Hydrological Problem during Urbanization Process

With the rapid economic and social development, China is in rapid development period of urbanization now. Urbanization is an inevitable trend of mankind development, and is also a necessary stage of a country moving toward modernization. The rapid development of urbanization has a major impact on urban hydrology. Urban hydrologic environment, hydrologic element, water resources and water quality were discussed in the pa- per. Based on the analysis of urban hydrological effect, from the angles of subject development and application, corresponding countermeasures and outlook of the urban hydrology problem were put forward. The research can provide support for reasonably planning and designing urban flood control and drainage systems to promote urban environment-friendly development, having certain practical significance.

Water dissipation mechanism of residential and office buildings in urban areas

Indoor humidity directly impacts the health of indoor populations. In arid and semi-arid cities, the buildings indoor humidity is typically higher than outdoors, and the presence of water vapor results from water dissipation inside the buildings. Few studies have explored indoor humidity features and vapor distribution or evaluated water dissipation inside buildings. This study examined temperature and relative humidity （RH） changes in typical residential and office buildings. The results indicate a relatively stable temperature with vary range of-4-1~C and a fluctuation RH trend which is similarly to that of water use. We proposed the concept of building water dissipation to describe the transformation of liquid water into gaseous water during water consumption and to develop a building water dissipation model that involves two main parameters： indoor population and total floor area. The simulated values were verified by measuring water consumption and water drainage, and the resulting simulation errors were lower for residential than for office buildings. The results indicate that bathroom vapor accounts for 70% of water dissipation in residential buildings. We conclude that indoor humidity was largely a result of water dissipation indoors, and building water dissipation should be considered in urban hydrological cycles.

Network Structure Optimization Method for Urban Drainage Systems Considering Pipeline Redundancies

Redundancy is an important attribute of a resilient urban drainage system.While there is a lack of knowledge on where to increase redundancy and its contribution to resilience,this study developed a framework for the optimal network structure of urban drainage systems that considers pipeline redundancies.Graph theory and adaptive genetic algorithms were used to obtain the initial layout and design of the urban drainage system.The introduction of additional water paths(in loop)/redundancies is suggested by the results of complex network analysis to increase resilience.The drainage performances of the urban drainage system with pipeline redundancies,and without redundancies,were compared.The proposed method was applied to the study area in Dongying City,Shandong Province,China.The results show that the total overflow volume of the urban drainage system with pipeline redundancies under rainfall exceeding the design standard(5 years) is reduced by 20-30%,which is substantially better than the network without pipeline redundancies.

A new strategy for integrated urban water management in China：Sponge city

Urban water-related problems associated with rapid urbanization, including waterlogging, water pollution, the ecological degradation of water, and water shortages, have caused global concerns in recent years. In 2013, in order to mitigate increasingly severe urban water-related problems, China set forth a new strategy for integrated urban water management(IUWM) called the "Sponge City". This is the first holistic IUWM strategy implemented in a developing country that is still undergoing rapid urbanization, and holds promise for application in other developing countries. This paper aims to comprehensively summarize the sponge city. First, this paper reviews prior studies and policies on urban water management in China as important background for the sponge city proposal. Then, the connotations, goals, and features of the sponge city are summarized and discussed.Finally, the challenges, research needs, and development directions pertinent to the sponge city are discussed based on investigations and studies conducted by the authors. The sponge city in China has a short history—given this, there are many issues that should be examined with regard to the stepwise implementation of the Sponge City Programme(SCP). Accordingly, the authors perceive this study as only the beginning of abundant studies on the sponge city.

Amplification of Flood Risks by the Compound Effects of Precipitation and Storm Tides Under the Nonstationary Scenario in the Coastal City of Haikou,China

In the context of climate change,coastal cities are at increased risk of extreme precipitation and sea level rise,and their interaction will aggravate coastal floods.Understanding the potential change of compound floods is valuable for flood risk reduction.In this study,an integrated approach coupling the hydrological model and copulabased design of precipitation and storm tides was proposed to assess the compound flood risk in a coastal city—Haikou,China.The copula model,most-likely weight function,and varying parameter distribution were used to obtain the combined design values of precipitation and storm tides under the nonstationary scenario,which were applied to the boundary conditions of the 1D-2D hydrological model.Subsequently,the change of the bivariate return periods,design values,and compound flood risks of precipitation and storm tides were investigated.The results show that the bivariate return period of precipitation and storm tides was reduced by an average of 34%under the nonstationary scenario.The maximum inundation areas and volumes were increased by an average of 31.1%and 45.9%respectively in comparison with the stationary scenario.Furthermore,we identified that the compound effects of precipitation and storm tides would have a greater influence on the flood risk when the bivariate return period is more than 50 years,and the peak time lag had a significant influence on the compound flood risk.The proposed framework is effective in the evaluation and prediction of flood risk in coastal cities,and the results provide some guidance for urban disaster prevention and mitigation.