Built Up Regional Green Infrastructure, Carry On the Smart Planing and Design-Stormwater Management in Planning Scale

In recent decades, the waterlogging issue result from stormwater became a severe hazard all over the world. Its degree intensified and frequency increased. To a large extent, the human activity is the key reason to the change of hydraulic functions. On the one hand, modern city construction resulted in an increased rate of impervious surface and artificial facilities, making the city's comprehensive runoff coefficient elevated and runoff volume enlarged. On the other hand, the high-intensity of human behavior exerted a strong disturbance on natural water cycle, beyond the regulatory capacity of the urban system in a certain time & space range. Namely, the limited rainfall tube-wells are vulnerable when the runoff volume climax to the peak in a short time. The reduced urban river & lake area would compress water convergence path and buffer space. A large area of continuous hardened underlying surface blockade the runoff infiltration process and result in a large scaled partial ponding. The simple & fast discharge pattern has changed the intensity and capacity of water drainage in the dimension of time & space. Water diversion canal, channel & pipeline and other manual routing disturbed the natural process considerably, such as runoff production, runoff gathering, runoff inflow, runoff infiltration, etc.

The current stormwater treatment strategy is mainly relied on the artificial engineering measures, the so-called gray infrastructure approach. (Gray Infrastructure) These measures are featured by a series of construction work ranged from the open channels, culverts, confluent/diffluent underground pipe network systems to the dikes, pumping stations, gated buffers, reservoirs and regulatory deep tunnels. All these serve for the only goal of quick discharge. But the continuously refining international concepts like BMPs, LID, WSUD, GSI, etc., all have emphasized on natural & ecological stormwater treatment strategy and highlighted in fully using all kinds of natural elements on site, particularly, green space, water body, wetland and wasteland, farmland, etc. To achieve runoff infiltration, retention, regulation, storage, purification and utilization through the soil and plants, and to tackle the stormwater issue in this manner, all these could be called green infrastructure approach. (Green Infrastructure)

Set out from the human settlement-environment demand of existence and development, binary water circulation and gray are both required to be taken into account. But in order to meet our own needs, people are more concerned about the artificial circulation for a long time. When confront with water source, only ask for, not contribute in, only alter it, not adapt to it. And in the face of water-related disasters, people are excessively depended on the gray infrastructure to ensure the security. The crucial task at present and in the future focuses on leaving enough space for the natural hydraulic cycle and path. Although the urban environment of high-density is dominant by artificial engineering & technical construction work, we should try our best to balance and coordinate the relation between artificial water circle and natural water circle. China published Technical Guide of the Sponge City Construction in October 2014 after Chinese cities suffered seriously from waterlogging, Started up with the declaration of pilot cities, and brought the waterlogging problem into the public concern and advocated nationwide action. The concept of Sponges City means the city can act like a sponge, to be resilient and flexible enough to adapt to the climate change and natural hazards. The city can absord water, store water, infiltrate water, purify water when it rains, while release the conversed water and utilize the water when it in need.

In a macro view of perception, the fundamental objective of Sponge City construction is to coordinate the contradiction between artificial water system and natural hydrological network, to reach to a balanced situation between altering natural water cycle and conforming to it, in this way to obtain the comprehensive benefits from water security, water resources and water ecology. Green infrastructure approach, undoubtedly, is the key strategy to build Sponge City. But it's difficult to coordinate the conflict among the water recycling process, regional land use and space layout. For green infrastructure, it can be regard as a greening, ecological, environment-friendly, and low-carbonized process towards the current grey engineering infrastructure. For instance, attach and strengthen the green elements' ecological-service function to the roads, bridges, riverbanks, pipelines, and even buildings. It is also refer to the continuous & systematic basic green spatial structure, include all kinds of green factors characterized by the infrastructural (fundamental and structural) significance, just like rivers, wetlands, woodlands, coastal banks, green parks, mountains and so on. They are all multi-level, complex, flexible, resilient and adaptable. In general, green infrastructure approach is an appealing, integrated and open strategy, which can inspire people to reflect on the relationship between people and land. But also a feasible and scientific strategy, which can guide the specific action and practice in the spatial dimensions (such as shape, size, boundary, etc.

In the terms of storewater management function, the direction of green infrastructure construction we could put effort in includes: (1) watershed management, ecological restoration, water conservation, soil & water conservation and comprehensive utilization of regional water resources (2) urban water system planning and lakes &rivers ecological restoration (3) urban ecological drainage and stormwater management system planning; (4) City waterfront & port area development and green city design; (5) urban wetlands, lakes and other open water space recreational landscape planning, etc.

In recent years, as a kind of integrated and innovative water study and design theory, landscape hydrology has gained a wide attention. The theory aims in discovering more knowledge and methods from the intersection of water science, ecological science, design and other disciplines. Instead of simply realize the embellishment &beautification of the landscape, the study dedicated in analyzing various types of hydrological phenomena &problems through the dynamic water relation mode of process-structure-function. We should establish a rational science-based water master design philosophy, in order to accomplish a comprehensive strategic solution to the water problem. In this way, the theory can be used as the guiding methods in the regional green infrastructure construction.

Therefore, the core idea of stormwater management in the urban plan scale was replaced by built up the regional green infrastructure, and move towards the smart plan &design. The outstanding cases over seas and at home in this chapter, illustrated &interpreted the above-mentioned objectives, strategies and practices incisively in the aspects of disparate visual angles, different regions and various types. They all reflected a breakthrough in the traditional green space system planning and land use planning. On the one hand, these cases have blurred the boundary of traditional green space. It considers the green ecological space protection and e stormwater management demand from a multi-scale, multi-level and multi-functioned view. On the other hand, these cases made a breakthrough in the planning concept, methods and techniques. Transform a passively remained meaningless blank-land into a cultural landscape system with its own hydraulic and ecological process, function and structure. Apart from this, negative protection &conservation, was replaced by positive management &practice. The impact on spatial development patterns and urban construction methods, have changed human' attitudes and behaving manners toward the surface space utilization on earth. There's an intrinsic link between the newly-emerged concepts domestically and internationally in recent years, namely, smart growth, anti-planning, landscape urbanism, etc.

Liu Hailong

Sep.2015

(Translated by ZhangXu)