Quantitative Analysis of Urban Pluvial Flood Alleviation by Open Surface Water Systems in New Towns: Comparing Almere and Tianjin Eco-City

Increased surface runoff generated in urban areas due to larger proportion of impervious surfaces has, in many cases, exceeded the capacity of urban drainage systems. In response to such challenge, this paper introduces the quantitative analysis of pluvial flood alleviation by open surface water systems in the case of Almere in the Netherlands and compares it with Tianjin Eco-City in China, with the aim of optimizing land use planning and urban design for new urban districts. The methodology is a combination of quantitative and qualitative analysis. With the analytical tool of ArcGIS, the authors have investigated the influence of spatial distribution of surface water system on the reduction of pluvial flood risks. The conclusions include some preliminary principles: (1) a densely distributed surface water network is preferable; (2) areas farther away from water body require water sensitive spatial intervention; and (3) optimizing the allocation of different types of ground surface could contribute to pluvial flood alleviation. An alternative design proposal for a typical urban block in Tianjin Eco-City has been put forward to illustrate these principles.