A Risk-Based Approach for Managing Hazardous Waste     

C.Y. Chiang  P.D. Petkovsky  P.M. McAllister 《Ground Water Monitoring & Remediation》1995,15(1):79-89

In 1992, the U.S. Environmental Protection Agency (EPA) proposed risk-based management of hazardous waste. A major component of the proposed rule is the determination of non-site- specific screening concentration levels from waste leachate. Ground water at a downgradient exposure point must not exceed those screening levels, or more stringent requirements would apply.
The screening concentration level is determined with verified models and equations that simulate the transport and attenuation of chemicals as they travel from the source area to the exposure point. A consortium of screening levels is determined in this paper by considering varying physical, chemical, and biological conditions. In addition, a method is developed for multi component leaching from contaminated soils in a landfill to determine the time-dependent behavior of a finite source. Finally, this paper discusses infiltration rate through the clay liner.  相似文献   

Hydrocarbon Thickness Fluctuations in Monitoring Wells     

M. W. Kemblowski  C. Y. Chiang 《Ground water》1990,28(2):244-252

  相似文献   

Fuzzy information processing in seismic hazard analysis and decision making     

W. M. Dong  W. L. Chiang  H. C. Shah 《Soil Dynamics and Earthquake Engineering》1987,6(4):220-226

This paper describes a methodology to incorporate vague information, based upon heuristic knowledge and expertise, into the conventional probabilistic approach for the seismic hazard analysis.

The interval analysis method is introduced to process interval information with interpretation from Dempster and Shafer's evidence theory. The Vertex Method is discussed to handle fuzzy information which is a generalization of interval information.

These methods, along with the current approach of seismic hazard analysis, are used to assess the seismic hazard for the San Francisco Bay Area in California and to provide information for deciding strengthening policy of existing buildings.  相似文献   

Merging multiple precipitation sources for flash flood forecasting   总被引：3，自引：0，他引：3  

Yen-Ming Chiang  Kuo-Lin Hsu  Fi-John Chang  Yang Hong  Soroosh Sorooshian 《Journal of Hydrology》2007,340(3-4):183-196

We investigated the effectiveness of combining gauge observations and satellite-derived precipitation on flood forecasting. Two data merging processes were proposed: the first one assumes that the individual precipitation measurement is non-bias, while the second process assumes that each precipitation source is biased and both weighting factor and bias parameters are to be calculated. Best weighting factors as well as the bias parameters were calculated by minimizing the error of hourly runoff prediction over Wu-Tu watershed in Taiwan. To simulate the hydrologic response from various sources of rainfall sequences, in our experiment, a recurrent neural network (RNN) model was used.

The results demonstrate that the merged method used in this study can efficiently combine the information from both rainfall sources to improve the accuracy of flood forecasting during typhoon periods. The contribution of satellite-based rainfall, being represented by the weighting factor, to the merging product, however, is highly related to the effectiveness of ground-based rainfall observation provided gauged. As the number of gauge observations in the basin is increased, the effectiveness of satellite-based observation to the merged rainfall is reduced. This is because the gauge measurements provide sufficient information for flood forecasting; as a result the improvements added on satellite-based rainfall are limited. This study provides a potential advantage for extending satellite-derived precipitation to those watersheds where gauge observations are limited.  相似文献   

Note on sediment sorting in a sandy bed under standing water waves     

Blake J. Landry  Matthew J. Hancock  Chiang C. Mei 《Coastal Engineering》2007

We present new quantitative data on the sorting of sediments on a sandy seabed under standing waves. Starting from a flat bed composed of a homogeneous mixture of a coarse and a fine sand with mean diameters 0.11 and 0.21 mm, we observed simultaneous ripple and sand bar formation and sand sorting on the seabed. Over days of wave action, sand bars formed with crests beneath the surface wave nodes and flat plateaus flanked by mounds beneath the antinodes. Bar crests were composed of sand coarser on average than 0.21 mm, while the flat plateaus were covered by sand finer on average than 0.11 mm. Comparison with two experiments involving sand beds of more homogeneous size distributions shows that the mounds are characteristic of the motion of fine suspensions.  相似文献   

Modified Kadomtsev–Petviashvili equation for tsunami over irregular seabed     

Li  Yile  Mei  Chiang C. 《Natural Hazards》2016,84(2):513-528

We derive an asymptotic equation governing the trans-ocean propagation of tsunami from source to the continental shelf. Focus is on disturbances originated from a slender fault of finite length. The variable sea depth is assumed to consist of a slowly varying mean and random fluctuations. The method of multiple scales is used to derive a Kadomtsev–Petviashvili equation with variable coefficients. Modifications by one- and two-dimensional random irregularities are shown to affect the wave speed, dissipation and additional dispersion. The result can be used to facilitate physical insight with modest numerical efforts.  相似文献   

