Ecological Landscape Planning and Design of Zhuxi River in Chongqing

Guoqing LI, Jie ZHU, Guohua WU

1. School of Architecture and Urban Planning, Chongqing University, Chongqing 400030, China; 2. Municipal Garden Engineering Co., Ltd. of Power Construction Corporation of China, Chongqing 401121, China; 3. Key Laboratory of New Technology for Construction of Cities in Mountain Area, Chongqing University, Chongqing 400044, China; 4. Chongqing Municipal Engineering Design & Research Institute, Chongqing 400023, China

Abstract Based on the theories and methods of ecology, landscape architecture and water conservancy, combined with the current status of the ecological environment of Zhuxi River in Chongqing, ecological environment protection, landscape space shaping and river culture creation are determined as the core of the design. Based on the design concept of ecological landscape restoration, river ecological protection, waterfront landscape layout, cultural shaping, wetland construction, sponge city construction, etc. are proposed. The design and construction of the Zhuxi River ecological landscape will effectively improve its ecological environment and help to shape a good social and economic environment. This is a useful exploration in the practical application of domestic river ecological landscape design research.

Key words Zhuxi River, Eco-landscape, Design

1 Introduction

China’s urban waterfront landscape construction started late and faces the severe situation of tight resource constraints, serious environmental pollution and ecosystem degradation. Due to unique topography and other features, the mountain waterfront area is more sensitive and fragile, and its spatial form is more complicated. How to make full use of the unique advantages of mountain water resources in urban development and construction to create a spatial environment[1], how to deal with the damage of urban expansion to the waterfront ecological environment, and how to build a riverside ecological landscape environment with distinctive characteristics and a significant cultural atmosphere,etc. have become important issues currently faced by landscape builders[2]. In recent years, with the rapid development of urban construction, landscape design and practice on the waterfront have become commonplace, but from a practical perspective, there are mainly the following problems. (i) The obvious artificial traces such as large excavation and large filling have destroyed the original ecological environment, or design about ecological environment protection lack systematic planning and design[2]. (ii) The design content is the same, lacking obvious theme characteristics and cultural precipitation, and lacking in-depth thinking about project characteristics and local culture[3]. (iii) The characteristics of mountain waterfront space have not been mastered sufficiently, and meticulous design is absent, making it impossible to meet basic functional requirements, such as drainage[4]. In this article, taking the ecological landscape design of Zhuxi River in Chongqing as an example, the ideas and strategies of mountain riverside landscape design are systematically elaborated from the aspects of ecological environment protection, landscape space layout, theme culture creation and sponge city construction. This is a further exploration of the systematicity and scientificity of domestic riverside ecological environment construction[5].

2 Overview of current conditions

Zhuxi River is located in the center of the Water and Soil Industrial Park in the High-tech Industrial Zone, Liangjiang New District, Chongqing. The total length of the river channel is about 5 km and the total area is about 138.5 ha. There are many types of landscapes along the river, such as canyon, rocky beach and shallow hill. The upper and lower reaches have large terrain height difference, and there are abundant vegetation resources along the river, including cliff plants, river valley meadows, farm crops, sparse forests and ecological dense forests. Around the river channel, scientific research and high-tech industrial centers are distributed. The ecological landscape of Zhuxi River has the role of leading the quality of local cities and regulating the urban ecological environment. The main existing problems of Zhuxi River are as follows: (i) the ecological environment is fragile and partially damaged, lacking systematic ecological protection measures. (ii) natural landscape has been destroyed, and landscape effect is poor. (iii) space vitality is insufficient, and river culture is lacked. (iv) the drainage system is chaotic, lacking unified planning and layout.

3 Design goals

According to the current situation of Zhuxi River and its strategic positioning, the following design goals are proposed: (i) improving the overall ecological environment of Zhuxi River, improving the ecological functions, and building a complete ecosystem; (ii) creating the unique landscape environment and river culture of Zhuxi River; (iii) emphasizing space design, improving the vitality of the space in addition to meeting the basic functional requirements, creating a good ecological, social and economic environment; (iv) creating a new type of sponge city park and paying attention to the use and protection of water resources.

4 Ecological landscape design of Zhuxi River

4.1Ecologicaldesign

4.1.1Ecological wetland. In the flat areas upstream and open areas downstream of Zhuxi River, the water resources are conserved and biological purification of external rainwater and sewage is performed, while taking advantage of the natural topography and native vegetation to create an ecological wetland landscape. The harmful substances in rain and sewage are absorbed and degraded by the animals, plants and microorganisms in the river, thereby effectively improving water quality[2].

