“The waterways on China’s Hainan Island have proven to be vulnerable to flooding, but a new landscape within the Sanya River restores previously decimated mangroves that alleviate some of that risk while serving as a lush pedestrian recreation zone within high-rise city. Developers had left behind concrete retaining walls and polluted waterways, but now a thriving ecotone welcomes ocean tides with a porous edge condition that supports new mangrove growth. Terraced landscapes and elevated pathways bring visitors from the city down to water level, and storm-resistant concrete pavilions offer protection from overhead sun and tropical rain. The mangrove rehabilitation serves as a case study of strategies to return parts of cities to nature.”
– 2020 Awards Jury
As an action of mitigating urban flood risk caused by climate change, the restoration of mangrove along the waterways and coastal shorelines are critical for the tropical city Sanya in China’s Hainan Island. One of the key challenges is to find an efficient and inexpensive method to restore the mangrove habitat extensively that have been destroyed in the past decades due to rapid urban development. Right in the middle of the city and in just three years, an area of lifeless land fill within a concrete flood wall has been successfully restored into a lush mangrove park, where nature and people harmoniously share the meeting of ocean tides and fresh water. The project demonstrates the success of the design strategy based on the ecological processes of wind and water, which produces a designed ecotone made of inter-locked fingers to speed up the natural process of mangrove rehabilitation. Such a mangrove rehabilitation method and be implemented at a large scale efficiently.
▲平面图：形式服从过程。指状相扣的红树林岛将海潮引入，同时避免河水的冲刷和强热带风暴的破坏。Site plan: form follow processes. The designed ecotones of inter-locked fingers help to induct ocean tides, avoid the fresh water flush and destructive tropical storm
▲场地现状条件：场地位于海潮最高水位边界，曾经的红树林群落被粗暴的城市开发和混凝土驳岸破坏了，场地里的建筑废料和垃圾随处可见。The preexisting conditions: the site is at the upper limit the ocean tide can reach, the former natural mangroves had been destroyed by careless urban development and concrete embankment, and was piled with construction debris and garbage
▲指状岛的形态设计大大加强了边界效应（水岸线从700米扩展到4000米，深度从0到1.5m范围内波动），随着潮汐变化创造动态的水环境。The designed ecotone of inter-locked fingers dramatically enhances the edge effects (water edge length increases from 700 to over 4000 meters, and water depth varies from 0 to 1.5 meters), and creates a dynamic aquatic environment following the rise and fall of tides
▲重新利用场地堆填的城市建筑垃圾，拆除防洪墙遗留的混凝土废料，通过填-挖方创造不同水位来适应以红树林为主的各类动植物的生长和栖息，形成丰富的驳岸生态系统。The former land fill of construction debris and concrete materials from the demolition of the flood wall are recycled on site, and by mean of cut-and-fill, ecotones of inter-locked fingers are created for diverse fauna and flora, particularly different species of mangroves
▲建成两年半后的红树林公园（2018年11月）。在这张航拍照片中，海潮从最上端的入口被引入指状岛中，再从右下角流出。The established mangrove park in just two and half year after its construction (November, 2018). The ocean tides are inducted into the inter-locked fingers of water ways from the singular inlet at the uppermost end and runs out at the lower right corner in this aerial photo
▲河边的指状岛专门用来保护野生动物，而城市旁的公园则可供居民使用。步道和场地空间随着地势起伏而变化。观鸟、遮阴、观景用的景观亭设置在最佳地点。While ecotone fingers by the river side are reserved for wild lives, the park at the urban side is made accessible for recreational uses. Paths and places are designed following the terrain. Pavilions for bird watching, shading and viewing are strategically positioned
▲利用道路与水面的9米高差来设置梯级净化系统，结合生态廊道截留净化来自城市道路和地面的雨水，同时在不同高度设置活动空间。Making use of the 9 meter drop from the urban road to the water level, terraces integrated with bio-swales are created to catch and filtrate stormwater from the pavement and road, meanwhile creating public places at different elevations
▲修复后的红树林公园成为市中心的一片城市绿洲，周边环绕着高层住宅。居民们在亭中观察仅几米之外的白鹭或是喂鱼。The ecologically restored mangrove park become an oasis right in the middle of the city, surrounded by skyscapes of residential buildings. Residents take leisure in the pavilions watching white egrets feeding fishes just feet’s away across the waterway
▲景观亭位置优越，可以在此观鸟、钓鱼。它们是这片宽阔绿色景观中的焦点，同时也为游客提供可休息的场所。The pavilions are strategically located for birdwatching and fishing. They become focal points in the massive green landscape and provide resting places for visitors
▲这是其中一个预制混凝土景观亭，它可以抵抗热带风暴，为市民提供观鸟场所，以及在不同天气状况下提供庇护或是遮荫（图中两个家庭正在此避雨）。One of five pavilions of modulated concrete that are designed to be resistant to strong tropical storm.They provides shelter and shading in the changeable local weather, and refuges for bird watching (two families are taking shelter from the rain)
▲这是预制混凝土景观亭中的一个，能遮挡正午刺目的阳光，清晨朝阳和傍晚落日的柔光却可以洒进来。一对夫妇正在凉亭里享受日落。One of five pavilions of modulated concrete that are designed in such a way so that the harsh sunlight in the middle day can be effectively blocked and the morning and sunset light can penetrate through. A couple is enjoying the sunset in the pavilion.
