Search

Since 2013, the Chinese government has issued a set of action plans catered toward the ecological civilization construction. To quantify and evaluate the ecological civilization development, this study has introduced the ecological civilization index of China (ECI), using different standardization methods (extreme standardization, single-benchmark progressive standardization, and double benchmark progressive standardization), to evaluate ecological civilization development on city-level (337 cities) of China. The issues of China's ecological civilization construction were analyzed. The evaluation results suggest that in the double benchmark progressive method, every evaluation score has its practical meaning and is therefore suitable for policy making. This study obtained an average ECI score of 61.16, for 337 cities. This is China's overall ECI score, which is classified as C-grade. Only 4.75% of cities' green environment (GE) score obtained A-grade, while 53.41% of cities' GE scored below the passing level, suggesting that the quality of the ecology and environment is neglected in the development of China eco-civilization. This study provides valuable knowledge for both the ecological and environment management and eco-civilization construction.

Air quality is one of the most critical environmental issues in Beijing, China. In this study, temporal and spatial variations in air quality in Beijing are characterised by two aggregate indexes, the air pollution index (API) and air quality index (AQI). API is calculated from PM10, SO2, and NO2 to indicate air quality before 2013. From then on, API was replaced with AQI, which is calculated from PM2.5, PM10, SO2, NO2, O3, and CO. API decreased significantly during 2001–2017, and AQI decreased significantly during 2013–2017 (p

Spatiotemporal variations of the pore-water pressure and water table response to small amounts of water exchange were measured in a sand column. In the dewatering experiment, the pressure head variation can be divided into three stages: the initial pressure head declining phase when water table is above the sand surface, a sudden drop in accordance with the capillary fringe when water level passes through the sand surface, and a slow declining phase with respect to the specific yield of the sand. As for the watering experiment of the shallow groundwater with different initial truncation factors (TF), the addition of a minute amount of water results in a rapid rise of the pressure head initially, then a gradually increase to its equilibrium. When the upper extent of the fully saturated capillary fringe coincides with the sand surface (TF ≤ 1), a thin film of water addition produces nearly instantaneous increase in pore-water pressure, corresponding to a rapid rise of groundwater table to the sand surface. Pressure head increment increases linearly with the TF value and reaches its maximum when TF value approaches unity. Considering the vertical distribution of the pressure head, its gradient becomes larger right after the water addition, then decreases to its initial value of hydrostatic condition in the end. In the case of TF > 1, there is an unsaturated layer above the groundwater table, the pressure head increases after the water addition, whose magnitude however decreases as the increase of TF value. Nevertheless, the final position of the groundwater table is still below the sand surface, and the gradient of the pressure head vertical distribution dose not vary significantly throughout the entire process. In consideration of hydrostatic pressure assumption, temporal variation of the water table was also quantitatively obtained based on the measured instantaneous pore-water pressure data, which is consistent with time-varying process of the pressure head during both the dewatering and watering experiments.

Effects of the improved seaward boundary condition on the swash zone hydrodynamics with bottom resistance are investigated using the method of characteristics. The characteristic equations including the Chezy-type resistance term are solved numerically by using the specified time interval scheme. Following Guard and Baldock (2007), the improved seaward boundary condition is introduced after incorporating a parameter k. Spatiotemporal distribution of the forward and backward characteristic lines under different bottom frictions and k parameters are specified. Large k parameter postpones the swash flow reversal time and extends the entire swash duration, which enhances/reduces the function of pressure force/bottom friction in swash hydrodynamics. During the late backwash stage, the bottom resistance effect becomes less influential with the increase of parameter k. Shoreline movement is mainly controlled by the bottom friction initially, then by gravity around the swash flow reversal, and by the joint actions of bottom friction and gravity (or hydrostatic pressure and gravity) in the case of k = 0 (or k = 1) near the late backwash stage. With respect to the entire swash duration, the flow reversal time at the shoreline, the maximum run-up height and the maximum backwash velocity, it is confirmed that the effects of the boundary condition parameter k on the swash hydrodynamics become more significant under the large bottom resistance. The present study extends Deng et al. (2016)'s work with the improved seaward boundary conditions and makes it more applicable to the actual swash process. Findings from the present study could further improve our understandings of the frictional swash hydrodynamics.

