Sponge City
The Spatial Optimization of LIDs Based on SWMM and NSGA-II Algorithm: A Case Study of a Residential Group in Tongzhou District, Beijing
As an important component of cities, the improvement of residential area’s stormwater system is of significance to sponge city construction. Although studies and discussions have been carried out by scholars around the world on low impact development (LID), but there is still lacking the comprehensive assessment and spatial optimization of the LID facilities. This paper focuses on the planning and spatial optimization of LID in a residential community in Tongzhou, Beijing. SWMM is selected as the monitoring tool, and NAGS-II algorithm is used for multi-objective optimization. By establishing the SWMM model of the community, the scale and location of the LID facilities are used as determinant variables, and the cost, flow volume and annual load of typical pollutants are calculated, analyzed, and compared. The approach could simulate and deliver pareto solutions for optimized layout of LID, which provides theoretical foundation and methodological reference for the comprehensive assessment of LID, and offers empirical evidence for urban planning under sponge city concept. This paper aims to improve the science and rationality of the comprehensive urban planning, and to solve the water problems faced by the city at this stage.
The LID database
中国开展城市雨洪管理研究起步较晚，在海绵城市建设中可参考借鉴的本地化数据不多。在开展“面向径流减控与污染削减的海绵设施空间优化技术研究”的过程中累积了大量的海绵城市径流控制设施建设和运行阶段的数据，为了更好利用这些数据支持我国海绵城市的建设，本研究初步构建了一个海绵城市径流控制设施数据库。首先分析了我国海绵城市试点建设中源头径流控制设施相关数据的实际情况，完成了海绵城市源头径流控制设施效能数据库的需求分析，进而通过概念设计、逻辑设计和物理设计三个步骤，设计了一个结构清晰、管理方便、执行效率高的海绵城市径流控制设施数据库。该数据库主要分为径流控制设施、研究区域、监测站、监测事件和监测数据五个实体集，包含45张表格和上千条字段属性。后续通过中国海绵城市径流控制设施数据库的建设，可以为海绵城市径流控制设施的效能评估、运营维护和成本效益分析提供数据支持，服务于海绵城市的规划设计和建设。
Quantifying the usage of small public spaces using deep convolutional neural network
Small public spaces are the key built environment elements that provide venues for various of activities. However, existing measurements or approaches could not efficiently and effec- tively quantify how small public spaces are being used. In this paper, we utilized a deep con- volutional neural network to quantify the usage of small public spaces through recorded videos as a reliable and robust method to bridge the literature gap. To start with, we deployed photographic devices to record videos that cover the minimum enclosing square of a small public space for a certain period of time, then utilized a deep convolutional neural network to detect people in these videos and converted their location from image-based position to real-world projected coordinates. To validate the accuracy and robustness of the method, we experimented our approach in a residential community in Beijing, and our results confirmed that the usage of small public spaces could be measured and quantified effectively and efficiently.
Benefits of coupled green and grey infrastructure systems: Evidence based on analytic hierarchy process and life cycle costing
Green infrastructure complements grey infrastructure to provide effective urban stormwater management. Design of coupled green and grey infrastructure systems need a systems-based analysis considering multiple criterion. This study used analytic hierarchy process (AHP) and life cycle costing (LCC) to evaluate environ- mental and economic benefits of various types of coupled green and grey infrastructure systems. AHP results showed that, based on the local conditions and characteristics, the coupled green and grey scenario with green space, permeable pavement, green roof, and stormwater detention cell performed better than other scenarios in urban residential drainage and flood control. Also for the coupled green and grey scenario, the simulation results showed that no flooding was occurred during the ten-year return period rainfall. Coupled green and grey in- frastructure scenarios can save the life cycle cost up to 94% compared to the traditional grey infrastructure scenario considering the design, construction, operation, and maintenance stages. Approximately 13% of commercial loan interest (1.03 million USD) can be saved for homebuyers. In future, urban designers and de- velopers should consider the optimization of coupled green and gray infrastructures system under multiple criterion for the environment, economy, and safety benefits.
Progress on environmental and economic evaluation of low-impact development type of best management practices through a life cycle perspective
A rapid progress of low-impact development type of best management practices for urban storm water runoff quantity and quality control at a global scale has occurred in the past decade. In-depth research on low-impact development type of best management practices as useful technologies and measures to control stormwater runoff is being conducted worldwide. This paper presents a literature review of the environmental and economic evaluation of low-impact development type of best management practices through life cycle perspective. Research gap and future agenda are also proposed. Results show that life cycle assessment or life cycle cost analysis for low-impact development type of best management practices are widely documented. However, certain challenges still exist. Most works involved only onsite or facility scale or just considered certain environmental effect aspect. In addition, the lack of onsite monitoring data of water quality and quantity affects further research on low-impact development type of best management practices evaluation. In most emerging and developing countries, low-impact development type of best management practices implementation is still in the start-up stage. Quantitative life cycle assessment or life cycle cost analysis studies of low-impact development type of best management practices can provide necessary and useful information for decision-makers in regional scale low-impact development type of best management practices arrangement. Low-impact development type of best management practices database based on specific regions should also be established to support further in-depth research. Finally, low-impact development type of best management practices can offer various benefits to urban eco-systems. Researchers should provide a combination of environmental, economic, and social benefits of low-impact development type of best management practices to fulfill sustainability.