4.1.2Ecological protective forest. The design of the protective forest belt is conducive to soil and water conservation and flood disaster prevention in the Zhuxi River Basin. In the open areas on both sides of the upstream river bank, aquatic plants are densely planted to form dense forests. During heavy rains and floods, protective forests can accumulate large amounts of water to avoid the waste of water resources, and at the same time, they improve the bank’s ability to resist erosion, reduce soil erosion and reduce the threat of flooding downstream. Besides, protective forest belt also provides ideal living space for the survival and reproduction of aquatic and terrestrial animals in the Zhuxi River[2, 6]. The plant design of the protective forest belt is divided into the following situations according to the area where the plants are located. Hydro-fluctuation belt is flooded all the year round, so water-resistant shrubs are often used in plant selection, such asHemarthriacompressa,Paspalumpaspaloides(Michx.) Scribn.,Cynodondactylon,Rosamultiflora,Buddlejadavidii,AlchorneadavidiiFranch., weeping willow andMetasequoiaglyptostroboidesHu & W. C. Cheng. The leisure activity area is usually far away from the flooded area, and more plants can be selected. The area is mainly based on the display of landscape effects, so the method of arbor-shrub-ground cover combination and multi-level layout can be adopted. In addition, at the node, some plants that are suitable for waterside and have excellent landscape effect, such asJacarandamimosifolia,Sophorajaponica,Acercan be arranged.

4.1.3Ecological revetment. The upper reaches of the Zhuxi River are mostly natural cliffs and revetments, and the idea of preservation first and supplementation by partial repair is adopted. Most areas in the middle and lower reaches adopt the method of planting grass to construct ecological grass slope revetment, greatly reducing the project cost and quickly restoring the ecological environment of the bank. In areas with dense crowd flow or focus of sight, natural rivers and stones are used and aquatic plants are arranged to enhance the landscape effect, and leisure facilities such as hydrophilic platforms are set up locally to maximize the preservation of ecology while enhancing the vitality of the space[8]. In the middle and lower reaches, the areas where the soil is loose and eroded seriously by water flow are protected by ecological stone cages which protect the embankment and maintain the ecology.

4.1.4Ecological building. The facades of supporting facilities such as toilet and management houses use double-layer vacuum glass, which plays the role of heat insulation and sound insulation and reduces energy consumption. The roof is equipped with solar light absorption panels, and roof garden and wall greening are designed to greatly enhance the landscape effect, make full use of sunlight and rain and play the ecological roles of thermal insulation and environmental beautification.

4.1.5Ecological parking lot. The ecological parking lot is paved with a permeable concrete surface layer. A blind drainage ditch is set around to collect rainwater, and an ecological grass ditch and rainwater garden are set in the middle green belt to further collect rainwater. After filtering and purifying, the water collected is drained to the nearest municipal rainwater pipeline or utilized by green irrigation and water features.

4.2Landscapedesign

4.2.1Overall landscape layout. Taking the Zhuxi River as the context, the stories of Chongqing’s local people are told, the local culture is shown, the living space of residents is enriched, and a vibrant, comfortable and pleasant waterfront park is created to attract a high degree of public participation and drive the development of the surrounding economy. The entire riverfront park is connected in series with the Zhuxi River water system as the axis, and is divided into two layers: the layer near the river bank is the ecological base layer, and the layer near the municipal road is the image display layer. At the same time, three distinctive landscape zones are created, including urban valley, urban idyll and ecological wetland (Fig.1).

Fig.1 Zoning of general layout

4.2.2Zoning planning and design. (i) Urban valley. The river channel included is about 1.9 km long, from Longmen Bridge to Baiyankou Bridge. The area is about 47.7 ha. The landforms include canyon, cliff and rocky beach. Based on the original ecological landscapes such as natural cliff, rocky beach, water channel, water fall and hydrological relic in the river area, interesting, hydrophilic, paddling and swimming spaces, such as valley along river and bamboo-river cascade are created. Combined with the characteristics of the water and soil high-tech industrial park, wisdom and cultural activity venues will be added to bring fun to education. (ii) Urban idyll. From Baiyankou Bridge to Wangjia Bridge, the length is about 2 km and the area is about 79.7 ha. The landforms mainly include river valley, native dense forest and grass slope. The winding promenade passes through the peach forest. Peach is taken as the theme plant, and a large number of peach trees are planted, such asPrunuspersica,AmygdaluspersicaL. var. persica f. duplex Rehd. andAmygdaluspersicaLinn. var. persica f. pyramidalis Dipp., to form a special scenic spot and create the best place for tourists to visit. Combined with the vineyard, Zhuxi memory, Fengyang photography base, ecological trestle and other nodes, the tour experience is enriched, and the fun and the vitality of the river space is enhanced. (iii) Ecological wetland. The length is about 1.3 km, from Wangjia Bridge to Belt Highway, with an area of about 29.4 ha. The landforms are mainly grass slope and shoal. The original site features such as natural grass slope, shoal, maple forest and poplar forest are retained and partially repaired and restored to form a natural ecological wetland. Ecological science popularization area and sewage purification display area are added. They not only protect the integrity of the wetland ecosystem but also exert the sightseeing and leisure functions of the landscape. Thus, ecological leisure and popular science education are integrated closely to create a characteristic culture of river landscape.

