The Longhu Project Chongqing

The Longhu project is located just outside the built up area of Chongqing, China. It is part of a widespread development zone, where living areas are combined with amenities, infrastructure and recreation (Bing et al., 2006).

2.9.1.1 Climate Change Effects

Chongqing is located in the transition area between the Qinghai-Tibet Plateau and the Middle-lower Yangtze Plain. It is part of the humid sub-tropical monsoon climate belt. The annual average temperature is 18-20°C with a low temperature of 4°C in winter and a high temperature of 40°C in summer. Chongqing is also a fog city that has about 100 foggy days a year usually in spring and summer. Chongqing receives abundant rainfall, averaging about 1000-1400 mm annually. It has plenty of evening rain all year round, but most of it falls in summer.

The effects of climate change in the region are expected to show an increase in number of hot days in summer. This will eventually lead to higher impact of heat island effects in urban areas. In the summer period the rainfall is predicted to decrease, which will, in combination with lesser snowfall in the Tibetan mountains, leading to lower water levels and droughts in summer. More farmland becomes too dry to cultivate and the aces to drinking water becomes for more people a problem. Due to droughts ecology will meet difficulties in surviving these hot and dry summers and biodiversity decreases.

2.9.1.2 Analysis of the Site

The landscape pattern is very rich: A diffuse network of hills, slopes, flat areas and curving routes can be distinguished in the site. There is a large difference in altitude between the northern and southern part of the site. The steepness of the slopes varies largely. A highly differentiated and fine mazed water system exists in the area. The water is slowed down in many steps. By putting open or close down little dikes or stones the water is kept or transported to the next field. Finally, the water is used over and over again for many different purposes, production of crops, washing clothes, etc.

In order to meet the difficulties caused by climate change a combination of measures are integrated in the plan. The increasing droughts and the heat island effect in summer as well as the decrease of biodiversity are seen as combined problems, which are solved by using the natural circumstances optimally: the existing water-bodies in the area are used to keep rain water as long as possible in the project area and have a cooling effect on the urban spaces, the hills and plains are used to create natural ventilation in order to minimise temperature rises and the different expositions of slopes are the base for an enriched ecology, which has a cooling effect on the city also.

2.9.1.4 Water-Bodies

The large amount of existing water-bodies in the project area cause a very flexible system. If much water is available it can be directed to many different places and kept in the area. If the landscape is transformed to an urban area, the water-bodies can be adjusted, but not minimised or removed. If they stay in the area the resilience can be kept at a high level. The water-bodies function as a system that is able to incorporate large amounts of water and the water can be kept for a long time in the project area, thus being available in dry summers. The water-bodies are also capable of mitigating the urban heat island effect, which is due to increase if the area is urbanised and the number of hot days is increasing

2.9.1.5 Natural Ventilation

During summer the site can get warm and sticky and the number of hot days is increasing in the future. The urban heat island effect will increase if the site is urbanised. The most natural way of cooling and ventilation is to create winds and ventilation in the area. This can be done by the positioning of buildings (in between he building stronger winds occur there occur, which create ventilation) or by implementing green walls.

The most common wind direction is from the Northwest. Positioning of high-rise buildings (Fig. 2.23) at this side of the area will lead to stronger ventilation in the northern part. Positioning of buildings at the edge of the site (located just at the top edges of the steepest slope) results in the same effect for the lower parts of the area. If a green belt is positioned at the edge (Fig. 2.23), the same effect is reached and it also adds more humidity to the air. If high-rise buildings are added at the bottom plateaus a cool breeze will occur in the stickiest parts of the site. Introduction of this natural ventilation does not increase energy use and mitigates the urban heat island effect.

Fig. 2.23 Increasing natural ventilation by positioning of buildings (left) and by introduction of a green belt (right) (Source: Bing, et al. 2006)

Positioning of buildings to improve the natural ventilation increases the readability of the landscape also. As a result of this the highest buildings are located at the highest altitudes, and lower buildings at the lowest places of the site. Different living environments emerge: On and In the Water-living, At and On the Slope-living, Water-garden-living and Living with a view (Fig. 2.24).

2.9.1.6 Biodiversity

In order to withstand a decrease in biodiversity the main element is to deal with droughts. Therefore, the ecological qualities and the water elements show a strong connection. If there is not enough water the ecological qualities will be different. Based on the existing landscape four different qualities are defined (Fig. 2.25):

1.0 A balanced eco-aquatic ecosystem. Clean water provides fish and water-plants with enough air and water at flat plains. Water is kept here as much as possible to provide wet circumstances in dry periods;

2.0 The ecology of slopes: these gradients are positioned in the middle of residential areas and buildings. Park-like gardens with water-basins form an ecology, which can be used by inhabitants;

Steep-slope ecology: at the steep slopes the water is running down quickly in the form of waterfalls. Grasses and mosses fill the slopes with vegetation. Humid and fresh circumstances attract specific birds, reptiles and insects;

4. Fagades-ecology: green building walls provide subtropical birds and insects with appropriate habitats.

2.9.1.7 The Elements: How and Where Positioned

The water bodies, ecological elements and green belts and building blocks are positioned in relation with each other and are based on the differences the existing landscape has to offer. The gradients and slopes direct the possibilities for the creation of water, natural ventilation or biodiversity. The intensity of altitude lines gives an estimate on the steepness of the slopes in four categories (flat, slow, steep and very steep) and the slopes direct the water system (Fig. 2.26). Is it possible to store the water at a certain place or is it running down. Stagnant water is apparent in the flat areas. Only when enough water is available or dikes are opened the water is transported to the neighbouring area. Slope categories two and three contains running

Fig. 2.26 Intensity of altitude lines, slope types and the water system (Source: Bing et al., 2006)
Fig. 2.27 Two climate adaptive models (Source: Bing et al., 2006)

water, but at a slow pace. The water at the steepest slopes is running down like waterfalls. Thus, every slope-type is connected with a specific water type.

2.9.1.8 Models

Based on the landscape and water system different models can be developed (Fig. 2.27). The first model reserves building sites next to the brooks and water-bodies. The buildings are surrounded by green, which is planned at the edges of the water. The second model combines building zones with the water system. Building structures are positioned on and across the water system. Both models are able to react and anticipate on future changes in precipitation, natural conditions and rises in temperature.

2.9.1.9 Integrated Water System

Based on the natural water system the scheme for the different water-flows can be derived (Fig. 2.28). In this scheme the water, which is discharged from the roads (purple) is cleaned with a different technique than water from the baths and showers (orange) or from ponds (green).

2.9.1.10 An Integral Model: Rough Zoning Plan

The models and ideas are integrated in one integrated vision on the site (Fig. 2.29). The building zones are projected between the natural water-structures. The residential areas are located at the slopes and the high-rise buildings are projected at the flat plains. Two car traffic routes connect the different building areas: one through the higher northern part and one cul-de-sac in the lower southern area. In the centre of the area the major amenities are placed and are combined with a green belt that provides the lower parts with natural ventilation. The site is able to store as much water as possible in the fine mazed water system and the differences in slopes are used to create different ecological typologies. Both natural ventilation, the ecological spaces as well as the water-bodies provide the area with a cooling effect. Thus, the expected droughts and increase of the number of hot days are dealt with in an integrated manner.

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