Local economic linkages to community‐based tourism in rural Costa Rica     

Bernardo Trejos  Lan‐Hung Nora Chiang 《Singapore journal of tropical geography》2009,30(3):373-387

This paper reports on the contribution of tourism to the wellbeing of rural residents through the development of economic linkages engaged by community‐based tourism (CBT) in rural Costa Rica. In a qualitative case study of local economic linkages surrounding one such project in Chira Island, economic linkages were assessed at two levels: discourse and practice. The findings indicate that CBT does not involve the collective property of the community, but rather, the collective property of a group of community members organized in a formal association. As a result, a discourse on local economic linkages has been promoted by CBT support organizations in which hopes of wider benefits are placed on small linkages to services and products provided by local community members. However, a field survey suggested that the economic linkages generated by CBT in the community were sporadic and polyvalent and, furthermore, that the linkages with agriculture are negatively affected by scale and seasonality, resulting in leakages out of the community. These findings caution practitioners that CBT may only have small‐scale positive impacts on the local economy.  相似文献   

Analysing the Relationship Between Typhoon‐Triggered Landslides and Critical Rainfall Conditions     

Kang‐tsung Chang  Shou‐Hao Chiang  Feng Lei 《地球表面变化过程与地形》2008,33(8):1261-1271

Many landslides are triggered by rainfall. Previous studies of the relationship between landslides and rainfall have concentrated on deriving minimum rainfall thresholds that are likely to trigger landslides. Though useful, these minimum thresholds derived from a log–log plot do not offer any measure of confidence in a landslide monitoring or warning system. This study presents a new and innovative method for incorporating rainfall into landslide modelling and prediction. The method involves three steps: compiling radar reflectivity data in a QPESUMS (quantitative precipitation estimation and segregation using multiple sensors) system during a typhoon (tropical hurricane) event, estimating rainfall from radar data and using rainfall intensity and rainfall duration as explanatory variables to develop a landslide logit model. Given the logit model, this paper discusses ways in which the model can be used for computing probabilities of landslide occurrence for a real‐time monitoring system or a warning system, and for delineating and mapping landslides. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Distribution of erosion across bedrock channels     

Jens M. Turowski  Niels Hovius  Hsieh Meng‐Long  Dimitri Lague  Chen Men‐Chiang 《地球表面变化过程与地形》2008,33(3):353-363

Lateral erosion in bedrock rivers is an important control on the shape of channel cross‐sections, and the coupling of channels and hillslopes. Recent observations link lateral erosion to the variability of flow. We propose two mechanisms to explain this. One is based on changing shear stress distributions within the channel with varying flood level, the other on the competition between cover and tool effects in fluvial bedrock erosion. We assess these processes for the Liwu River, Taiwan, and conclude that cover and tool effects dominate the partitioning of lateral and vertical erosion in this case. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Particulate carbohydrates and uronic acids in the northern East China Sea   总被引：1，自引：0，他引：1  

Chin-Chang Hung  Gwo-Ching Gong  Kuo-Ping Chiang  Hung-Yu Chen  Kevin M. Yeager 《Estuarine, Coastal and Shelf Science》2009,84(4):565-572

Carbohydrate species, such as uronic acids, play an important role in oceanic carbon cycling, coagulation and adsorption processes. Concentrations of particulate carbohydrates (PCHO) and uronic acids (PURA) were measured in the northern East China Sea (ECS) during June and November, 2006. In June, maximum concentrations of PCHO and PURA were observed in the surface layer of coastal waters. Their concentrations rapidly decreased with depth, suggesting that they are both bio-reactive. Moreover, phytoplankton abundance and bacterial biomass seem to be associated with observed PCHO and PURA concentrations in the ECS during June, suggesting that production of carbohydrate species in the ECS is regulated by phytoplankton assemblages, bacterial assimilation or degradation. In November, however, PCHO and PURA concentrations were homogenous within the water column due to strong vertical mixing. No strong correlations were observed between carbohydrate species (PCHO and PURA) and phytoplankton or bacterial biomass, suggesting that production of these compounds in November might be caused by the physiological difference between nutrient limited and non-nutrient limited phytoplankton. Furthermore, strong negative correlations between nutrients and PCHO species suggest that nutrient levels may be one of the driving forces behind the production of these compounds in the ECS.  相似文献