► The integrated modeling system proved to be a useful approach for studying the effects of urbanization on runoff and flood. ► Smaller flood event is more affected by urbanization than larger flood. ...► Floods discharges are more affected by urbanization than annual runoff. ► At daily time step modeling, flood volume is more affected by urbanization than flood peak.
This study developed and used an integrated modeling system, coupling a distributed hydrologic and a dynamic land-use change model, to examine effects of urbanization on annual runoff and flood events of the Qinhuai River watershed in Jiangsu Province, China. The Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) was used to calculate runoff generation and the integrated Markov Chain and Cellular Automata model (CA-Markov model) was used to develop future land use maps. The model was calibrated and validated using observed daily streamflow data collected at the two outlets of watershed. Landsat Thematic Mapper (TM) images from 1988, 1994, 2006, Enhanced Thematic Mapper Plus (ETM+) images from 2001, 2003 and a China–Brazil Earth Resources Satellite (CBERS) image from 2009 were used to obtain historical land use maps. These imageries revealed that the watershed experienced conversion of approximately 17% non-urban area to urban area between 1988 and 2009. The urbanization scenarios for various years were developed by overlaying impervious surfaces of different land use maps to 1988 (as a reference year) map sequentially. The simulation results of HEC-HMS model for the various urbanization scenarios indicate that annual runoff, daily peak flow, and flood volume have increased to different degrees due to urban expansion during the study period (1988–2009), and will continue to increase as urban areas increase in the future. When impervious ratios change from 3% (1988) to 31% (2018), the mean annual runoff would increase slightly and the annual runoff in the dry year would increase more than that in the wet year. The daily peak discharge of eight selected floods would increase from 2.3% to 13.9%. The change trend of flood volumes is similar with that of peak discharge, but with larger percentage changes than that of daily peak flows in all scenarios. Sensitivity analysis revealed that the potential changes in peak discharge and flood volume with increasing impervious surface showed a linear relationship, and the changes of small floods were larger than those of large floods with the same impervious increase, indicating that the small floods were more sensitive than large floods to urbanization. These results suggest that integrating distributed land use change model and distributed hydrological model can be a good approach to evaluate the hydrologic impacts of urbanization, which are essential for watershed management, water resources planning, and flood management for sustainable development.
► We conducted the case study on the hydrologic response to urbanization using SWAT model. ► Hydrological responses were different in different seasons and hydrological years. ► Urbanization and its ...impacts were more sensitive in the suburban basin close to city. ► Urbanization had a more remarkable impact on surface runoff than on total streamflow. ► Urbanization tended to increase peak discharge and flood volume.
The Main objective of the study is to understand and quantify the hydrological responses of land use and land cover changes. The Yangtze River Delta is one of the most developed regions in China with the rapid development of urbanization which serves as an excellent case study site for understanding the hydrological response to urbanization and land use change. The Xitiaoxi River basin, one of the main upstream rivers to the Taihu Lake in the Yangtze River Delta, was selected to perform the study. The urban area in the basin increased from 37.8km2 in 1985 to 105km2 in 2008. SWAT model, which makes direct use of land cover and land use data in simulating streamflow, provides as a useful tool for performing such studies and is therefore used in this study. The results showed that (1) the expansion of urban areas had a slight influence on the simulated annual streamflow and evapotranspiration (ET) as far as the whole catchment is concerned; (2) surface runoff and baseflow were found more sensitive to urbanization, which had increased by 11.3% and declined by 11.2%, respectively; (3) changes in streamflow, evapotranspiration and surface runoff were more pronounced during the wet season (from May to August), while baseflow and lateral flow had a slight seasonal variation; (4) the model simulated peak discharge increased 1.6–4.3% and flood volume increased 0.7–2.3% for the selected storm rainfall events at the entire basin level, and the change rate was larger for smaller flood events than for larger events; (5) spatially, changes of hydrological fluxes were more remarkable in the suburban basin which had a relative larger increase in urbanization than in rural sub-basins; and (6) analysis of future scenarios showed the impacts of urbanization on hydrological fluxes would be more obvious with growth in impervious areas from 15% to 30%. In conclusion, the urbanization would have a slight impact on annual water yield, but a remarkable impact was found on surface runoff, peak discharge and flood volume especially in suburban basins in the study area. The study suggested that more attention must be paid for flood mitigation and water resources management in planning future urban development in the region.
Alpine snow is an important part of the water cycle in arid/semiarid regions and has a great influence on runoff and ecosystems. In this study, both optical and passive microwave remote sensing data ...were used to characterize the vertical distribution of snow cover area (SCA) and snow water equivalent (SWE) on the north slope of Central Tianshan Mountain, northwest China, focusing on exploring the different spatial–temporal characteristics between SCA and SWE, as well as their different responses to climatic factors at different altitudes. The results show that (1) the SCA and SWE have similar vertical distribution characteristics but show different changing rates and changing directions over time at different altitudes. (2) In the snow accumulation period and snowmelt period, the correlation relationships between precipitation/temperature and SCA are the same (positive or negative) as those between precipitation/temperature and SWE at low-middle altitudes but opposite at high altitudes. (3) The influence of precipitation/temperature on SWE has a linear relationship with altitude but not with SCA. (4) The relative importance of precipitation/temperature for SCA is the same as that for SWE at different altitudes. The results illustrated the different vertical responses to climatic factors between SCA and SWE, which could be beneficial to predicting the changes in mountain snow under the climate change scenario.