Time averaged groundwater table above the mean sea level has been observed in unconfined coastal aquifers. Several theoretical solutions were presented to investigate the groundwater table overheight (super-elevation) in response to tidal oscillations. Nevertheless, previous analytical solutions are generally limited to Dupuit-Forchheimer assumptions or a two-dimensional free surface model. In this paper, we introduced a more general condition that a three-dimensional kinematic boundary condition is considered. An exact analytical solution of the groundwater table overheight under the multi-tidal constituents was derived using the Fourier transform method. The solution shows the local groundwater table overheight is related to the mean aquifer thickness, tidal amplitude, damping coefficient as well as its positions in sand beaches. In addition, the analytical solution illustrates the simple linear superposition is not applicable to the multi-tidal components condition, whose groundwater table overheight becomes weak due to the non-linear effect of the three-dimensional kinematic boundary condition. In addition, concentrations were focused on the time averaged total flux density illustrating the groundwater exchange occurs both in the shore normal and shore parallel directions, which however is missing in the previous two-dimensional solution. Further cognitions on the groundwater circulation mechanism were also achieved, which originates from the large tidal amplitude region and fans out towards the small tidal amplitude region. These new findings are of great importance to extend our understandings of the groundwater hydrodynamics in unconfined coastal aquifers.

The accurate prediction of surge height is vitally important in designing coastal defense structures. With the advancement of computation efficiency, many researchers have studied the wave-current interaction on surge height by coupling hydrodynamic and wave models. In this study, Deflt3D Flow model was interacted dynamically with Delft3D Wave model to simulate the storm surge process caused by typhoon Khanun to obtain the spatiotemporal properties on wave setup induced by storm wind. Simulations with and without wave model have been conducted, revealing that the spatiotemporally varying wave setup distribute along the coastal line when typhoon is in the open sea with large wave height and surge height around. The spatial distribution of nearshore wave setup at landfall moment was obtained. Nevertheless the contribution of wave effects on storm surge increases slightly under intensive storm wind, with the maximum wave setup near typhoon center accounting for 10% of the peak surge height.

Developing electric ride-hailing vehicles (ERVs) is an integral part of promoting green transportation. To understand how ERVs operate, and in turn to improve their battery systems, we have developed a comprehensive, methodological framework to construct their utilization patterns and driving cycles. The methodology is based on a multi-state model (MSM). It builds one-day activity patterns of electric vehicles that belong in an ERV fleet. The driving patterns outline when (time of occurrence), for how long (duration), and under what battery conditions (state of charge) a driver typically decides to either operate or charge a vehicle. Two driving patterns, pointing toward two typical types of drivers, have been identified. By utilizing operational data in Xiamen, China, obtained from Didi Chuxing, we propose a novel method to build the first driving cycle series of ERVs, which can delineate how ERV drivers drive under the operating state. The cycle series consists of four driving cycles, synthesized by the micro-trip-based method using operational data from four time slices. Analysis against real data has shown that our method significantly outperforms existing methods, demonstrating the representativeness of the cycles.

Intensive anthropogenic impacts have been implemented in the Yangtze estuary during the last several decades, which significantly modified the global and local hydro- and morpho-dynamics. Subsequently, sediment movement characteristics in the vicinity of the Deepwater Navigation Channel (DNC) change in accordance with such human interactions. The present study is focusing on the recent sediment moving features around the DNC in between 2017 and 2019, after the elevation of the partition dike in 2016. Five successive in-situ regular campaigns for flood and dry seasons, together with field surveys pre- and post-typhoon in 2018, were conducted to collect bottom surface sediment samples. Sand and silt samples with different physical properties were identified. Under the normal weather condition, sand samples are generally found in the South Channel (SC) and the middle reach of the North Passage (NP), whereas silt samples are prevailed elsewhere. Considering the different features in the grain size distribution curve of sand samples, more attentions were paid to the spatiotemporal variations of sand samples. Grain size parameters of sand samples indicate that under the normal weather condition, relatively pure sands with almost no silt constituent exist in the SC, whereas relatively mixed sands with certain silt compositions are located in the middle reach of NP. Nevertheless, only relatively mixed sands could be found in the SC and there are no sand samples in the NP after typhoon events. Subsequently, the recent sediment movement characteristics in the vicinity of DNC were figured out. Under the normal weather condition, relatively mild siltation owing to the back-filings from the dike fields and seaward of DNC occurs in the middle and lower reaches of DNC, which is consistent with the temporal variations of the magnetism analysis of sand samples. In contrast, intensive siltation occurs inside the DNC after the extreme weather events, which comes from three possible provenances, i.e., overtopping from the south dike, back-fillings from dike fields and seaward of DNC. These findings provide some helpful information for the efficient management and reasonable regulation in the Yangtze estuary.