▲景观亭不仅为游客提供遮荫和庇护的场所，这也是一种艺术装置，从不同的视角看过去，可以欣赏它不同的姿态。The self standing pavilion not only provide shading and shelter for visitors, but is an artistic installation that has different facades seen from different viewing points.
▲经过精心设计的景观亭，位置优越，可以让游客在白天、夜晚不同的时间里，都能欣赏风景。在喧闹的城市中，既可以与家人和朋友在此聚会，也可以享受独处的宁静。The pavilions are strategically located and sensitively designed for visitors to experience the landscape day and night. They are the places for family and friend gathering as well as for solo enjoyment of the tranquility right in amid the noisy city.
▲水面与城市道路之间的9米高差为场地设计带来挑战。坡道可以将游人带至水边，享受在修复后的红树林中的沉浸式体验。The 9 meter drop from the urban road to the water is a challenge for access design. A universally accessible ramp is designed to allow visitors to get down to the waterfront to have in immersive experience of the rehabilitated mangrove
▲被设计为坡道的空中步道，为游人创造在红树林树冠间穿梭的体验。A skywalk is designed as a ramp to create an experience of walking above the mangrove canopy that connect the urban road with the park
▲该公园已成为当地居民的日常休闲去处，也是当地的生态修复展示区，不仅有益于自然环境，而且能够提供公共服务。无论是在夜晚还是在热带晴朗的天气里，这里对于当地居民来说都极富吸引力。The park has become a daily recreational place for the local communities, and a showcase of ecological restoration that not only benefits the natural environment, but the public welfare, and is particularly attractive in the night for the local residents tourists in the clear tropical weather
1.Site Challenges and Objectives
Three decades of ruthless development has left Sanya，a tropical tourist city in China’s Hainan Island, a mess of destruction in terms of landscape. Almost all waterways in the developed districts have been polluted and filled with garbage. Concrete flood walls were built to claim land for development that killed the mangroves, wiped out the riparian habitats, and blocked tides from the sea and storm water from the upper land causing urban inundation and reducing the resiliency against climate change. Meanwhile, increased population, particularly seasonal tourists and immigrants are demanding more connected parks along the rivers, which were sadly inaccessible. In 2015, the city government decided to make dramatic changes, and the landscape architect was called upon to design this demonstration project: Sanya Mangrove Park. The method tested in this experimental project will be implemented in other mangrove rehabilitation projects at large scale throughout the region.
The site is 10 hectares (2.471 acres) in size, on the east bank of Sanya River that bears the name of the city itself, and in the central area of the city. Analysis shows that the site is also critical in terms of ecological relationships between the sea and inland, where the daily sea tides meet with the fresh water of the river. Typical of the city, the water is polluted due to the urban runoffs. High concrete walls have enclosed the site that is filled with urban debris for a new development project that has been stopped by the government. An artery road runs by, and there is a 9 meter steep drop from the road to the water, challenging public access to the water.
The design objectives are to rehabilitate the mangroves and make the site a park showcase for citywide urban renewal and ecological recovery. Several site challenges have to be addressed: (1) Wind–the strong annual tropical monsoon storms may harm the process of mangrove rehabilitation and destroy the fledging mangrove planting; (2) Water– the upper stream floods from the monsoon storm water may wash away the young mangrove community; (3) Pollution: The polluted urban runoffs may damage sensitive mangrove seedlings and the biodiversity of the mangrove community; (4) Access: public accessibility and natural restoration need to be well integrated.
2.Design Strategies：Form follows processes
In addressing the above site challenges and to achieve the project objectives, the following design strategies were taken:
(1)Balanced earth work and recycling of materials: the land fill composed of urban construction debris and concrete materials from the demolition of the flood wall are recycled on site, and by means of cut-and-fill, ecotones of water ways and riparian habitats of various elevations are created for diverse fauna and flora, particularly different species of mangroves;
(2) Inter-locked fingers: a land form of inter-locked fingers was designed to lead ocean tides into the park. This is necessary for the mangroves, but they must at the same time avoid annual strong tropical storms from the sea and the storm water flood and pollution from the upper stream mountain and urban area that may harm the establishment process of the mangrove community. This also maximizes the edge effects (water edge length increases 6 times from 700 meters to over 4000 meters) and habitat diversity with water depth varies from 0 to 1.5 meters, and creates a dynamic aquatic environment following the rise and fall of tides, which are necessary for some aquatic species.
(3) Terraces and bio-swales: Making use of the 9-meter drop from the urban road to the water level, terraces are integrated with bio-swales to catch and filtrate the stormwater from the urban pavement and road, creating public spaces at different elevations.
(4) Adaptive design of pavilions and access: a network of pedestrian passageways follow the landform. A skywalk is designed as a ramp to create an experience of walking above the mangrove canopy; five pavilions are strategically allocated allow visitors to enjoy the tranquility and beauty within the mangroves, as well as providing necessary shelter and shading in the changeable local weather. The modulated concrete shelters are designed to resist strong tropical storms; they open to views from various angles. The twisted pavilions make good shelters for bird watching.
This project is a great success. Just three years after its construction, its objectives have been fulfilled. The mangroves within the interlocked fingers have established well. Along with the flourishing mangroves, fish and birds are abundant, attracting visitors of different ages. The park has become a daily recreational place for the local communities, and a showcase of ecological restoration that not only benefits the natural environment, but the public welfare. The approach tested in this experimental project has been implemented in other mangrove rehabilitation projects at large scale throughout the region.