Background and objective Heatstroke (HS) is a life-threatening condition resulting from thermal injury within the body, and it is associated with a significantly high mortality rate. This study aimed ...to assess the knowledge, attitudes and practices (KAP) among the general community population toward heatstroke. Methods The web-based cross-sectional study was conducted between September 2023 and October 2023 at the Emergency Department of Dongyang People's Hospital. A self-designed questionnaire was developed to collect demographic information of the general community population and to assess their knowledge, attitudes and practices toward heatstroke. Results A total of 1,356 valid questionnaires were collected. Among the participants, 875 (64.53%) were female, and 496 (36.58%) had regular exercise. The mean knowledge, attitudes and practices scores were 12.73 ± 1.42 (possible range: 0–14), 33.74 ± 2.91 (possible range: 8–40) and 34.65 ± 5.30 (possible range: 8–40), respectively. The structural equation model demonstrated that education had direct effects on knowledge (β = 0.017, p < 0.001), attitudes (β = 0.123, p < 0.001), and practices (β = −0.094, p < 0.001). Moreover, knowledge had direct effects on attitudes (β = 1.920, p < 0.001), and attitudes had direct effects on practices (β = 0.642, p < 0.001). Conclusion The findings revealed that the general community population have sufficient knowledge, active attitudes and proactive practices toward the heatstroke. However, there is still room for improvement and it is necessary to develop and implement educational initiatives and interventions designed to further enhance their KAP toward heatstroke.
In-plane shear mechanical experiments of ceramic matrix mini-composites (CMMC) were realized in this paper by overcoming the difficulties of material preparation, specimen design, gripping and ...loading, deformation measurement, etc. The in-plane shear stress-strain responses of different matrix volume fractions were obtained based on the method. The stress-strain response of CMMC was strongly non-linear, and its elastic modulus and strength were positively correlated to the matrix volume fraction. The main factors affecting the digital image correlation (DIC) based micro-region shear deformation measurement are analyzed quantitatively, and the corresponding solutions are discussed. The DIC calculation time model is established, and the accurate estimation of DIC processing time is realized. The shear strain field evolution clearly captured the matrix crack initiation and propagation.
The “seesaw relationship” between thermal conductivity and thermal expansion coefficient (CTE) in most high temperature ceramics has become an obstacle to the design of long-life multilayer ...thermal/environmental barrier coatings (T/EBC). Due to low thermal conductivity and CTE, defect fluorite type high-entropy rare earth (RE) hafnates have drawn a lot of interest for potential application in T/EBC systems. This work designs and synthesizes the (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 with comprehensive thermal performance and investigates the thermophysical mechanism from the phonon scale. In addition to the lattice distortion effect caused by the point defects of multicomponent substitutional atoms in (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7, the oxygen vacancies in the defect fluorite lattice also play a critical role in reducing the thermal conductivity. From microscopic thermal expansion behavior, the low-frequency optic phonons originated from the vibration of RE atoms are the key factors in altering CTE for hafnates. And doping smaller RE ions is beneficial for enhancing the RE–O bond strength and further reducing CTE. The results contribute to the understanding of high-entropy strategic design and suggest that (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 is a promising top layer material in the implementation of T/EBC.
Abstract
Both flood magnitude and frequency might change under the changing environment. In this study, a procedure combining statistical methods, flood frequency analysis and attribution analysis ...was proposed to investigate the response of floods to urbanization and precipitation change in the Qinhuai River Basin, an urbanized basin located in Southeast China, over the period from 1986 to 2013. The Mann–Kendall test was employed to detect the gradual trend of the annual maximum streamflow and the peaks over threshold series. The frequency analysis was applied to estimate the changes in the magnitude and frequency of floods between the baseline period (1986–2001) and urbanization period (2002–2013). An attribution analysis was proposed to separate the effects of precipitation change and urbanization on flood sizes between the two periods. Results showed that: (1) there are significant increasing trends in medium and small flood series according to the Mann–Kendall test; (2) the mean and threshold values of flood series in the urbanization period were larger than those in the baseline period, while the standard deviation, coefficient of variation and coefficient of skewness of flood series were both higher during the baseline period than those during the urbanization period; (3) the flood magnitude was higher during the urbanization period than that during the baseline period at the same return period. The relative changes in magnitude were larger for small floods than for big floods from the baseline period to the urbanization period; (4) the contributions of urbanization on floods appeared to amplify with the decreasing return period, while the effects of precipitation diminish. The procedure presented in this study could be useful to detect the changes of floods in the changing environment and conduct the attribution analysis of flood series. The findings of this study are beneficial to further understanding interactions between flood behavior and the drivers, thereby improving flood management in urbanized basins.
The accurate simulation and prediction of flood response in urbanized basins remains a great challenge due to the spatial and temporal heterogeneities in land surface properties. We hereby propose an ...integrated modelling approach that consists of a semi-distributed conceptual hydrological model and a novel parameterization strategy. The modelling approach integrates the Xinanjiang (XAJ) model, Taihu Basin (TB) model, and Nash instantaneous unit hydrograph (IUH) into a framework. Model parameters are calibrated by optimizing their relationships with corresponding physical factors. The proposed modelling approach is applied in the Qinhuai River basin (QRB), China. The modelling approach shows satisfactory performance in flood simulation both for calibration and validation of flood events in the QRB. The approach has temporal and spatial prediction capability by using the established relationships between parameter values and physical factors. Robustness analysis reveals that the different sets of flood events used for parameter relationship calibration led to similar model performance. Numerical experiments show that impervious coverage poses strong influences on the model performance and needs to be considered in flood routing simulations for small- or medium-intensity flood events.
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