Sponge Design

Abstract

Water is cherished as treasure in traditional Chinese culture and expected to stay in harmony with human. However, the disharmony between water and urban life is looming especially after over thirty-year rapid urbanization in China with notable global climate change. Faced with water-related issues, e.g. flooding, water pollution, water shortage, etc., Government of China initiated a so-called Sponge City Program (SCP) in 2014 for constructing ‘sponge-like’ water-resilient cities. Nevertheless, challenges and gaps lie in practice of SCP, one of which is that an operationalizable design approach of a sponge city to realise its multiple objectives is neither available in current guidelines, nor thoroughly studied or proposed in recent literatures.
The aim of this master thesis was to formulate an improved approach, as well as to improve planning & design framework for supporting integrated sponge design process and enhancing the involvement of various stakeholders. Literature study, the study of current guidelines and sponge plans of Nanjing, and interviews with sponge city practitioners were performed to evaluate current Sponge City (SC) concept and assess SC planning & design practice. Analysis of SC concept development showed that SC has been evolving from a term mainly describing measures with ecological benefits towards a more inclusive urban development paradigm, considering not only water ecology, but also water safety, water environment and water resource. Analysis on SC practice identified the gaps in current SC water management contents, including a lack of design method for calculating storage capacity against pluvial flooding, ignorance of extreme drought assessment, missing groundwater management, etc. Challenges that might impede comprehensive sponge city planning & design process were also enumerated, including data availability and accessibility, the bond between SC and other sector plans, etc. 
Based on the identified challenges and gaps, improvements on current planning & design practices were given and a new design approach was proposed, including changing collaboration method, introducing a co-design workshop and using a sponge design toolbox to facilitate planning & design process. The approach provided a method to calculate the required sponge capacity for not only preventing flood damage but also mitigating water shortage in dry spells, as well as quantifying other co-benefits. The improved design approach was tested by a case study in Nanjing, in the Qinhuai District sponge city planning project. Case study results showed that most steps in the proposed design process were successfully taken in Qinhuai project, and the toolbox was able to facilitate planning and design of sponge measures to have functions not only for pluvial flooding prevention and control, but also for water shortage mitigation, ecological benefits and other day-to-day values. The design process also demonstrated the collaborative contribution to a sponge city plan from water managers, water engineers and landscape architects. Therefore, the new design approach can contribute to a more integrated SC planning and design.