Vankes Stream Valley Shenzhen

The Stream Valley project is located in the surroundings of Shenzhen in the Southern part of China. The area is of high value. The ecological values in the area must be maintained or the existing qualities must be improved if urban developments are undertaken. The effluent of water leaving the area must meet high quality levels. The quantity of water leaving the area must be kept at the same amount. Building

activities should minimise their impact, both during the building period as afterwards and if road are build eco-crossings must be provided to ensure the richness of biodiversity (Bing et al., 2008b).

2.9.3.1 Climate Change Effects

Shaped by the subtropical marine climate, Shenzhen has a mild climate as well as plentiful sunshine and rainfall all year round. The measured temperature is 22.4°C on average. However it should perhaps be noted that Shenzhen is located at the estuary of the Pearl River and is therefore an area, which is often influenced by typhoons. Generally the most significant typhoons occur from May to December and especially from July to September. The annual rainfall is 1900 mm, of which 75% is falling between May an September. The differences between the seasons indicate extraordinary circumstances in the project area of Stream Valley. Abundant growing circumstances, combined with a high runoff of rainwater and steamy air are present in summer, while a shortage of water and less abundant circumstances characterise the winter period. These basis climatic differences lead to extremely high ecological qualities.

Based on the meteorological data during 1953-2004, the characteristics of climate change in Shenzhen in the recent 50 years are studied. The temperature is increased. The warming rate is larger in summer and autumn. The increase in temperature at night is larger, which means that the daily temperature ranges become smaller, particularly in autumn and winter. The lowest temperature increases as do hot days. Precipitation days, sunshine times and relative humidity are decreasing. The main concern in this area is that the differences between summer and winter increase. Differences in temperature and precipitation increase. For the project area this means that the hot summers become warmer and the runoff water leaves the area at a rapid pace. The winters are dry and there is almost and lesser water available. These circumstances lead also to a decreasing biodiversity. Especially the steep slopes in the area are under pressure due to heavy showers in summer or the absence of water in winter.

The expected changes in climate are incorporated in the design for the project area. Measures are taken to slow down runoff water in summer. This is meant to store more water in the project area than currently in order to have water available in the dry winter period. Water in the public space has also a cooling effect in the urban environment, which is desirable if temperatures are rising in the future. The vulnerable ecology in the area profits also from apparent water, both in summer as winter. The land degradation of the hillsides needs to be stopped by planting and water deliverance, but also by taking care of valuable ecology during the building activities.

2.9.3.3 A Short History of Stream Valley

Before 1998 the area was occupied with low-scale agricultural activities. In 1998 the farmers, who owned the area were removed. Between 1998 and 2004 the ecological quality improved a lot, because of the absence of human activities. In 2004 Vanke got the right to build sparsely (120 houses) in the area. But in 2005 national regulations prohibit building developments in ecological valuable areas like Stream Valley. This dilemma of the right to build and at the same time the impossibility to build the area is only to solve if the building activities prove to be able to improve the ecological and water system qualities.

2.9.3.4 Ecology

The ecological system shows a clear distinction between the southern, uphill areas and the northern, downhill area. The ecological qualities are strongly linked to the water system and the year-round availability of streaming water. The ecological developments differ between the northern and southern slopes. The northern slope has a relatively low quality and is degraded. Grassy plants overgrow the northern slope bit by bit and lead to a decreasing quality. This natural process is difficult to stop and turn into an ecological emergent system. Removal of the grassy plants might not be a good idea because removal will lead to slide of the uphill plants, leading to erasure of all ecological qualities. The creation of wet and stable habitats uphill might be a better solution. These 'hotspots' are able to function as centres of dispersion and feed the other areas on the hill. The southern slope is ecologically much richer and more in balance. Even here, the creation of these hotspots may support the ecological system.

2.9.3.5 Water System

The natural qualities in the project area are dependent on the availability of water. The water in the area has also a regional function. After leaving the project area it feeds the drinking water reservoir (Fig. 2.36). The drinking water reservoir depends on the Stream Valley water. Therefore it is important that the amount of water from Stream Valley stays at least the same as now.

