protection Act” to make the whole disaster managing system more consistently, combining the “Central Disaster Prevention and Response Council” and “National Disaster Prevention and Response Committee” to reduce the problem of affairs overlapping, and establishing “Office of Disaster Management” to supervise central and local governments to execute disaster prevention and response plans.

Time and Flow Characteristics of Component Hydrographs Related to Rainfall–Streamflow Observations

OBJECTIVE On April 27, 2011, a train derailed and crashed in Taiwan, causing a mass casualty incident (MCI) that was similar to a previous event and with similar consequences. In both disasters, the emergency operating centers (EOCs) could not effectively integrate associated agencies to deal with the incident. The coordination and utilization of resources were inefficient, which caused difficulty in command structure operation and casualty evacuation. METHODS This study was designed to create a survey questionnaire with problem items using disaster management phases mandated by Taiwans Emergency Medical Care Law (EMCL), use statistical methods (t test) to analyze the results and issues the EOCs encountered during the operation, and propose solutions for those problems. RESULTS Findings showed that EOCs lacked authority to intervene or coordinate with associated agencies. Also, placing emphasis on the recovery phase should improve future prevention and response mechanisms. CONCLUSIONS To improve the response to MCIs, the EMCL needs to be amended to give EOCs the lead during disasters; use feedback from the recovery phase to improve future disaster management and operation coordination; and establish an information-sharing platform across agencies to address all aspects of relief work.(Disaster Med Public Health Preparedness. 2014;0:1-6).

A research on the three-year performance of the regional emergency operation centers in Taiwan

This study investigates the shape characteristics of hydrograph components of the Wu-Tu watershed in Taiwan based on ob- servations of rainfall and streamflow. Component hydrographs were modeled using a model of three serial tanks with one parallel tank. The block kriging method was used to calculate the hourly mean rainfall of events, and eight model parameters of 34 cases were derived from the shuffled complex evolution optimal algorithm. The remaining 18 events were used to verify the applicability of the calibrated parameters. Results show that (1) times to peak of hydrograph components are positively nonlinearly correlated to peak time of rainfall; (2) peak dis- charges of hydrograph components are linearly proportional to those of streamflow hydrograph; and (3) relationships of total discharges also have direct ratios between hydrograph components and observed streamflow. Using the procedures proposed in this study, three evaluated shape characteristics of component hydrographs can be easily used to rapidly determine shapes of simple hydrographs. DOI: 10.1061/ (ASCE)HE.1943-5584.0000675.