4.2.3Node landscape design: children’s paradise. The design of the panda-themed children’s paradise was inspired by the name of the Zhuxi River and the large number of bamboos distributed at the base. In addition, pandas are China’s national treasures distributed in Sichuan and Chongqing. In the children’s field, pandas are faithful interesting playmates for children and are the guardian of children’s utopia and the mark of children’s play culture. The current terrain of the children’s playground is relatively flat, and special-shaped flower ponds are set up locally by making use of the uneven terrain to increase the fun of the venue. The paving is mainly based on EPDM colorful plastics, with a variety of colors and rich lines. Combined with the flower pond, anti-corrosion wood trail, sandpit, lawn and other spaces, a relaxed, lively, very interesting and cultural children’s playground is created, with a variety of amusement facilities. Children’s activity space is divided according to different ages. Children of all ages have different behavioral characteristics and needs. By combining with landscape design, a diversified children’s space is formed. Children at the age of 0-3 years are classified as young children, and children at the age of 3-12 years are older children. In the venues for young children, simple and safe children’s devices are set, such as tunnel, seesaw and football field; and the venues for older children are equipped with more adventurous and exploratory equipment such as trampoline, large slide and swing. In addition, the color of children’s activity space has been richly designed, and a variety of colors such as yellow, orange, green, blue, purple, black and white are used, in order to bring a pleasant visual experience to children and create a colorful dream space for children, while beautifying the space (Fig.2).

Fig.2 Graphic design of children’s park

4.3ThemeculturedesignThe supporting buildings in this design, such as management house, restaurant and toilet adopt the architectural style of southeast Chongqing with local cultural characteristics. Local red rock, blue stone, blue brick, small blue tile, wooden door, wooden window and wooden fence are used extensively. Besides, cultural elements such as stone mill, watermill and plow, as well as wooden boat, helmsman, horn, lighthouse,etc. that represent Chongqing’s terminal culture are equipped, to tell the local stories of Chongqing and make the local culture more distinctive. In addition, the benches, trash cans, lamps and identification systems used in the supporting facilities all incorporate local cultural elements or design theme elements, in order to well reflect the theme and culture of this design. From the perspective of original building renovation design, taking Fuxing Longmen Bridge as an example, after reinforcing, the outer edges of the bridge are decorated with localPhyllostachyspubescens, making it look ecological and full of emotion and echoing the theme element of bamboo in the landscape design of Zhuxi River. Water wave and bamboo are extracted as design elements. Through the composition of flowing lines, the texture of bamboo and the color tone harmonized with the landscape of the river cliff, a set of service facilities that have distinctive culture and are integrated with the surrounding natural environment is designed, such as seats, trash cans, lamps and lanterns.

4.4SpongecitydesignThis ecological landscape design makes a comprehensive analysis of the site drainage and runoff organization. On this basis, a comprehensive design of the LID drainage facility is made, including the layout of ecological roof drainage pipe, ecological drainage ditch, rain garden and ecological wetland and the vertical design and drainage design of the site, to ensure smooth drainage and make full use of rainwater resources[7]. The paving of the roads and plazas is all permeable, and permeable concrete and permeable bricks are used as the main pavement materials. Ecological drainage ditches are set up on the edge of the roads. In the large-scale paved areas such as plazas and parking lots, drainage blind ditches and drainage pipes are arranged[8]. The rainwater collected flows into the rainwater garden for filtration and purification, and finally, it flows into the ecological wetland or Zhuxi River for secondary use.

5 Conclusions and prospects

With the goals of improving the ecological environment of the river, shaping landscape space, building river culture and building sponge city, a systematic design is performed for Zhuxi River from aspects of river ecological design, landscape planning and design, theme culture creation, space vitality enhancement and sponge city construction, by adhering to the ecological and humanistic design concept of taking river ecological environment design as the inner core and natural landscape and human landscape as the external expression of river value and adhering to the principle of paying equal attention to protection and development. The concept and practice of the Zhuxi River ecological landscape design provide a reasonable and feasible plan for the ecological restoration of Zhuxi River, thematic landscape creation and the improvement of the social and economic environment. It is conducive to the sustainable development of Zhuxi River and has positive practical significance for further improving the environmental and social benefits of river landscapes in China.