The water-function at the project level is based on the existing altitudes and slopes. The water storage and retention is best done at the lower and flat areas. Runoff water, feeding the streams, is located uphill. This typology of natural functions may be used to increase the future sustainability within the project-area.

There is a big difference between the summer and winter period (Fig. 2.37). The summer period is wet and humid. Almost all rain falls in this period. The winter period is less warm and dry. Precipitation in this period is low or absent. This has consequences for the project area. In summer there is more water available in the project area. Currently this water is transported rapidly from the area towards the drinking water reservoir or further away. To prevent the streams from flooding the water is discharged as quickly as possible. In winter period the water level drops and

almost no water is discharged anymore. By the end of the winter period (in May) the water level is lowest and the area no longer functions as a resource for the drinking water reservoir. The shortage at the end of winter leads to a decreased water quality. The shortage of water in winter is flushed away during summer. It is proposed to store more water in summer in order to keep enough water in the system for the winter.

Fig. 2.37 Amount of water in summer (left) and winter (right) (Source: Bing et al., 2008b)

2.9.3.6 Conceptual Suggestions

If the central objectives of storing more water in summer and increase the overall biodiversity are met, the area is prepared for future climate change and an interesting area with high qualities can be realised. Because the area is very vulnerable a strategic approach is chosen. In this approach the measures, which restore the natural qualities of the water and ecological system are realised before any building activities take place. Even if buildings are realised, they should be kept foot-loose from the underlying natural system of water, soil and ecology. In Fig. 2.38 this strategy is visualised.

The central stream is the main structure in the valley. In order to increase the storage capacity at several places ponds and lakes may be created, which slow down the discharge speed in summer and preserve water for the drier winter period. The water flows from the hillsides towards the central stream. In order to keep these side streams intact there should be created enough space to let these streams function undisturbed. There should be as much as possible side streams and every building activity should respect the required space. The side streams also store and slow

Fig. 2.38 Step-by-step development of Stream Valley (Source: Bing et al. 2008b)
Fig. 2.39 Cross-sections of possible measures to slow down runoff water (Source: Bing et al., 2008b)

down runoff water. In order to slow down the runoff rocks might be positioned in both central and side streams (Fig. 2.39). Where ever small flat spaces can be found half way uphill storage ponds can be realised. These ponds not only store water, but function also as ecological hotspots. Water is essential to increase biodiversity and especially in dry winter periods these ponds function as ecological centres. These ponds can be realised by positioning groups of rocks in the side streams. Water, which runs off the hill, can be cleaned extra in a natural way. Even if the water that runs off the hill is very clean already, the introduction of natural wetlands before water from side streams enters the central stream may be encouraged. This way the quality may increase even more, anticipating on potential developments later on, which may decrease the quality of runoff water. If wetlands are created before any building activities take place, the area anticipates on future developments. Later on, water from roads can be cleaned in these, already functioning, wetlands. This improved water and ecological system shall be realised before any building activity takes place in the area. After realisation of this ecological improved situation a minimal impact road may be constructed and the first houses can be built. The houses should be build in a way that they minimise their impact, during building and afterwards, on their environment. This can be realised by lifting the houses above the landscape and construct them on one pole/column (Fig. 2.40). It is suggested to

Fig. 2.40 The house like a tree in the landscape, connected by a bridge and the chimney effect (Source: Bing et al., 2008b)

start the phasing at the northern slopes, because the ecological value at that hillside is relatively low. By doing so, the building process can be stopped any time. The most valuable parts of Stream Valley are occupied latest.

The construction of the houses with minimal impact on the landscape and ecology and improving sustainability in comfort and energy use at the same time can be visualised in several steps. The house is built on one pole like a tree and connected with the road, above the houses, with a bridge. The house provides shade beneath it on the hillside. Within the houses natural ventilation through the so-called chimney effect is reached.

Water and electricity is provided from the road and the sewage system is organised through the pole. The required amount of external electricity is minimised by the provision of PV-panels on the roofs (Figs. 2.41 and 2.42).

Fig. 2.40 The house like a tree in the landscape, connected by a bridge and the chimney effect (Source: Bing et al., 2008b)

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