In the swash zone, an assessment of swash flow properties requires an understanding of swash depth and swash velocity, which can affect sediment movement, as well as the design of coastal structures. The method of characteristics provides a useful tool to model unsteady shallow water flows, such as dam-break flow, swash flow and tsunami run-up. In this paper, bottom resistance was incorporated into the nonlinear shallow water equations to extend the application of the method of characteristics to account for frictional effects in the swash zone. The new characteristic equations are solved by the specified time interval scheme. The bottom resistance has little influence on the seaward swash hydrodynamics (initial swash stage), e.g., water depth and flow velocity, while its influence becomes significant in the small water depth region near the swash front, which reduces the maximum run-up height. At a specified time and location, and comparing with a frictionless swash solution, the uprush flow velocity reduces due to the bottom resistance, while the flow velocity increases during the initial phase of the backwash owing to the earlier reversal time with the bottom resistance. However, the differences with the inviscid solution are small within the swash lens. Conversely, the maximum backwash velocity is reduced significantly as a result of the shorter duration of the backwash. Consistent with previous field observations, friction does not significantly alter the gradient of the water surface elevation and a seaward-dipping water surface elevation is observed during the majority of the swash process. The dominant effect of bottom resistance is to reduce the range of inundation, particularly with larger resistance coefficients. The incorporation of the bottom resistance extends the application of method of characteristics in the swash zone to more practical problems, particularly where run-up elevation is critically important, e.g. overtopping flows.

Recent environmental justice studies have focused on measuring access to parks for young people due to the decreasing contact with nature for outdoor activities in most developed countries. Results of these analyses reflect the disparities in accessibility better but with digress among different access models. The present study aims to explore an appropriate accessibility measurement for youth and proposes a supply-demand improved two step floating catchment area (2FSCA) method to estimate environmental justice in access to parks in developing countries. Results indicated that the proposed method could identify more underserved communities and youth population with lower mean values of accessibility compared with the traditional 2SFCA method. Spatial accessibility exhibited clustering characteristics in three scenarios wherein high-accessibility areas were clustered nearby the center along the Yangtze River with larger parks, whereas those with low-accessibility were distributed in the eastern and southern regions. Among three age groups, the 0–6 years age group had slightly higher disparity of accessibility than the 7–12 years age group and the majority of teenagers could enjoy equitable park service. Spatial correlation analysis suggested that policy strategies and housing price were the main factors influencing accessibility and several non-dominating influencing factors were also identified from surrounding land use patterns. These findings may provide a comprehensive and realistic perspective on acquainting with accessibility and availability of green space for youth and help urban planners formulate effective policies and strategies to ease spatial imbalance.

Grain size is one of the most important parameters in geology and coastal engineering. However, all traditional methods are time consuming, laborious, and expensive. In this study, the autocorrelation technique, which was first expounded by Rubin (2004), was extended to estimate the size of well-sorted sediments and the grain-size distribution of mixed-size sediments. Long and intermediate axes of well-sorted sediments ranging from 1 to 20 mm obtained from applying the autocorrelation method are compared with the corresponding results measured using a vernier caliper. Using the autocorrelation technique, the sediment mean size was calculated and was found to compare better with point counts than sieving. Regarding the mixed-size sediment, a nonlinear programming method, which is different from the conventional ‘least-squares with non-negativity’ method, the kernel density method, and the maximum entropy method, was used to obtain the representative grain sizes and associated sediment inherent parameters, such as mean diameter, median diameter, sorting, skewness, and kurtosis. Image pre-processing was used in the present analysis to enhance the contrast of the recorded image, and a conversion method applied to take into account the difference between the two-dimensional digital image method and the three-dimensional sieving method. Using the modified fitting points and the improved Gaussian function fitting method, the cumulative grain-size distribution curve and the probability density curve of the mixed-size sediments were obtained. The enhanced autocorrelation technique that was developed from the traditional ‘look-up-catalogue’ approach provided a more accurate estimation of the grain-size distribution, as well as the relevant physical parameters of the mixed-size sediment.

In the swash zone, the vertical flow of water into and out of the bed is one of the factors that may affect the surface sediment transport. To understand swash zone hydrodynamics, detailed measurements of swash front velocity were obtained in the swash zone by image analysis. During wave up-rush, surface water, in general, infiltrates generally perpendicularly into the beach and deflects direction when reaching groundwater table. Swash velocity plays a significant role in the up-rush infiltration process, which can be divided into three stages and positively related to the surface infiltration. As for the subsurface infiltration rate, it decreases rapidly and reaches a steady rate at the end. It is confirmed that swash front velocity can modify the infiltration process and its influence decreases towards the up-rush end. Calculated infiltration rates after incorporating the influence of swash front velocity into Darcy's law fit closely with the measurements.

Prototype scale physical model tests were conducted to investigate the sheetflow sediment transport of uniform sand under different skewed-asymmetric oscillatory flows with and without the presence of relatively strong currents in the opposite direction against wave propagation. Experiments show that in most cases with fine sands, the “cancelling effect” which balances the on-/off-shore net transport under pure asymmetric/skewed oscillatory flows and results a moderate net transport was developed for combined skewed-asymmetric shaped oscillations. However, under certain conditions ( T > 5 s) with coarse sands, the onshore sediment transport was enhanced for combined skewed-asymmetric flows. Additionally, the new experimental data under collinear oscillatory flows and strong currents show that offshore net transport rates increase with decreasing velocity skewness and acceleration skewness. Sediment movement behaviors were investigated through analysis of experimental data obtained from the image analysis technique and attempts were made to estimate and formulate the sheetflow layer thickness. Accordingly, sediment transport under oscillatory sheetflow conditions was studied and successfully explained by comparing the bed shear stress and the phase lag parameter at each half cycle. Consequently, these parameters were incorporated in an improved Dibajinia and Watanabe's type sediment transport model. The formula is calibrated against a comprehensive experimental data (331 in total). Good agreement obtained between predictions and measurements shows that the new formula is fulfilled for practical purposes.

In this study, unlike most previous investigations for wave-induced soil response, a simple semi-analytical model for the random wave-induced soil response is established for an unsaturated seabed of finite thickness. Two different wave spectra, the B-M and JONSWAP spectra, are considered in the new model. The influence of random wave loading on the soil response is investigated by comparing with the corresponding representative regular wave results through a parametric study, which includes the effect of the degree of saturation, soil permeability, wave height, wave period and seabed thickness. The maximum liquefaction depth under the random waves is also examined. The difference on the soil response under the two random wave types, B-M and JONSWAP frequency spectra, is also discussed in the present work.

A newly developed two-phase flow model was applied to simulate the sediment movement under 2nd-order Stokes wave sheetflow conditions with different sediment sizes and wave periods. As for the distribution of eddy viscosity and sediment diffusion coefficient, the difference between onshore and offshore phases was considered by using an equivalent sinusoidal velocity amplitude for the asymmetric velocity profile. Sophisticated comparisons between laboratory measurements [O'Donoghue, T., Wright, S., 2004b. Flow tunnel measurements of velocities and sand flux in oscillatory sheetflow for well-sorted and graded sands. Coast. Eng., 51 (11–12), 1163–1184.] and the present numerical simulation were performed for sediment concentration, sediment velocity, sand flux and net transport rate. Four existing engineering models, together with the present two-phase flow model, were introduced for net transport rate prediction. Taking both the net sand transport rate magnitude and direction into account, the present process-based two-phase flow model provided the best estimations, which can simulate both the onshore net transport for medium/coarse sand cases and offshore net transport for fine sand cases with the agreement by a factor of 2 for almost all the considered cases.